UNIVERSIDADE FEDERAL DO PARANÁ

Transcription

UNIVERSIDADE FEDERAL DO PARANÁ
SETOR DE CIÊNCIAS AGRÁRIAS
DEPARTAMENTO DE FITOTECNIA E FITOSSANITARISMO
PROGRAMA DE PÓS GRADUAÇÃO EM AGRONOMIA – PRODUÇÃO VEGETAL
Leonardo Deiss
OAT GROWTH AND GRAIN YIELD UNDER NITROGEN LEVELS IN
AGROFORESTRY SYSTEM IN SUBTROPICAL BRAZIL
Curitiba, 2012
Leonardo Deiss
Dissertação apresentada ao Programa de PósGraduação
Concentração
em
Agronomia,
em
Departamento
Produção
de
Área
de
Vegetal,
Fitotecnia
e
Fitossanitarismo, Setor de Ciências Agrárias,
Universidade Federal do Paraná, como parte
das exigências para obtenção do título de
Mestre em Ciências.
Comitê de orientação: Dr. Anibal de Moraes,
Dr. Adelino Pelissari, Dr. Francisco Skora
Neto, Dr. Edilson Batista de Oliveira e Dr.
Vanderley Porfírio da Silva.
Curitiba, 2012
Dedicatória: Dedico este trabalho a Deus, aos meus pais Graça e Edgar e a Georgia.
AGRADECIMENTO
Agradecimento ao Comitê de orientação: obrigado Prof. Dr. Anibal de Moraes pela aceitação
como seu orientado no programa de pós-graduação, confiança depositada ao me encarregar de
realizar este trabalho, orientação, amizade e respeito cedidos incondicionalmente. Ao Prof. Dr.
Adelino Pelissari pelos ensinamentos de vida e agronomia. Ao Dr. Francisco Skora Neto pelos
presentes ensinamentos agronômicos. Ao Dr. Edilson Batista de Oliveira pelo amparo de seu
conhecimento estatístico. Ao Dr. Vanderley Porfírio da Silva pelos ensinamentos sobre os sistemas
integrados arborizados.
Agradecimento especial: Agradeço a Georgia Bascherotto Kleina pela ajuda nos trabalhos de
laboratório e de tabulação de dados e principalmente pela compreensão dos momentos que não
podemos ficar juntos, que espero poder retribuí-la pelo resto de nossas vidas.
Agradecimento a outros pesquisadores: Agradeço a Dra. Laíse Silveira Pontes pelas
considerações morfológicas e experimentais e amparo financeiro do projeto. A Dra. Raquel
Santiago Barro pela imensurável ajuda cedida durante a condução dos experimentos. Ao Prof. Dr.
Sebastião Brasil Campos Lustosa e ao Msc. Newton de Lucena Costa pelas considerações feitas à
primeira versão desta dissertação.
Agradecimento aos professores da Universidade Federal do Paraná: Especialmente a
professora Dra. Maristela Panobianco por permitir a utilização das balanças de precisão do
Laboratório de Análise de Sementes, ao professor Dr. Átila Francisco Mógor pelo empréstimo do
pulverizador e aos professores Ricardo Augusto de Oliveira e Claudete Reisdorfer Lang pelas
considerações científicas feitas ao trabalho.
Agradecimento aos funcionários da Universidade Federal do Paraná: A Técnica do
Laboratório de Fitotecnia Maria Emilia Kudla. A secretária do Programa de Pós Graduação
Lucimara Antunes. A Técnica do Laboratório de Análise de Sementes Roseli do Rocio Biora.
Agradecimento aos funcionários do Instituto Agronômico do Paraná: Agradeço a todos que
participaram de maneira direta e indireta durante a realização deste trabalho. Assim como na
incessante busca pelo conhecimento, que possibilitou conviver com vocês, acredito e espero que
meu agradecimento fique guardado em seus corações, muito obrigado. Agradecimento aos
administradores Renério Ribeiro de Almeida da Estação Experimental Fazenda Modelo e Giovani
Luiz Thomaz da Estação Experimental de Ponta Grossa. E a todos os outros funcionários da
Estação Experimental Fazenda Modelo do Iapar e aos funcionários Antônio Carlos Campos
(mineiro) e Sandoval Carpinelli do Polo Regional de Pesquisa de Ponta Grossa.
Agradecimento aos colegas: Acredito que os novos e os já conhecidos amigos
compreenderam os motivos da realização deste trabalho e muito ajudaram para que este pudesse ser
concluído. Ana Carolina Oliveira, Gederson Buzzello, Isabel Cristina Bonometti Stieven, Ivan
César Furmann Moura, Luciana Helena Kowalski e Sérgio Rodrigues Fernandes.
Agradecimento aos estagiários: Agradeço a ajuda dos estagiários vinculados à Universidade
Federal do Paraná: Adriano Gomes Bueno, Leidimara Nascimento, Lurdes Marina Oracz e Marcelo
Palazim e vinculado ao Iapar Polo Regional de Ponta Grossa: Erisson Felipe. Agradecimento
especial a Mêmora Bitencourt estagiaria da Universidade Federal do Rio Grande do Sul, pela sua
grandiosa ajuda.
Na ciência não existe verdade,
a ciência é a verdade.
CRESCIMENTO E RENDIMENTO DE GRÃOS DA AVEIA SUBMETIDA A NÍVEIS DE
NITROGÊNIO EM SISTEMA AGROFLORESTAL NO SUBTRÓPICO BRASILEIRO
RESUMO
A adequação das práticas agronômicas tem um papel fundamental no desenvolvimento dos
sistemas integrados. A hipótese deste trabalho é que a resposta da aveia aos sistemas
integrados não é passível de melhoramento, portanto esta é uma cultura que não possui
condições morfofisiológicas para coabitar com as árvores, no subtrópico brasileiro. O objetivo
geral deste trabalho foi avaliar se a aveia (Avena sativa L. cv. IPR 126) possui características
agronômicas que possibilitam o seu cultivo nos sistemas integrados com árvores, utilizando
como referência, a forma de agricultura predominante no subtrópico brasileiro e como prática
agronômica, a fertilização nitrogenada. O experimento foi realizado em faixas no
delineamento de blocos ao acaso com quatro repetições, dois níveis de nitrogênio (12 e 80 kg
N ha-1) em cinco posições equidistantes entre faixas adjacentes de linhas duplas [20 m (4 m x
3 m)] de eucaliptos (Eucalyptus dunnii Maiden) em sistema agroflorestal (SAF) e agricultura
tradicional em semeadura direta, no subtrópico brasileiro. As variáveis de crescimento
avaliadas foram a taxa de crescimento relativo, taxa de assimilação líquida, fração de massa
foliar e taxa de enchimento relativo da panícula. As características dos perfilhos avaliadas
foram relação de massa seca e de grãos do colmo principal e perfilhos e número de perfilhos
por planta. Na colheita as variáveis avaliadas foram o rendimento biológico e de grãos,
componentes de rendimento e índice de colheita. O nitrogênio aumentou o crescimento da
aveia quando semeada entre faixas de árvores, entretanto os níveis de nitrogênio alteraram o
crescimento diferentemente em posições relativas às faixas adjacentes de eucalipto. A
persistência do perfilhamento para produção de grãos da aveia foi dependente do nível de
nitrogênio em distâncias relativas as faixas de eucaliptos no SAF. Houve compensação do
menor número de cariopses por panícula pelo maior número de grãos por cariopse, assim
como maior índice de colheita aonde a aveia acumulou menor fitomassa, nos ambientes com
alta interação interespecífica. O nitrogênio promoveu mudança na produção da aveia
diferentemente em posições relativas às árvores no sistema integrado. O crescimento e
rendimento da aveia em SAF pode ser incrementada através da fertilização nitrogenada. As
variáveis que descrevem o crescimento, o perfilhamento e o rendimento de grãos da aveia
interagem com os níveis de nitrogênio e as posições relativas as árvores dentro do SAF,
portanto diferentes níveis de nitrogênio devem ser utilizados nas posições, para aumentar o
potencial de rendimento da aveia nos sistemas integrados.
Palavras chave: Avena sativa L., Eucalyptus dunnii Maiden, sistemas integrados, análise do
crescimento, perfilhamento, componentes de rendimento
ABSTRACT
The adequacy of agronomic practices plays a key role in the development of integrated
systems. The hypothesis of this work is that the oat (Avena sativa L. cv. IPR 126) response to
the arborized integrated systems is not amenable to improvement through agronomic
practices; therefore it is a crop which has not morphophysiological conditions for cohabitate
with trees, in subtropical Brazil. The general objective was evaluate if the oat has agronomic
characteristics which allow its cultivation in the arborized integrated systems, using as
reference the predominant agriculture form in subtropical Brazil and as agronomic practice,
the nitrogen fertilization. The experiment was carried out in a split-block randomized block
design with four replicates, two nitrogen levels, in five equidistant positions between two
adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] in
alley cropping agroforestry system (ACS) and traditional no till agriculture in subtropical
Brazil. It was evaluated the growth variables relative growth rate, unit leaf rate, leaf weight
fraction, panicle relative filling rate and grains to panicle ratio. The tiller traits evaluated was
tillers to main shoot phytomass ratio, tillers per main shoot, grain yield and tillers to main
shoot grain yield ratio. At harvest was evaluated biological and grain yield, yield compounds
and harvest index. The nitrogen increased the oat growth between the tree tracks, however the
nitrogen levels altered the growth response differently in positions relative to adjacent
eucalyptus tracks. The oat tillering persistence for grains production depended of different
nitrogen level in distances relative to adjacent eucalyptus tracks. At the end of oat cycle, there
was compensation of the lower number of spikelets per panicle by the greater number of
grains per spikelet, as well as higher harvest indexes where less phytomass was accumulated,
in environments with high interspecific interaction. The nitrogen levels increased the oat yield
differently at positions relative to the trees in the integrated system. The oats growth and yield
in ACS can be improved through the nitrogen fertilization. The variables that describe growth,
tillering and grain yield of oat interact with nitrogen levels and positions relative to eucalyptus
inside ACS, therefore different nitrogen levels should be used in those positions, to improve
the oats yield potential inside ACS.
Key words: Avena sativa L., Eucalyptus dunnii Maiden, integrated systems, growth analysis,
tillering, yield compounds
SUMMARY
1. General introduction ............................................................................................... 18
1.1 Economical, social and environmental importance of oats ........................................ 18
1.2 Economical, social and environmental importance of the integrated systems ........... 19
1.3 Hypothesis .................................................................................................................. 21
1.4 Objectives ................................................................................................................... 21
2. Bibliographic review .............................................................................................. 21
2.1 Ecological basis of the interactions between species in the integrated systems ......... 21
2.2 Microclimate conditions in agroforestry systems ....................................................... 22
2.3 Trees interference in the agroforestry systems ........................................................... 23
2.4 Small cereals growth and development ...................................................................... 25
2.5 Morphophysiological responses of small cereals to the light, water, temperature and
nutrients as well as its interactions ................................................................................... 26
3. CHAPTER 1........................................................................................................................ 31
OAT GROWTH UNDER NITROGEN LEVELS IN EUCALYPTUS ALLEY CROPPING
SYSTEM IN SUBTROPICAL BRAZIL ................................................................... 31
Abstract ............................................................................................................................. 31
Introduction ...................................................................................................................... 32
Materials and methods ...................................................................................................... 33
Results .............................................................................................................................. 36
Discussion......................................................................................................................... 40
Conclusion ........................................................................................................................ 42
Acknowledgements .......................................................................................................... 43
References ........................................................................................................................ 43
4. CHAPTER 2........................................................................................................................ 50
TILLERING AND TILLER TRAITS OF OAT UNDER NITROGEN LEVELS IN
EUCALYPTUS ALLEY CROPPING SYSTEM IN SUBTROPICAL BRAZIL...... 50
Abstract ............................................................................................................................. 50
Introduction ...................................................................................................................... 51
Results .............................................................................................................................. 55
Discussion......................................................................................................................... 58
Conclusion ........................................................................................................................ 61
Acknowledgements .......................................................................................................... 61
References ........................................................................................................................ 61
5. CHAPTER 3........................................................................................................................ 69
OAT GRAIN YIELD UNDER NITROGEN LEVELS IN EUCALYPTUS ALLEY
CROPPING SYSTEM IN SUBTROPICAL BRAZIL ............................................... 69
Abstract ............................................................................................................................. 69
Introduction ...................................................................................................................... 70
Results .............................................................................................................................. 74
Discussion......................................................................................................................... 77
Conclusion ........................................................................................................................ 80
Acknowledgments ............................................................................................................ 80
References ........................................................................................................................ 80
6. General conclusions ................................................................................................ 86
7. Final thoughts ......................................................................................................... 86
8. General references .................................................................................................. 86
GENERAL SUPPLEMENT ....................................................................................... 91
LIST OF FIGURES
CHAPTER 1
Fig. 1 Oat (Avena sativa L. cv. IPR 126) growth traits in days after emergence (DAE), relative
growth rate (RGR), unit leaf rate (ULR), leaf weight fraction (LWF), panicle phytomass
(PDW) panicle relative filling rate (PRFR) from 126 to 152 DAE under nitrogen levels (12.0
kg N ha-1 and 80.0 kg N ha-1), in alley cropping agroforestry system, at A: 2.8 m, B: 6.4 m, C:
10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest elevation of the
slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m
(4 m x 3 m)] in subtropical Brazil. Vertical bars denote standard errors ................................ 49
CHAPTER 2
Fig. 1 Oat (Avena sativa L. cv. IPR 126) phytomass (a), tillers to main shoot phytomass ratio
(b) and tillers number (c) under nitrogen levels (80.0 kg N ha-1 and 12.0 kg N ha-1) in alley
cropping agroforestry system, at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m
away from track positioned at the lowest elevation of the slope, between two adjacent
eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] and traditional
no till agriculture (F), in subtropical Brazil. Vertical bars denote standard errors ................... 63
Fig. 2 Oat (Avena sativa L. cv. IPR 126) traits under nitrogen levels (12.0 kg N ha-1 and 80.0
kg N ha-1) in days after emergence (DAE), above ground biological yield, tillers to main shoot
phytomass ratio, tillers per main shoot and tillers to main shoot grain yield ratio in alley
eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] in subtropical
Brazil. Vertical bars denote standard errors ............................................................................. 64
CHAPTER 3
Fig. 1 Oat (Avena sativa L. cv. IPR 126) above ground biological yield (a), yield compounds
spikelets per panicle (b) and grains per spikelet (c), yield (d) and harvest index (e) in alley
eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)], under levels of
nitrogen (12.0 kg N ha-1 and 80.0 kg N ha-1 fertilizer), in subtropical Brazil. Vertical bars
denote standard errors ............................................................................................................... 82
GENERAL SUPPLEMENT
Supplement 1 Experimental sketch. Oat (Avena sativa L. cv. IPR 126) under nitrogen levels [12.0
kg N ha-1(clear) and 80.0 kg N ha-1 (dark)] in alley cropping agroforestry system (A_E), at A:
2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest
elevation of the slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line
tracks [20 m (4 m x 3 m)] and traditional no till agriculture (F) in subtropical Brazil ..................91
LIST OF TABLES
CHAPTER 1
Table 1 Oat (Avena sativa L. cv. IPR 126) relative growth rate under nitrogen levels (12.0 kg
N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till
agriculture (F) in subtropical Brazil ......................................................................................... 45
Table 2 Oat (Avena sativa L. cv. IPR 126) unit leaf rate under nitrogen levels (12.0 kg N ha-1
and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till
Table 3 Oat (Avena sativa L. cv. IPR 126) leaf weight fraction under nitrogen levels (12.0 kg
N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till
Table 4 Oat (Avena sativa L. cv. IPR 126) panicle phytomass, panicle relative filling rate and
grains to panicle ratio, under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley
cropping agroforestry system (A_E) and traditional no till agriculture (F) in subtropical Brazil
.................................................................................................................................................. 48
CHAPTER 2
Table 1 Oat (Avena sativa L. cv. IPR 126) grains yield per plant and tiller to main shoot grain
yield ratio, under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping
agroforestry system (A_E) and traditional no till agriculture (F) in subtropical Brazil ........... 65
Supplementary Table 1 Oat (Avena sativa L. cv. IPR 126) above ground phytomass under
nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system
(A_E) and traditional no till agriculture (F) in subtropical Brazil ............................................ 66
Supplementary Table 2 Oat (Avena sativa L. cv. IPR 126) tillers to main shoot phytomass
ratio under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry
system (A_E) and traditional no till agriculture (F) in subtropical Brazil................................ 67
Supplementary Table 3 Oat (Avena sativa L. cv. IPR 126) tillers number per main shoot under
nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system
(A_E) and traditional no till agriculture (F) in subtropical Brazil ............................................ 68
CHAPTER 3
Table 1 Biological yield of oat (Avena sativa L. cv. IPR 126) under levels of nitrogen [12.0 kg
N ha-1 and 80.0 kg N ha-1] in alley cropping agroforestry system (A_E) and traditional no till
Table 2 Yield compounds of oat (Avena sativa L. cv. IPR 126) under levels of nitrogen (N)
[12.0 kg N ha-1(-) and 80.0 kg N ha-1 (+)] in alley cropping agroforestry system (A_E) and
traditional no till agriculture (F) in subtropical Brazil
84
Table 3 Yield and harvest index of oat (Avena sativa L. cv. IPR 126) under levels of nitrogen
(N) [12.0 kg N ha-1(-) and 80.0 kg N ha-1 (+)]in alley cropping agroforestry system (A_E) and
traditional no till agriculture (F) in subtropical Brazil ............................................................. 85
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1. General introduction
Currently in the world, the agriculture is undergoing a time of change, in which the
values of high yielding crops, are being replaced by other values that give greater emphasis on
the systems performance that consider environmental, social and economic aspects. This new
type of agriculture emphasizes the better utilization of the land units, with high yielding
components during all seasons of the year, and promotes balanced development in the long
term, mainly based on the diversification of the production system.
In Brazil, particularly in the subtropical region, is emerging a proposal to integrate the
components crop, livestock and forest, in the same unit of area, for better utilization and
greater conservation of the available natural resources. This system concept is fundamentally
based on the knowledge more consolidated until then, of the integrated crop-livestock systems
(Carvalho et al. 2010). Although the conception of this research is based on the integration of
all three components, it will be addressed issues related to the crop and forest components. At
world level, the intercropping of trees and crops has already been widely discussed, at the
optics of the agroforestry.
The sustainability of an agricultural system is supported by environmental, social,
economic, political and cultural issues. The introduction of trees on the annual crop land is
bumping in that the cultural issue, because they do not have concrete answers both on the
economic response at the system level, as well as the productivity of the components when it
is integrated. As the transition from the conventional system to the no tillage system, the
agronomic practices should be readapted for the intercropping systems with trees. To take a
step to fill this gap, in order to contemplate responses of the crop component, it will be
addressed in this research issues related to the oat culture, one of the main crops used in
traditional no till agriculture in subtropical Brazil.
1.1 Economical, social and environmental importance of oats
The oats originate from Mediterranean and are domesticated back to the ancient times
(Suttie and Reynolds 2004). The white or yellow-hulled is thought to be the progenitor of the
common oat (Avena sativa L.) (Stevens et al. 2004) and this is the naked type (6n=42) used in
the commerce (Suttie and Reynolds 2004). Avena sativa is self pollinating hexaploid specie,
compatible with the hybridizing techniques (Stevens et al. 2004).
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Oats are grown principally in cool moist climates around the world, the production for
grain, forage, fodder, straw, bedding, hay, haylage, silage and cheaff are concentrated
between latitudes 35-65ºN and 20-46ºS, being sensitive to hot and dry weather (Stevens et al.
2004). Oat is a cereal crop used for human food and animal feed throughout the world
(Buerstmayr et al. 2007).
For some time oat has been recognized as a kind of healthy food (Cai et al. 2012).
Among cereals, oat is considered one of the most nutritious, rich in protein and fiber, with
their vitamins and minerals are concentrated in the bran and germ (Stevens et al. 2004).
Significant attention was given for oat in recent years due to the human health benefits of
consuming it as a whole-grain food (Newell et al. 2011). In contrast, the grain is mainly used
as animal feed, because for human consumption need more laborious preparation than wheat,
since that has to be milled (Suttie and Reynolds 2004). During the milling process, oat kernels
are removed from the husk and other contaminants (White and Watson 2010).
Oat remain the important as a grain crop, for specialist uses in developed economies
and for common people in marginal developing world (Stevens et al. 2004). Oats are
important crop for the grain transforming industry in Brazil, Argentina and Chile; in addition
is an economical and technical alternative crop in many production systems in the region
(Federizzi and Mundstock 2004). “Oats are finding new uses and farmers and researchers are
finding ways of integrating them into their productions systems” (Suttie and Reynolds 2004).
Oats importance for the integrated systems is related to their multiple uses, since the
integrated rural proprieties have diversified components, which necessity of agronomic
particularities, such as fodder for the livestock or cover crops for the no tillage soil
management.
1.2 Economical, social and environmental importance of the integrated systems
In production systems, the agronomic practices (e.g. fertilization and plant
arrangement) and the plant species (e.g. additional non-foliar photosynthesis) with improve
the capacity for better utilize natural resources (e.g. water, nutrients and light), contribute to
the agroecosystems sustainability. The integrated systems importance for the world is related
to the following question: how we (rural producers, researchers and government) improve
sustainably the production of food, fibers, energy and wood, without the need to opening new
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agricultural areas, and to sustain a world population expected by future, in a conservationist
way?
Integrating the trees in the agricultural land provide a sustainable land use
management (Tsonkova et al. 2012). The agroforestry is a land use practice which combine
trees and agricultural crops or livestock in the same field (Quinkenstein et al. 2009). The
components combination, on space and time, determine the structure of these systems. The
components integration could be made between: crops and trees, livestock (pastures and
animals) and trees or crops, livestock (pastures and animals) and trees. These integrated
systems provide an array of benefits for the animals or cultivated plants (Quinkenstein et al.
2009), maximizing the provision of ecosystem goods and services (Tsonkova et al. 2012).
In temperate regions, the objectives for establishing agroforestry systems are the
production of tree or wood products, agronomic crops or forage, livestock, and improvement
of crop quality and quantity, at a scale and magnitude corresponding to the prevailing social
as well as economic conditions, and environmental benefits (Jose et al. 2004). One variant of
the traditional agroforestry system is the alley cropping, when several crops are cultivated in
strips or alleys between hedgerows of trees or shrubs (Quinkenstein et al. 2009). Currently in
Brazil, this modality of integrated system is referred to as crop forest integration system
(Balbino et al. 2011). The potential application of this modality of integrated system are the
biomass production, multipurpose windbreaks, riparian buffer strips, contour planting for
erosion control and fertility improvement by nitrogen-fixing trees (Quinkenstein et al. 2009).
Fast growing tree species, planted in high densities (10,000–20,000 trees per hectare)
enable, in a period of 20 years, two to ten harvests, when the biomass harvested consists of
small diameter stems, twigs and branches, with a large fraction of bark being used for the
wood chips production (Quinkenstein et al. 2009). In the alley cropping systems, the
harvested biomass of trees is mainly consisted of large diameter stems, with low percentage of
bark (Quinkenstein et al. 2009).
Compared to the conventional agriculture, the alley cropping systems with strips of
short rotation plantations, have more intensive nutrient cycling, in terms of higher rates of
turnover or transfer of nutrients within the system, lower outputs (Tsonkova et al. 2012) and
reduced nutrients exportation (Quinkenstein et al. 2009; Tsonkova et al. 2012). The leaching
of nutrients below the rooting zone of the crops cause a reduction in the seepage water quality
and consequently of the groundwater, and implicate on the temporarily lost of nutrients from
the agricultural system (Tsonkova et al. 2012). The trees have the capacity for intercepting
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and absorbing the lost nutrients below the annual intercropped rooting zone, and re-deposit on
litter form, for subsequent annual crops use.
The correct choice of which annual crop can cohabitate with the selected trees in
integrated systems should be based in ecological principles that promote sustainably yield
potential of these system. The comparison of the agronomic response of crops, obtained
inside the arborized integrated systems, with those obtained in the traditional no till
agriculture, should be made taking into consideration that these crops have not gone through
breeding programs, to be grown in these types of systems.
1.3 Hypothesis
The hypothesis of this work is that the oat response to the arborized integrated systems is not
amenable to improvement through agronomic practices; therefore it is a crop which has not
morphophysiological conditions for cohabitate with trees, in subtropical Brazil.
1.4 Objectives
The general objective was to evaluate if the oat has agronomic characteristics which allow its
cultivation in arborized integrated systems, using as reference, the predominant agriculture
form in subtropical Brazil and as agronomic practice, the nitrogen fertilization.
The specifics objectives were to determine how growth and yield of oat (Avena sativa L. cv.
IPR 126) are influenced by nitrogen levels, in eucalyptus (Eucalyptus dunnii Maiden) alley
cropping agroforestry system and traditional no till agriculture in subtropical Brazil.
2. Bibliographic review
2.1 Ecological basis of the interactions between species in the integrated systems
The environment utilization by the plant species includes three main components:
space, resources and time (Jose et al. 2004). In the integrated systems, the interactions
between species include aspects of the water and nutrient cycle, the microclimate and the
biodiversity (Quinkenstein et al. 2009). The key for improving the yield potential of the
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integrated systems is understand how the biotic and abiotic environmental resources are
utilized in the time and the space. Ecological niches are created by the trees planted in alley
cropping within the agricultural landscape, for plants with different environmental
requirements (Tsonkova et al. 2012).
The interactive relationship between species in the agroforestry systems can occur
such as predation, parasitism, amensalism, mutualism, commensalism and neutralism (Jose et
al. 2004). When the interaction between components is positive or synergistic, the
complementarity results in an overyielding system, when the interaction is negative or
antagonistic the species become competitive resulting in an underyielding system (Jose et al.
2004). The net result of synergistic and antagonistic interactions among the components
results on the system productivity (Jose et al. 2004).
2.2 Microclimate conditions in agroforestry systems
The enhancement of agricultural sustainability and profitability are benefited by the
alley cropping microclimates contribution (Quinkenstein et al. 2009). The microclimate is
modified by the trees presence, in terms of temperature, light quality and intensity, wind
speed and water vapor content or partial pressure (Jose et al. 2004). The microclimatic site
dependant space effect, from close to wide spacing between hedgerows, is modified by
increasing temperature extremes, wind speed, soil evaporation, humidity balance and
decreasing shading of crops (Quinkenstein et al. 2009). The temperatures in the alley cropping
systems have small variation amplitude.
The microclimatic conditions within the agroforestry system, in the time advancement,
could be deteriorated or ameliorated, trough the altered interaction patterns between sunrays
and tree canopies, resulting from changing solar elevation and angle at various times of the
day (Kohli and Saini 2003) and seasons. In addition to sun angle variations during the day,
wind induces tree canopy movement, with produces frequent fluctuations in radiation within
the agroforestry system (Kohli and Saini 2003). The shading degree is controlled by the
hedgerows orientation (Quinkenstein et al. 2009) in relation to the sun pathway. The tree
canopies reduce the radiation intensity altering the light wave lengths arriving in the soil
surface (Taiz and Zeiger 2010).
Intercropped trees intercept the radiation and reduce the wind speed (Kohli and Saini
2003). The hedgerows are a permeable wind break, the porosity is determinant on wind speed
23
as well as on the quiet zone size, the height determines the efficiency, and the orientation in
relation to the prevailing wind direction, exerts important influence on the wind
characteristics inside the system (Quinkenstein et al. 2009).
An increase in the amount of soil water available can be attributed for the reduction in
the soil water evaporation, which is related to a decrease in wind speed, promoted by the
hedgerows planted in alley cropping (Quinkenstein et al. 2009). In hot and dry environments,
the primary effect of trees as windbreak is to reduces the turbulent transfer of heat and water
vapor (Kohli and Saini 2003). The evaporation from the bare soil is reduced due to a wind
speed reduction, as well as the water vapor transfer away from the surface, helping to
conserve soil moisture (Tsonkova et al. 2012).
In agroforestry systems, the spatial distribution of water reaching the soil from the
rainfall is determined by its partition between through fall, stem-flow and interception loss by
plant canopies (Siles et al. 2010). The tree rows reduce the soil evaporation by shading and
“by the creation of a rain shadow on the leeward side or trapping rain fall on the windward
side or through the more even distribution” (Quinkenstein et al. 2009).
2.3 Trees interference in the agroforestry systems
The hedgerows in the alley cropping system could enhance or reduce the crop growth
and yield, through the microclimate improvement or the interspecific competition for water,
nutrients, and light (Tsonkova et al. 2012). The prevalence of benefits or competition is
dependent of the site conditions and crop species (Tsonkova et al. 2012). Other benefits can
be generated by the trees in the integrated systems, by alteration on the water balance and
nutrient cycling. The trees interference can be malefic or benefic. The study of the interactive
relationship between species needs to consider all biotic and abiotic elements which can
influence that coexistence.
2.3.1 Facilitating conditions in agroforestry systems
Late sown wheat in an agroforestry system, have possibility for grown under higher
temperatures during the vegetative stages and lower temperatures during the reproductive
stages (Kohli and Saini 2003). Intercropped trees promote alteration on crop energy balance
by interception of radiation and reduction of wind speed (Kohli and Saini 2003).
24
Reduction of the turbulent transfer of heat and water vapor promoted by the
windbreaks in the hot and dry environments, modify the crop water use efficiency by reducing
evapotranspiration (Kohli and Saini 2003). The trees reduces evaporative stress by slowing
the movement of air, and the temperature reduction promoted by the trees can attenuate heat
stress of crops (Jose et al. 2004). For ameliorate plant water stress, plant canopies generate
cooler and moister atmosphere (Holmgren et al. 2012).
The shade could improve the performance of shade tolerant species for the negative
effect of drought, and shade intolerant species have non-linear response along the light
gradient increases, more severely affected at higher and lower light availability (Holmgren et
al. 2012).
A new component is introduced into the nutrient cycle when trees are integrated on
agricultural systems (Quinkenstein et al. 2009). The safety net hypothesis of nutrient capture
assumes that the roots of trees retrieve the nutrients below the rooting zone of adjacent crops,
and have capacity for recycling these nutrients as litterfall and root turnover in the cropping
zone (Jose et al. 2004), implying in a better use of nutrients by the integrated systems.
According to Moreno et al. (2007), 80 to 100 years old Holm-oak trees (Quercus ilex L.)
promoted a positive effect beneath the tree canopy than beyond the canopy projection, on the
soil chemical characteristics organic matter, total nitrogen, exchangeable-K+, cation exchange
capacity, sum of exchangeable base cations, nitrate, available P and exchangeable-Ca2+.
In intercropped oat plants, the contents of potassium, nitrogen and calcium, oppositely
to the phosphorus and magnesium, were increased by the fertilization, which did not interact
with the distances of the trunk of old Holm-oak, in Spanish dehesas (Moreno et al. 2007).
These five elements contents decreased with increasing the distance from the oak trunk and
significant correlations existed between soil and crop nutrients (Moreno et al. 2007).
Wheat intercropped by poplar (Populus deltoides Bartr.) had grains nutrient
concentrations with higher nitrogen followed by potassium and phosphorus, whereas in straw
the nutrient concentration of potash was followed by nitrogen and phosphorus, this variation
could be due to genetic potential to extract nutrients from the soil (Gill et al. 2009).
Tsonkova et al. (2012) and there cited authors concluded that at post mining sites soil
nitrogen of alley cropping systems with the tree species black alder (Alnus glutinosa (L.)
Gaertn.), black locust (Robinia pseudoacacia L.), poplar (Populus spp.) and grey alder (Alnus
incana L. Moench) increased in 0-30 cm soil layer with increasing age of trees.
A comprehensive study of nitrogen mineralization from eucalyptus yardwaste mulch,
applied to young avocado trees, demonstrate the influence of elevated moisture, in addiction
25
to higher minimum temperatures and lower maximum temperatures, at lower position of
mulch layer (in relation to abstinence), which promote higher rates of nitrogen mineralization
and enhancing of microbial decomposition (Valenzuela-Solano et al. 2005).
2.3.2 Competition in agroforestry systems
The plant responses to light quality and intensity is dependent to the carbon fixation
mechanism. The photosynthetic rate of C3 plants increases as photosynthetic active radiation
increases until 25 % to 50 % of full sunlight, then remains constant, in contrast to C4 plants,
that continues to increase the photosynthetic rate up to full sunlight (Jose et al. 2004).
Theoretically, C4 plants planted under shade should be able to perform worse than C3 plants
in agroforestry systems (Jose et al. 2004), however the shade is not the unique factor which
can cause interference on the adjacent crops of these systems.
In terms of water resources, trees planted in hedgerows are competitors for crops
(Quinkenstein et al. 2009). The root distribution of the trees and crops species determines the
intensity for water competition (Quinkenstein et al. 2009). The root distribution of Eucalyptus
and Pinus species in agricultural land adjacent to tree lines, have greater potential for
competing for water with annual crops, because the greatest density of roots are distributed in
the top 0,5 m of the soil profile and are negatively correlated to soil water content (Sudmeyer
et al. 2004). Furthermore, the intensity of water competition is dependent of the site
conditions, such as the depth of table water and amount and seasonal distribution of
precipitation (Quinkenstein et al. 2009).
Decrease in yield is expected with the absence of fertilization in agroforestry systems
(Jose et al. 2004). When fertilizer is applied to annual crops, “some of the nutrients will be
intercepted and taken up by tree roots” (Zamora et al. 2009).
The degree to allelochemicals (allelopathic chemicals) negatively affecting the growth
of plants depends to their rates and residence times as well as the combinations into the
ecosystem (Jose et al. 2004).
2.4 Small cereals growth and development
Small cereals development is categorized into the major phases vegetative, generative
and grain filling (Peltonen-Sainio and Rajala, 2007). The earlier development comprises the
26
vegetative stage, which initiate with the leaf primordia formation and their associated axillary
bud, followed by the maturing of the leaf (Klepper et al. 1982). After that, begins the tillering.
The tillers origin from the axillary buds (Evers et al. 2006). When the tiller are synchronized
with the main stem, a new individual plant is introduced for compose community. The grain
filling phase starts post-anthesis (Peltonen-Sainio and Rajala, 2007).
The inflorescence in wheat and barley is a spike rather than a panicle as in oats
(Browne et al. 2006). The panicle is a compost inflorescence in oats which is constituted by
rachis where at nodes origin branches, and at that ends appear spikelets, which comprises one,
two or three grains (Browne et al. 2006). Sheehy et al. (2004) demonstrated that rice has a biphasic growth, which comprises the vegetative growth followed by the reproductive growth.
In high yielding rice, the heterotrophic growth of panicle had the same maximum growth rate
of the autotrophic vegetative component (Sheehy et al. 2004). During the reproductive phase
oat panicle and wheat spike promote additional non-foliar photosynthesis (Jennings and
Shibles 1968; Maydup et al. 2010).
In grasses the spikelet represents the basic inflorescence, and is constituted by glumes,
lemma and palea. The husk, comprises the lemma and palea, and constitutes a quarter of the
oat grain weight (Browne et al. 2006), proportion which is principally genetically determined
and it‟s not suitable for human consumption, because is fibrous (White and Watson 2010).
“Oats comprise two very distinct sub-populations of primary and secondary grain” (Browne et
al. 2006). Reduced photoassimilates during oat grain filling promote the abortion of grains,
resulting in substantial investment wasted on a per grain basis, because the size and weight
dimensions of the husks (Browne et al. 2006).
In the British Isles, oat suitability for milling is derived from screenings (proportion of
the grain by weight which passes through a 2.0-mm sieve), hectolitre weight (kg hl−1), kernel
content (%), hullability and the content of free kernels (Browne et al. 2006). These
characteristics were mainly influenced by variety and little influenced by nitrogen, seed rate
and plant regulator, even thought nitrogen largely increases yield (Browne et al. 2006). The
hullability is the ease with the kernels is separated from the husks (White and Watson 2010).
2.5 Morphophysiological responses of small cereals to the light, water, temperature and
nutrients as well as its interactions
27
In the agroecosystems, the crops rarely respond to one isolate environmental stimulus.
So the environmental resources availability, which could promote benefits or stress on the
plant community, must be taking into account. The plants morphophysiological apparatus
responds to a natural environment variation (e.g. cumulus cloud cover) or to the anthropic
purpose alteration (e.g. sunflecks in agroforestry or agronomic practices).
In oat intact leaves, the quantum yield of photosystem II decreased when photonic flux
density increased (between 60 and 1250 µmol−2 s−1 PAR), and was higher in plants grown
under low light intensity than in high light intensity (Quiles and López 2004). The
photoinhibition occurred when leaves were exposed to more photons than they can utilize for
the photosynthesis; the excess promoted the production of reactive oxygen, which can cause
damage on the photosystem II (Quiles 2005). In consequence of high light intensity the
maximum value of the quantum yield of photosystem II of oat intact leaves was reduced
approximately 9% (Quiles and López 2004).
The optimum line between increasing light intensity and the relative electron transport
rate, which the last plays in the photoprotection (Quiles and López 2004), occurred when this
relationship was linear, and determined the maximum value of quantum yield of photosystem
II of oat intact leaves (Tallón and Quiles 2007). When the photosystem II quantum yield
decreased, the relative electron transport rate decreased below the values predicted by the
optimum line, reflecting a nonradiative dissipation of excitation energy (Tallón and Quiles
2007).
The synergistic effect of high light intensity and moderate heat promoted a severe
decrease in the maximal quantum yield of PSII (Quiles 2006), and reduction on the capacity
of photosynthetic electron transport, indicating a moderate and chronic inhibition of PS II, in
all development stages (young, mature and senescent) of the first leaf of oat (Tallón and
Quiles 2007).
A leaf has fast adaptation to shade environments, altering chloroplast protein and
pigment composition to optimize light capture and light use efficiency, even though has lower
rates of assimilate production (Paul and Foyer 2001). Plant responses to red: far red ratio, due
to competition with neighbours under natural conditions, are detrimental for the yield of crops
(Ugarte et al. 2010).
The wheat did not produce any secondary tillers under 75 % reduction of full daylight,
and the maximal tillers number per plant produced for population densities of 100, 262,3 and
508 plants m-2, were 8,9, 5,7 and 3,7 in full daylight, and 3,0, 1,3 and 0,7 in shaded plants,
respectively (Evers et al. 2006). The percentage of mortality of tillers by senescence, after the
28
wheat reaching a tillering peak, were 44% higher in plants in full daylight than in shade of
25% of full daylight, for population densities of 100 and 262,3 plants m-2 and approximately
12% higher for population of 508 plants m-2 (Evers et al. 2006).
The relationship between the phytochromes and the phytohormones could affect
emission and maintaining of the tillers, like that on growth, because alters the apical
dominance (Almeida and Mundstock 2001). Induced by far red enriched light, the auxin
transport inhibitor abolishes hypocotyl elongation (Stamm and Kumar 2010). The exposition
of wheat plants to low red: far red light ratio promoted lower dry matter accumulation at the
early stages of the stem (peduncle) and the ear development, which are partially compensated
at the later stages of development by the higher rates of dry matter accumulation; stem length
was chronically delayed during this period (Ugarte et al. 2010). The reduction in grain yield
of wheat, occasioned by the supplemented low red: far red light cannot be regarded, to the
resources investment for increase plant stature (Ugarte et al. 2010).
During oat (Avena sativa L. cv. Larry) grain filling, measurements made in variable
sun light, at the first or second leaves below the inflorescence, indicated with the rates of net
photosynthesis during shade periods showed decline, with insignificant concomitant
reductions of the rates of net photosynthesis (~3 µmol m-2 s-1) after periods of shade (steadystate full sun) (Fay and Knapp 1993). Oats has high levels of net photosynthesis, high
stomatal conductance to H2O vapor, and moderately low leaf water potential, when is
subjected to a variable light level, and it is species with highly dynamic stomata (Fay and
Knapp 1993).
The oat water use efficiency decreased when leaves were shaded, and is partially
recovered even during the shade period as stomata closed, than when full day light returned,
water use efficiency re-increased above of initial full day light, and returned to steady state as
stomata opened (Fay and Knapp 1993). During shade periods their stomata closed slowly or
not at all and then reduced water use efficiency (Fay and Knapp 1993). The stomatal
conductance to H2O vapor in the variable sun light environment, had insignificant rates of
stomatal opening and closure, with decreases from sun to shade, with progressively lower reincreases in response to sun, and concomitant delays of stomata fully reopen, at beginning of
full light periods (Fay and Knapp 1993).
The performance of ecotypes xeric and mesic of Avena barbata in response to
moderate drought stress reduce 221% vegetative biomass accumulation and 54% seeds
production, despite in the well-watered ambient occurred eight-day delay in flowering time
and 146% higher seed abortion (Sherrard et al. 2009). Physiological traits of these ecotypes
29
under wet conditions compared to the dry ambient, seventy days after germination, increased
39% photosynthetic rate, 303% stomatal conductance, and 69% photosynthetic capacity and
decreased 26% chlorophyll concentration (Sherrard et al. 2009). Morphological traits leaf
mass per area and stomata longer of well-watered genetic lines had increment of 9% and 8%,
respectively, compared to the dry genetic lines (Sherrard et al. 2009).
Plant performance of different species at environmental gradients tend to be non-linear
response (humped-back shape) of interactive effects of water availability and light, drought
negative effect being lower at intermediate irradiance and more severe at the extremes of light
availability (higher and lower) levels (Holmgren et al. 2012). Maximum photosynthetic
capacity, maximum photochemical efficiency of photosystem II and stomatal conductance are
very sensitive to combined effects of water and light, and lower negatively affected by
drought at intermediate light availability (Holmgren et al. 2012).
Oats have a positive correlation between vegetative growth rate and panicle filling rate
under a favorable climatic conditions (precipitation and temperature), this association was
insignificant and the rates are lower under stress of low precipitation and temperature above
normal (Peltonen-Sainio 1993).
The nitrogen could be considered a fundamental nutrient for small cereals, because is
determinant for growing, which results in yield, although are highly sensitive to the lodging,
which is one main factor that cuts down productivity. Furthermore, in order to optimize
economic returns and minimize environmental impacts, improving the agricultural use of
nitrogen is needed (Carranca et al. 2009). The nitrogen uses during the plant life cycle are
subdivided in the vegetative and reproductive stages. In the vegetative phase, the young
leaves and roots are sinks for inorganic N uptake, through the amino acids synthesis and
storage, via the nitrate assimilation pathway, which are utilized in the synthesis of proteins
and enzymes, involved in biochemical pathways and the photosynthetic apparatus, for
conduct plant growth and development (Kant et al. 2011). During the reproductive phase, the
leaves and shoot act as a source of nitrogen assimilation and remobilization providing amino
acids to flowering and grain filling, than resulting in yield (Kant et al. 2011). In wheat,
“during the final stages of grain development, glumes play a major role in feeding grains with
nitrogen” (Lopes et al. 2006).
When the nitrogen rate increased the number of panicles and spikelets, greater
competition resulted in greater grain mortality (Browne et al. 2006). As the nitrogen rate
increased from 40 to 200 kg ha-1, the oat proportion of primary grain relative to secondary
grain decrease more in weight than in number, due to a greater increase in weight of
30
secondary grain compared to the primary grain, even though the mean weight of secondary
grain was smaller than primary grain (Browne et al. 2006).
31
3. CHAPTER 1
OAT GROWTH UNDER NITROGEN LEVELS IN EUCALYPTUS ALLEY CROPPING
SYSTEM IN SUBTROPICAL BRAZIL
Leonardo Deiss 1, Anibal de Moraes 1, Adelino Pelissari 1, Francisco Skora Neto 2, Edilson
Batista de Oliveira 3 and Vanderley Porfírio da Silva 3
1
Federal University of Paraná, Agricultural Sciences Sector, Phytotechique and Phytosanitary
Department, Rua dos Funcionários, 1.540, 80035‑050, Curitiba, Paraná, Brazil. 2 Agronomic
Institute of Paraná, Research Regional Center of Ponta Grossa, Rod. do Café, km 496, Av.
Presidente Kennedy, s/nº, Post Office Box 129 - 84001-970, Ponta Grossa, Paraná, Brazil. 3
Embrapa Florestas, Post Office Box 319, CEP 83411‑000, Colombo, Paraná, Brazil.
L Deiss
leonardodeiss@ufpr.br
00 55 41 3505633
00 55 41 3505601
Abstract
Plant growth analysis was performed to access how the oat (Avena sativa L. cv. IPR 126)
cultivated for grain, responds to the eucalyptus alley cropping system (ACS) in subtropical
Brazil. The hypothesis of this work is that the nitrogen does not increase the oat tolerance to
the trees interference, then the oat growth response is not modified by the nitrogen in
distances relative to the eucalyptus tracks. Thus, the nitrogen can not be utilized to improve
the oat growth in ACS. The objective of this study was to determine how the oat growth is
influenced by the nitrogen levels (12 and 80 kg N ha-1), in five equidistant positions between
two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] in
ACS and traditional no till agriculture, in subtropical Brazil. The experiment was carried out
in a split-block randomized block design with four replicates. It was evaluated the oat relative
growth rate, unit leaf rate, leaf weight fraction, panicle phytomass, panicle relative filling rate
and grains to panicle ratio. The nitrogen levels altered the growth response differently in
positions relative to adjacent eucalyptus tracks, therefore different nitrogen levels should be
used in positions relative to the trees, to improve sustainably the oat yield potential in ACS.
Key words: Avena sativa L., Eucalyptus dunnii Maiden, integrated systems, growth analysis,
agroforestry
32
Abbreviations: ACS, alley cropping agroforestry system; AGR, traditional no till agriculture,
RGR, relative growth rate; ULR, unit leaf rate; LWF, leaf weight fraction; DAE, days after
emergence
Introduction
The crop yield reflects how the crop expresses its genetic potential, allocating recourses at
each stage of development, due to the environmental resources availability. In an agroforestry
system, the annual crop growth response is dependent of a range of facilitation and
competition relationships, mainly influenced by the trees, which promote biotic and abiotic
changes, on the agroecosystem. The growth analysis is a tool that can be used to help
understand how these relationships promoted or not promoted changes on the crop cycle, to
support the productive responses.
The central parameter in plant growth analysis is relative growth rate (RGR), which is
composed by the unit leaf rate (ULR), specific leaf area (SLA) and leaf weight fraction
(LWF) (Hunt et al. 2002). The RGR measures the plant growth efficiency, the ULR is a
physiological trait which reflects the plant balance between photosynthesis and respiration per
unit of leaf area (Useche and Shipley 2010) or mass (Reich et al. 2003), the SLA is a
morphological trait which reflects the area for light interception per unit of mass invested in
leaves (Useche and Shipley 2010) and the LWF measures the productive investment dealing
with the relative expenditure on potentially photosynthesizing organs (Hunt 2003).
The arboreal component of the agroforestry systems promotes interference on the annual crop
community, which can be negative or positive. In this sense, the agronomical practices
commonly used for the annual crop, must be readapted taking into account, the interaction
between species in the integrated systems.
The oats under full daylight compared to partial light availability, reduced leaf area and
increased the allocation to roots, and the nutrient stress increased the roots production with
concomitant decrease in allocation to leaf mass (Semchenko and Zobel 2005). The response
to an intense interspecific competition for nitrogen is positively related with plant ability to
minimize plasticity in RGR, when nitrogen availability is reduced (Useche and Shipley 2010).
The hypothesis of this work the oat growth response is not modified by the nitrogen in
distances relative to the eucalyptus tracks, in ACS. Thus, the nitrogen not can be utilized to
improve the oat growth in ACS.
33
The objective of this study was to determine how the oat (Avena sativa L. cv. IPR 126)
growth is influenced by the nitrogen levels, in positions relative to adjacent eucalyptus
(Eucalyptus dunnii Maiden) tracks in ACS and traditional no till agriculture (AGR), in
subtropical Brazil. The oat IPR 126 is a cultivar with ability for forage and cover crop,
however in this work were addressed issues related to the growth until the end of its cycle.
Materials and methods
Study site
The experiment was conducted at the Experimental Station Model Farm of the Agronomic
Institute of Paraná (25°06‟19” S 50°02‟38” W, 1020 m above mean sea level) located in
Ponta Grossa, Paraná, Brazil. The climate classification of the region, according to the
Köppen classification system, is a temperate, with no definite dry season, the average of total
annual rainfall, temperature, evapotranspiration and relative humidity are between 1600 to
1800 mm, 17 to 18 °C, 900 to 1000 mm and 70 to 75 %, respectively
(http://www.iapar.br/modules/conteudo/conteudo.php?conteudo=677).
The soil classification of the study area according to Santos et al. (2006) is a red-yellow
latosol typical dystrophic, moderate, mild medium texture, wavy soft relief phase (4-8%
slope). Soil samples were collected at 0-0.20 m depth, at the positions level (described
below), and formed a composite sample for the experimental area. The soil analysis resulted
in the following characteristics (means ± standard deviation, n = 6): pH (CaCl2) 4.9 ± 0.20,
pH (SMP) 6.2 ± 0.15, Al+3 0.13 ± 0.13 cmolc dm-3, H++Al+3 4.43 ± 0.55 cmolc dm-3, Ca+2 3.07
± 0.79 cmolc dm-3, Mg+2 2.47 ± 0.37 cmolc dm-3, K+ 0.12 ± 0.03 cmolc dm-3, P 6.65 ± 2.17
mg dm-3, C 26.4 ± 1.3 g dm-3 and clay 447 ± 16 g kg-1.
The tree specie of ACS is Eucalyptus dunnii Maiden, which were implemented in 2007 in
double line tracks. AGR was used to compare the predominant form of agriculture of the
region and was located next to the arborized system (less than 200 m). Both systems were
previously areas of native grassland, and had similar crop historic.
The tracks of trees were positioned in levels with guideline, where the track of trees located in
the center of the slope of the area was set in level, and the other adjacent tracks were placed
parallel to up and down on the slope. The spacing between two adjacent tree tracks
34
(intercropped track) along the guideline level direction is 20 m, the distance between two
adjacent rows in a track is 4 m, and the distance of two trees in a row is 3 m.
The average tree height and diameter on April 2010 were 11.9 m and 13.9 cm, respectively.
The eucalyptus trees were thinned out and the remaining trees had their branches pruned to
half of trees height. Intercropped annual crops are planted one m from the tree stems because
of physical limitation to approximation of agricultural implements, making oat track with 18
m long.
Before sowing (six days) the oat, glyphosate (0.9 kg ae ha-1) was applied to eliminate
remaining weeds from the corn (Zea mays L.), the preceding crop. Using a no tillage
implement, the oat (Avena sativa L. cv. IPR 126) was sown at the rate of 40 kg seeds ha-1 and
fertilized at 300 kg ha-1 of 04-30-10 (N-P2O5-K2O), on June 16th 2011. Ten days after sowing,
the emergence occurred and this date was used as reference. During the oat cycle, for weed
control metsulfuron-methyl (2.4 g ai ha-1) was applied before the tillering stage and to
diseases control pyraclostrobin + epoxiconazole (183 g ai ha-1) was applied at the booting
stage.
Experimental design
The experiment was carried out in a split-block, where each set of treatments were in a
randomized complete block design arrangement, with four replicates, that included two levels
of nitrogen (12.0 and 80.0 kg N ha-1) and blocks as main plots and six positions (five
positions between two eucalyptus tracks and one outside the system) as split-blocks. At the
tillering stage, 28 days after emergence (DAE), additional nitrogen in urea form (46 % N) was
uniformly hand-applied (68.0 kg N ha-1) or non-applied (0.0 kg N ha-1). The split-blocks were
14 rows 5 m long with 18 cm between rows. A border of 0.4 m was left on each side of the
split-block. The five positions between the eucalyptus tracks and latter one outside of the
intercropping system are denoted as A, B, C, D and E for ACS and F for AGR. The positions
within the integrated system (A_E) are distances between tree tracks. The letter A represents
the smallest elevation of the slope, and the letter E the highest elevation of the slope. This is
always valid because the system was implemented in curve level. Therefore, the distances,
denoted as positions, represents the oats growing at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m
and E: 17.2 m away from track positioned at the lowest elevation of the slope, between two
adjacent eucalyptus double line tracks.
35
Growth analysis of oat
For growth analysis, the area (12.6 m-2) of split-blocks was subdivided in seven crescent
portions (0.3 m for the first with increment of 0.1 m for subsequent, until 0.9 m for the last)
for sampling in time during the oat cycle. The samplings were done in the central position of
each portion (described below).
Plant measurements during oat growth
Oat growth was assessed by harvesting 1 m-1 in seven sampling dates during the oat cycle.
The oat development stages at the sample time were: leafy at 21 DAE, tillering at 42 DAE,
tillering peak at 63 DAE, elongation start at 84 DAE, booting/flowering at 105 DAE, grain
filling at 126 DAE and maturation at 152 DAE.
The plants were uprooted to enable the identification of the tillers, and then the roots were cut
for determination of dry matter. 1 m-1 was collected from a central position of the portion
designated for each sample (described above), by placing a rectangle cast iron, of 1.8 m long
(positioned perpendicular to the tracks of trees) by 10 cm wide, that always comprised 10
rows of crop with 10 cm length.
All plants of 1 m-1 collected, were counted and separated into main shoot and tillers and each
one into leaves, shoots (stems) and senescent material in the vegetative stages, as well as
panicles in the reproductive stages, dried at 65° C and weighed after reaching a constant
weight. The dry weights of panicles were evaluated at 126 DAE and 152 DAE. The grains
were threshed using a motorcycle tire chamber and separated from other materials (rachis,
branches, and glumes) with a pressurized air blower. The grains were re-dried at 65° C and
weighed after reaching a constant weight. The grain to panicle ratio was determined at 152
DAE.
Growth data analyses
The oat phytomass per plant was determined from the product of the phytomass per square
meter and the total number of plants per square meter. The growth data analysis was
performed according to purely classical approach (Hunt et al. 2002).
From the oat phytomass per plant RGR (mg mg-1 day-1) was calculated using the respective
equation (Hunt et al. 2002):
36
RGR = (1 / W) (∆W / ∆t) = (ln W2 – ln W1) / (t2 - t1)
(equation 1)
where W 1 and W 2 are total dry weights in milligrams of the whole plant at times t 1 and t 2.
Using a mass basis (Reich et al. 2003) ULR (mg mg-1 day-1) was calculated using the
respective equation (Hunt et al. 2002):
ULR = [(W2 – W1) (ln L W2 – ln L W1)] / [(L W2 – L W1) (t2 - t1)]
(equation 2)
where LW1 and LW2 are leaf dry weights in milligrams of the whole plant.
LWF (mg mg-1) was determined using the respective equation (Hunt et al. 2002):
LWF = LW / W = (LW1 / W1 + LW2 / W2) / 2 (equation 3)
Substituting the total dry weigh per plant on the equation 1, by the panicle dry weight in
milligrams, was determined the panicle relative filling rate (PRFR) (mg mg-1 d-1) from 126
DAE to 152 DAE.
Statistical analyses
The statistical analyses were performed using the framework split block design, in the
General Linear Models procedure of Statistica 8.0 for Windows (StatSoft, Inc., Tulsa, OK,
USA), with the following factors: levels of nitrogen (supply or non-supply of additional
nitrogen on tillering) and positions (five positions between two eucalyptus tracks and AGR).
Other analyses were performed same as described, only with the five positions between two
eucalyptus tracks, in order to test the effects inside the integrated system. The block and its
interactions were treated as random effects. For verification of the distribution of a set of data,
was used the Shapiro-Wilk test at α = 0.01 significance. Differences between means
considering nitrogen effect, were determined using the Duncan method at α = 0.05
significance. For compare means of AGR (control treatment) with positions inside ACS, the
Dunnett two sided method was utilized, at α = 0.05 significance. For the significant positions
effects inside ACS, simple regression analyses for linear, quadratic and cubic polynomial
degrees were determined. The mathematical models were chosen according to the equations
with the best fit, confirmed by the higher determination coefficients and the significance of
the regression F test, until 5% probability, or the lowest value of significance when it was
above 5%.
Results
37
Relative growth rate
In the systems comparison, the interaction of nitrogen and positions occurred only at 105
DAE (P = 0.04), however the AGR did not differ to ACS in both two nitrogen levels. At 105
DAE was observed with 12 kg N ha-1 had higher RGR than 80 kg N ha-1, inside positions C
and F. The nitrogen influence occurred from 42 DAE until 105 DAE (42 DAE P = 0.02; 63
DAE P = 0.0004; 84 DAE P = 0.089; 105 DAE P = 0.09), however only until 84 DAE, RGR
increased with 80 kg N ha-1, because at 105 DAE, 12 kg N ha-1 promoted the higher RGR.
The position effect were significant at 21 DAE (P = 0.006), 42 DAE (P = 0. 017) and 126
DAE (P = 0.01), however only at 42 DAE, AGR had a higher RGR than ACS, which
occurred relative to positions A and B (Table 1).
Within ACS there was not any significant interaction for RGR, in all assessments during oat
cycle. The nitrogen effect increased RGR both at 42 DAE (P = 0.04) and 63 DAE (P = 0.001)
(Table 1). RGR was altered by the position effect at 21 DAE (P = 0.005) and 126 DAE (P =
0.007), which were fitted by the regression analysis, to the quadratic degree and cubic
polynomial degree, respectively. At 21 DAE RGR increased to the extent that the oats were
furthest from the trees. At 126 DAE, RGR had a peak of the concavity facing downwards,
between positions C and E, on position D, and a peak of the concavity facing upwards,
between positions A and C, on position B, and the two positions next to the trees (i.e.
positions A and E) as well as the central position between two tree tracks, remained
approximately equals (Fig. 1a).
Unit leaf rate
In the systems comparison, there was ULR (mass basis) interaction with nitrogen and
positions at 105 DAE (P = 0.045) and 152 DAE (P = 0.009). Where was applied 80 kg N ha-1,
AGR had a lower ULR than ACS, however differing only to the position A, where was
obtained the higher ULR at 105 DAE. With 12 kg N ha-1 at 105 DAE, AGR had similar ULR
than ACS, being lower than the position C inside ACS. At 152 DAE where was applied 80 kg
N ha-1, AGR as well as the position C inside ACS, had total leaves senescence (i.e. null ULR),
however did not occur any difference between the positions in the systems comparison. In
contrast to 12 kg N ha-1, wherewith AGR had a higher ULR than ACS, however did not
differing to positions E and A, inside ACS. All other positions inside ACS had a null ULR at
152 DAE. The nitrogen effect was significant at 42 DAE (P = 0.011), 63 DAE (P = 0.017), 84
38
DAE (P = 0.077) and 152 DAE (P = 0.039). Until 84 DAE, 80 kg N ha-1 promoted the higher
ULR, in contrast to the end of oat cycle (152 DAE), when 12 kg N ha-1 began to promote the
higher ULR. The position effect were significant at 42 DAE (P = 0.016), 126 DAE (P =
0.005) and 152 DAE (P = 0.032). At 42 DAE, AGR had a higher ULR than positions A and B
inside ACS. ULR of AGR did not differ to ACS at 126 DAE and was superior to the positions
C and D at 152 DAE (Table 2).
For ULR within ACS, the interaction of nitrogen and position occurs only at 152 DAE. The
regression analysis denoted for the nitrogen levels 80 kg N ha-1 and 12 kg N ha-1 the cubic and
quadratic polynomial degrees, respectively. With 80 kg N ha-1, ULR had higher values
between positions A and C, and lower values between positions C and E, with the peaks of
concavities facing downwards and upwards, occurred on positions B and D, respectively.
With 12 kg N ha-1 ULR was most expressive next to the trees, being higher at the highest than
the smallest slope elevation, between two adjacent tree tracks (Fig. 1b). The nitrogen effect
was significant at 42 DAE (P = 0.029) and 63 DAE (P = 0.029). In both stages of oat cycle 80
kg N ha-1 increase ULR (Table 2). Significant position effect occur at 126 (P = 0.003) DAE
and 152 DAE (P = 0.099). The regression analysis denoted cubic and quadratic polynomial
degree effect at 126 DAE and 152 DAE, respectively. At 126 DAE, ULR had on position B, a
peak of the concavity facing upwards, which occur between positions A and C, and the lower
values of ULR occurred between positions C and E, described by the concavity facing
downwards. And at 152 DAE the concavity facing upwards comprised the entire oat track,
which higher values on position E than position A (Fig. 1c).
Leaf weight fraction
Did not any interaction of nitrogen and positions was significant for LWF, both in the system
comparison and within ACS. In the systems comparison, during oats reproductive phase, from
105 DAE until 152 DAE, 12 kg N ha-1 compared to 80 kg N ha-1 past to be increased LWF
(105 DAE P = 0.02; 126 DAE P = 0.02; 152 DAE P = 0.08). The significant position effect
occurred at 63 DAE as well as from 105 DAE to harvest (63 DAE P = 0.069; 105 DAE P =
0.06; 126 DAE P = 0.069; 152 DAE P = 0.03). The oat LWF cultivated in AGR did not differ
to ACS, in exception at 105 DAE, from position A inside ACS (Table 3).
Within ACS, LWF at 63 DAE increased with 80 kg N ha-1 (P = 0.09), and from 105 DAE (P
= 0.007) to 126 DAE (P = 0.02) with 12 kg N ha-1 (Table 3). The regression analysis denoted
39
the linear degree both at 105 (P = 0.02) and 126 DAE (P = 0.02). LWF at 105 DAE and 126
DAE had subtle linear increment from the position A to the position E (Fig.1d).
Panicle phytomass per plant
In the systems comparison, the interaction of nitrogen and positions were not significant both
at 126 DAE and 152 DAE. The panicle dry weight was influenced by the nitrogen at 126
DAE (P = 0.006), and did not differ between nitrogen levels at 152 DAE. At 126 DAE, was
heavier the panicle dry weight, where was applied 80 kg N ha-1. The position effect were
significant both at 126 DAE (P = 0.002) and 152 DAE (P = 0.089). At 126 DAE AGR had a
heavier panicle than the ACS, did not differing only to the central position between two
adjacent tree tracks. In contrast to 152 DAE, when AGR had a heavier panicle only than the
position A, not differing from other positions inside ACS (Table 4).
Within ACS, the interaction of nitrogen and positions were not significant both at 126 DAE
and 152 DAE. 80 kg N ha-1 increased the panicle weight only at 126 DAE (P = 0.019) (Table
4). The position effect was significant also only at 126 DAE (P = 0.009) and the regression
analysis denoted the quadratic polynomial degree effect, which the trees negative interference,
decreased the panicle weight as the distance from the trees reduced (Fig. 1e).
Panicle relative filling rate
The interaction of nitrogen and positions was not significant for PRFR, both inside ACS and
in the systems comparison. In the systems comparison, PRFR had significant effects of
nitrogen (P = 0.04) and position (P = 0.037). The nitrogen level 12 kg N ha-1 promoted a
higher PRFR, and AGR had a lower PRFR than positions D and E inside ACS, not differing
from the other positions (Table 4).
Within ACS also the nitrogen (P = 0.048) and positions (P = 0.067) effects were significant
for PRFR. Also the nitrogen level 12 kg N ha-1 increased the PRFR (Table 4). Between the
positions, the linear degree effect denoted by the regression analysis indicated increasing
trend of PRFR, from the smallest to the highest slope elevation, between two adjacent tree
tracks (Fig. 1f).
Grains to panicle ratio
40
The grains to panicle ratio did not interact with nitrogen and positions both in the systems
comparison and inside ACS. The nitrogen effect was not significant in the systems
comparison, however inside ACS (P = 0.096) the lower nitrogen level had a higher panicle
ratio. In the systems comparison, the position effect was significant (P = 0.055), however
AGR did not differ to ACS. Inside ACS the positions effect did not occur.
Discussion
During earlier oat development, it was possible to perceive the trees interference on the
annual crop, which made RGR reduced to the extent crop plants approached the tree
component. The tree canopies are relatively transparent to the far red light of the direct sun
light, because the chlorophylls present in the green leaves absorb principally the wave lengths
corresponding to the red color (Taiz and Zeiger 2010). Plants sense changes in the ratio of red
to far red light through the phytochromes, and respond in order to emerge from the blockage
of shading, by elongating and altering plant architecture (Stamm and Kumar 2010). However,
the shade avoidance was not sufficient to increased RGR near to the trees in a greater degree
than RGR farther away from trees, until 21 DAE (Fig. 1a).
After additional nitrogen application on tillering phase, can be observed the nitrogen effect by
increasing RGR both in the systems comparison until 84 DAE as well as within ACS until 63
DAE, ULR until 84 DAE in the systems comparison, as well as LWF at 63 DAE inside ACS.
Growth limiting responses promoted by the shade compared to full sunlight, only occurred in
wild rice (Zizania palustris L.), after nitrogen addition (Sims et al. 2012). Until 84 DAE small
differences occurred between the growths traits (RGR, ULR and LWF) in the systems
comparison, in exception of the lower RGR and ULR at 42 DAE, of the positions A and B
into ACS compared to AGR (Tables 1, 2 and 3).
At 105 DAE, after oat post heading was observed the lodging occurrence in the central and
intermediate positions inside ACS and in AGR. The clearest evidence of the lodging damage
on the oat growth, were the RGR and ULR reduction at 105 DAE on positions C and F, where
was applied 80 kg N ha-1. And RGR became more expressive in the systems comparison at
105 DAE, by the lower nitrogen level (Tables 1 and 2). In wheat, the earlier lodging promote
losses in grain filling, due to blockage of the flow of conducting vessels and the smaller plant
photosynthetic rates (Espindula et al. 2010). Possibly, the lodging was also responsible for the
reduction in both RGR and ULR at 126 DAE, between positions B and C, inside ACS (Figs.
1a and 1c).
41
Within ACS at 105 DAE, LWF started to had a subtle linear increase from the lowest to the
highest slope elevation between two adjacent tree tracks, which remained until 126 DAE (Fig.
1d), and the lower nitrogen level increased LWF both at 105 DAE and 126 DAE, both in the
system comparison and inside ACS, as well as at 152 DAE only in the systems comparison.
Wheat growing in the 5 m by 20 m Paulownia (9 years old) (Paulownia x „Tomentosi-fortunei
33‟) intercropping system, did not differ in the estimation of saturated leaf photosynthetic rate
(Pmax) of flag leaves, compared to outside the intercropping system, and inside ACS P max
during flowering was not different from that during grain filling, but was higher than that
during maturing (Li et al. 2008). During 7 days prior to anthesis, the photosynthetically active
radiation intercepted by wheat can explain 97% of the variation of grain number inside and
outside the system (Li et al. 2008). This highlights the importance of having a photosynthetic
apparatus, to enable the maximum contribution of photosynthesis for grain filling, during the
reproductive phase (Table 3).
At 126 DAE was higher the panicle phytomass where was applied the higher nitrogen level,
possibly due to increased growth rates promoted by this nitrogen level, until 84 DAE, and
AGR did not differ, also in terms of panicle phytomass at 126 DAE, only to the central
position between two adjacent tree tracks, inside ACS (Table 4). Within ACS at 126 DAE, the
panicle had a subtle increase in phytomass weight, to extend that is distanced from the trees
(Fig. 1e). Dry-matter accumulation and post-heading growth rate in oats are “associated with
grain-yielding ability” (Salman and Brinkman 1992).
From 126 DAE to 152 DAE, the PRFR was pronounced where it had been applied the lower
nitrogen level, both in the systems comparison and inside ACS. The PRFR of AGR was lower
than positions D and E (Table 4), which was emphasized by the linear increase, from the
position A to position E, inside ACS (Fig. 1f). What made the panicle phytomass became
unchanged by nitrogen effect and only the position A inside ACS had lighter panicle than
AGR at 152 DAE (Table 4). Correlation between oat panicle filling rate and grain yield was
slightly in stress of precipitation, and in favorable climatic conditions low temperatures as
well as panicle filling rate possess strong correlation with panicle weight (Peltonen-Sainio
1993).
In addition to the effect described for LWF (described above), where was applied the lower
nitrogen level ULR had a great expression at 152 DAE (Tables 2 and 3), and was stronger
ULR next to trees inside ACS (Fig. 1b). Within the Paulownia-wheat intercropping system,
yield and number of grains of wheat, can be fully explained by the amount of
photosynthetically active radiation intercepted from flowering to grain filling, and during
42
grain filling, is strongly correlated with the dry weight per 1000 grains (Li et al. 2008). Wheat
increased the duration of grain filling in eucalyptus ACS (Kohli and Saini 2003). In addition
to the remaining green leaves, panicles remained green in these same locations at 152 DAE
(unpublished data).
In cereals, the yield formation process is resultant of two processes: development, where
grains are formed and filled and growth, where the substrate for forming and filling the grains
is provided by photosynthesis (Browne et al. 2006). During the reproductive phase (postheading), a significant portion of photosynthesis is performed by the constituents of panicle in
oat (Jennings and Shibles 1968) or ear in wheat (Maydup et al. 2010). Added to the
contribution of photosynthesis should be considered the translocation of the photoassimilates
accumulated during the growth. In wheat plants, the translocation of storage carbon
contributed to grain growth (Li et al. 2008).
Since oats reduced the allocation to roots under partial light availability and the nutrient stress
decreased the allocation to leaf mass (Semchenko and Zobel 2005), and inside the ACS oats
accumulated less above ground phytomass per plant next to the trees. In environments with
high interspecific interaction, should be valued agronomic practices that improve the
photosynthesis performed in the reproductive structure (e.g. morphological traits: Jennings
and Shibles 1968; Maydup et al. 2010). During grain filling, the mobilization of
photosynthate produced by the constituents of panicle, affect the quality of grains (Browne et
al. 2006).
In spring and winter cultivations with finish cycle of annual cultures on summer, the
agroforestry systems could “increase heat load during vegetative phases and reduce heat load
during reproductive phase”, removing economically the excess of energy (Kohli and Saini
2003). The synergistic effect of high light intensity and moderate heat is detrimental to the
maximal quantum yield of photosystem II of oat (Quiles 2006), and could be reduced by the
microclimatic conditions promoted by the agroforestry.
At 152 DAE, the oats grains to panicle ratio did not differ between systems and was higher
for the lower nitrogen level inside ACS (Table 4).
Conclusion
43
The nitrogen levels alter the growth response differently in positions relative to adjacent
eucalyptus tracks, therefore different nitrogen levels should be used in positions relative to the
trees, to improve sustainably the oat growth in ACS in subtropical Brazil.
Acknowledgements
Work resulting from the technical cooperation agreement SAIC / AJU No. 21500.10/0008-2
signed by Iapar and Embrapa Florestas.
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45
Table 1 Oat (Avena sativa L. cv. IPR 126) relative growth rate under nitrogen levels (12.0 kg N ha -1 and 80.0 kg
N ha-1) in alley cropping agroforestry system (A_E) and traditional no till agriculture (F) in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
-1
-1
c
Relative growth rate (mg mg day )
A-F
A-E
21 days after emergence
80 kg N ha-1 0.13
0.14
0.14
0.13
0.12
0.13
0.13
0.13
-1
12 kg N ha
0.14
0.14
0.15
0.12
0.12
0.15
0.14
0.14
Mean
0.14
0.14
0.15
0.13
0.12
0.14
0.13
0.13
ns b
ns
ns
ns
ns
Control
80 kg N ha-1 0.07
0.07
0.08
0.07
0.08
0.1
0.08 A 0.08 A
-1
12 kg N ha
0.04
0.05
0.06
0.07
0.06
0.07
0.06 B 0.06 B
Mean
0.06
0.06
0.07
0.07
0.07
0.09
0.07
0.07
ns
ns
ns
*
*
Control
80 kg N ha-1 0.04
0.04
0.04
0.05
0.03
0.05
0.04 A 0.04 A
-1
12 kg N ha
0.01
0.03
0.04
0.01
0.01
0.01
0.02 B 0.02 B
Mean
0.02
0.03
0.04
0.03
0.02
0.03
0.03
0.03
80 kg N ha-1 0.02
0.04
0.03
0.03
0.04
0.05
0.04 A 0.03
-1
12 kg N ha
0.03
0.03
0.01
0.03
0.04
0.03
0.03 B 0.03
Mean
0.02
0.03
0.02
0.03
0.04
0.04
0.03
0.03
80 kg N ha-1 0.04 a 0.03 a 0.02 b 0.03 a 0.03 a
0.01 b
0.03 B 0.03
ns
ns
ns
ns
ns
Control
12 kg N ha-1 0.03 a 0.03 a 0.04 a 0.03 a 0.03 a
0.05
a
0.04 A 0.03
ns
ns
ns
ns
ns
Control
Mean
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
80 kg N ha-1 0.03
<0.01
0.03
0.02
0.03
0.02
0.02
0.02
12 kg N ha-1 0.04
0.01
0.03
0.03
0.02
0.03
0.03
0.03
Mean
0.03
0.01
0.03
0.02
0.03
0.03
0.02
0.02
ns
ns
ns
ns
ns
Control
80 kg N ha-1 <0.01
0.02
0.01
0.02
0.01
0.01
0.01
0.01
-1
12 kg N ha
0.02
0.03
0.01
0.02
0.03
0.02
0.02
0.02
Mean
0.01
0.02
0.01
0.02
0.02
0.01
0.01
0.01
a
positions: at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest
elevation of the slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4
m x 3 m)]. Values followed (within column) by the same capital case and lowercase letters, are not significantly
different using the Duncan´s test (α = 0.05). b *, ** and ns (within line) indicates the significance at 0.05, 0.01
and non significant, respectively of the comparison with a control by the Dunnett two sided test. c Means
including traditional no till agriculture (A_F) or within alley cropping system (A_E).
46
Table 2 Oat (Avena sativa L. cv. IPR 126) unit leaf rate under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1)
in alley cropping agroforestry system (A_E) and traditional no till agriculture (F) in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
-1
-1
c
Unit leaf rate (mg mg day )
A-F
A-E
80 kg N ha-1 0.16
0.18
0.18
0.17
0.16
0.17
0.17
0.17
-1
12 kg N ha
0.21
0.18
0.19
0.16
0.15
0.21
0.18
0.18
Mean
0.19
0.18
0.19
0.16
0.16
0.19
0.18
0.17
80 kg N ha-1 0.11
0.11
0.12
0.12
0.12
0.15
0.12 A 0.12
12 kg N ha-1 0.06
0.08
0.1
0.11
0.09
0.12
0.09 B 0.09
Mean
0.09
0.09
0.11
0.12
0.11
0.13
0.11
0.1
ns
ns
ns
** b
*
Control
80 kg N ha-1 0.06
0.07
0.07
0.1
0.05
0.08
0.07 A 0.07
12 kg N ha-1 0.02
0.05
0.12
0.03
0.01
0.01
0.04 B 0.05
Mean
0.04
0.06
0.09
0.06
0.03
0.05
0.06
0.06
80 kg N ha-1 0.05
0.09
0.09
0.06
0.09
0.14
0.09 A 0.08
12 kg N ha-1 0.06
0.06
0.01
0.08
0.08
0.07
0.06 B 0.06
Mean
0.06
0.08
0.05
0.07
0.08
0.1
0.07
0.07
80 kg N ha-1 0.13 a 0.08 a 0.06 b 0.1 a 0.1 a 0.05 b
0.09
0.1
ns
ns
ns
ns
*
Control
12 kg N ha-1
0.1
a 0.09 a 0.12 a 0.08 a 0.08 a 0.12 a
0.1
0.09
ns
ns
ns
ns
ns
Control
Mean
0.12
0.09
0.09
0.09
0.09
0.08
0.09
0.09
80 kg N ha-1 0.21
0.02
0.3
0.16
0.18
0.17
0.17
0.17
12 kg N ha-1 0.24
0.05
0.15
0.14
0.1
0.21
0.15
0.14
Mean
0.23
0.04
0.22
0.15
0.14
0.19
0.16
0.16
0.99
0.36
0.99
0.99
0.98
Control
80 kg N ha-1
0.2
a 0.54 a 0.05 a
0
a 0.22 b
0
b
0.17 B 0.2
ns
ns
ns
ns
ns
Control
12 kg N ha-1 0.43 a
0
a
0
a 0.03 a 1.37 a 1.54 a
0.56 A 0.37
ns
ns
**
**
**
Control
Mean
0.32
0.27
0.03
0.01
0.79
0.77
0.37
0.28
ns
ns
ns
*
*
Control
a
positions: A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest
and non significant, respectively, of the comparison with a control by the Dunnett two sided test. c Means
47
Table 3 Oat (Avena sativa L. cv. IPR 126) leaf weight fraction under nitrogen levels (12.0 kg N ha-1 and 80.0 kg
Positions
Aa
B
C
D
E
F
Mean
-1
c
Leaf weight fraction (mg mg )
A-F
A-E
80 kg N ha-1 0.7
0.66
0.69
0.66
0.64
0.67
0.67
0.67
-1
12 kg N ha
0.6
0.69
0.7
0.64
0.67
0.62
0.65
0.66
Mean
0.65
0.68
0.69
0.65
0.66
0.64
0.66
0.66
80 kg N ha-1 0.69
0.66
0.67
0.6
0.65
0.69
0.66
0.65
12 kg N ha-1 0.63
0.65
0.67
0.64
0.66
0.63
0.65
0.65
Mean
0.66
0.66
0.67
0.62
0.65
0.66
0.65
0.65
80 kg N ha-1 0.63
0.58
0.55
0.55
0.6
0.6
0.59
0.58 A
12 kg N ha-1 0.56
0.56
0.51
0.54
0.57
0.61
0.56
0.55 B
Mean
0.6
0.57
0.53
0.55
0.59
0.61
0.57
0.57
ns b
ns
ns
ns
ns
Control
80 kg N ha-1 0.47
0.44
0.4
0.47
0.48
0.44
0.45
0.45
12 kg N ha-1 0.43
0.48
0.4
0.44
0.46
0.53
0.46
0.44
Mean
0.45
0.46
0.4
0.45
0.47
0.49
0.45
0.45
80 kg N ha-1 0.28
0.31
0.29
0.32
0.34
0.31
0.31 B 0.31 B
-1
12 kg N ha
0.34
0.38
0.35
0.38
0.38
0.41
0.37 A 0.37 A
Mean
0.31
0.35
0.32
0.35
0.36
0.36
0.34
0.34
ns
ns
ns
ns
*
Control
80 kg N ha-1 0.15
0.16
0.14
0.15
0.21
0.14
0.16 B 0.16 B
-1
12 kg N ha
0.19
0.23
0.2
0.23
0.24
0.21
0.22 A 0.22 A
Mean
0.17
0.2
0.17
0.19
0.22
0.18
0.18
0.19
ns
ns
ns
ns
ns
Control
80 kg N ha-1 0.04
0.04
0.04
0.03
0.07
0.02
0.04 B 0.04
-1
12 kg N ha
0.05
0.07
0.05
0.07
0.07
0.05
0.06 A 0.06
Mean
0.04
0.06
0.04
0.05
0.07
0.03
0.05
0.05
ns
ns
ns
ns
ns
Control
a
m x 3 m)]. Values followed (within column) by the same capital case letters, are not significantly different using
the Duncan´s test (α = 0.05). b *, ** and ns (within line) indicates the significance at 0.05, 0.01 and non
significant, respectively, of the P value of the comparison with a control by the Dunnett two sided test. c Means
48
Table 4 Oat (Avena sativa L. cv. IPR 126) panicle phytomass, panicle relative filling rate and grains to panicle
ratio, under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and
Positions
A
B
C
D
E
F
Mean
A-F c
A-E
-1
Panicle phytomass (mg plant ) at 126 days after emergence
80 kg N ha-1 131
107.1
174.9
118.6
111.8
194
139.6 A 128.7 A
-1
12 kg N ha
60.9
48.4
99.2
50.4
44.4
105.7
68.2 B 60.6 B
Mean
95.9
77.8
137.1
84.5
78.1
149.8
103.9
94.7
ns
*b
**
**
**
Control
Panicle phytomass (mg plant-1) at 152 days after emergence
-1
80 kg N ha
234
256.5
327.3
426.9
328.8
398.2
328.6
314.7
-1
12 kg N ha
210.1
337.4
348
322.9
264.4
401.6
314.1
296.5
Mean
222
297
337.7
374.9
296.6
399.9
321.3
305.6
ns
ns
ns
ns
**
Control
Panicle relative filling rate (µg mg-1) from 126 to 152 days after emergence
80 kg N ha-1 23.2
31.2
22.2
42.7
40.8
26.4
31.1 B
32
B
-1
12 kg N ha
44.5
65.4
42.9
66
65.5
46.7
55.2 A 56.9 A
Mean
33.8
48.3
32.5
54.4
53.1
36.6
43.1
44.4
ns
ns
ns
*
*
Control
Grains to panicle ratio (mg mg-1)
-1
80 kg N ha
0.81
0.75
0.7
0.76
0.73
0.77
0.75
0.75 B
-1
12 kg N ha
0.83
0.79
0.76
0.78
0.77
0.69
0.77
0.79 A
Mean
0.82
0.77
0.73
0.77
0.75
0.73
0.76
0.77
ns
ns
ns
ns
ns
Control
a
the Duncan´s test (α = 0.05). b *, ** and ns (within line) indicates the significance at 0.05, 0.01 and non
significant, respectively, of the comparison with a control by the Dunnett two sided test. c Means including
traditional no till agriculture (A_F) or within alley cropping system (A_E).
49
LWF
(mg mg-1)
RGR
(mg mg-1 day -1)
a
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
A
B
C
D
21 DAE
42 DAE
63 DAE
84 DAE
105 DAE
126 DAE
152 DAE
E
Positions
A
B
C
D
E
A
D
E
B
C
D
E
D
E
Positions
c
PRFR
0.6
0.4
0.2
0.0
B
C
Positions
D
E
21 DAE
42 DAE
63 DAE
84 DAE
105 DAE
126 DAE
152 DAE
(mg mg
0.8
0.06
0.05
-1
-1
day )
f
1.0
ULR
(g g-1 day -1)
C
21 DAE
42 DAE
63 DAE
84 DAE
105 DAE
126 DAE
152 DAE
Panicle 126 DAE
Panicle 152 DAE
e
450
400
350
300
250
200
150
100
50
Positions
A
B
Positions
PDW
(mg plant -1)
ULR (g g-1 day -1)
at 152 DAE
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
d
A
80 kg N ha-1
12 kg N ha-1
b
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.04
0.03
A
B
C
Positions
Fig. 1 Oat (Avena sativa L. cv. IPR 126) growth traits (days after emergence, DAE) relative growth rate (RGR)
(21 DAE: Y = 0.128 + 0.0037 x – 2.38 10-4 x2, R2 = 77.3, P = 0.04; 126 DAE: Y = 0.071 - 0.021 x + 0.0023 x2 –
7.08 10-5 x3, R2 = 56.3, P = 0.20), unit leaf rate (ULR) (126 DAE: Y = 0.529 - 0.158 x + 0.018 x2 – 5.70 10-4 x3,
R2 = 46.1, P = 0.15; 152 DAE: Y = 0.861 - 0.189 x + 0.010 x2, R2 = 75.6, P = 0.02; 152 DAE: 80 kg N ha-1: Y = 0.663 + 0.462 x - 0.057 x2 + 0.0019 x3, R2 = 83.7, P = 0.23 and 12 kg N ha-1: Y = 1.29 - 0.341 x + 0.020 x2, R2 =
91.5, P = 0.004), leaf weight fraction (LWF) (105 DAE: Y = 0.309 + 0.0027 x, R2 = 58.86, P = 0.008; 126 DAE:
Y = 0.162 - 0.0029 x, R2 = 55.03, P = 0.088), panicle phytomass (PDW) (126 DAE: Y = 66.6 + 8.94 x – 0.49 x2,
R2 = 26.05, P = 0.02) panicle relative filling rate (PRFR) from 126 to 152 DAE (Y = 0.032 + 0.0012 x, R2 =
44.8, P = 0.002) under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1), in alley cropping agroforestry system,
at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest elevation of
the slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)], in
subtropical Brazil. Vertical bars denote standard errors.
50
4. CHAPTER 2
TILLERING AND TILLER TRAITS OF OAT UNDER NITROGEN LEVELS IN
EUCALYPTUS ALLEY CROPPING SYSTEM IN SUBTROPICAL BRAZIL
1
L Deiss
00 55 41 3505633
00 55 41 3505601
Abstract
In oat production, the tillering persistence is determinant to one important yield component,
the number of panicles. This process is highly influenced by the interspecific and intraspecific
interactions on the agroecosystem, which in turn depends of the agronomic practices. The
hypothesis of this work is that the nitrogen does not increase the oat tolerance to the trees
negative interference, and then the oat tillering persistence for grains production is not
modified by the nitrogen in distances relative to the eucalyptus tracks, in the alley cropping
agroforestry system (ACS). Thus the nitrogen should not be used to increase the oats yield
potential on these systems. The objective of this study was to determine how the tillering
persistence for grains production and tiller traits of oat (Avena sativa L. cv. IPR 126) are
influenced by nitrogen levels (12 and 80 kg N ha-1), in five equidistant positions between two
adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] in
ACS and traditional no till agriculture, in subtropical Brazil. The experiment was carried out
in a split-block randomized block design with four replicates. It was evaluated the oat
phytomass, tillers to main shoot phytomass ratio, tillers per main shoot, grain yield and tillers
to main shoot grain yield ratio. The oat tillering persistence for grain production is dependent
of different nitrogen level in distances relative to adjacent eucalyptus tracks, in ACS in
subtropical Brazil.
Key words: Avena sativa L., Eucalyptus dunnii Maiden, integrated systems, agroforestry
51
Abbreviations: ACS, alley cropping agroforestry system; AGR, traditional no till agriculture;
DAE, days after emergence
Introduction
Gramineous species produces tillers, which originate from axillary buds of parent shoot, at the
base of internode of the parent phytomer, immediately above the node and the sheath insertion
of the preceding phytomer (Evers et al. 2006). Oat plants with lower values of the ratio
between the mass of main stem and tillers, could present a higher productivity potential,
because the tillers development are similar to the main stem development (Almeida and
Mundstock 2001). The development synchronism of tillers in relation to main stems is
substantial for the oats tillers survival, and is dependent of the agronomic practices (e.g.
population density). The tillering persistence is determinant for the number of panicle
production.
The fertile tillers number of the cereals is dependent to the environmental conditions at the
tillers primordium initiation and the subsequent stages until the flowering (Almeida and
Mundstock 2001). Increases in oat yield are resultant from nitrogen by increasing panicle
number and grain number per panicle and from seed rate only by increasing panicle number
(Browne et al. 2006). During earlier growth and development, different competition scenarios
in response to nitrogen, resulted in different balances of supply and demand for photosynthate
when initiating the grain filling period (Browne et al. 2006).
The hypothesis of this work is that the nitrogen does not increase the oat tolerance to the trees
negative interference, and then the oat tillering persistence for grains production is not
modified by the nitrogen in distances relative to the eucalyptus tracks, in ACS. Thus the
nitrogen should not be used to increase the oats yield potential on these systems.
The objective of this study was to determine how the tillering persistence for grains
production and tiller traits of oat (Avena sativa L. cv. IPR 126) are influenced by nitrogen
levels (12 and 80 kg N ha-1), in positions relative to adjacent eucalyptus (Eucalyptus dunnii
Maiden) tracks in ACS and traditional no till agriculture (AGR), in subtropical Brazil.
Study site
52
Institute of Paraná (25°06‟19” S 50°02‟38” W, 1020 m above mean sea level) located in
Köppen classification system, is a temperate, with no definite dry season, the average of total
slope). Soil samples were collected at 0-0.20 m depth, at a positions level (described below),
and formed a composite sample for the experimental area. The soil analysis resulted in the
following characteristics (means ± standard deviation, n = 6): pH (CaCl2) 4.9 ± 0.20, pH
(SMP) 6.2 ± 0.15, Al+3 0.13 ± 0.13 cmolc dm-3, H++Al+3 4.43 ± 0.55 cmolc dm-3, Ca+2 3.07 ±
0.79 cmolc dm-3, Mg+2 2.47 ± 0.37 cmolc dm-3, K+ 0.12 ± 0.03 cmolc dm-3, P 6.65 ± 2.17 mg
dm-3, C 26.4 ± 1.3 g dm-3 and clay 447 ± 16 g kg-1.
The tree of ACS is Eucalyptus dunnii Maiden, which were implemented in 2007 in double
line tracks. AGR was used to compare the predominant form of agriculture of the region and
was located next to the arborized system (less than 200 m). Both systems were previously
areas of native grassland, and had similar cultures historic.
parallel to up and down on the slope. The spacing between two adjacent tree tracks
(intercropped track) along the guideline level direction is 20 m, the distance between two
adjacent rows in a track is 4 m, and the distance of two trees in a row is 3 m.
The average tree height and diameter on April 2010 were 11.9 m and 13.9 cm, respectively.
The eucalyptus trees were thinned out and the remaining trees had their branches pruned to
half of trees height. Intercropped annual crops are planted one m from the tree stems because
of, physical limitation of approximation to agricultural implements, making oat track had 18
m long.
implement, the oat (Avena sativa L. cv. IPR 126) was sown at the rate of 40 kg seeds ha-1 and
fertilized at 300 kg ha-1 of 04-30-10 (N-P2O5-K2O), on June 16th 2011. Ten days after sowing,
53
the emergence occurred and this date was used as reference. During the oat cycle, for weed
control metsulfuron-methyl (2.4 g ai ha-1) was applied before the tillering stage and to
stage.
Experimental design
The experiment was carried out in a split-block, where each set of treatments were in a
randomized complete block design arrangement, with four replicates, that included two levels
of nitrogen (12.0 and 80.0 kg N ha-1) and blocks as main plots and six positions (five
positions between two eucalyptus tracks and one outside the system) as split-blocks. At the
tillering stage, 28 days after emergence (DAE), additional nitrogen in urea form (46 % N) was
uniformly hand-applied (68.0 kg N ha-1) or non-applied (0.0 kg N ha-1). The split-blocks were
14 rows five m long with 18 cm between rows. A border of 0.4 m was left on each split-block
side.
The five positions between the eucalyptus tracks and latter one outside of the intercropping
system are denoted as A, B, C, D and E for ACS and F for AGR. The positions within the
integrated system with trees (A_E) are distances between tree tracks. The letter A represents
the smallest elevation of the slope, and the letter E the highest elevation of the slope. This is
always valid because the system was implemented in curve level. Therefore, the distances,
Tillering analysis of oat
For the tillering analysis, the area (12.6 m-2) of split-blocks was subdivided in seven crescent
portions (0.3 m for the first with increment of 0.1 m for subsequent, until 0.9 m for the last)
for sampling in time during the oat cycle. The samplings were done in the central position of
each portion (described below).
Plant measurements
54
The oat growth was assessed by harvesting 1 m-1 in seven sampling dates during the oat cycle.
The oat development stages at the sample time were: leafy at 21 DAE, tillering at 42 DAE,
tillering peak at 63 DAE, elongation start at 84 DAE, booting/flowering at 105 DAE, grain
filling at126 DAE and maturation at 152 DAE.
The plants were uprooted to enable the tillers identification, and then the roots were cut for
determination of dry matter. 1 m-1 was collected from a central position of the portion
designated for each sample (described above), by placing a rectangle cast iron, of 1.8 m long
(positioned perpendicular to the tracks of trees) by 10 cm wide, that always comprised 10
rows of crop with 10 cm length. All plants of 1 m-1 collected, were counted and separated into
main shoot and tillers and each one into leaves, shoots (stems) and senescent material in the
vegetative stages, and more panicles in the reproductive stages, dried at 65° C and weighed
after reaching a constant weight. The oat phytomass per plant was evaluated during the entire
oat cycle. From the oat phytomass per plant less the senescent material, was determined the
tillers to main shoot phytomass ratio (mg mg-1) (phytomass ratio).
The oat phytomass per plant and of its tillers were determined from the product of oat
phytomass and its tillers per square meter and the total number of plants per square meter
collected.
The grains were threshed using a motorcycle tire chamber and separated from other materials
(rachis, branches, and glumes) with a pressurized air blower. The grains were re-dried at 65°
C and weighed after reaching a constant weight. The grains yield per plant was determined by
summing the grains with husks of tillers and main shoot. The tillers to main shoot grain yield
ratio (mg mg-1) (grain yield ratio) was obtained by dividing the grains yield of tillers by the
grains yield of main shoot. The grain weight was measured on a dry basis, without moisture.
Other analyses were performed same as described, only with the five positions between two
eucalyptus tracks, in order to test the effects inside the integrated system. The block and its
interactions were treated as random effects. For verification the distribution of a set of data,
was used the Shapiro-Wilk test at α = 0.01 significance. Only the tillers to main shoot
55
phytomass ratio, both at 84 and 126 DAE not reached normality, and to improve that, the
square-root transformation was used. Differences between means considering nitrogen effect,
were determined using the Duncan method at α = 0.05 significance. For compare means of
AGR (control treatment) with positions inside ACS, were utilized the Dunnett two sided
method at α = 0.05 significance. For the significant positions effects inside ACS, simple
regression analyses for linear, quadratic and cubic polynomial degrees were determined. The
mathematical models were chosen according to the equations with the best fit, confirmed by
the higher determination coefficients and the significance of the regression F test, until 5%
probability, or the lowest value of significance when it was above 5%.
Results
Phytomass per plant
For the oat phytomass per plant, the interaction of nitrogen and positions were significant
both at 63 DAE (P = 0.058) and 84 DAE (P < 0.0001). Where was applied 80 kg N ha-1, at 63
DAE only the position C inside ACS did not differ to AGR, in contrast to 84 DAE, when
AGR was higher than all positions inside ACS. Where was applied 12 kg N ha-1, both at 63
DAE and 84 DAE, the AGR did not differ to all positions inside ACS. The nitrogen increases
the oat phytomass inside positions A, B, D and F at 63 DAE, and all positions at 84 DAE
(Fig. 1a and Supplementary Table 1). From 42 DAE until harvest (i.e. 152 DAE), the nitrogen
increase the oat phytomass per plant (21 DAE P = 0.21; 42 DAE P = 0.01; 63 DAE P =
0.006; 84 DAE P = 0.004; 105 DAE P = 0.02; 126 DAE P = 0.02; 152 DAE P = 0.004). At
21 DAE was significant the positions effect, however AGR did not differ to any positions
inside ACS (P = 0.08). Also from 42 DAE until 105 DAE, only the central position between
two adjacent eucalyptus tracks (i.e. position C) did not differ to AGR, in exception at 84 DAE
as well as from 126 DAE to 152 DAE, when AGR was superior to all positions inside ACS
(42 DAE P = 0.001; 63 DAE P = 0.003; 84 DAE P < 0.0001; 105 DAE P = 0.0002; 126 DAE
P < 0.0001; 152 DAE P < 0.0001) (Supplementary Table 1).
In the phytomass assessment inside ACS, did not occur any significant interaction of nitrogen
and position, during all oat cycle. The nitrogen increases the oat phytomass from 42 DAE to
152 DAE (21 DAE P = 0.45; 42 DAE P = 0.02; 63 DAE P = 0.02; 84 DAE P = 0.007; 105
DAE P = 0.04; 126 DAE P = 0.03; 152 DAE P = 0.007) (Supplementary Table 1). The effect
56
of positions were significant during all oat cycle, starting at 21 DAE with the linear degree
effect, followed by the quadratic polynomial degree effect from 42 DAE until 152 DAE,
according to the regression analysis. At 21 DAE the oat phytomass decreased linearly from
the smallest (i.e. position A) to the highest (i.e. position E) slope elevation, between two
adjacent tree tracks. From 42 DAE until 152 DAE the trees promoted a negative interference
on the oat phytomass, and the interference degree reduced as the distance from the trees
increased (Fig. 2a).
Tillers to main shoot phytomass ratio
In the systems comparison, the interaction of nitrogen and positions were significant both at
63 DAE (P = 0.001) and 152 DAE (P = 0.002). At 63 DAE in both nitrogen levels, the
phytomass ratio of AGR was higher than all positions inside ACS. In contrast to 152 DAE,
when only with 12 kg N ha-1, AGR had a higher phytomass ratio than all positions inside
ACS. Where was applied 80 kg N ha-1, the phytomass ratio of ACS did not differ to AGR.
The phytomass ratio was increased by 80 kg N ha-1 at 63 DAE, inside positions A and F, and
by 12 kg N ha-1 at 152 DAE inside positions B and F (Fig. 1b and Supplementary Table 2).
The nitrogen effect on the phytomass ratio were significant at 42 DAE (P = 0.081), 63 DAE
(P = 0.013), 84 DAE (P = 0.047) and 152 DAE (P = 0.046). 80 kg N ha-1 increased the
phytomass ratio from 42 DAE until 84 DAE, in contrast to 152 DAE, when the higher
phytomass ratio was promoted by 12 kg N ha-1. The positions effect denoted with AGR had a
higher phytomass ratio than all positions inside ACS at 42 DAE (P < 0.0001), 63 DAE (P <
0.0001), 84 DAE (P = 0.0002) and 152 DAE (P = 0.0003). At 126 DAE (P = 0.003) only the
central position between two adjacent tree tracks inside ACS did not differ to AGR and at 105
DAE, the position effect was not significant (Supplementary Table 2).
Within ACS, the interaction of nitrogen and positions occurred only at 152 DAE (P = 0.066).
The regression analysis denoted the linear degree and cubic polynomial degree effects for the
nitrogen levels 80 kg N ha-1 and 12 kg N ha-1, respectively. With 80 kg N ha-1 the phytomass
ratio increased from the smallest to the highest slope elevation, between two adjacent tree
tracks, and with 12 kg N ha-1, the phytomass ratio had on position B, a peak of the concavity
facing downwards, which occur between positions A and C, whose it was so intense that
became negative the concavity facing upwards, between positions C and E. The nitrogen level
12 kg N ha-1 increase the phytomass ratio only inside position B, and no nitrogen effect were
significant in the other positions (Fig. 2b). The phytomass ratio were increased by 80 kg N ha-
57
1
at 63 DAE (P = 0.059) and 84 DAE (P = 0.087) (Supplementary Table 2) and the position
effect was not significant during the oat cycle.
Tillers number per plant (main shoot)
At 21 DAE the oats tillers had not yet issued. In the systems comparison, the interaction of
nitrogen and positions were significant at 42 DAE (P = 0.04) and 84 DAE (P < 0.0001). At 42
DAE, in both nitrogen levels, AGR had more tillers per plant than all positions inside ACS,
and the nitrogen effect increases the tillers number inside positions A, C and F. At 84 DAE,
AGR with 80 kg N ha-1, was also superior in terms of tillers number than ACS. However, at
84 DAE where was applied 12 kg N ha-1, the tillers number of AGR did not differ to all
positions inside ACS. At 84 DAE, where was applied 80 kg N ha-1, the positions B, C, D and
F remained with more tillers per plant (Fig. 1c and Supplementary Table 3). The nitrogen
effect on tillers per plant were significant from 42 DAE until 84 DAE (42 DAE P = 0.047; 63
DAE P = 0.021; 84 DAE P = 0.014), and positions promoted effect from 42 DAE until 152
DAE (42 DAE P < 0.0001; 63 DAE P < 0.0001; 84 DAE P < 0.0001; 105 DAE P = 0.0018;
152 DAE P < 0.0001), in exception of at 126 DAE (P = 0.2603), where did not any effect
were significant. The higher nitrogen level increased the tillers number until 84 DAE. The
position effect denoted with AGR had more tillers per plant than all positions inside ACS
until 84 DAE, at 105 DAE only the position D did not was different to AGR and at 152 DAE
AGR went again had more tillers per plant than ACS (Supplementary Table 3).
Within ACS, the interaction of nitrogen and positions occur only at 84 DAE (P = 0.054), the
higher nitrogen level increased the tillers number within intermediaries and central positions
(i.e. positions B, C and D), between two adjacent eucalyptus tracks. For positions, the
regression analysis fitted the quadratic and cubic polynomial degrees, into the nitrogen levels
80 kg N ha-1 and 12 kg N ha-1, respectively. With 80 kg N ha-1 the oats had more tiller per
plant to extend that increased the distance from the trees. In contrast, where was applied 12 kg
N ha-1, the oat had more tillers per plant between positions A and C, and less tillers per plant
between positions C and E (Fig. 2c). The nitrogen effect was significant and increased the
tillers per plant, also until 84 DAE (42 DAE P = 0.09; 63 DAE P = 0.02; 84 DAE P = 0.069)
(Supplementary Table 3). The significant effect of positions occurred at 63 DAE (P = 0.007)
and 84 DAE (P = 0.007), and for both the regression analysis fitted the quadratic polynomial
degree effect. From 63 DAE to 84 DAE, the eucalyptus promoted a greater negative
interference on the tiller number, in extend that oats approached the trees (Fig. 2d).
58
Grain yield per plant
Both in the systems comparison and inside ACS the interaction of nitrogen and positions did
not occur for the grain yield per plant. In the systems comparison (P = 0.03) and inside ACS
(P = 0.03) the nitrogen level 80 kg N ha-1 increases the grains yield per plant. In contrast to
the position effect which did not alters the grain yield per plant (Table 1).
Tillers to main shoot grain yield ratio
In the systems comparison, the interaction of nitrogen and positions was not significant for
the grain yield ratio. The grain yield ratio did not differ between the nitrogen levels, however
the position effect (P = 0.0004) was significant, and denoted with AGR had a higher grain
yield ratio than ACS (Table 1).
Within ACS the grain yield ratio did interact with nitrogen and position (P = 0.085). The
regression analysis indicated quadratic and cubic polynomial degree effects for the nitrogen
levels 80 kg N ha-1 and 12 kg N ha-1, respectively. Where was applied 80 kg N ha-1, the grain
yield ratio was suppressed as it approached the tree component. Differently of the response
obtained with 12 kg N ha-1, which it had a higher grain yield ratio on the peak of the
concavity facing downwards in position B, tending to the negative ratio between positions C
and E. The nitrogen level 80 kg N ha-1 increased the grain yield ratio inside position C and no
other nitrogen effect occurred in other positions (Fig. 2e). The grain yield ratio not differed
between the nitrogen and position effects.
Discussion
At 42 DAE, the tillering had already started, and additional nitrogen application began to
promote a greater phytomass accumulation, both in the systems comparison and inside ACS,
moment also which only the central position between the tracks of trees did not differ to AGR
(Supplementary Table 1). The trees reduce the radiation intensity and alter the light wave
lengths arriving in the soil surface (Taiz and Zeiger 2010). Oats detecting precociously
alterations on the light quality and this modulated the growth and the tillering, thought the
lower emission of tillers and accumulation of tillers mass (Almeida and Mundstock 2001).
59
Low intensity of supplemented far red light increases the ratio between the mass of main stem
and tillers of oat, demonstrating prioritization of the resources allocation to the main stem in
detriment to the tillers (Almeida and Mundstock 2001). In wheat, supplemented red light did
not promote tillering compared to no supplemented light, however supplementing red light to
supplemented far red light, back-reversed the tiller inhibition promoted by far red light,
demonstrating the mediation of phytochrome on the detrimental effect of far red light (Ugarte
et al. 2010). At this time (i.e. 42 DAE), the nitrogen effect increased the phytomass ratio only
in the systems comparison, AGR had a higher phytomass ratio than ACS (Supplementary
Table 2), and in both nitrogen levels, AGR had more tillers per main shoot than ACS (Fig. 1c
Supplementary Table 3).
During earlier tillering, in addition to the oat less phytomass accumulated next to the trees,
was evident the eucalyptus tiller-delaying. In a 75% of shade, wheat (Triticum aestivum L. cv.
Minaret) tiller emergence occur at a higher physiological age than in plants under full
sunlight, and the maximal delay was proximal of one phyllochron (Evers et al. 2006). Wheat
grown in an eucalyptus ACS, with trees planted in a fan design and root pruned to a depth of
50 cm in northern India, had lower number of tillers per row length and longer duration of
tillering (days after sowing to 50% tillering) than wheat cultivated as a sole crop (Kohli and
Saini 2003).
At 63 DAE was observed the peak tillering. The oat phytomass of AGR did not differ only to
position C inside ACS, where was applied 80 kg N ha-1, and with 12 kg N ha-1 AGR is
similar, in terms of phytomass, to ACS (Fig. 1a and Supplementary Table 1). However, AGR
had a higher phytomass ratio in both nitrogen levels (Fig. 1b and Supplementary Table 2), and
more tillers per plant than ACS (Supplementary Table 3). Inside ACS at 63 DAE, the tillers
number was reduced to the extent that the oat plants were closer to the eucalyptus. In the peak
tillering, the tiller-delaying became to the eucalyptus tiller-suppression, possibly by both light
intensity reduction and quality alteration, not allowing to take into account other factors
(competition for water and nutrients), that may had limited the growth of oats until then.
Competition below ground for water could significantly reduced cotton plant size and
nitrogen use efficiency in Pinus taeda ACS (Zamora et al. 2009). The shade reduced tillering
and “a fixed red: far red and photosynthetic active radiation (PAR) intercepted inside the
canopy” determined the ceasing of wheat tillering (Evers et al. 2006). Then, it is natural to
expected that in environments most shaded by trees, the plant ceases the tillering even before
that the intraspecific community interaction, determines this moment (Fig. 2d).
60
At 84 DAE with 80 kg N ha-1, the phytomass of AGR became higher than all positions inside
ACS and with 12 kg N ha-1 the systems remained indifferent (Fig. 1a and Supplementary
Table 1). Only where it had been applied additional nitrogen, AGR remained with more tillers
per plant than ACS (Fig. 1c and Supplementary Table 3), and AGR remained with a higher
phytomass ratio than ACS (Supplementary Table 2). Inside ACS, where was applied the
higher nitrogen level, the tillers per main shoot increased approximately from 0.05 to 0.3 to
the extent that the oats are distanced from trees, and with the lower nitrogen level, there was a
subtle increase of the tillers number from 0.03 to 0.06, from position D to B, followed by a
decrease to 0.02 tillers number until position A (Fig. 2c).
From 105 DAE to 152 DAE, oats growing in AGR had a higher phytomass than that inside
ACS, did not differing only to position C inside ACS, both at 105 DAE and 152 DAE
(Supplementary Table 1). The phytomass ratio of AGR did not differ to position C inside
ACS at 126 DAE, and at 152 DAE only with the lower nitrogen level, had a higher phytomass
ratio than ACS (Fig. 1b and Supplementary Table 2). Inside ACS at 152 DAE, where was
applied the lower nitrogen level, the phytomass ratio had a greater expression only on position
B (Fig. 2b). And in terms of tillers number, AGR was superior to ACS at 105 and 152 DAE,
did not differing only to position D inside ACS at 105 DAE (Supplementary Table 3).
In our study the higher nitrogen level favored a greater oat tillering, although, at the end of the
cycle, the tillering was more persistent where had been applied the lower nitrogen level. This
may occurred due to the high intraspecific competition where was applied the higher nitrogen
level, promoted by the higher number of tillers at 63 DAE during the tillering peak, which is
succeeded by a greater phytomass accumulation and phytomass ratio at 84 DAE, added to the
lodging occurrence in AGR and on positions B and C inside ACS. A greater tiller persistence
occurred in traditional systems (e.g. AGR) as the plant density reduced (e.g. Evers et al.
2006), as well as the environmental conditions favored that inside ACS (e.g. Kohli and Saini
2003).
At the end of oat cycle, in the maturation phase (i.e. 152 DAE) was higher the grains yield
where was applied the higher nitrogen level, both in the systems comparison and inside ACS.
The grains yield did not differ between systems. However the grain yield ratio of AGR was
higher than that inside ACS (Table 1). Oats under tiller-depressing long day conditions, the
tiller traits phytomass, vegetative phytomass, total weight of grains, harvest index and its
tillers to main shoot ratios, did not respond to 120 kg N ha-1 or 80 kg N ha-1 application rate,
except in that the numbers of tillers and head-bearing tillers per main shoot (Peltonen-Sainio
et al. 2009).
61
Inside ACS, the grain yield ratio was increased by the higher nitrogen level only on position
C, and by the lower nitrogen level only on position B. Where was applied 12 kg N ha-1 (where
lodging did not interfere on growth), probably on position B is the local where oats use the
light more efficiently inside ACS, to promote the tillering persistence for grains production
(Fig. 2e). At 84 DAE, after the peak tillering, already stood a greater number of tillers in this
position, which could persist providing a significant contribution to the grains yield (Fig. 2c).
In a fan design, nearest eucalyptus tree rows, at a distance of 5.15 m from a center towards
east and west, wheat had maximum emergence and maximum tillering, which may had
resulted from the more efficient utilization of available light by the crop (Kohli and Saini
2003).
Both in AGR and ACS, the contribution of tillers to the total yield were small. However, near
the trees, was strong the eucalyptus tiller-suppression during oat cycle, suggesting that in
these sites must be used in addition to nitrogen, other agronomic practices such as a higher
seeding rate (e.g. Peltonen-Sainio et al. 1995 and Almeida et al. 2003) combined or not with
other plant arrangement, “forcing” in this way the community to the uniculm growth habit.
Gill et al. (2009) observed a declining trend in the number of tillers of wheat varieties, which
increase in age for 4 to 6 years old of poplar plantation.
Conclusion
The nitrogen levels did not alleviate the eucalyptus tiller-suppression and the tiller
contribution for grain production is small, in ACS in subtropical Brazil.
Acknowledgements
Work resulting from the technical cooperation agreement SAIC / AJU No. 21500.10/0008-2
signed by Iapar and Embrapa Florestas.
References
Almeida, M. L.; Mundstock, C. M. Oat tillering affected by light quality, in plants under
competition. Ciência Rural 31: 393–400, 2001. doi: 10.1590/S0103-84782001000300005
62
Almeida, M. L.; Sangoi, L.; Ender, M.; Wamser, A. F. Tillering does not interfere on white
oat grain yield response to plant density. Scientia Agricola 60: 253–258, 2003. doi:
10.1590/S0103-90162003000200008
10.1017/S0021859606006538
Evers, J. B.; Vos, J.; Andrieu, B.; Struik, P. C. Cessation of Tillering in Spring Wheat in
Relation to Light Interception and Red : Far-red Ratio. Annals of Botany 97: 649–658, 2006.
doi: 10.1093/aob/mcl020
Gill, R. I. S.; Singh, B.; Kaur, N. Productivity and nutrient uptake of newly released wheat
varieties at different sowing times under poplar plantation in north-western India.
Agroforestry Systems 76: 579–590, 2009. doi: 10.1007/s10457-009-9223-0
10.1023/A:1026090918747
Peltonen-Sainio, P.; Järvinen, P. Seeding rate effects on tillering, grain yield, and yield
components of oat at high latitude. Field Crops Research 40: 49–56, 1995. doi:
10.1016/0378-4290(94)00089-U
Peltonen-Sainio, P.; Jauhiainen, L.; Rajala, A.; Muurinen, S. Tiller traits of spring cereals
under tiller-depressing long day conditions. Field Crops Research 113: 82–89, 2009. doi:
10.1016/j.fcr.2009.04.012
M. R.; Lumbreras, J. F.; Cunha, T. J. F. Brazilian system of soil classification. 2nd. edn.
Embrapa Soils, Rio de Janeiro, 2006.
Ugarte, C. C.; Trupkin, S. A.; Ghiglione, H.; Slafer, G.; Casal, J. J. Low red/far-red ratios
delay spike and stem growth in wheat. Journal of Experimental Botany 61: 3151–3162, 2010.
doi: 10.1093/jxb/erq140
Zamora, D. S.; Jose, S.; Napolitano, K. Competition for 15N labeled nitrogen in a loblolly
pine–cotton alley cropping system in the southeastern United States. Agriculture, Ecosystems
and Environment 131: 40–50, 2009. doi: 10.1016/j.agee.2008.08.012
63
80 kg N ha-1
12 kg N ha-1
3.0
a
-1
(g plant )
Phytomass
2.5
2.0
1.5
1.0
0.5
0.0
-1
(g g )
Phytomass ratio
21
42
63
84 105 126 152
21
42
63
84 105 126 152
b
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
21
42
63
84 105 126 152
21
42
63
84 105 126 152
c
3.5
Tillers
-1
(number plant )
4.0
3.0
2.5
2.0
1.5
1.0
21
42
63
84 105 126 152
21
42
63
84 105 126 152
Days after emergence
Position
Position
Position
Position
Position
Position
A
B
C
D
E
F
Fig. 1 Oat (Avena sativa L. cv. IPR 126) phytomass (a), tillers to main shoot phytomass ratio (b) and tillers
number (c) under nitrogen levels (80.0 kg N ha-1 and 12.0 kg N ha-1) in alley cropping agroforestry system, at A:
2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest elevation of the
slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] and
traditional no till agriculture (F), in subtropical Brazil. Vertical bars denote standard errors.
64
0.25
a
Phytomass ratio
(g g-1)
2.0
1.6
1.4
1.2
1.0
0.20
0.15
0.10
0.05
0.00
-0.05
A
0.8
B
C
D
E
D
E
D
E
Positions
0.6
0.4
0.2
0.0
A
B
C
D
E
Positions
21 DAE
42 DAE
63 DAE
84 DAE
105 DAE
126 DAE
152 DAE
c
0.5
0.4
Tillers plant-1
at 84 DAE
Phytomass (g plant-1)
1.8
80 kg N ha-1
12 kg N ha-1
b
d
0.3
0.2
0.1
0.0
-0.1
0.8
A
0.7
B
C
Positions
0.5
e
0.10
0.4
0.3
0.2
0.1
0.0
A
B
C
Positions
D
E
42 DAE
63 DAE
84 DAE
105 DAE
126 DAE
152 DAE
Grain yield ratio
(mg mg-1)
Tillers plant-1
0.6
0.08
0.06
0.04
0.02
0.00
-0.02
A
B
C
Positions
Fig. 2 Oat (Avena sativa L. cv. IPR 126) traits under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in days
after emergence (DAE), above ground biological yield (21 DAE: Y = 0.023 – 5.00 10-4 x, R2 = 60.0, P = 0.06; 42
DAE: Y = 0.039 + 0.010 x – 5.46 10-4 x2, R2 = 58.1, P = 0.0056; 63 DAE: Y = 0.023 + 0.037 x – 0.0019 x2, R2 =
80.6, P = 5.55 10-5; 84 DAE: Y = 0.037 + 0.065 x – 0.0033 x2, R2 = 85.3, P = 1.19 10-5; 105 DAE: Y = 0.172 +
0.099 x – 0.0049 x2, R2 = 87.3, P = 0.003; 126 DAE: Y = 0.514 + 0.081 x – 0.0036 x2, R2 = 19.4, P = 0.07; 152
DAE: Y = 0.448 + 0.191 x – 0.0085 x2, R2 = 80.8, P = 0.007), tillers to main shoot phytomass ratio at 152 DAE
(80 kg N ha-1: Y = 0.0011 + 0.0019, R2 = 49.1, P = 0.42 and 12 kg N ha-1: Y = – 0.235 + 0.124 x – 0.014 x2 +
4.38 10-4 x3, R2 = 70.4, P = 0.01) tillers per main shoot (63 DAE: Y = 0.318 + 0.058 x – 0.0033 x2, R2 = 74.7, P =
0.02; 84 DAE: Y = – 0.074 + 0.047 x – 0.0023 x2, R2 = 89.3, P = 0.003; 84 DAE: 80 kg N ha-1: Y = – 0.161 +
0.085 x – 0.0041 x2, R2 = 82.4, P = 0.0005 and 12 kg N ha-1: Y = – 0.072 + 0.047 x – 0.0049 x2 + 1.49 10-4 x3, R2
= 99.8, P = 0.54) tillers to main shoot grain yield ratio (80 kg N ha-1: Y = – 0.042 + 0.015 x – 6.63 10-4 x2, R2 =
60.55, P = 0.076 and 12 kg N ha-1: Y = – 0.095 + 0.049 x – 0.0055 x2 + 1.72 10-4 x3, R2 = 68.4, P = 0.09) in alley
cropping agroforestry system, at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track
positioned at the lowest elevation of the slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden)
double line tracks [20 m (4 m x 3 m)], in subtropical Brazil. Vertical bars denote standard errors.
65
Table 1 Oat (Avena sativa L. cv. IPR 126) grains yield per plant and tiller to main shoot grain yield ratio, under
nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional
no till agriculture (F) in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
A-F c
A-E
-1
Grains yield (mg plant )
80 kg N ha-1 187
191.1
221.3
302.7
235.6
304.7
240.4 A 227.5 A
12 kg N ha-1 152.6
223.4
260.3
189.4
170.7
231.5
204.7 B 199.3 B
Mean
169.8
207.3
240.8
246.1
203.1
268.1
222.5
213.4
Tiller to main shoot grain yield ratio (µg mg-1)
80 kg N ha-1
0
6.64
60.59
28.62
18.05
105.13
36.51
22.78
12 kg N ha-1 0.08
52.14
1.82
4.03
0.32
162.75
36.86
11.68
Mean
0.04
29.39
31.2
16.33
9.19
133.94
36.68
17.23
** b
**
**
**
**
Control
a
the Duncan´s test (α = 0.05).
b
*, ** and
ns
(within line) indicates the significance at 0.05, 0.01 and non
significant, respectively, of the comparison with a control by the Dunnett two sided test.c Means including
traditional no till agriculture (A_F) or within alley cropping system (A_E).
66
Supplementary Table 1 Oat (Avena sativa L. cv. IPR 126) above ground phytomass under nitrogen levels (12.0
kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till agriculture (F)
in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
Above ground phytomass (mg plant-1)
A-F c
A-E
80 kg N ha-1 15.4
18.7
21.1
16.5
14
15.9
16.9
17.1
-1
12 kg N ha
24.9
20.4
23.2
13.3
13
22.5
19.6
19
Mean
20.2
19.5
22.1
14.9
13.5
19.2
18.2
18
ns b
ns
ns
ns
ns
Control
80 kg N ha-1 80.2
92
118.6
73.4
72.1
128.2
94.1 A 87.3 A
-1
12 kg N ha
50.1
57.3
90.7
59.5
49
105.3
68.7 B 61.3 B
Mean
65.1
74.6
104.7
66.5
60.6
116.8
81.4
74.3
ns
**
**
**
**
Control
80 kg N ha-1 171 a 214 a 254 a 220 a 131 a 369 a
226 A 198 A
ns
**
*
*
**
Control
12 kg N ha-1 66
b 102 b 216 a
80
b
59
a 126 b
108 B 105 B
ns
ns
ns
ns
ns
Control
Mean
118
158
235
150
95
248
167
151
ns
**
*
*
**
Control
80 kg N ha-1 266 a 466 a 531 a 382 a 310 a 1063 a
503 A 391 A
**
**
**
**
**
Control
12 kg N ha-1 108 b 188 b 272 b 166 b 128 b 250 b
185 B 172 B
ns
ns
ns
ns
ns
Control
Mean
187
327
401
274
219
657
344
282
**
**
**
**
**
Control
80 kg N ha-1 577
843
834
781
633
1405
845 A 734 A
12 kg N ha-1 231
374
618
298
255
642
403 B 355 B
Mean
404
608
726
540
444
1023
624
544
**
**
*
**
**
Control
-1
80 kg N ha 1084
821
1510
1038
1328
2004
1298 A 1156 A
12 kg N ha-1 485
469
1002
565
410
1291
704 B 586 B
Mean
784
645
1256
802
869
1648
1001
871
**
**
*
**
**
Control
-1
80 kg N ha
997
1280
1875
1750
1688
2436
1671 A 1518 A
12 kg N ha-1 858
1206
1458
907
815
2172
1236 B 1049 B
Mean
927
1243
1666
1329
1252
2304
1454
1284
**
**
*
**
**
Control
a
67
Supplementary Table 2 Oat (Avena sativa L. cv. IPR 126) tillers to main shoot phytomass ratio under nitrogen
levels (12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till
agriculture (F) in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
Tillers to main shoot phytomass ratio (mg mg-1)
A-F c
A-E
80 kg N ha-1 0.046
0.022
0.044
0.018
0.024
0.227
0.063 A 0.031
-1
12 kg N ha 0.011
0.007
0.02
0.001
0.006
0.172
0.036 B 0.009
Mean
0.028
0.015
0.032
0.009
0.015
0.2
0.05
0.02
** b
**
**
**
**
Control
80 kg N ha-1 0.182 a 0.127 a 0.173 a 0.121 a 0.113 a 0.863 a
0.263 A 0.143 A
**
**
**
**
**
Control
12 kg N ha-1 0.048 b 0.029 a 0.055 a 0.033 a 0.009 a 0.357 b
0.089 B 0.035 B
**
**
**
**
**
Control
Mean
0.115
0.078
0.114
0.077
0.061
0.61
0.176
0.089
**
**
**
**
**
Control
80 kg N ha-1 0.055
0.089
0.093
0.109
0.062
0.924
0.222 A 0.082 A
12 kg N ha-1 0.047
0.026
0.036
0.039
0.049
0.15
0.058 B 0.039 B
Mean
0.051
0.058
0.065
0.074
0.056
0.537
0.14
0.061
**
**
**
**
**
Control
80 kg N ha-1 0.015
0.052
0.065
0.115
0.034
0.108
0.065
0.056
-1
12 kg N ha
0
0.01
0.022
0.011
0.027
0.107
0.03
0.014
Mean
0.008
0.031
0.044
0.063
0.03
0.108
0.047
0.035
80 kg N ha-1 0.013
0.025
0.029
0.006
0.003
0.046
0.02
0.015
12 kg N ha-1 0.023
0.001
0.017
0.028
0.007
0.103
0.03
0.015
Mean
0.018
0.013
0.023
0.017
0.005
0.075
0.025
0.015
ns
*
**
*
**
Control
80 kg N ha-1
0
a 0.009 b 0.038 a 0.03 a 0.024 a 0.07 b
0.028 B 0.02
ns
ns
ns
ns
ns
Control
12 kg N ha-1 0.005 a 0.132 a 0.008 a 0.01 a 0.006 a 0.276 a
0.073 A 0.032
**
*
**
**
**
Control
Mean
0.003
0.071
0.023
0.02
0.015
0.173
0.051
0.026
**
**
**
**
**
Control
a
68
Supplementary Table 3 Oat (Avena sativa L. cv. IPR 126) tillers number per main shoot under nitrogen levels
(12.0 kg N ha-1 and 80.0 kg N ha-1) in alley cropping agroforestry system (A_E) and traditional no till agriculture
(F) in subtropical Brazil
Positions
Aa
B
C
D
E
F
Mean
Tillers (main shoot-1)
A-F c
A-E
80 kg N ha-1 0.25 a 0.15 a 0.33 a 0.16 a 0.13 a 1.18 a
0.37 A 0.2 A
b
**
**
**
**
**
Control
12 kg N ha-1 0.03 b 0.03 a 0.05 b 0.02 a 0.02 a 0.72 b
0.15 B 0.03 B
**
**
**
**
**
Control
Mean
0.14
0.09
0.19
0.09
0.08
0.95
0.26
0.12
**
**
**
**
**
Control
80 kg N ha-1 0.73
0.65
0.85
0.66
0.51
2.16
0.93 A 0.68 A
12 kg N ha-1 0.22
0.34
0.44
0.24
0.18
1.06
0.41 B 0.28 B
Mean
0.47
0.5
0.65
0.45
0.35
1.61
0.67
0.48
**
**
**
**
**
Control
80 kg N ha-1 0.06 a 0.21 a 0.23 a 0.31 a 0.06 a 1.00 a
0.31 A 0.17 A
**
**
**
**
**
Control
12 kg N ha-1 0.02 a 0.06 b 0.05 b 0.03 b 0.03 a 0.13 b
0.06 B 0.04 B
ns
ns
ns
ns
ns
Control
Mean
0.04
0.14
0.14
0.17
0.05
0.56
0.18
0.1
**
**
**
**
**
Control
80 kg N ha-1 0.01
0.07
0.06
0.05
0.04
0.12
0.06
0.05
12 kg N ha-1
0
0.04
0.04
0.06
0.01
0.2
0.06
0.03
Mean
0.004
0.05
0.05
0.05
0.03
0.16
0.06
0.04
ns
**
*
*
*
Control
80 kg N ha-1
0
0.02
0.06
0.17
0
0.07
0.05
0.05
12 kg N ha-1 0.01
0.01
0.03
0.01
0.01
0.17
0.04
0.01
Mean
0.01
0.02
0.04
0.09
0.003
0.12
0.05
0.03
80 kg N ha-1
0
0.04
0.06
0.04
0.07
0.11
0.05
0.04
12 kg N ha-1 0.010
0.05
0.02
0.02
0.02
0.23
0.06
0.02
Mean
0.003
0.04
0.04
0.03
0.04
0.17
0.05
0.03
**
**
**
**
**
Control
a
69
5. CHAPTER 3
OAT GRAIN YIELD UNDER NITROGEN LEVELS IN EUCALYPTUS ALLEY
CROPPING SYSTEM IN SUBTROPICAL BRAZIL
1
L Deiss
00 55 41 3505633
00 55 41 3505601
Abstract
The adequacy of agronomic practices plays a key role in the development of integrated
systems. The hypothesis of this work is that the oat grain yield is not modified by the nitrogen
in positions between eucalyptus tracks in alley cropping agroforestry system (ACS), thus the
nitrogen does not improve the oat yield in ACS. The objective of this study was to determine
how the phytomass accumulation, yield compounds and yield of oat (Avena sativa L. cv. IPR
126) are influenced by nitrogen levels (12 and 80 kg N ha-1), in five equidistant positions
between two adjacent eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x
3 m)] in ACS and traditional no till agriculture in subtropical Brazil. The experiment was
carried out in a split-block randomized block design with four replicates. At the end of oat
cycle, there was compensation of the lower number of spikelets per panicle by the greater
number of grains per spikelet, as well as higher harvest indexes where less phytomass was
accumulated, in environments with high interspecific interaction. The nitrogen levels increase
the oat yield differently at positions relative to the trees in the ACS.
Key words: Avena sativa L., Eucalyptus dunnii Maiden, integrated systems, agroforestry,
yield compounds
Abbreviations: ACS, alley cropping agroforestry system; AGR, traditional no till agriculture
70
Introduction
The trees cause an impact on the ecological balance of the integrated systems, which could be
benefic or malefic. Since tree crops have more competition ability, agronomic and
silvicultural practices should favor the growth and development of the annual crop under
interspecific interference. The competition for water and nutrients affects more the annual
crop component than the trees, and the intensity increases with increase of density and age of
the trees (Gill et al. 2009). For example, pruning the branches of the trees, reducing the trees
density by altering row spacing (Prasad et al. 2010) and thinning, are practices that could
improve the yield potential of the system. Pruning could promote receiving more sunflecks
over intercropped culture; with tendency to alleviate the qualitative imbalance of transmitted
photosynthetic active radiation (Kohli and Saini 2003).
The oat breeding programs still do not have as the principal focus create varieties for the
arborized integrated systems. Semchenko and Zobel (2005) investigated four oat (Avena
sativa L.) varieties originating from four different ages (1930, 1952, 1980 and 1999), in order
to find the effect of light and nutrients on the phenotypic plasticity of oats. The authors
observed that oats did not have ontogenetic plasticity in allocation of photoassimilates to
leaves in response to light, nor to panicles and stems in response to light and nutrients
(Semchenko and Zobel 2005). Alteration in wheat yield inside a 4 to 6 years old poplar
(Populus deltoides Bartr.) agroforestry are attributed to genetic variation in response to shade
and stress of nutrient as well as moisture caused by the trees (Gill et al. 2009).
Since variety principally determines the quality of grains, agronomic practices should be
made focusing on yield and lodging risk (Browne et al. 2003). The adjustment of the nitrogen
level in the oats cultivation is important because in addition to increasing yield, reduces
lodging (Browne et al. 2006). Increases of oat yield are resultant from nitrogen, by increasing
panicle numbers and grain numbers per panicle (Browne et al. 2006). Oats are taller and
lodging negatively affects the culture by reducing yield and difficulting and prolonging
harvest (White et al. 2003). The poorly filled grains have an increase in moisture content,
decrease in specific weight and discolor due to pathogenic activity (White et al. 2003).
The hypothesis of this work is that the oat grain yield is not modified by the nitrogen in
positions between eucalyptus tracks in ACS, thus the nitrogen does not improve the oat yield
in ACS, in subtropical Brazil.
The objective of this study was determine how the phytomass accumulation, yield compounds
and yield of oat (Avena sativa L. cv. IPR 126) are influenced by nitrogen levels in positions
71
between adjacent tracks of eucalyptus (Eucalyptus dunnii Maiden) ACS and AGR, in
subtropical Brazil.
Study site
Institute of Paraná (25°06‟19” S 50°02‟38” W, 1020 m above mean sea level), located in
Köppen classification system, is a temperate, with no definite dry season and the average total
slope). Soil samples were collected at 0-0.20 m depth and formed a composite sample at a
positions level (described below), and formed a composite sample for the experimental area.
The soil analysis resulted in the following characteristics (means ± standard deviation, n = 6):
pH (CaCl2) 4.9 ± 0.20, pH (SMP) 6.2 ± 0.15, Al+3 0.13 ± 0.13 cmolc dm-3, H++Al+3 4.43 ±
0.55 cmolc dm-3, Ca+2 3.07 ± 0.79 cmolc dm-3, Mg+2 2.47 ± 0.37 cmolc dm-3, K+ 0.12 ± 0.03
cmolc dm-3, P 6.65 ± 2.17 mg dm-3, C 26.4 ± 1.3 g dm-3 and clay 447 ± 16 g kg-1.
The tree of ACS is Eucalyptus dunnii Maiden, which were implemented in 2007 in double
line tracks. AGR was used to compare the predominant form of agriculture of the region and
was located next to the arborized system (less than 200 m). Both systems were previously
areas of native grassland, and had similar cultures historic.
parallel to up and down on the slope. The spacing between two adjacent tree tracks along the
guideline level direction is 20 m, the distance between two adjacent rows in a track is 4 m,
and the distance of two trees in a row is 3 m [20 m (4 m x 3 m)]. The average tree height and
diameter on April 2010 were 11.9 m and 13.9 cm, respectively. The eucalyptus trees were
thinned out (from 278 to 166 tress ha-1) and the remaining trees had their branches pruned to
72
half of trees height. Intercropped annual crops are planted one m from the tree stems, because
the limitation of approximation to agricultural implements, making oat track had 18 m long.
implement, the oat (Avena sativa L. cv. IPR 126) was sown on June 16th 2011, at the rate of
40 kg seeds ha-1 and fertilized at 300 kg ha-1 of 04-30-10 (N-P2O5-K2O). Ten days after
sowing, the emergence occurred and this date was used as reference. During the oat cycle, for
weed control metsulfuron-methyl (2.4 g ai ha-1) was applied before the tillering stage and to
stage.
Experimental design
The experiment was carried out in a split-block, in a randomized complete block design, with
four replicates, that included two nitrogen levels (80.0 and 12.0 kg N ha-1) as main plots and
six positions (five positions between two eucalyptus tracks and one outside the system) as
split-blocks. At the tillering stage, additional nitrogen in urea form (46 % N) was uniformly
hand-applied (68.0 kg N ha-1) or non-applied (0.0 kg N ha-1).The split-blocks were 14 rows 5
m long with 18 cm between rows. A border of 0.4 m was left on each split-block side. The six
different positions, which five are equidistance‟s between the eucalyptus tracks and one is
outside of the intercropping system, versus two levels of nitrogen combinations are denoted as
A+, B+, C+, D+, E+, F+, A-, B-, C-, D-, E- and F- with the letter indicating the position (A,
B, C, D and E for ACS and F for AGR) and the symbols „+‟ or „-‟ indicating 80.0 kg N ha-1or
12.0 kg N ha-1 applied until tillering stage, respectively. Within the integrated system (A_E),
taking into account the slope, the letter A represents the smallest elevation of the slope, and
the letter E the highest elevation of the slope, between two adjacent tree tracks. This is always
valid because the system was implemented in a guideline level. Therefore, the distances,
Above ground biological yield, grain yield, yield compounds and harvest index analysis
73
When the plants were physiologically mature, evaluations were made for determine the
phytomass accumulated (biological yield), yield compounds, yield and harvest index. The
yield of oat was estimated only for the area of oat track, did not including the area of
eucalyptus tracks, which determine the real oat yield ha-1 of the ACS. Only the grains yield
was estimated with 13% moisture.
Plant measurements
At the end of oat cycle, the plants were collected, from a central position of the split-block, by
placing a rectangle cast iron, of 1.8 m long (positioned perpendicular to the trees tracks) by 10
cm wide, that always comprised 10 rows of crop with 10 cm length. The plants were uprooted
to enable the identification of the tillers, and then the roots were cut for the dry matter
determination. All plants collected were separated into main stem and tillers and each one into
leaves, stems, senescent material and panicles, and dried at 65° C and weighed after reaching
a constant weight.
The panicles were counted and by random selection, twelve main stem panicles and five
tillers panicles were chosen for determining by hand the spikelet number, spikelet aborted
number, and number and weights of primary and secondary grains with husks. For the other
panicles, the grains were threshed using a motorcycle tire chamber and separated from other
materials (rachis, branches, and glumes) with a pressurized air blower. The grains were redried at 65° C and weighed after reaching a constant weight. At the harvest, from the total
above ground biological yield and grain with husks yield were determined the harvest index
(without grains moisture). The proportion of husks of the harvested grains was accessed by a
sub sample of 10 primary and secondary grains of each sample (split-block). The linear
relationship of the grains weight with and without husks, demonstrates increment of 1.27 g g-1
(intercept = 0.0025) for primary grains (R² = 0.96) and 1.19 g g-1 for secondary grains (R² =
0.95) (intercept = 0.0016) compared to the same without husks. Then was assumed the values
of grains with husks.
74
Other analyses were performed same as described, excluding the treatment control (AGR),
only with five positions between two eucalyptus tracks (five positions), for test the effects
within the integrated system. The block and its interactions were treated as random effects.
The normality of the residuals was verified by the Shapiro-Wilk test at α = 0.01 significance,
and for secondary grain, only in the systems comparison at α = 0.001 significance. The values
of weight of primary grain from spikelet with one grain, not reached normality, and to
improve that, the square-root transformation was used. Differences between means of
nitrogen levels were determined using the Duncan method. For compare means of AGR
(control treatment) with positions inside ACS, the Dunnett two sided method were utilized,
considering treatment effects at α = 0.10 significance.
For the significant effects of positions inside ACS, simple regression analyses for linear,
quadratic and cubic polynomial degrees were determined. The mathematical models were
chosen according to the equations with the best fit, confirmed by the higher determination
coefficients and the significance of the regression F test, until 10% probability, or the lowest
value of significance when probability was above 10%.
Results
Above ground biological yield
The interaction of nitrogen and positions was significant in the estimation of the above ground
biological yield of oat, including AGR (five positions of ACS and AGR) (P = 0.002) (Table
1) or excluding AGR (five positions) (P = 0.013) (Fig. 1a). Appling both 80 kg N ha-1 or 12
kg N ha-1, the biological yield of AGR was superior to all positions inside ACS (Table 1).
Where was applied 12 kg N ha-1 within ACS, the oat biological yield tend to be nonlinear,
which the negative effects of the trees being lower at central position of oat track and
becoming more severe close to the tree tracks (R2 = 59.26, P = 0.001). 80 kg N ha-1 promote
the linear response of oat biological yield, taking into account the slope between two adjacent
tree tracks, the smallest elevation (position A) accumulated less phytomass than the highest
elevation of the slope (position E) (R2 = 68.31, P = 0.007) (Fig. 1a). The higher nitrogen level
increased the oat biological yield inside ACS (P = 0.006) (80 kg N ha-1: 287.4 ± 20.8 and 12
kg N ha-1: 195.3 ± 17.3) and in comparison to AGR (P = 0.005) (Table 1). Inside ACS, the oat
phytomass presented between positions (P = 0.001) the quadratic tendency. The oat
75
accumulated more phytomass as the distance from the trees increased, being heavier at the
highest elevation compared to the lowest elevation of the slope (Y = 394.60 + 5.71 x – 0.25
x2, R2 = 85.5, P = 0.10).
Yield compounds, yield and harvest index
The number of plants (m-2) was not altered by nitrogen in ACS (P = 0.94) (80 kg N ha-1:
200.3 ± 12.4 and 12 kg N ha-1: 201.4 ± 12.3) and in the systems comparison (P = 0.52), as
well as positions in ACS (P = 0.21) and in the systems comparison (P = 0.16). The number of
panicle did not differ between nitrogen levels inside ACS (80 kg N ha-1: 207.5 ± 12.9 and 12
kg N ha-1: 205.0 ± 12.1) and in the systems comparison, and varied across the positions in the
systems comparison (P = 0.0396), however not when considering only ACS (P = 0.18).
Relative to AGR, the number of panicles was inferior at positions A, B and C inside ACS (P
= 0.04) (Table 2). Wheat growing in a nine years old eucalyptus ACS, in a fan design and root
pruned to a depth of 50 cm in northern India, had lower number of earheads than wheat in a
sole crop (Kohli and Saini 2003).
In the systems comparison, the number of spikelets per panicle was influenced by effects of
nitrogen (P = 0.062) and position (P = 0.008). Compared to AGR, ACS were inferior at
positions A and B. The number of spikelets per panicle of oat submitted to 80 kg N ha-1 was
superior compared to 12 kg N ha-1, although the higher nitrogen level increased the number of
aborted spikelets per panicle (P = 0.007). Inside ACS, the higher nitrogen level increase both
the number of spikelets (P = 0.027) (80 kg N ha-1: 17.8 ± 1.3 and 12 kg N ha-1: 15.6 ± 1.4)
and aborted spikelets per panicle (P = 0.019) (80 kg N ha-1: 2.7 ± 0.3 and 12 kg N ha-1: 0.9 ±
0.2) (Table 2). The number of spikelets per panicle were negatively affected by the presence
of the trees (P = 0.0497), occurring the maximal number between positions C and D (R2 =
85.46, P = 0.052) (Fig. 1b).
The proportion of the primary and secondary grains in the spikelets of oats, considering
ponderously the spikelets from panicles of tillers or main stem, are dependent of nitrogen
level both in the systems comparison (P = 0.014) and inside of ACS (P = 0.004), as well as
positions within ACS (P = 0.007) and in the systems comparison (P = 0.001). The higher
nitrogen level reduced the number of grains per spikelets including AGR or inside ACS (80
kg N ha-1: 1.48 ± 0.03 and 12 kg N ha-1: 1.62 ± 0.03). The numbers of grains per spikelets was
lower in AGR compared to positions A, D and E, into ACS (Table 2). Within the arborized
system, is lower the number of grains per spikelets at central and one intermediate positions
76
(i.e. positions B and C) than near to the trees and other intermediate position (i.e. positions A,
D and E) (R2 = 99.72, P = 0.04) (Fig. 1c). The weight of the primary grains with husks,
including separately spikelets with one or two grains, and the secondary grains were not
different between the nitrogen levels in the systems comparison and inside ACS (80 kg N ha1
: 1.13 ± 0.05, 2.72 ± 0.14, 1.12 ± 0.07 and 12 kg N ha-1: 1.08 ± 0.13, 2.91 ± 0.11, 1.23 ±
0.05, respectively), as well as positions in the systems comparison and inside ACS, in
exception of the position A inside ACS, which had a higher weight of the primary grains of
spikelets with one grain, than AGR (Table 2). There was not any presence of the tertiary
grains in the spikelets observed.
In the systems comparison, the oat yield interact with nitrogen levels and positions (P =
0.069). Comparing the AGR with 80 kg N ha-1, where are obtained the higher yield of 743.6 ±
113.9 kg ha-1 (mean ± standard error, n = 4), to the positions inside ACS with the same
nitrogen level, that higher yielding did not differ only to the positions D+ and E+. AGR with
12 kg N ha-1 as the treatment control did not differ to other positions with the lower nitrogen
level. Inside of each position, 80 kg N ha-1 increase the yield of oat only, in one position close
to the trees (i.e. positions E) inside ACS and AGR. In the systems comparison, the yield of
AGR was superior to the positions A and B of ACS (P = 0.087), and the application of 80 kg
N ha-1 compared to 12 kg N ha-1 increases the oat yield (P = 0.114). In the area designated
for the annual crops into ACS, the yield of oat are also resultant of the interaction of the
nitrogen level and the positions between the tree tracks (P = 0.109) (Table 3). Where was
applied 12 kg N ha-1, the yield tended to be non linear, increasing as the distance from the
trees increased, ranching a peak yield of the concavity facing downward between positions C
and D (R2 = 66.55, P = 0.20) (Fig. 1d). The cubic response was observed where was applied
80 kg N ha-1, which a strong yield decreased on a concavity facing upward between positions
A and D (R2 = 97.61 P = 0.089) (Fig. 1d). The nitrogen levels (P = 0.23) (80 kg N ha-1: 517.0
± 44.4 and 12 kg N ha-1: 500.0 ± 31.1) and the positions (P = 0.15) did not cause significant
differences of the oats yield grown inside ACS (Table 3).
The harvest index was negatively affected by increases the nitrogen level, in both the systems
and inside of ACS (P = 0.015) (80 kg N ha-1: 20.2 ± 1.5 and 12 kg N ha-1: 29.0 ± 2.2). In
AGR was observed inferior value of the harvest index related with to all positions into ACS,
except of the position C, which did not differ (P = 0.001) (Table 3). Inside ACS (P = 0.056),
the harvest index had a cubic tendency, decreasing from position A until the middle between
position B and C, increasing until the middle between position D and E, and re-decreasing
slightly until the end of oat track at the highest elevation of the slope (R2 = 89.58, P = 0.055)
77
(Fig. 1e). The harvest index of wheat under a poplar plantation, decreased with increase in age
of the trees, from 4 to 6 years old and with delayed sowing (Gill et al. 2009). The wheat
intercropped with eucalyptus, had similar harvest index but lower aboveground biological
yield than wheat as a sole crop (Kohli and Saini 2003).
Discussion
Above ground biological yield
The total biomass accumulation of oat tended to saturate at 50 % of daylight availability, and
at severe shade (10% of daylight availability) there was no effect of fertilization on biomass
production (Semchenko and Zobel 2005). Though the light possibly is not the unique resource
which interacted between species, it is also necessary to take into account the water and
nutrients dynamics inside ACS. The nitrogen increased the above ground biological yield in
both extremes and one intermediary position at the highest elevation of slope of oat track
inside ACS (Fig. 1a). However it was not sufficient to match the biological yield of oats
obtained in AGR (Table 1).
The higher amplitude of biological yield did not occur where was applied the higher nitrogen
level, because lodging affected principally the reproductive phase, in AGR and positions B
and C inside ACS. In shady conditions, oat increases lignin and cellulose contents of stems,
fact that compensates the insufficient ontogenetic plasticity of stem biomass in response to
environment (light and nutrients), and provides mechanical support for plants growth under
shade, enabling produce more length stems per unit of stems biomass (Semchenko and Zobel
2005). Under higher nitrogen levels, the higher interspecific interaction promotes the growth
regulation of oat, for cereal production inside ACS.
Yield compounds, yield and harvest index
In the earlier development of oat, the light quality modulates the stem elongation and the
tillering, therefore the interrelationship between the light availability and the development
degree of the tillers, is determinant to the intraspecific competition and the structure of the
community (Almeida and Mundstock 2001). The tillering persistence determines the number
of panicle at harvest. The number of panicles varied across the systems but not between the
nitrogen levels in the systems comparison. Compared to AGR, significantly lower values
78
occurred in positions A, B and C in ACS. Within ACS, no differences were observed for the
panicle number between nitrogen levels and positions (Table 2).
In oats, the tiller survival, stem elongation and initiation of spikelets and florets at the apical
meristem will all be affected by competition (Browne et al. 2006). The number of spikelets
per panicle of AGR was superior to the positions A and B into ACS, and the higher nitrogen
level increased the number of spikelets per panicle (Table 2). Within ACS, as increased the
distance from the trees (Fig. 1b) as well as increased the nitrogen level, the number of
spikelets per panicle also increased. However, when AGR is compared to and only within
ACS, the higher nitrogen level increased the abort of spikelets. At the outset of oat
fertilization followed by grain-filling, an imbalance of the photoassimilate supply and
demand, due from competition between fully developed florets, results in grain abortion
(Browne et al. 2006). When higher nitrogen rates did not produce large response in panicle
and spikelet numbers, the competition was less intense and fewer grains were aborted
(Browne et al. 2006). The increased on the number of spikelets per panicle promoted by the
higher nitrogen level, probably resulted in the reduction of the number of grains per spikelet
(Table 2).
The higher number of grains per spikelets in both positions close to the trees (i.e. positions A
and E) and one intermediate position at smallest elevation of the slope between two adjacent
tree tracks (i.e. position D), partially compensated the lower number of spikelets per panicle
within ACS and compared to AGR (Table 2). Within ACS, the number of grains per spikelet
had a reduction between positions A and D (Fig. 1c) and with increased the nitrogen level
(Table 2). After anthesis the “competition will be confined to grains that are being filled”
(Browne et al. 2006). The weight of grains with husk no differed between the systems and the
nitrogen levels, in exception of the heavier primary grains of spikelets with one grain of
position A inside ACS compared to AGR (Table 2). As the nitrogen rate decreased from 80 to
12 kg N ha-1, as well as decreased the distance from the arboreal component, inside the ACS,
oat proportion of secondary grain relative to primary grain increased more in number than in
weight (Table 2 and Fig. 1c).
Compared to the higher yielding treatment, the AGR with 80 kg N ha-1, the positions D and E
with 80 kg N ha-1 did not differ in the terms of yield (Table 3). The benefits promoted by the
additional nitrogen application released at the tillering, for the grain yield, could be only
observed in AGR and on highest elevation of the slope (i.e. position E) inside ACS (Table 3
and Fig. 1d). This is an evidence with the adjustment of the nitrogen level in the integrated
system should take in account, the interspecific interaction between annuals and perennials
79
crops. In the central position between eucalyptus tracks, the higher compared to the lower
nitrogen level, did not increase both the biological and grain yields, suggesting with the
nitrogen level for these place should be inferior of 80 kg N ha-1. The higher nitrogen level
increased the grain yield in position E inside ACS, indicating that the nitrogen level should be
maintained or even increased.
In Spanish dehesas, the close vicinity of Holm-oak trees (Quercus ilex L.) reduced the yield of
the oat cereal, which are attributed principally to the competition for light and water, since the
trees improved the fertility, by reduction on plant density, since the height and weight of
plants as well as number and weight of grains per plant did not vary with the distance from
the trees (Moreno et al. 2007). In our study, the factors effect on the plants number was
disregarded. However its important emphasize that, where were detected the lodging
interference, the reduction in productivity would have been more pronounced if the harvest
had been made mechanically, since lodged plants are not harvested (Espindula et al. 2010).
Inside ACS, the cubic response of grain yield, observed where was applied 80 kg N ha-1 (Fig.
1d), may had occurred due to a yield reductions, probably aggravated by lodging, in the
positions B and C. In contrast, possibly, the rainwater interception and redistribution (Rao et
al. 1998; Ong et al. 2000) by the eucalyptus added to the alleviation of below ground
competition promoted by the nitrogen fertilization, favored the grain yield at the highest
elevation of the slope (i.e. positions D and E) between two adjacent tree tracks (Fig. 1d).
Since the trees were planted in a guideline level, the runoff of rainwater intercepted by the
trees, always favors the highest elevation of the slope between tree tracks. Furthermore,
Thevathasan and Gordon (1997) measured the increased on nitrification rates near (<2.5 m) to
the poplar row (Populus spp. clone DN 177), in a 7 to 9 years old poplar-barley intercropping,
disc ploughed for the first 4 years, in Ontario, Canada, and attributed that to the poplar leaf
distribution close to the tree row, which increased the aboveground biomass and nitrogen
grain concentration of barley.
The lower heat load during wheat grain filling promoted by eucalyptus in ACS, combined
with subsequent increased duration of grain filling, can mitigate the effect of quantitative and
qualitative reductions of the radiant energy, during the initial stages of wheat growth (Kohli
and Saini 2003). The oat above ground biological yield reached a peak, both where was
applied 80 kg N ha-1 (Table 1 and Fig. 1a) and outside of ACS (Table 1). However, on the
same locations where the growth was better (Table 1 and Fig. 1a), the harvest indexes were
poorer, in exception of the positions E next to the trees, with had a subtle decrease next to the
trees (Table 3 and Fig. 1e). The nitrogen increased the biological yield while decreased the
80
harvest index, to a greater extent of the antagonistic effect, where there were low interaction
between oats and eucalyptus, mainly on the lowest elevation of the slope, between two
adjacent tree tracks (Table 3).
Further studies combining nitrogen levels with other agronomic practices, e.g., cultivars, plant
growth regulators and plant arrangement, are necessary to sustainably increase the yield
potential of small cereals into the integrated systems in subtropical regions.
Conclusion
In subtropical Brazil, oats have the capacity for cohabitate with eucalyptus, in integrated
systems, and nitrogen levels increase the oat yield differently at distances from the trees inside
ACS.
Acknowledgments
This work results from the technical cooperation agreement SAIC / AJU No. 21500.10/00082 signed by Instituto Agronômico do Paraná and Embrapa Florestas.
References
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82
80.0 kg N ha-1
12.0 kg N ha
24
Spikelets
panicle-1
Phytomass (g m-2)
450
b
a
-1
400
350
300
250
20
16
12
8
200
A
B
C
D
E
Positions
150
100
c
A
B
C
D
E
Positions
d
80.0 kg N ha-1
12.0 kg N ha-1
800
1.7
1.6
1.5
1.4
1.3
A
B
C
D
E
Positions
700
e
600
500
400
300
A
B
C
D
E
Positions
Harvest Index
(%)
Yield (kg ha-1)
Grains spikelet-1
50
25
20
15
10
A
B
C
D
E
Positions
Fig. 1 Oat (Avena sativa L. cv. IPR 126) above ground biological yield (a) (80.0 kg N ha -1: Y = 162.18 + 12.52
x, R2 = 96.36, P = 7.5 10-5; 12.0 kg N ha-1: Y = 45.73 + 35.52 x – 1.63 x2, R2 = 68.31, P = 0.007), yield
compounds spikelets per panicle (b) (Y = 7.18 + 1.99 x – 0.83 x2, R2 = 85.46, P = 0.052) and grains per spikelet
(c) (Y = 2.00 – 0.19 x + 0.020 x2 – 5.76 10-4 x3, R2 = 99.72, P = 0.04), yield (d) (80.0 kg N ha-1: Y = 867.81 –
188.71 x + 21.10 x2 – 0.631 x3, R2 = 97.61, P = 0.089; 12.0 kg N ha-1: Y = 274.18 + 38.71 x – 1.68 x2, R2 =
66.55, P = 0.20) and harvest index (e) (Y = 36.07 – 5.86 x + 0.556 x2 – 0.016 x3, R2 = 89.58, P = 0.055) in alley
cropping agroforestry system, at A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track
positioned at the lowest elevation of the slope, between two adjacent eucalyptus (Eucalyptus dunnii Maiden)
double line tracks [20 m (4 m x 3 m)], under nitrogen levels (12.0 kg N ha-1 and 80.0 kg N ha-1 fertilizer), in
subtropical Brazil. Vertical bars denote standard errors.
83
Table 1 Biological yield of oat (Avena sativa L. cv. IPR 126) under nitrogen levels (12.0 kg N ha-1 and 80.0 kg
Aa
Positions
B
C
D
E
F
Mean
-2
Above ground phytomass (g m )
80 kg N ha
-1
212
***
12 kg N ha
-1
b
a 223 a 291 a 324 a 387 a
***
***
***
***
610
a
341
A
Control
136 b 186 a 279 a 193 b 184 b
408
b
231 B
***
***
**
***
***
Control
Mean
174
204
285
258
286
509
***
***
***
***
***
Control
a
m x 3 m)]. Values followed (within column) by the same capital case letters and lowercase letters, are not
significantly different using the Duncan´s test at the 0.05 level of probability. b *, **, *** and ns (within line)
indicates the significance at 0.10, 0.05, 0.01 and non significant, respectively, of the comparison with a control
by the Dunnett two sided test.
84
Table 2 Yield compounds of oat (Avena sativa L. cv. IPR 126) under nitrogen levels (N) [12.0 kg N ha-1(-) and 80.0 kg N ha-1 (+)] in alley cropping agroforestry system (A_E) and
W. 100
W. 100
W. 100 sole 1º
Panicle
Spikelets
Grain
-2
b
1º
(g)
c
2º
Plant (m )
ASP
(m-2)
(panicle-1)
(spikelet-1)
(g) c
(g) d
(g) e
Aa+
B+
C+
D+
E+
F+
80 kg N ha1
ABCDEF12 kg N ha1
219
179
156
204
243
251
219
186
163
211
258
278
14.9
14.9
18.4
23.5
17.2
25.2
209
219
19
181
172
194
228
232
192
182
179
199
232
233
235
10.5
16.3
18.1
18
15.3
19
200
210
16.2
A
B
2.45
2.64
3.27
2.75
2.4
2.96
1.46
1.34
1.48
1.6
1.51
1.4
2.75 A
1.47
0.5
1.21
1.28
0.43
1.02
0.82
1.77
1.53
1.51
1.6
1.72
1.43
0.88 B
1.59
B
A
3.1
2.7
2.7
2.4
2.6
2.6
1.3
1.1
1.1
1.1
1
1.2
1.4
1.1
1
1
1.1
1.1
2.7
1.1
1.1
3.1
3.1
2.7
2.7
2.9
2.7
1.3
1.3
1.1
1.1
1.2
1.2
1.5
1.1
0.9
0.9
0.9
0.8
2.9
1.2
1
Positions
Aa
200
201 * f
12.7 **
1.48
1.61 **
3.1
1.3
1.5
**
ns
ns
B
176
183 **
15.6
*
1.93
1.44
2.9
1.2
1.1
ns
ns
ns
C
175
181 **
18.3
2.27
1.5
2.7
1.1
0.9
ns
ns
ns
D
216
222
20.8
1.59
1.6
*
2.6
1.1
1
ns
ns
ns
E
238
246
16.3
1.71
1.61 **
2.8
1.1
1
F
222
256 Ctl
22.1 Ctl
1.89
1.41 Ctl
2.6
1.2
0.9
Ctl
Mean
204
215
17.6
1.81
1.53
2.8
1.2
1.1
a
positions (P): A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest elevation of the slope, between two adjacent eucalyptus (Eucalyptus
dunnii Maiden) double line tracks [20 m (4 m x 3 m)]. b ASP: Aborted spikelets (panicle-1). Weight of c primary and d secondary grains with husks, from spikelets with two or e one
grains. Values followed by the same capital case letters (within column) are not significantly different using the Duncan´s test. f *, **, *** and ns (within column) indicates the
significance at 0.10, 0.05, 0.01 and non significant, respectively, of the comparison with a control by the Dunnett two sided test.
85
Table 3 Yield and harvest index of oat (Avena sativa L. cv. IPR 126) under nitrogen levels (N) [12.0 kg N ha-1(-)
and 80.0 kg N ha-1 (+)] in alley cropping agroforestry system (A_E) and traditional no till agriculture (F) in
subtropical Brazil
Harvest index
Yield (kg ha-1) d
(%) e
Aa+
486.5 a
*b
21.06
B+
377.2 a
***
15.57
C+
433.3 a
**
13.42
ns
D+
636.4 a
17.29
ns
E+
651.6 a
14.9
F+
743.6 a Control
10.66
80 kg N ha-1 554.8 A
15.48
B
ns
A385.7 a
25.83
ns
B404.9 a
20.47
ns
C540.8 a
18.09
ns
D475.5 a
22.49
ns
E443 b
21.59
F496.2 b Control
10.78
12 kg N ha-1 457.7 B
19.88
A
Positions
Aa
436.1
** b
23.44 ***
B
391.1
***
18.02 ***
ns
C
487.1
15.76
**
ns
D
555.9
19.89 ***
ns
E
547.3
18.24 ***
F
619.9
Control
10.72 Control
Mean
506.2
17.68
a
positions (P): A: 2.8 m, B: 6.4 m, C: 10.0 m, D: 13.6 m and E: 17.2 m away from track positioned at the lowest
m x 3 m)]. Values followed by the same capital case letters (within column) and lowercase letters (within
column inside each position) are not significantly different using the Duncan´s test. b *, **, *** and ns (within
column) indicates the significance at 0.10, 0.05, 0.01 and non significant, respectively, of the comparison with a
control by the Dunnett two sided test. c Estimated with 13% moisture. d Calculated without moisture of grains.
86
6. General conclusions
The oat growth and yield response to the alley cropping agroforestry system are
agronomically acceptable and amenable to improvement through the nitrogen fertilization.
The growth, tillering and grains yield of oat interact with nitrogen levels and positions relative
to eucalyptus inside alley cropping agroforestry system, therefore different nitrogen levels
should be used in positions relative to the trees, to improve sustainably the oat yield potential
in alley cropping agroforestry system.
The oats has morphophysiological conditions for cohabitate with eucalyptus in the lands of
subtropical Brazil.
7. Final thoughts
Inside the alley cropping agroforestry system oats accumulated less above ground phytomass
per plant and remained green (leaves and panicles) for more time near the trees, therefore
agronomic practices that increase the photosynthesis performed in the reproductive structure
as well as its contribution to grain filling, can be an alternative for improve the oat grains
yield inside the arborized integrated systems.
Near the trees, the contribution of tillers to grain yield were very small, suggesting that in
these sites, should be used other agronomic practices which conduct the oat community to the
uniculm growth habit, e.g., increase seeding rate with plant arrangement alteration, and higher
nitrogen levels to increase the main shoot grain yield.
Further studies combining nitrogen levels with other agronomic practices, e.g., specialized
cultivars for cereal production, plant growth regulators or grazing to regulate the growth of
dual purpose taller oats and plant arrangement are necessary to sustainably increase the yield
potential of oat in the integrated systems in subtropical regions.
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GENERAL SUPPLEMENT
Supplement 1 Experimental sketch. Oat (Avena sativa L. cv. IPR 126) under nitrogen levels [12.0 kg N ha1
(clear) and 80.0 kg N ha-1 (dark)] in alley cropping agroforestry system (A_E), at A: 2.8 m, B: 6.4 m, C: 10.0 m,
D: 13.6 m and E: 17.2 m away from track positioned at the lowest elevation of the slope, between two adjacent
eucalyptus (Eucalyptus dunnii Maiden) double line tracks [20 m (4 m x 3 m)] and traditional no till agriculture
(F), in subtropical Brazil.

UNIVERSIDADE FEDERAL DO PARANÁ

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Pedee Ewing, Jim B. Davis, Bradley Pakish, Megan Wingerson, and

Performance of Two Hybrid Clones of Eucalyptus - Alice

NOWE NAWOZY Z PUŁAW