Physiological determinants of maize and sunflower grain yield as affected by nitrogen supply

Utilisation of nitrogen (N) has been closely related to increases in crop productivity. However, not all crops respond similarly and the objective of this study is to identify physiological processes that determine responses to N supply for maize and sunflower. Grain yield in maize (range: 210-1255 g m(-2)) was greater and more responsive to N supply than in sunflower (1106-555 g m(-2) in carbohydrate equivalents) over a wide range of total N uptake (3->20 g N m(-2)). In maize, differences in grain yield among levels of N supply were associated more with variation in biomass than in harvest index. in sunflower, differences in grain yield (in carbohydrate equivalents) among levels of N supply were related similarly to variation in both biomass and harvest index. The decrease in biomass production with decreasing N supply was associated with decreases in both radiation interception and radiation use efficiency (RUE). Decreased interception was due to effects of N supply on reducing canopy leaf area, whereas the reduced RUE was associated with decreased SLN. Total biomass production in maize was more responsive to N supply than in sunflower. The major determinants of the differences in response of biomass accumulation to N supply found between maize and sunflower are: (i) sunflower tends to maintain SLN with increase in partitioning of N to leaves under N limitation whereas maize tends to maintain leaf area with increase in partitioning of biomass to leaves and (ii) the ability of maize to maintain N uptake following cessation of leaf production. (C) 2009 Elsevier B.V. All rights reserved

A species-specific critical nitrogen dilution curve for sunflower (Helianthus annuus L.)

For annual and perennial crops, mathematical models have been developed to describe tissue nitrogen (N) dilution during crop growth and to estimate the plant N status applying the N nutrition index (NNI), the ratio between the actual tissue N concentration ([N]) and the tissue N concentration needed to obtain the maximum instantaneous crop growth rate (critical tissue N concentration, [N] ). The relationship between shoot [N] and shoot dry matter (DM, tha ) can be described by an allometric power equation: [N] =aDM , where a and b are crop-specific parameters. Critical N dilution curves (CNDC) have been determined for several C crops but not specifically for sunflower (Helianthus annuus L.). The objectives of this work were to (i) determine and validate the N dilution curves for critical, minimum, and maximum [N] for sunflower from the juvenile stages to the end of flowering, (ii) compare the critical curve with published CNDCs for other C crops, and (iii) estimate the range of variation of NNI for different levels of N fertilization and irrigation. A wide range of field experiments from Argentina, Australia, France, Italy, and Spain was used to establish the dilution curve for sunflower and to independently validate it. The fitted CNDC [N] =4.53DM yielded lower values for [N] than references used until now for diagnosis and decision making in sunflower. The value of parameter a was generally similar to that of other C species, but the value for parameter b differed. This was possibly associated with species differences in dry mass partitioning, and justified the development of a sunflower-specific CNDC. A preliminary reference curve for maximum [N] suggested an evolution from the juvenile stages to the end of flowering similar to that of [N] . Minimum [N], in contrast, appeared to be more constant over time. Relationships between relative grain yield and NNI across a range of locations indicated that in general, maximum grain yield was reached around NNI=0.8, although at one location this was around NNI=1.0. The CNDC can provide useful applications for crop modeling, N status diagnosis, and N fertilization decision

Zoneamento climático associado ao potencial produtivo da cultura do café no Estado de Minas Gerais Climatic zoning associated to the productive potential of coffee crop in Minas Gerais State, Brazil

Os sistemas de informações geográficas podem ser considerados instrumentos para mapear e indicar respostas às várias questões sobre o planejamento urbano e regional, o meio rural e levantamento dos recursos renováveis. A execução do zoneamento climático para a cultura do café, utilizando-se sistemas de informações geográficas, proporciona resultados mais satisfatórios, visto que os dados inicialmente coletados são armazenados, facilitando sua manipulação e análise e exibindo um resultado final de melhor qualidade, quando comparado com outros métodos mais tradicionais. As características agroclimáticas das diversas regiões influenciam, diferentemente, a produtividade final da cultura do café. Assim, este trabalho teve como objetivo analisar o grau de correspondência entre o zoneamento climático para a cultura do café e o potencial produtivo da cultura no Estado de Minas Gerais. O zoneamento climático mostrou-se eficiente na delimitação das regiões climaticamente homogêneas quanto à capacidade produtiva da cultura do café no Estado; Minas Gerais apresenta 37% de seu território com condições adequadas ao cultivo do café, 45% com alguma restrição e 18% são considerados inaptos; as áreas aptas ao cultivo do café se concentram no Centro-Sul do Estado.<br>The geographical information system (GIS) is a data management computational program, which is used to capture, store, recover, analyze and exhibit the geographically referenced space data. So, it is an important tool in elaboration of the climatic zonings, besides making the work faster and exhibiting a better-quality final result as compared to other traditional methods. The climatic characteristics of the areas may influence the final productivity of the coffee crop in different ways. Thus, the objective of this study was to analyze the degree of correspondence between climatic zoning and the productive potential for coffee crop in Minas Gerais State, Brazil. It was found that the climatic zoning was efficient to define the homogeneous areas in relation to the productive capacity of coffee crop; 37% of Minas Gerais territory has the suitable conditions for coffee crop, whereas 45% might be cropped with some restriction, and 18% considered as inadequate. The potential areas for coffee crop are concentrated in the Central-Southern part of the State

Modelos agrometeorológicos de estimativa da duração do estádio floração-maturação para três cultivares de café arábica

Modelos agrometeorológicos que relacionam condições ambientes, como temperatura do ar e disponibilidade hídrica no solo, com a fenologia do cafeeiro são importantes para subsidiar os programas de previsão de safra de café do Brasil. O objetivo foi parametrizar e testar diferentes modelos agrometeorológicos para a estimativa da duração do estádio floração-maturação para diferentes cultivares de café arábica. Dados fenológicos das cultivares Mundo Novo, Catuaí e Obatã IAC 1669-20 foram obtidos de experimentos em Campinas e Mococa nos anos agrícolas de 2001/2002 a 2007/2008. Os anos de 2001/2002 a 2004/2005 foram utilizados na calibração e os de 2005/2006 a 2007/2008 no teste dos modelos. Consideraram-se três modelos de acumulação com base em evapotranspiração potencial (ETp), real (ETr), combinação entre ETr e ETp (ETr-ETp) e dois em graus-dia clássico (GD ) e corrigido pelo fator hídrico (GDcorr), para considerar a influência de períodos com deficiência hídrica durante a frutificação. Resultados indicaram que os modelos com correção pelo fator hídrico (ETr, e GD corr) tiveram estimativas da duração do estádio floração-maturação com maior consistência. Os modelos que consideram durante todo o estádio fenológico da floração-maturação valores de ETr de 746, 762 e 799 mm ou de GDcorr de 2733, 2816 e 3008 GD , respectivamente, para as cultivares Mundo Novo, Catuaí e Obatã IAC 1669-20, podem ser considerados consistentes parâmetros para a estimativa da duração deste subperíodo. Nos modelos parametrizados houve estimativas consistentes da duração do estádio floração-maturação. Os resultados confirmam a necessidade de se considerar o fator hídrico para a quantificação das somas térmicas, seja considerando ET ou graus-dia

Substratos para cultivo de feijoeiro em vasos com fertirrigação Substrates for common bean grown in flowerpots with fertirrigation

Considerando a necessidade de se identificar um substrato apropriado para o cultivo de feijoeiro em vasos - objetivo deste trabalho - foram desenvolvidos dois experimentos em casa-de-vegetação, durante o ano de 2005, com a cultivar de feijoeiro TPS Nobre. Sete substratos foram avaliados: Plantimax®, casca de arroz carbonizada, vermiculita, areia, casca de arroz carbonizada + 20% de Plantimax®, casca de arroz carbonizada + 20% de vermiculita e casca de arroz carbonizada + 20% de areia. O delineamento experimental utilizado foi inteiramente casualizado, com cinco repetições. Os nutrientes foram fornecidos semanalmente por fertirrigação e a água foi adicionada de maneira a ser reposto o volume consumido. Nos substratos avaliados constataram-se características químicas e físicas diferenciadas. Caracterizou-se o substrato comercial Plantmax® pela elevada capacidade de troca de cátions (30,6 cmol c L-1) e maior capacidade de armazenamento de água por unidade de volume, o que contribuiu para a superioridade na produção de fitomassa seca das plantas e dos componentes do rendimento de grãos de feijão. O substrato comercial Plantmax® é apropriado para o cultivo de feijoeiro em vasos com o uso de fertirrigação.<br>The objective of this paper was to identify an appropriate substrate for common bean grown in flowerpots. The experiments were carried out in a green house during 2005, with the TPS Nobre common bean cultivar. Seven substrates were evaluated: Plantimax®, carbonized rice husks, vermiculite, sand, carbonized rice husks + 20% of Plantimax®, carbonized rice husks + 20% of vermiculite and carbonized rice husks + 20% of sand. The experimental design was completely randomized with five replications. The nutrients were supplied weekly to fertigation and the water was added to refill the consumed volume. The evaluated substrates had different chemical and physical characteristics. The commercial substrate Plantmax® was characterized by high cations capacity exchange (30.6 cmol c L-1) and the highest water storage capacity per volume unit, which contributed for the higher dry matter yield of the plants and for common bean grains yield components. Therefore, we concluded that commercial substrate Plantmax® is appropriate for the common bean cultivation in flowerpots with fertigation