Simulating maize yield in sub-tropical conditions of southern Brazil using Glam model

The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales (greater than 100,000 km2), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small spatial scales (lower than 10,000 km2). Large area models can contribute to monitoring or forecasting regional patterns of variability in maize production in the region, providing a basis for agricultural decision making, and Glam‑Maize is one of the alternatives

Interactive effects of water-table depth, rainfall variation, and sowing date on maize production in the Western Pampas

tShallow water-tables strongly influence agro-ecosystems and pose difficult management challenges tofarmers trying to minimize their negative effects on crops and maximize their benefits. In this paper, weevaluated how the water-table depth interacts with rainfall and sowing date to shape maize performancein the Western Pampas of Argentina. For this purpose, we analyzed the influence of water-table depthon the yields of 44 maize plots sown in early and late dates along eight growing seasons (2004–2012)that we rated as dry or wet. In addition, we characterized the influence of the water-table depth onintercepted radiation and crop water status by analyzing MODIS and Landsat images, respectively. Thefour conditions we evaluated (early sown-dry growing season, early-wet, late-dry, late-wet) showedsimilar yield response curves to water-table depth, with an optimum depth range (1.5–2.5 m) whereyields were highest and stable (∼11.6 Mg ha−1on average). With water-table above this range, yieldsdeclined in all conditions at similar rates (p > 0.1), as well as the crop water status, as suggested bythe Crop Water Stress Index, evidencing the negative effects of waterlogging. Water-tables deeper thanthe optimum range also caused declines of yield, intercepted radiation and crop water status, beingthese declines remarkably higher in early maize during dry seasons, evidencing a greater reliance of thiscondition on groundwater supply. Yield in areas with deep water-tables (>4 m) was significantly reducedto between a quarter and a half of yields observed in areas with optimum water-tables. Rainfall occurredaround flowering had a strong impact on maize yield in areas with deep water-tables, but not in areaswith optimum depth, where yields showed high temporal stability and independence from rainfall in thatperiod. Our study confirmed the strong influence of water-table on rainfed maize and provides severalguidelines to help farmers to take better decisions oriented to minimize hydrological risks and maximizethe benefits of shallow water-tables

Desempenho agronômico da cultura do girassol em diferentes condições edafoclimáticas do Sudeste paranaense

O objetivo do presente trabalho foi quantificar as faixas de rendimentos acessíveis em diferentes condições edafoclimáticas do Sudeste paranaense e hierarquizar os fatores relacionados à variabilidade dos rendimentos observados. Foram avaliadas 26 situações culturais em 13 estabelecimentos familiares, em 2007 e 2008. As variáveis de componente do rendimento e estado nutricional da cultura foram determinadas pela coleta de dados em campo, e as variáveis de estado hídrico foram estimadas com o uso de um modelo de simulação do balanço hídrico. Estas foram analisadas pela Análise de Componentes Principais, classificando-se, posteriormente, as observações pela Análise de Agrupamento. Foram utilizadas as cultivares BRS 122, CATISSOL e Helio 250. Foram grupados os valores de rendimento de aquênios em três classes, segundo os seguintes valores médios: rendimentos altos: 1995 kg ha-1; rendimentos médios: 1359 kg ha-1; rendimentos baixos: 961 kg ha-1. Os valores de rendimento de óleo também foram agrupados nas seguintes classes, segundo os seguintes valores médios: rendimentos altos: 927 kg ha-1; rendimentos médios: 543 kg ha-1; rendimentos baixos: 423 kg ha-1. A variabilidade dos rendimentos (aquênios e óleo) foi explicada pela variabilidade no número de aquênios por capítulo. Em 2008, a variabilidade no número de aquênios por capítulo esteve correlacionada à deficiência hídrica em R1-R4 e R4-R6 e aos teores de Ca, B e P no tecido foliar. Ocorreu inibição competitiva entre K e Mg, porém este fenômeno não esteve correlacionado à variabilidade do número de aquênios por capítulo. Ocorreu estresse hídrico durante o enchimento de aquênios, porém este não explicou a variabilidade no rendimento de aquênios e de óleo