Abstract
In recent years, maize has become one of the main alternative crops for the autumn–winter growing season in the central‐western and southeastern regions of Brazil. However, water deficits, sub‐optimal temperatures and low solar radiation levels are common problems that are experienced during this growing season by local farmers. One methodology to assess the impact of variable weather conditions on crop production is the use of crop simulation models. The goal of this study was to evaluate the effect of climate variability on maize yield for a subtropical region of Brazil. Specific objectives for this study were (1) to analyse the effect of El Niño Southern Oscillation (ENSO) on precipitation and air temperature for four locations in the state of São Paulo and (2) to analyse the impact of ENSO on maize grown off‐season for the same four locations using a crop simulation model. For each site, historical weather data were categorised as belonging to one of three phases of ENSO: El Niño (warm sea surface temperature anomalies in the Pacific), La Niña (cool sea surface temperature anomalies) or neutral, based on an index derived from observed sea surface temperature anomalies. During El Niño, there is a tendency for an increase in the rainfall amount during May for the four selected locations, and also during April, mainly in three of the locations, resulting in an increase in simulated maize yield planted between February 15 and March 15. In general, there was a decrease in the simulated yield for maize grown off‐season during neutral years. This study showed how a crop model can be used to assess the impact of climate variability on the yield of maize grown off‐season in a subtropical region of Brazil. The outcomes of this study can be very useful for both policy makers and local farmers for agricultural planning and decision making. Copyright © 2009 Royal Meteorological Society