CONICET | Buscador de Institutos y Recursos Humanos

Climate variability is examined and discussed in this work, emphasizing its influence over the fluctuation ofsoybean yield in the Pampas (central-eastern Argentina). Monthly data of rainfall, maximum and minimum temperatures,thermal range and seasonal rainfall were analysed jointly with the soybean yield in the period 1973-2000. Low-frequencyvariability was significant only in the minimum temperature during November in almost all the stations. This situationis favourable to the crop since during this month, seed germination, a growth stage sensitive to low temperatures, takesplace. In the crop?s core production region, 72% of the series of soybean yield presented a positive trend. Except inyears with extreme rainfall situations, interannual variability of the soybean yield is in phase with the seasonal rainfallinterannual variability. During these years, losses in the soybean crop occurred, with yield negative anomalies greater thanone standard deviation. Soybean yield showed spatial coherence at the local scale, except in the crop?s core zone. Theassociation between each climate variable and yield did not show a defined regional pattern. Summer high temperatureand rainfall excesses during the period of maturity and harvest have the greatest negative impact on the crop, whilst higherminimum temperatures during the growing season favour high yields. The joint effect of climate variables over yield wasstudied with multivariate statistical models, assuming that the effect of other factors (such as soil, technology, pests) iscontained in the residuals. The regression models represent the estimates of the yield satisfactorily (high percentage ofexplained variance) and can be used to assess expected anomalies of mean soybean yield for a particular year. However,the predictor variables of the yield depend on the region. Copyright  2007 Royal Meteorological Society

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