Onset and end of the rainy season and corn yields in São Paulo State, Brazil

Abstract

The relationships between the rainy season and corn yields in São Paulo State were investigated. The results showed that rainfall and corn yields are strongly positively correlated in most of the region, particularly in the northeastern, eastern, northwestern and western parts of the state (i.e. values are higher than 0.5 significant at 95% confidence level). The analysis of the trends in the duration of the rainy season and the associated accumulated precipitation showed a tendency of higher precipitation and shorter rainy seasons. It has been suggested to be due to global warming. Although rainfall and crop yields were positively correlated, an increase in heavy rainfall events in future may lead to landslides, flash floods and consequently crop damage. During the period 1970-2003 there was an increase of the rainy season and rainfall in strong El Niño episodes while in the case of La Niña events the rainy season was shorter and the rainfall decreased. Results of case studies considering the 1997-98 El Niño and the 1998-99 La Niña suggested that the increase (decrease) of the duration of the rainy season during the El Niño (La Niña) event is associated with the increase (decrease) of corn yields in São Paulo State. Further studies with a record of corn yields longer than 14 years and considering other El Niño/La Niña episodes are needed to obtain a firm connection between corn yields and ENSO events in São Paulo State.