Interannual rainfall variability and soybean yields in Mata Roma municipality, Maranhão

Among the activities affected by rainfall variability, agriculture is one of the most vulnerable. In this sense, this work aimed to relate the interannual rainfall variability with the soybean yields variability in Mata Roma municipality, Maranhão, considering dry and rainy events. For this, for the period from 2003 to 2019, data on average soybean yield and rainfall in this producing region, which is one of the main ones in the State, were analyzed. Monthly rainfall data for the period 1985-2019 were also analyzed and the dry and rainy events were identified in these two meteorological data series. The results showed that rainfall from January to May explains about 99%, on average, of the interannual variation of yields and that occurrence of dry and very humid periods disfavor the soybean crop, causing, in most cases, yields and productions far below the average for the study region. Based on the regression analysis, it was found that maximum average yield of 2942.52 kg×ha?1 was reached with an average rainfall of 1709 mm.