Spatial variability of the ten-day rainfall in the months in which the sowing of soybean and winter corn begins in the state of Mato Grosso

Abstract

Knowledge of the spatial variability of rainfall in the state of Mato Grosso is very important in decision mak­ing, especially in agriculture, aiming at proper planning and optimization of water resources to reduce envi­ronmental impacts and increase profitability. The spatial distribution of this variable through geostatistical methods has been highlighted, but it is needed to select the best semivariance model for proper data inter­polation. Thus, the objective of this study was to evaluate the spatial and temporal variability of rainfall in the state of Mato Grosso by ordinary kriging, referring to ten-day periods in October and January, a period of great importance for the soybean crop and the cultivation of second crop corn. It was used the 75th percen­tile of the rainfall of 177 state posts of Mato Grosso and neighboring states. It was observed, through the RE, SDRE and GD values, that the exponential model adjusted better to the semivariograms. Spatial variability was observed in all the analyzed periods of ten days, and the north region of the state is the one which starts the rainy season and that has the highest rainfall rates. The ten-day average rainfall in October did not exceed 20 mm, resulting in the germination and establishment of soybean in the field, and the ten-day aver­age for January was close to 52 mm, which is considered to be harmful to the mechanical harvesting of early maturing soybeans and favorable to the grain filling of the varieties with average and late cycle, being still beneficial to the cultivation of second crop corn.