PROBABLE WATER DEFICIENCY AND SURPLUS FOR CORN AND SOYBEAN IN THE STATE OF PARANÁ, SOUTHERN BRAZIL

Abstract

We aimed to calculate the probable values ​​of water deficiency (Def) and surplus (Exc) for corn and soybean in the State of Paraná, in order to obtain the best sowing periods. Climatic data (1980 to 2013) were spatialized in a regular grid of 0.25º x 0.25º. The agricultural water balance was calculated daily using the AquaCrop program, with the values ​​added up and grouped into 37 ten-days per year. Frequency distributions were carried out and adherence tests were applied to ten-days periods to adjust them to probability density functions (PDF’s). The probable decennial values ​​of Def and Exc were determined at 10%, 25% and 50% of probability. Gamma and Exponential were the PDF’s that showed adherence to the greatest number of locations, while Uniform can be discarded for future adjustments. In the State of Paraná, on average, the lowest Def occurs when soybean is sown from December 27th to 31, while the lowest Exc occurs from October 8th to 17. For season and off-season corn, the smallest Def’s occur when they are sown from December 17th to 26 and March 22nd to 31, respectively, and the smallest Exc’s depend on the level of probability.