Corn and soybean water deficit at different phenological stages and Aquacrop model evaluation

Doctoral thesis abstract

Abstract

The agricultural sector in the country has presented unprecedented changes in the last years; among the transformations, it outlines the growth in the production of summer grains, particularly soybean. The growth in grain production was based in the increase of the sown area, since yields have not changed being low and variable.  The main environmental limitation of corn and soybean in drought is water availability, given the inter-annual variability of precipitations (PP) that do not cover the requirements, generating water deficiencies in any stage of the cycle.  This work pretended to determine, during four seasons, soybean and corn yields in water welfare situations and to quantify grain losses caused by water deficit at different stages of the cycles. Additionally, FAO´s Aquacrop model, which simulates crop yields with different water availabilities, was evaluated. The experimental methodology applied in the field trials was aimed to control the water available at different stages of crop and soybean cycles, through the application of irrigation in water welfare stages and PP interception in water deficit stages. The medium yields achieved in water welfare conditions were 14.400 kg ha-1 for corn and 6000 kg ha-1 for soybean. The major yield losses were noted with water deficiencies situated within the critical period (PC), these were 43% for corn and 35% for soybean. Water deficiencies during non-critical periods provoked yield drops of 25% in corn and 15% in soybean and deficiencies accumulated during vegetative period and PC did not cause greater losses than the ones observed for deficiencies only in the PC. The Aquacrop model estimated accurately corn and soybean yields in situations of favorable water availability, whereas simulations were poor in conditions of severe water deficiencies.