YIELD RESPONSE FACTOR (KY) FOR WINTER CORN CROP IN THE REGION OF DOURADOS, MS, BRAZIL

ABSTRACT Plant yield is strongly influenced by the amount of water used by it. In this sense, yield response factor (Ky) allows evaluating the decrease in yield as a function of the evapotranspiration that occurs, which may be an important tool for harvest forecasting. Therefore, this study aimed to determine Ky for winter corn crop grown in the region of Dourados, MS, Brazil. The yield function analysis based on the water factor, which requires actual (Ya) and maximum (Ym) yield data, as well as actual (ETa) and maximum (ETm) evapotranspiration, was used to adjust Ky. Ym was assumed to be 8,820 kg ha−1, while Ya was obtained for each season from the database SIDRA from IBGE. ETm and ETa were estimated by sequential daily water balance, considering four different sowing dates (all in the off-season). In total, seasons from 2001 to 2013 were analyzed. The high Ky value obtained (1.22) for winter corn crop showed its high sensitivity to water deficit. Its yield is strongly influenced by water availability so that for every 1% reduction in evapotranspiration, there is a 1.22% yield reduction.