Specific adjustment functions for daily crop coefficient in Brazil

Crop coefficient (Kc) has a key role in order to reach high precision crop evapotranspiration data. This study aimed to obtain functions to estimate the daily crop coefficient (Kc) in specific locations and check advantages in its use compared with grouped and generalized values. For that purpose,daily values of Kc based on days after planting named “Kc(DAP)”were estimated by specificadjustment functions and compared to field measured crop coefficient values of peanut, sugarcane, bean, corn and soybean. Estimated crop responses were compared and quatitatively analyzed through linear regression, index "d" of performance, index "c" of agreement and statistical deviation technique. It was possible obtain functions for setting daily crop coefficient for both studied crops and sites. Daily crop coefficient functions improved the accuracy of estimated crop evapotranspiration when compared to widely used values, by better reflect local climate and soil conditions of the crops; and, also for grouped values, because the curve decreases the variability of the data estimated daily.