ESTIMATION OF THE PAPAYA CROP COEFFICIENTS FOR IMPROVING IRRIGATION WATER MANAGEMENT IN SOUTH OF HAVANA

Abstract

The papaya (Carica papaya L.) is a main irrigated fruit crop in Cuba and in the tropical and subtropical regions. For environmental and irrigation management purposes, it is important to accurately estimate its crop evapotranspiration and irrigation requirements. The objective of the present study is to determine the crop coefficients (Kc) and the depletion fraction for no stress (p) of the papaya, variety Maradol, as cultivated in southern Havana. Experiments took place during the period March - November, 1997 in an experimental area where soils are compacted red iron soils. The ISAREG irrigation simulation model was applied to those observed data. The calibration of the model consisted in searching the crop coefficients and the depletion fraction for no stress that minimize the differences between observed and simulated available soil water. Several statistical indicators were used to assess the goodness of fit. Results show a good adjustment between observations and model predictions, with the regression coefficient forced to the origin close to 1 (b = 1.01) and a high R2 = 0.86. The root mean square error (RMSE) and the average absolute error (AAE) are small, respectively RMSE = 6.5 mm and AAE = 4.9 mm. After calibration, the model was used to assess the current irrigation scheduling; results show that irrigation dates were anticipated relative to the required and irrigation depths were excessive, thus significant percolation occurred. The ISAREG model will be further used to generate and evaluate alternative irrigation schedules aimed at improved water productivity.