Single crop coefficients for agricultural irrigation in Guyana.

Abstract

Irrigated agriculture is the activity that consumes the most water in the world. The crop coefficient (Kc) is widely used to estimate evapotranspiration (ETc), and is used in various water and soil engineering activities, as a calculation of the water balance. It is important to adjust the Kc values for the specific conditions of each place. A study was conducted in Guyana from 2014 to 2018 where the periods of crop development were established. The meteorological variables were processed for each stage of crop growth and the reference evapotranspiration values were determined. With these values, the crop coefficients were adjusted in the initial, middle and end stages (Kc_ini, Kc_mid and Kc_end respectively), using the FAO 56 method (Allen et al., 1998). The results showed that there is a tendency to overestimate the values of K_ini and underestimate Kc_mid and Kc_end, coinciding with some authors. A close relationship was found between the Kc_mid and Kc_end values according to FAO and the adjusted Kc_mid and Kc_end (R² = 0.9848 and R² = 0.9963 respectively), not with the FAO 56 Kc_ini values and Kc_ini adjusted. It was concluded that with the adjusted Kc values, it is possible to determine the crop water requirements and the irrigation schedule in agricultural areas of Guyana.