EXPERIMENTAL AND EMPIRICAL ESTIMATION OF REFERENCE CROP EVAPOTRANSPIRATION

Abstract

Efficient and good water management strategy requires knowledge of crop water use of which reference evapotranspiration (RET) and crop curves are important inputs. Field experiments bahama grass (cynodon dactylon) were conducted to estimate consumptive and four drainage microlysimeters microlysimeters. were installed. using one weighing The grass was planted on 12m by 16m plot in which the The weighing microlysimeter principles using mercury-in-glass use on manometer. was construction Its calibration based on hydraulic was carried out using a static load process. Ten years of climatic data were used to estimate following empirical methods; Hargreaves (HG) models. Penman (PEN), reference Jensen-Haise evapotranspiration using the (J-H) , Blaney-Criddle(B-C) and The values obtained were compared to experimental values and were also subjected to standard statistical analysis. Crop curves were obtained from the ratio oflysimeter to reference evapotranspiration values (using empirical formulae). The crop curves were presented as a function of independent variables which were Days After Planting (DAP) and Thermal Time (T>T). For the crop curves based on DAP, the coefficient of determinatioruk/) and standard errors (SE) in the crop coefficients (K) estimates were 0.90 and 0.17 respectively for the J-H ; 0.90 and 0.09 for PEN; 0.89 and 0.07 for B-C; 0.81 and 018 for HG. Based on TT method, R2 and SE for J-H were 0.90 and 0.18 respectively. 0.90 and 0.09 for PEN; 0.89 and 0.07 for B-C; and 0.81 and 0.18 for HG.