Estimation of rice evapotranspiration using a microlysimeter technique and comparison with FAO Penman-Monteith and Pan evaporation methods under Moroccan conditions

This paper reviews field measurements of evapotranspiration from paddy rice fields ( ET) in an experimental station in the Gharb region of Morocco, during the summer seasons in 1995 and 1996. The results showed that the seasonal average water consumption of rice was 6.7 mm . day(-1) with a maximum value of 8.3 mm . day(-1) during the panicle enlargement stage (R2). The average daily ET for 1996 was compared with US Class 'A' open pan evaporation (Ep) and with reference evapotranspiration (ET0) calculated using a validated FAO Penman-Monteith equation. Both methods gave good estimates of ET with a correlation coefficient of 0.78 (P < 0.001, slope = 1.06) with Ep and 0.79 with ET0 (P < 0.001, slope = 1.3). The derived mean crop coefficients were 1.06 and 1.3, respectively, for the average of the two years. The cumulated ET over the growing season was nearly equal to the cumulated Ep, and greater by about 20% of cumulated ET0. This superiority might be attributed to an advective energy transferred from areas surrounding the rice zone activated by wind speed.