Mehdi Zangiabadi
Abstract
Measuring the actual evapotranspiration of rice is very important for appropriate and optimal water management in the Northern provinces of Iran. The present study aimed to measure the actual evapotranspiration for two Shiroudi and Hashemi cultivars of rice, in paddy fields of Sari Agricultural and Natural ...
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Measuring the actual evapotranspiration of rice is very important for appropriate and optimal water management in the Northern provinces of Iran. The present study aimed to measure the actual evapotranspiration for two Shiroudi and Hashemi cultivars of rice, in paddy fields of Sari Agricultural and Natural Resources University (SANRU). For this propose, six drainage lysimeters were designed and constructed. After cultivating rice inside the lysimeters, the amount of precipitation, irrigation water, and deep percolation were measured in 5-days intervals. Investigation of the lysimeter results showed differences between water requirement and also deep percolation of the two studied cultivars in growth period (seeding to harvest): water requirement was 351 and 397 mm and the deep percolation was 48 and 97 mm, for cultivars Shiroudi and Hashemi, respectively. Also, the crop coefficients were obtained by comparison of the lysimeter’s actual evapotranspiration and 14 indirect methods of reference evapotranspiration estimation. Considering the cultivars and the estimating method, the crop coefficients were in the following ranges: 0.73-1.12 for the initial stage, 0.83-1.41 for the middle stage, and 0.64-1.15 for the final stage. Also, the average estimation Error Percentage (PE) of the resulting crop coefficients compared to the recommended coefficients of FAO-Penman-Monteith method, is 11%, 11% and 8% for Hashemi cultivar and 15%, 23%, and 16% for Shiroudi cultivar, in initial, middle and final stages, respectively; which shows the necessity of determining crop coefficients for each cultivar under local conditions. The coefficients obtained in the current study can be useful to calculate the water requirements of Hashemi and Shiroudi cultivars based on indirect estimation methods for designing water projects and water delivery in the irrigation and drainage networks in the research area.