Determining the Amount of Water Use and Evapotranspiration of Bean Using Tafteh, Pasquale and Raes Methods under the Conditions of Drip and Furrow Irrigation

Due to the limitation of water resources, proper use of water is necessary, and the use of appropriate irrigation methods in fields is an appropriate strategies to use water. Water stress can affect crop yield in the field. Therefore, the correct method of irrigation and management of water consumption is one of the basic issues in farms. The deficit irrigation strategy with the water requirement supply approach can be considered as a practical and efficient technique to ensure more crop yield, without compromising the physiological processes and yield. Therefore, the scope of this research is to estimate the amount of water consumed and the amount of evapotranspiration of the bean plant with the aim of evaluating the field conditions and comparing it with Tafteh, Pasquale and Raes methods.

The present study aims to determine the amount of water use and evapotranspiration of bean using Tafteh, Pasquale and Raes methods and based on the inverse solution of the yield production function in Markazi Province and at the Khomin Bean National Research Station at an altitude of 1930 meters above sea level with a length of 49 degrees and 57 minutes of latitude and 33 degrees and 39 minutes of latitude were implemented in 2016 and 2017. In this experiment, the irrigation treatment including furrow and drip-tape as the main factor and, the values of water requirement including 100, 75 and 55% of water requirement as a sub-factor and in the form of split plots in the form of randomized complete blocks design were done in three replications. Cultivated variety was of native type and its planting time was on the 10th and 9th of June respectively in the first and second year. Drip irrigation tapes were placed on the stacks and irrigation was carried out in the same way until the seedling was fully established in the stage of emergence of the third three leaves.

The highest seed yield with an average of 2683 kg/ha was obtained in the furrow irrigation method and by providing 100% of the water requirement. In evaluating evapotranspiration, the root mean square error (RMSE) in Tafteh, Pasquale and Raes methods were 0.160, 117.8 and 0.185 mm respectively and the root mean square normal error (RMSEn) were 0.448, 0.330 and 0.518 percent respectively. The index of agreement or compatibility (d) in Tafteh, Pasquale and Raes methods were 0.295, 0.600 and 0.081% respectively. In the investigation of irrigation water amounts, the root mean square error (RMSE) in Tafteh, Pasquale and Raes methods was 156.7, 117.5, and 181.3 mm, respectively, and the root mean square normal error (RMSEn) was 0.446, 0.335 and 0.516 percent respectively. The index of agreement or compatibility (d) in Tafteh, Pasquale and Raes methods were 0.324, 0.602 and 0.118% respectively.

In general and according to the statistical results, Tafteh, Pasquale and Raes methods had an acceptable estimate of the amount of irrigation water and the amount of evapotranspiration in the furrow and drip conditions under different amounts of water requirement. Therefore, they can be used as appropriate tool in the estimation of water use in the studied area.