Estimation of Basil Water Requirement for Effective Field Water Management

It is very important to estimate the actual water requirement of the plant for irrigation planning and hence effective water management in the field. The purpose of this study was to evaluate the conventional methods of estimating crop water demands and the actual water requirement of basil plant under field conditions. For this purpose, an experiment was carried out on three separate hectares, with three different methods of estimating basil water requirement, including the method of Standard Class A evaporation pan, the method of TethaProbe soil moisture set, and a proposed weighing micro-lysimeter method. Besides, the study compared four irrigation treatments including full irrigation (FI) and deficit irrigation at (DI 80%), (DI 60%), and (DI 40%) of water requirement for two consecutive years in 2017 and 2018. The results showed that the highest amount of basil evapotranspiration was measured at 11.2 mm/day, 53 days after planting. Also, basil crop coefficient values at the initial stages, development, middle, and end of growth were 0.63, 1.08, 1.12, and 0.97 respectively, and the highest basil coefficient in the 25th of July was equal to 1.26. The highest yield of fresh matter in the direct method of estimating water demand was obtained at 5998 and 5966 kg ha^-1, respectively, in 2016 and 2017 in full irrigation. Also, the results of this study showed that the proposed lysimeter method improved the method of Class A pan and soil sampling by, respectively, 10% and 8% water consumption, and yields by 10% and 5%, respectively. Also, with this method, the maximum economic return was 4186 Rials per cubic meter of water.