Evaluation of Water Productivity Indicators in Wheat Irrigated Fields

Because of the scarcity of water resources in Iran, agricultural water productivity indices measuring and analyzing is very important. Purposes of this study, are to simulate the components of water balance in field level, to predict moisture in soil profile and to analyze water productivity indices in wheat irrigated fields for Neyshabur plain. Three wheat farms were selected at different parts of Neyshabour plain in 2008 2009. All required data for running SWAP model were collected. The model was calibrated and validated for all soil hydraulic parameters and wheat agricultural characteristics in each field, separately. Results show that SWAP could predict moisture profiles satisfactorily, in different times and depths. Water productivity indices were calculated using components of water balance, by SWAP. Averages of these indices that hereafter we called as T WP (yield to crop actual transpiration ratio), ET WP (yield to crop actual evapotranspiration ratio), ETQ WP (yield to crop actual evapotranspiration plus deep percolation ratio) and Irr WP (yield to total applied water ratio) were 1.28, 0.99, 0.6 and 0.88, respectively. According to results of this study, it is possible to increase wheat yield by 14% if irrigation scheduling is planned correctly. Moreover, deficit irrigation by 30% show no significant effect on yield. These results indicate that using a appropriate irrigation scheduling, in addition to reducing consumptive water, ETQ WP and Irr WP indices will increase up to 48 and 61 percent, respectively. High evaporation rete at initial stages of crop growth due to traditional irrigation method, has decreased ET WP by 28% compared to T WP. The ET WP value could be improved employing agricultural practices like mulching or using subsurface irrigation. Decreasing applied water depth did not have notable effect on ET WP and T WP indices, but resulted in increasing ETQ WP and Irr WP values remarkably.