Quantitative and qualitative changes of drain water by installation of controlled drainage in Moghan plain lands

Controlled drainage is one of the practices which aim to improve the conditions of the growing environment, increase the plant's yield and reduce the losses of chemical fertilizers and consequently reduces environmental pollution. The present study was conducted to investigate the effect of controlled drainage with constant and variable depth on discharge and salinity changes, as well as transfer of drainage nitrate and phosphorus during the growing season in the dominant products of Moghan plain, barley and corn. For this purpose, three treatment included, Free Drainage (FD) or conventional drainage is used to area, Controlled Drainage with a control level of 70 cm below the soil surface (CD70) and Controlled Drainage with variable control during the growing season (CDch) and each treatment in Three repetitions were considered. The results of the study showed that discharge rate of drainage in barley field in CD70 and CDch treatments was 55.0 and 44.9 percent lower than free drainage respectively, and in corn, decreased by 51.2 and 43.8 percent, respectively. The amount of nitrate losses in barley filed in the CD70 and CDch treatments was 48.4 and 42.4 percent, compared to free drainage and 50.8 and 46.0 percent, respectively. Changes in phosphorus concentration in treatments were low, but phosphorous losses between controlled drainage treatments and free drainage showed a significant difference at level of one percent. drainage salinity in controlled drainage treatments was lower than free drainage treatment. Controlled drainage treatments, in addition to reducing the amount of drainage volume, have improved the quality of drainage in terms of nitrate, phosphorus and salinity.