Water Table Fluctuation, Drainage Rate and Nitrogen Dynamic in the Farms of Sugarcane Cropping with Controlled Drainage System

In arid and semiarid regions، controlled drainage is the next logical step towards improving water management in irrigated agriculture and reducing the environmental impacts of subsurface drainage flow. Controlled drainage has been practiced in humid areas for a long time. In this research a controlled drainage system in Khuzestan Province، Southwest Iran was tested as a strategy for continuous water table management with the benefits of optimizing water use and reducing unnecessary drainage and nitrogen losses from agricultural fields. To study the feasibility and performance of water table management، Field experiments were carried out on a 63. 41 ha with 3 treatments on the farms under subsurface drainage of Imam Khomeini''s sugarcane agro-industry. 3 treatments compared consisted of a free drainage treatment (FD) and tow controlled drainage treatment with water table controls set at 90 centimeter (CD90) and 70 centimeter (CD70) below the soil surface. Collected data during a sugarcane growing season included water table depth، drained volume، nitrate-nitrogen and ammonium-nitrogen concentration in the drainage water and groundwater. Controlled drainage had a significant hydrological and environmental effect during studding period. Compared with CD، the total drain outflow from CD70 and CD90 area were 62. 48 and 48. 98% less، respectively. Compared with CD، the total amounts of nitrate-nitrogen and ammonium-nitrogen in drain outflow were about 45 to 60 % and 50 to 65 % less، respectively. Nitrate-nitrogen and ammonium-nitrogen concentration in the both of drainage water and groundwater did not differ significantly in all of the treatment. These data suggest that controlled drainage can be applied at big scale in the Khuzestan Province with the most installed subsurface drainage in Iran، with advantages for water conservation and environment.