INFLUENCE OF SUBSURFACE TILE DRAINAGE OPERATIONAL PERFORMANCE ON NUTRIENT LOSSES UNDER SEMI-ARID ENVIRONMENT

An appropriate designed subsurface tile drainage system plays an important role in agricultural productivity, reclamation of water logging and also minimizes nutrient losses with better crop management practices. A field study was conducted to find nutrient losses from the subsurface tile drainage system during the year 2011. The tile drainage system was installed under Swabi Salinity Control and Reclamation Project (SCARP) in July, 1997 in the North-West of Pakistan. The study area is being drained by nine subsurface tile drains spaced 100 to 150 m and length ranging from 500 to 700m at design depth of 1.5 m from the ground surface. Drainage water was collected from these tile drains on a monthly basis for the measurement of the drainable amount of macro nutrients. Ammonium, nitrate and potassium losses from unblocked and partially blocked tile drains were 90, 230, 130 g month(-1) ha(-1) and 110, 125 and 144 g month(-1) ha(-1), respectively. Phosphorus losses were 0.53 g month(-1) ha(-1) from unblocked and 0.44 g month(-1) ha(-1) from partially blocked tile drains of the system. Our results also indicated that copper (Cu), iron (Fe) and zinc (Zn) concentrations were considerably higher in blocked (1.65, 8.28 and 1.94 mg kg(-1)) and partially blocked (1.12, 7.49 and 1.76 mg kg(-1)) than unblocked (1.07, 5.96 and 1.65 mg kg(-1)) tile drains command area. In conclusion, it is recommended that over irrigation should be avoided to minimize the nutrient losses and contamination of surface and ground water resources.