Subsurface drainage for reversing degradation of waterlogged saline lands

In irrigated agriculture of and and semiarid regions waterlogging coupled with salinity is a serious problem. Experimental evidence at several locations has led to the realization that subsurface drainage is an essential intervention to reverse the processes of land degradation responsible for the formation of waterlogged saline lands. This paper presents the results of a study conducted from 1995 to 2000 to evaluate the impacts of subsurface drainage on soil properties, groundwater-table behaviour and crop productivity in a waterlogged saline area of 2200 ha. A subsurface drainage system was installed at 1.6 m depth with 60m drain spacing covering an area of 1200ha (23 blocks) during 1997-99 and compared with an undrained block of 1000ha. Subsurface drainage facilitated the reclamation of waterlogged saline lands and a decrease in the soil salinity (ECe, dS m(-1)) that ranged from 16.0 to 66.3 per cent in different blocks. On average, 35.7 per cent decrease in salt content was observed when compared with the initial value. Provision of subsurface drainage controlled the water-table below the root zone during the monsoon season and helped in bringing the soil to optimum moisture content for the sowing of winter crops. In the drained area, the increase in yields of different crops ranged from 18.8 to 27.6 percent. However, in the undrained area the yield of different crops decreased due to the increased waterlogging and soil salinity problems. Overall the results indicated that investment in subsurface drainage is a viable option for reversing the land degradation of waterlogged saline lands in a monsoon climate. Copyright (c) 2006 John Wiley & Sons, Ltd.