Long-term Impact of Cyclic Use of Sodic and Canal Water for Irrigation on Soil Quality and Wheat Yield in Cotton-Wheat Cropping System

Abstract

Increasing scarcity of good quality water in many arid and semi-arid regions necessitates the cyclic use of sodic water (SW) and canal water (CW) for irrigation. Six irrigation treatment combinations of CW (good quality) and SW (residual sodium carbonate, 10 me L-1) were applied in a cyclic mode in a long-term field experiment in cotton-wheat system for investigating their impact on soil quality parameters and wheat yield. Irrigation with SW alone resulted in high soil pH (>9), sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) and bulk density (BD), and decreased soil organic carbon (SOC) content and availability of macro (N, P, K and S) and micronutrients (Fe, Mn, Zn and Cu). Infiltration rate, saturated hydraulic conductivity, mean weight diameter of soil aggregates, microbial biomass carbon and dehydrogenase activity were lower compared with that under CW irrigation. Continuous irrigation with SW reduced grain yield of wheat by 24 per cent over CW. However, alternate irrigation with CW and SW significantly improved soil quality, resulting in 7-26 per cent higher wheat yields compared with irrigation with SW alone. Ameliorative effect of using 2CW in cyclic use with 1 SW (2CW: SW, SW: 2CW) on soil quality parameters was more significant than 1CW with 1SW (CW: SW, SW: CW) or 2SW irrigations (CW: 2SW, 2SW: CW). The effect of different treatments on crop productivity was adequately explained by changes in either soil ESP or SAR (82%), soil pH and OC (~73%) demonstrating their importance in determining soil quality and wheat yields in a sodic environment. The study also suggested that in situations where canal water is initially not available, occasional pre-sowing irrigation with sodic water can be given to avoid delay in sowing provided canal water irrigations are applied later.