Long-Term Impact of Cyclic Use of Sodic and Canal Waters for Irrigation on Soil Properties and Crop Yields in Cotton–Wheat Rotation in a Semiarid Climate

Abstract

A 12-year field experiment (1996–2008) was conducted on a sandy loam soil under semiarid climate to study the impact of use of sodic water (SW) and canal water (CW) in various cyclic modes in a cotton–wheat rotation. Treatments included irrigation with CW and SW (residual sodium carbonate 10 meq L−1) and different variants of cyclic modes of CW and SW irrigation. Irrigation with SW caused increase in pH, electrical conductivity (EC), exchangeable sodium percentage (ESP) that resulted in reduced cotton and wheat yields. The mean yield reduction after 6 years was more for seed-cotton (28%) than for wheat (15%); yield reduction in cotton and wheat after 12 years was 35 and 22%, respectively. Cyclic irrigation of CW and SW resulted in lower pH, EC and ESP than under SW irrigation and increased mean yields of both crops. Cyclic treatments starting with CW involving one SW (2CW:SW, CW:SW) or starting with one SW followed by 2CW irrigations (SW:2CW) produced optimum (>90% yields relative to CW) wheat and seed-cotton yields after 6 years. These cyclic modes could sustain optimum crop yields even after 12 years. Reduction in cotton yield after 6 years was more (18%) than in wheat (10%) in cyclic modes starting with SW involving one CW (SW:CW, 2SW:CW). However, extent of reduction in seed-cotton (25%) and wheat yields (17%) after 12 years made these treatments unsustainable on long-term basis. Based on sustainable yield index and buildup of sodicity, 2CW:SW treatment was found to be the most sustainable among various cyclic modes for the cotton–wheat rotation.