Water footprint assessment of surface and subsurface drip fertigated cotton-wheat cropping system – A case study under semi-arid environments of Indian Punjab

The advanced methods of irrigation and nutrient supply may save huge quantity of costly inputs over the prevalent practice of surface flood (SF) irrigation and fertilizer broadcasting in Indian Punjab. Surface drip fertigation (SDF) and subsurface drip fertigation (SSDF) enables the combined application of fertilizer and irrigation for improving the input use efficiency in Cotton-Wheat cropping system (CWCS) over the SF. Though, both SDF and SSDF perform better than SF, but their suitability in reducing the water footprint (WF) of CWCS has been least assessed. Therefore, a 2 yr field study at two distinct agro-climatic zones has been conducted to quantify and compare the WF of SDF and SSDF in comparison to SF for CWCS under semi-arid environments. Results revealed that under SSDF, cotton and wheat crops consumed 32 and 37% lower water than respective SF, indicative of huge water saving over the prevalent practice. Contribution of green, blue and grey components towards total WF under SF was 42, 48 and 10% respectively for cotton, and 24, 59 and 18% for wheat. SSDF application at 80% crop evapotranspiration (ETc) along with 100% recommended dose of nitrogen remarkably reduced the WF without any yield loss for CWCS. Higher total WF for CWCS under SF (5.30 m³ kg⁻1) revealed it to be inferior as compared to SDF (3.71 m³ kg⁻1) and SSDF (3.52 m³ kg⁻1). Cotton alone consumed 65–78% of WFtotal of the CWCS, while the remaining 22–35% was attributed to wheat. A lowered WFtotal for CWCS under SDF and SSDF over that of SF elucidated them to be immensely helpful to conserve limited water resources under semi arid climates. A cropping system based assessment was much reliable option to obtain a clear indicator about the annual WF as compared to single crop based estimation. These results could be utilized to access the performance of alternative irrigation and cultivation systems for developing the WF reduction approach over extended geographical scale.