Agricultural water-saving potentials with water footprint benchmarking under different tillage practices for crop production in an irrigation district

The water footprint (WF) of crop production is a measure of the volumes of blue water (irrigation water) and green water (effective precipitation) consumed during crop growth. Setting the WF benchmarks of crop pro-duction in an irrigation district, exploring the optimal tillage practices, and clearly specifying blue and green water-saving potentials (WSPs) are essential for efficient utilization and reasonable allocation of agricultural water resources. However, related studies disregarded the WF benchmark setting according to tillage practices and the corresponding WSPs at the irrigation district scale. Meanwhile, the evaluation of WSP is limited to blue water. Considering summer maize and winter wheat grown in Baojixia Irrigation District (BID) of Shaanxi Province in China as the study case, this study aims to evaluate the gross irrigation WSP, actual blue and green WSPs based on crop WF simulation and WF benchmark setting for the "best" tillage practice. Eighteen water -saving tillage practice scenarios were set considering three irrigation techniques, three irrigation strategies, and two mulching practices. Results show that crop responses to different tillage practices differ. Maize WF has low sensitivity whereas wheat WF shows a significant difference following a change in irrigation techniques. In the practice under 40% deficit irrigation with no mulching, there is the highest actual WSPs, but at the cost of at least 57% reduction in crop yield. Whereas the practice of 20% deficit irrigation, furrow irrigation, and mulching has no yield reduction and relatively low WF, which can save 20% blue water and 8-12% green water in the BID, which is the optimal balance point between the yield and water consumption of the two crops. From the perspective of crop WF, this study quantified the agricultural WSPs of different water resources, and formulated a method for evaluating agricultural WSPs based on set WF benchmarks, to provide reference for building a water -saving culture, and sustainable development.