Reducing gray, blue, green, and total water footprint in wastewater irrigated silage maize in zero tillage

ABSTRACT No study has been found examining the contribution of gray water footprint input per unit yield to reducing blue and green water footprint output in silage maize irrigated with different levels of wastewater under different tillage practices. Therefore, this 2-year silage maize field study examined the effect of three different levels of recycled wastewater (100, 67, and 33% of irrigation need in W100, W67, and W33) and 100% irrigation with freshwater on water footprint under conventional and zero tillage. Under zero tillage, W100 had the lowest blue, green, and total water footprint per unit yield of 2.8, 6.1, and 47 m3 ton−1 for fresh biomass, respectively, and 9.2, 20.1, and 155.3 m3 ton−1 for dry biomass. Among the wastewater treatments, the W33 resulted in the highest water footprints per unit yield under conventional tillage. Blue, green, gray, and total water footprints per unit fresh yield under zero tillage were 9.8, 5.9, 13.1, and 10.3% lower than conventional tillage, while the values for dry biomass were 15, 14.3, 18.6, and 16.6% lower. In conclusion, W100 under zero tillage can be an effective way to protect freshwater resources by reducing blue, green, and total water footprint outputs with less gray water footprint input per unit yield.