Reduction of blue and total water footprints per unit biomass yield of silage maize with grey water footprint input in subsurface drip irrigation

Reducing blue and total water footprint outputs in irrigated agriculture with greywater footprint input from irrigation with recycled wastewater is an issue that needs to be investigated in protecting freshwater resources by increasing water availability. Therefore, the effect of three different irrigation levels of recycled wastewater and freshwater in the subsurface drip irrigation (SSDI), surface drip irrigation (SDI), and furrow irrigation (FI) methods on the blue, green, grey, and total water footprints per unit yield of silage maize, which is widely produced worldwide and has high water consumption, was investigated with a 2-year field study. The blue and total water footprints per unit fresh and dry biomass yields in the SSDI were 1.20-1.23-fold lower than that in the SDI and 1.69-1.76-fold lower than that in the FI. Full wastewater irrigation provided the lowest blue, green, and total water footprints per unit yield across all methods. Full wastewater irrigation under SSDI provided the lowest total water footprint per unit fresh biomass yield, similar to the 33% deficit irrigation practice with wastewater. It was concluded that full irrigation with recycled wastewater as a greywater resource under SSDI may be the most suitable application for the sustainable management of scarce blue water resources.