Effects Of Green Manure And Reduced Irrigation On Water And Carbon Footprint Of Wheat-Green Manure Sequential Cropping System

Aiming at the problems of resource-based water shortage,large greenhouse gas emissions,and there is lack of academic and technical basis on water-saving and emission-reduction in oasis irrigation areas.A field experiment was conducted to investigate the productivity,water and carbon footprint,water use efficiency,and carbon emission efficiency of wheat under three green manure returning methods（green manure returning to the field,green manure removal,no green manure）and three irrigation levels（high irrigation I3:420 mm,middle irrigation I2:370 mm,low irrigation I1:320 mm）.The purpose of the study to reduce water and carbon footprint of wheat and reveal the mechanism of water and carbon footprint in response to green manure returned to the field combined to reduced irrigation.It also provided provide a theoretical basis for low emissions and efficient production technology of wheat in oasis irrigation areas.The main results are follows:1.Low irrigation can guarantee the stable grain yield of wheat,and the green manure overturning can increase the grain yield of wheat.Green manure returning integrated low irrigation further improved grain yield of wheat.Compared with monoculture wheat,wheat-green manure has increased energy yield,and green manure overturning integrated low irrigation can weaken this effect.Compared to no green manure,green manure overturned increased wheat grain yield by 7.8%.The effect of low irrigation on wheat yield was not significantly different from that of middle irrigation.Green manure overturned combined to low irrigation increased yield by 6.9%compared with non-green manure combined to middle irrigation.Compared with monoculture wheat,wheat-green manure has increased energy yield by 38.2%,green manure overturned combined to low irrigation increased wheat-green manure energy yield by 44.4%compared with the non-green manure combined to middle irrigation.2.Compared with monoculture wheat,wheat-green manure has reduced water footprint,green manure overturned and low irrigation further strengthened the effect of reducing water footprint.Compared with monoculture wheat,wheat-green manure reduced water footprint by6.2%.Green manure overturned reduced water footprint by 5.1%over green manure removal.Low irrigation reduced water footprint by 6.0%over the middle irrigation.Green manure overturned combined to low irrigation reduced water footprint by 11.4%over non-green manure combined to middle irrigation.Compared with monoculture wheat,wheat-green manure has increased blue water footprint,green manure overturned and low irrigation further weakened the effect of increasing blue water footprint.Wheat-green manure increased blue water footprint by 9.4%over monoculture wheat.Green manure overturned reduced blue water footprint by 5.6%over green manure removal.Low irrigation reduced blue water footprint by9.3%over the middle irrigation.Compared with monoculture wheat,wheat-green manure has reduced green water footprint,green manure overturned and low irrigation further strengthened the effect of reducing green water footprint.Wheat-green manure reduced green water footprint by 27.6%over monoculture wheat.Green manure overturned combined to low irrigation reduced green water footprint by 30.8%over non-green manure combined to middle irrigation.Based on the water footprint,green manure returned integrated low irrigation can be used as one of water saving and efficiency production models of wheat.Compared with monoculture wheat,wheat-green manure increased greenhouse gas emissions and greenhouse gas warming potential of farmland,and green manure overturned and low irrigation weakened the effect.Wheat-green manure increased total CO₂ emissions by16.9%,the total N₂O emissions by 18.4%,and greenhouse gas warming potential of farmland by 19.6%over monoculture wheat.Compared with green manure removal,green manure overturning reduced total CO₂ carbon emissions by 5.0%,total N₂O emissions by 5.7%,greenhouse gas warming potential of farmland by 4.8%.Low irrigation reduced total CO₂carbon emissions by 10.2%,total N₂O emissions by 10.3%,greenhouse gas warming potential of farmland by 9.7%over middle irrigation.Compared with monoculture wheat,wheat-green manure reduced carbon footprint of energy yield,green manure overturned and low irrigation further strengthened the effect of reducing carbon footprint.Wheat-green manure reduced carbon footprint of energy yield by13.5%over monoculture wheat.Green manure overturned reduced carbon footprint of energy yield by 8.6%compared with removal of green manure.Low irrigation reduced carbon footprint of energy yield by 9.6%compared to medium irrigation.Compared with non-green manure combined to middle irrigation,green manure overturned integrated with low irrigation reduced carbon footprint of energy yield by 27.9%.Based on carbon footprint,green manure returned integrated low irrigation can be used as a low emissions and high-efficiency production model of wheat.3.Compared with monoculture wheat,wheat-green manure significantly improved the water use efficiency and carbon emission efficiency,green manure overturned and low irrigation further strengthened the effect of improving the water use efficiency and carbon emission efficiency and obtained the largest sustainability assessment index.Wheat-green manure improved the water use efficiency by 7.3%,carbon emission efficiency by 15.2%over monoculture wheat.Green manure overturned improved the water use efficiency by 7.3%,carbon emission efficiency by 15.2%over green manure removal.Low irrigation improved the water use efficiency by 7.2%,carbon emission efficiency by 10.9%over middle irrigation.Compared with non-green manure combined to middle irrigation,green manure overturned integrated with low irrigation improved the water use efficiency by 15.6%,carbon emission efficiency by 39.4%.Overall,the integrated technique on green manure returned to the field and low irrigation is one of the low emissions and efficient cropping systems of wheat green production system in the oasis irrigation regions,because the stable-yield potential,reducing the water and carbon footprint and obtaining the largest sustainability assessment index.