Mitigation of global warming potential and greenhouse gas intensity in arable soil with green manure as source of nitrogen

Abstract

This study was conducted to determine the effect of different green manure treatments on net GWP and GHGI in upland soil. Barley (B), hairy vetch (HV), and a barley/hairy vetch mixture (BHV) were sown on an upland soil on November 4, 2017 and October 24, 2018. The aboveground biomass of these green manures was incorporated into soil on June 1, 2018 and May 8, 2019. In addition, a fallow treatment (F) was installed as the control. Maize was transplanted as the subsequent crop after incorporation of green manures. Green manuring significantly affected CO₂ and N₂O emission, but not CH₄. Average cumulative soil respiration across years with HV and BHV were 37.0 Mg CO₂ ha^-1 yr^-1 and 35.8 Mg CO₂ ha^-1 yr^-1, respectively and significantly higher than those with under F and B (32.7 Mg CO₂ ha^-1 yr^-1 and 33.0 Mg CO₂ ha^-1 yr^-1, respectively). Cumulative N₂O emissions across years with F and HV were 6.29 kg N₂O ha^-1 yr^-1 and 5.44 kg N₂O ha^-1 yr^-1, respectively and significantly higher than those with B and BHV (4.26 kg N₂O ha^-1 yr^-1 and 4.42 kg N₂O ha^-1 yr^-1, respectively). The net ecosystem carbon budget for HV (-0.5 Mg C ha^-1 yr^-1) was the greatest among the treatments (F; -1.61 Mg C ha^-1 yr^-1, B; -3.98 Mg C ha^-1 yr^-1, and BHV; -0.91 Mg C ha^-1 yr^-1) because of its high biomass yields and the yield of maize after incorporation of HV. There was no significant difference of GHGI among F, HV, and BHV. Incorporation of HV or BHV could reduce net CO₂ emissions per unit of maize grain production as well as F.

Keywords: Green manure; Greenhouse gas intensity; Maize field; Net ecosystem carbon budget.