Increasing net ecosystem carbon budget and mitigating global warming potential with improved irrigation and nitrogen fertilization management of a spring wheat farmland system in arid Northwest China

Background and aimsInappropriate irrigation and nitrogen fertilization caused high global warming potential (GWP) while reduced carbon sequestration of farmland systems in arid regions. Understanding the effects of irrigation and nitrogen fertilization on net ecosystem carbon budget (NECB) and its components are crucial to mitigate GWP and increase carbon sequestration.MethodsA field experiment was carried out to investigate the impact of irrigation and nitrogen fertilization on soil greenhouse gas (GHG) emissions, crop net primary productivity (NPP), NECB and net GWP from spring wheat farmland in arid Northwest China. Three irrigation depth levels, 180, 315, and 450 mm and three nitrogen fertilization levels, 170, 250, and 340 kg ha(-1) were designed.ResultsIrrigation and fertilization significantly affected GHG emissions and carbon sequestration of farmland system. Reducing irrigation depth from 450 to 315 mm reduced soil CO2 and N2O emissions but did not significantly reduce NPP. Increasing nitrogen fertilization from 170 kg ha(-1) to 250 kg ha(-1) improved NPP, but continuously increasing nitrogen input decreased NPP while increasing soil CO2 and N2O emissions. Therefore, the NECB first increased and then decreased, while the net GWP first decreased and then increased as the irrigation depth and nitrogen fertilization decreased. Overall, the moderate irrigation and fertilization treatment (i.e., 315 mm irrigation and 250 kg ha(-1) nitrogen fertilization) obtained the highest NECB and the lowest net GWP.ConclusionImproving irrigation and fertilization management can increase carbon sequestration and mitigate the net GWP of farmland systems by increasing crop NPP and reducing soil GHG emissions.

Automated summary

Appropriate irrigation and nitrogen fertilization can increase carbon sequestration and reduce greenhouse gas emissions in farmland systems, thereby mitigating global warming potential. Experimental results demonstrate that moderate irrigation depth and fertilizer application can achieve the highest net ecosystem carbon budget and the lowest net greenhouse gas emissions.