Improved Nitrogen Management as a Key Mitigation to Net Global Warming Potential and Greenhouse Gas Intensity on the North China Plain

Abstract

Core Ideas Effects of improved N management on net GWP and GHG intensity were investigated. Fertilizer production and irrigation were the main contributors to GWP. Optimized chemical N and manure N can decrease net GWP and GHG intensity relative to conventional N. Improved N management could realize food security and net GWP mitigation concomitantly. Agricultural production is one of the main sources of greenhouse gas (GHG) emissions globally. Net global warming potential (net GWP) and greenhouse gas intensity (GHGI) were investigated in a maize–wheat rotation from 2011 to 2014 on the North China Plain by summarizing the net exchange of CO2 equivalent (CO2–eq) from direct and indirect GHG emissions. The experiment included four managements: no N input (N0), conventional chemical‐N management (Ncon), optimized chemical N management (Nopt), and balanced chemical‐N management incorporated with dairy manure (MNbal). Cumulative N2O emissions were significantly increased by N input rates. Soil organic carbon (SOC) content increased linearly in all treatments with 0.11 to 0.46 g C kg–1 yr–1 at 0 to 20 cm. The energy consumption associated with chemical N‐fertilizer production and irrigation was the main contributor to GWP. Compared with Ncon, a 45% decrease in chemical‐N input by Nopt brought about a 33% decrease in net GWP, but a 10% decrease in grain yield, and thus only reduced 25% of GHGI. A 40% decrease in total N application in the MNbal treatment saved chemical N by 66% and increased soil organic carbon sequestration by 45%, increased grain yield by 18%, and finally, decreased net GWP and GHGI by 48 and 56%, respectively, relative to the Ncon treatment. We conclude that the incorporation of dairy manure with chemical N is a promising strategy for reducing net GWP and ensuring food security concomitantly in these intensive maize–wheat cropping systems on the North China Plain.