Integrated nitrogen management strategies for mitigating carbon and nitrogen footprints in the North China Plain

Excessive nitrogen (N) fertilization in intensive cropping systems induces substantial carbon (C) and reactive nitrogen (Nr) emissions. To address the challenge of synergistic C-N emission reduction while ensuring agricultural sustainability, a two-year field experiment studied the effects on this of N input reduction (OU), deep placement of fertilizer (DP), alternative fertilizers (calcium ammonium nitrate, CAN), enhanced-efficiency N fertilizers (controlled-release urea [CRU], urease inhibitors [UI], nitrification inhibitors [NI], a microbial agent [UB]) and organic substitution (organic manure plus urea [UOM] or urea amended with urease inhibitors [ULOM]). Life cycle assessment (LCA) and scenario analysis applied the results to the whole of the North China Plain (NCP). The key findings were: (1) N reduction was fundamental. Advanced strategies decreased C and Nr emissions by 4.2-15.2 % (excluding CAN) and 20.6-59.3 %, respectively, compared to conventional practices. (2) A multi-criteria assessment highlighted three key treatments with the best performing strategies being CRU and UI, but also with ULOM as a strategic measure for reducing N emissions. Specifically, compared to OU, CRU and UI reduced the C footprint (CF) by 14.7 and 15.8 %, the N footprint (NF) by 54.4 and 54.6 %, and increased the net eco-economic benefit (NEEB) by 21.9 and 28.1 %, respectively. ULOM reduced CF by 1.9 %, NF by 51.6 %, and enhanced NEEB (+18.4 %). (3) Significant regional disparities in emission patterns were identified, with Beijing and Henan as hotpots for C and Nr emissions, respectively. (4) Scenario analysis validated that UI and CRU reduced CF by 26.9 %, NF by 61.4 %, and environmental damage cost (EDC) by 26.3 %. To harmonize environmental security with agricultural transition we propose a regional integrated "emission reduction-efficiency enhancement" framework. Prioritizing CRU and UI technologies, alongside synergistic organic-inorganic fertilizer combinations, offers a scalable pathway for sustainable intensification in the NCP.