Spatiotemporal synergy among chemical fertilizer-related greenhouse gas emissions, cultivated land area and grain yield at the provincial scale in China

Objectives Chemical fertilizer-related greenhouse gas (GHG) emissions have become an urgent issue for sustainable agricultural production.

Methods Based on chemical fertilizer input data for China’s major grain crops (rice, wheat, corn, and legumes) from 2005 to 2021, this study quantified GHG emissions from fertilizer production and application processes and analyzed the multivariate spatiotemporal synergy among fertilizer GHG emissions, grain yield, and cultivated land area using an improved centroid-based model.

Results 1) From 2005 to 2014, fertilizer input increased at an annual rate of 2.7%, followed by a slight decline thereafter. The fertilizer input structure shifted from urea (36.5%) to NPK compound fertilizers (34.1%), with the quantity of the latter nearly tripling. GHG emissions from fertilizer production and application exhibited a rise-decline pattern, with production processes accounting for 41.5% of total emissions. 2) Fertilizer-related GHG emissions by crop were ranked as maize (40.62×10⁶ t) > wheat (29.28×10⁶ t) > rice (28.66×10⁶ t) > legumes (3.64×10⁶ t). Among these, maize showed the fastest growth in emissions during 2005−2014, with an annual increase of 7.3%. Major grain-producing provinces (e.g., Heilongjiang, Henan) exhibited higher emission levels, whereas Beijing experienced an average annual decline of 6.53% due to reductions in farmland area. 3) From 2005 to 2021, China exhibited a relatively high level of multivariate temporal synergy among fertilizer-related greenhouse gas emissions, cultivated land area, and grain production (0.46−0.71). Among the 13 major grain-producing provinces, most demonstrated moderate-to-high synergy (0.53−0.84), whereas Shandong Province showed relatively poor synergy (0.40). Spatial synergy remained generally stable nationwide (average 0.90), with a notable improvement in Heilongjiang (2.6% per year) and a decline in Henan (from 0.60 to 0.49).

Conclusions Overall, China showed strong spatiotemporal synergy among cultivated land area, grain production, and fertilizer-related GHG emissions. The temporal synergy shows moderate fluctuations (0.46−0.71), indicating relatively stable agricultural dynamics, while spatial synergy was consistently high, reflecting a generally rational regional allocation of agricultural resources. Provinces with poor synergy should optimize fertilizer production, adjust application structures (e.g., reducing nitrogen dependence), and promote green agricultural development.