Effects of long-term fertilization regimes on greenhouse gas emissions and carbon footprint of spring maize production in reclaimed cropland

Objectives The responses of maize yield and carbon footprint to different fertilization regimes were studied in reclaimed cropland, and the yield-increasing and emission-reducing effects of different fertilization methods were systematically evaluated, thereby providing a scientific basis and technical support for sustainable agricultural development in reclamation areas.

Methods A long-term field experiment was initiated in 2012 in a reclaimed cropland in Gujiao, Shanxi Province, China. Four fertilization treatments were established: no fertilization (CK), mineral fertilization (NPK), organic manure alone (M), and combined application of organic manure and mineral fertilizers (MNPK). In 2021, maize yield and greenhouse gas emissions were determined after harvest. A life cycle assessment (LCA) approach was used to quantify the carbon footprint of maize production under different fertilization treatments. Global warming potential (GWP) and greenhouse gas emission intensity (GHGI) were used to comprehensively evaluate the carbon sequestration and emission reduction effects of different fertilization regimes.

Results Compared with CK, long-term fertilization significantly increased maize yield by 161.8%–258.1%, with the M treatment showing the greatest yield increase. The production and application of nitrogen fertilizers were the major contributors to greenhouse gas emissions. The yield-scaled carbon footprint (CF_y) ranged from −1.40 to 1.06 kg CO₂-eq/kg across the fertilization treatments. Compared with NPK, both M and MNPK significantly reduced CF_y. When accounting for soil organic carbon (SOC) sequestration effect, CF_y under both M and MNPK treatments changed from positive to negative, indicating a shift from ‘carbon sources’ to ‘carbon sinks’. Notably, the MNPK treatment achieved net carbon sequestration while maintaining high maize yield and significantly reduced both GWP and GHGI.

Conclusions The combined application of organic manure with mineral fertilizers (MNPK) can simultaneously increase maize yield and reduce greenhouse gas emissions, thereby lowering the yield-scaled carbon footprint and promoting synergistic yield enhancement and emission reduction in reclaimed cropland.