Abstract
Reducing the use of nitrogen fertilizers and returning straw to field are being promoted in northeast China (NEC). In this paper, the agricultural production system model (APSIM) was applied to assess the long-term variations of crop yield and soil GHG emissions in a maize mono-cropping system of NEC, and the simulation results were combined with lifecycle assessment to estimate annual GHG emissions (GHGL) and GHG emission intensity (GHGI, GHG emissions per unit yield) of different agricultural practices. Under current farmers’ practice, emissions due to machinery input (including production, transportation, repair, and maintenance) and soil organic carbon (SOC) decline accounted for 15% of GHGL, while emissions from nitrogen fertilizer input (production and transportation) and direct N2O emissions from soil accounted for the majority (~60% of GHGL). Current farmers’ practice in terms of N application and residue management are nearly optimal for crop production but not for climate change mitigation. Reducing N input by 13% and increasing straw retention by 20% can maintain crop yield and SOC, and also reduce GHGL and GHGI by 13% and 11%, respectively. However, it is not feasible to incorporate the straw used as household fuel into soil, which could incur substantial fossil CO2 emissions of 3.98 Mg CO2-eq ha−1 resulting from the substitution of coal for straw. APSIM was successful in simulating crop yield, N2O emissions, and SOC change in NEC, and our results highlight opportunities to further optimize management strategies (especially for the nitrogen and straw management) to reduce GHG emissions while maintaining crop yield.
Highlights
Agricultural production has a significant impact on global climate change
The performance of the calibrated APSIM model in terms of simulating maize yield, N dynamics, soil water, and direct N2O emissions from soil is shown in Figures 1 and 2
Using the calibrated model parameters based on the N0MN0 and N230MN0 treatments, the model was validated using the observed grain yield from the other three treatments (N270(200)MN67, N230(200)MN84, 3.1
Summary
Agricultural production has a significant impact on global climate change. About 65% of global nitrous oxide (N2O) emissions derive from agricultural soils, mainly attributed to nitrogen (N) fertilizer application [1]. Increasing SOC stocks of agricultural soils (top 1 m of soil) by 0.4% can offset about 30% of global greenhouse gas emissions [7]. SOC change is tended to be ignored when estimating GHG emissions of different management in the short term [8,9,10,11]. In addition to the soil CO2 and N2O emissions, CO2 emissions from agricultural inputs (e.g., fuel combustion, production, transportation, and application of fertilizers, pesticides, etc.) are a significant component of the carbon footprint [12,13]
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