Managing trade-offs among yield, carbon, and nitrogen footprints of wheat-maize cropping system under straw mulching and N fertilizer application in China's Loess Plateau

Contexts

Although soil mulching and nitrogen application have long been used in rainfed agriculture, there are still significant uncertainties about their effects on crop yield, carbon sequestration, greenhouse gas emissions, and reactive nitrogen losses.

Objectives

This study aimed to investigate yield responses, carbon footprint (CF), and nitrogen footprint (NF) changes following long-term straw mulching and N application, thereby identifying cleaner production management practices for wheat-maize rotation system in the Loess Plateau.

Method

This study conducted a three-year field experiment in the Loess Plateau from 2019 to 2022 to investigate the comprehensive effects of straw disposal methods (straw mulching and conventional treatment with no straw mulching) and nitrogen fertilization rates (0, 120, 240 kg N ha⁻¹) on soil properties, crop yield, GHG emissions, net global warming potential, CF and NF in wheat-maize rotation system.

Results

Straw mulching and N fertilization significantly increased soil organic carbon (SOC), total nitrogen, NO₃⁻-N, microbial biomass carbon, and nitrogen content. Compared to conventional treatment, straw mulching enhanced CO₂ emission by 15.23–21.15 % and reduced CH₄ uptake by 5.60–14.61 % while having negligible effects on N₂O emissions. Straw mulching reduced CF and yield-scaled CF but increased NF due to the boost of SOC sequestration. N fertilization significantly increased GHG emissions, particularly at higher N rates. Straw mulching and N fertilization significantly enhanced wheat-maize yield and straw mulching boosted the contribution rate of N application to yield. A significant positive correlation was observed between GHG emissions and crop yield. Despite this, yield-scaled CF decreased significantly due to increased crop production. Among the treatments, straw mulching combined with 120 kg N ha⁻¹ treatment had the lowest CF (–1613.92 kg CO₂ ha⁻¹ yr⁻¹), yield-scaled CF (–155.40 g CO₂ kg⁻¹). It also achieved lower NF (122.83 kg N ha⁻¹ yr⁻¹) and yield-scaled NF (11.66 g N kg⁻¹) while producing the highest wheat-maize yield.

Conclusions

The study's findings suggest that straw mulching combined with 120 kg N ha⁻¹ treatment achieved a better trade-off between crop yields and environmental impacts in the wheat-maize rotation system in the Loess Plateau of China.

Significance

Quantifying the straw mulching and N fertilization on crop yield and environmental impacts strengthens carbon sequestration and promotes sustainable and clean production in the wheat-maize rotation system.