Residue return and nitrogen application optimization can not balance crop yield increase and reducing emission in semi-arid region

Context: Agricultural systems face the dual challenge of reducing greenhouse gas (GHG) emissions while ensuring food security in the context of future climate change and population growth. Farm practices, such as conservation agriculture practices and optimal nitrogen (N) fertilization, are widely promoted for their potential to sustain crop production and mitigate climate change impacts. However, the long-term effectiveness of these practices in balancing crop yields and GHG emissions under future climate scenarios remains uncertain. Objective: This study investigates the impacts of residue retention and N fertilization strategies on crop yields, soil organic carbon (SOC) sequestration, and GHG emissions in the Riverina region of New South Wales, Australia, using the well-validated APSIM model under two Shared Socioeconomic Pathways (SSP245 and SSP585). Methods: We used the APSIM model to evaluate three crop rotation systems—wheat-canola (WC), wheat-field pea-wheat-canola (WFWC), and wheat-wheat-canola (WWC)—under varying residue retention levels (10%, 50%, and 100%) and two N fertilization strategies (conventional and optimal). The conventional strategy was based on rainfall, while the optimal strategy adjusted N application according to in-season rainfall and soil moisture availability. Results and conclusions: Our results indicate that the combined management practice of residue retention and optimized nitrogen application increases greenhouse gas intensity (GHGI) under future scenarios. Although this practice enhances short-term soil organic carbon (SOC) sequestration and boosts crop yield (a 22.1% increase in wheat yield under SSP245), it also significantly raises N₂O emissions (under SSP585, N₂O emissions were 13.7% higher than the baseline when 100% residue was retained). SOC peaked in the mid-21st century but declined thereafter due to accelerated decomposition driven by rising temperatures, leading to increased GHGI with higher residue retention rates. This suggests that the benefits of yield gains are offset by enhanced SOC decomposition and elevated N₂O emissions. Our findings highlight that the combination of residue retention and optimal N fertilization fails to achieve a long-term balance between crop yield and GHG emissions under climate change. Significance: The findings underscore the need for integrated management strategies that consider both agronomic and environmental outcomes, including the potential for carbon credits and reduced N inputs, to sustainably address the dual challenges of food security and climate change mitigation.