Optimal lime materials for mitigating global warming potential with and without straw application in acidic upland soil

Abstract

Lime and crop straw are widely applied to mitigate soil acidification and improve soil fertility. However, how different lime materials interact with straw to influence greenhouse gas (GHG) emissions from acidic upland soils remains poorly understood. This study explored how different lime materials and their interaction with straw affect GHG emissions. Here, we conducted incubation experiments with acidic red soil to investigate the individual and combined effects of liming materials, including Ca(OH)₂, CaO, and CaCO₃, as well as rice straw addition on nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions. Our findings demonstrated that in the absence of straw, liming increased N₂O emission by 20.3% (CaO) to 78.2% (Ca(OH)₂). CaCO₃ application raised CO₂ emissions by 182.7%, while CaO and Ca(OH)₂ decreased CO₂ emissions by 37.3% and 43.2%, respectively. Adding straw alone enhanced N₂O and CO₂ emissions by 80.69% and 302.7%, respectively. When combined with straw, liming further increased N₂O emissions by 85.0% to 140.1%, with Ca(OH)₂ causing the highest emissions. CaCO₃ increased CO₂ emissions by 37.3% when combined with straw, whereas CaO and Ca(OH)₂ reduced CO₂ emissions by 31.6% and 32.2%, respectively. Straw addition significantly increased global warming potential (GWP). Applying CaO and Ca(OH)₂ decreased GWP, whereas CaCO₃ increased it with straw application. Compared to CaCO₃, CaO and Ca(OH)₂ application resulted in a lower GWP, making them optimal lime materials for reducing acidification and mitigating GHG emissions. Linear regression and partial least squares path (PLS-PM) analyses indicated that soil carbon, nitrogen, and microbial biomass significantly influenced N₂O emissions under lime and straw application, while CO₂ emissions were unaffected by these soil properties. Both lime and straw addition increased microbial biomass carbon (MBC) and nitrogen (MBN), dissolved organic carbon (DOC), and NH₄⁺–N contents, but decreased NO₃⁻–N content, leading to higher N₂O emissions. CO₂ emissions were influenced by the chemical reactions of various lime materials in the soil. These findings suggest that selecting appropriate lime materials can significantly mitigate greenhouse gas emissions from acidic soils, contributing to more sustainable agricultural practices.