Effects of calcium-based amendments on carbon and nitrogen emissions from soil and composting systems: a...

Nitrogen (N) and carbon (C) losses from cropping and livestock systems contribute significantly to global warming and other ecological crises. Calcium-based materials, such as lime, gypsum, phosphogypsum (PG), and single superphosphate (SSP), are widely used in agriculture because of their affordability and multifunctional benefits; however, their overall efficacy in mitigating C and N losses across soil and compost systems remains insufficiently quantified. Therefore, this study conducted a comprehensive meta-analysis of 279 published studies (200 on soil and 79 on compost) to evaluate the effects of Calcium-based amendments on C and N emissions. The results showed that liming significantly reduced N₂O emissions by 27.9% in soil and 36.5% in composting systems. However, liming significantly increased soil NH₃ emissions by 68.4% and CO₂ emissions by 26%. Gypsum, SSP, and PG reduced NH₃ emissions by 15.0%, 49.6%, and 64.6% in soil, and by 39.5%, 39.9%, and 54.8%, respectively, in compost. Gypsum and PG reduced CH₄ emissions by 52.7% and 29.2% in soil, and by 23.2% and 71.8%, respectively, in compost. PG reduced soil N₂O and CO₂ emissions by 17.9% and 20.5%, respectively, but increased N₂O emissions from compost by 101.9%. SSP increased soil CO₂ emissions by 5.4%, whereas it reduced N₂O, CO₂, and CH₄ emissions from compost by 25.2%, 14.1%, and 36.9%, respectively. Soil N₂O emissions decreased with increasing liming rates, whereas C emissions showed the opposite trend. Increasing the N application rate stimulated both N₂O and NH₃ emissions. In composting systems, the effects of SSP were governed by the application rate, C/N ratio, and initial pH. This study provides a comprehensive assessment of the effects of Calcium-based amendments and identifies key factors influencing their efficacy and differences in their effects across soil and compost systems. These findings provide a scientific basis for developing targeted strategies to mitigate greenhouse gas and NH₃ emissions while delivering co-benefits for agriculture and the environment.