Impacts of inhibitors on soil N2O emissions and crop yield: A mega-analysis

Abstract

A central challenge for agriculture is to secure global food supplies while minimizing its environmental impact, with a focus on greenhouse gas emissions. The use of Nitrogen (N) fertilizers is vital for crop yield; however, they are a major source of soil nitrous oxide (N₂O), which is a powerful greenhouse gas. To mitigate soil N₂O emissions, nitrification inhibitor (NI), urease inhibitor (UI), and double inhibitor (DI) have been recommended. However, field experiments and existing meta-analyses show conflicting results regarding their impacts on both crop yield and mitigation efficacy, due to differences in study selections and inclusion criteria, variation in handling of moderators and heterogeneity, and statistical model choices. To resolve these discrepancies, we conducted a mega-analysis, synthesizing data from ten meta-analyses on N₂O emissions and nine on crop yield. Our results show that, overall, inhibitors had a significant and positive effect on crop yields (4.6%), although the magnitude of this effect varied by crop type. Conversely, inhibitors caused a strong and highly significant decrease in N₂O emissions from soil by 42.9%. This mitigation effect was consistent across inhibitor types, products, and management practices. However, soil characteristics and farming practices had a major influence on both yield and N₂O responses. N₂O mitigation was most noticeable in acidic soils and when inhibitors were banded with fertilizer, and yield increases were noteworthy for cereals. This mega-analysis confirms that agricultural inhibitors are a potent climate-smart strategy that can significantly reduce N₂O emissions without compromising crop productivity, offering a more thorough quantification than individual meta-analyses.