A meta-analysis to disentangle the effects of land management on soil denitrification

Land management in grasslands and agricultural systems influences soil denitrification, the microbial conversion of nitrate to nitrogen gases, which is a critical ecosystem function that underpins multiple ecosystem services. Agricultural practices, including grazing, fertilization, tillage, and overall land management intensity, can alter soil denitrification activities, yet few studies have systematically synthesized how management type and intensity affect denitrification across a range of managed grasslands and agricultural systems. In this study, we conducted a meta-analysis of 160 studies to investigate and analyze how agricultural land management drives soil denitrification rates. Studies were categorized by land management type and intensity to assess their individual and interactive effects. Our results showed that fertilization significantly altered soil denitrification. Specifically, aggregating across selected studies, fertilizer application increased soil denitrification rates, while grazing, tillage, and species conversion overall showed no significant effects. Management intensity further modulated these responses, with higher fertilizer application rates leading to proportionally greater denitrification rates. Moreover, our analyses showed no consistent relationships between denitrification rates and edaphic and climatic variables, such as soil nitrate, moisture, or mean annual temperature and precipitation. Our findings demonstrate that agricultural management intensification can increase soil denitrification rates, with the magnitude of effect varying by management type. Our synthesis contributes to an improved understanding of how agricultural land use affects nitrogen cycling and underpins ecosystem services in agroecosystems.