Evaluating the Short-Term Potential of Volcanic Ash to Reduce Agricultural N2O Emissions

This study is the first to investigate volcanic ash (VA) as a soil amendment to mitigate nitrous oxide (N2O) emissions, a potent greenhouse gas mainly produced through nitrification and denitrification processes in agricultural soils. The experiment assessed the effects of VA mixed with soil and combined with mineral (NH4NO3, N) or organic (poultry manure, O) fertilizer on N2O emissions, soil mineral nitrogen (NO3− and NH4+), trace metals (Zn, Cu, Mn), and crop yield in a 4-month pot experiment including treatments with and without VA. Results showed that VA reduced N2O emissions by 55% in mineral fertilizer treatments and 71% in organic fertilizer treatments compared to soils without VA. This reduction was associated with significant changes in nitrogen availability. In mineral fertilizer treatments with VA, soil NO3− concentrations remained high, potentially limiting denitrifier activity, while in organic treatments VA appeared to inhibit nitrogen mineralization. Additionally, VA increased soil concentrations of Zn, Cu, and Mn, which were negatively correlated with N2O emissions, suggesting an influence on microbial processes. Importantly, crop yields were not affected by VA application. Although promising, these preliminary findings highlight the need for further research to optimize application rates and evaluate long-term effects across soil types and management systems.