Biochar-based fertilizer decreased while chemical fertilizer increased soil N2O emissions in a subtropical Moso bamboo plantation

Abstract

While there is a sound understanding of the range of mechanisms by which biochar can contribute to the mitigation of soil N2O emissions, a paucity of information remains on the efficacy and mechanisms associated with biochar-based fertilizer (BF). The present 12-month field trial aimed to: (1) investigate the responses of the seasonal variations in soil N2O emissions and environmental factors, including soil temperature and moisture content, concentrations of NH4+-N, NO3−-N, water-soluble organic N (WSON), microbial biomass N (MBN), water-soluble organic C (WSOC) and microbial biomass C (MBC), and urease and protease activities, to application of BF, chemical fertilizer (CF) and a mixture of BF and CF (BCF) within a Moso bamboo plantation, and (2) reveal contributions of variation in soil properties to change in soil N2O emissions. The fertilized treatments matched doses of N, P and K among BF, CF and BCF, with an unfertilized treatment as a control. Compared to the control, BF treatment decreased soil N2O emissions (P < 0.05), whereas treatments of CF and BCF enhanced soil N2O emissions (P < 0.05). Soil N2O emissions were predominantly related to the soil temperature (P < 0.01), and correlated with soil WSON concentration and soil urease and protease activities in all fertilized treatments (P < 0.05). In addition, BF treatment markedly (P < 0.05) reduced soil WSON concentration, as well as soil urease and protease activities, whereas the CF and BCF treatments enhanced them (P < 0.05). Results of structural equation modelling indicated that the mechanisms by which BF decreased soil N2O emissions within the subtropical Moso bamboo plantation was via lowering WSON concentration and N-cycling enzyme activity in soils. In conclusion, results of the present work indicated that BF application could provide an important management strategy for the mitigation of N2O emissions from subtropical plantation soils.