Biochar Combined with Vermicompost Increases Crop Production While Reducing Ammonia and Nitrous Oxide Emissions from a Paddy Soil

Organic amendments such as vermicompost and biochar have been reported to enhance soil fertility and crop productivity.However, whether the co-application of both amendments has synergistic effects or whether such benefits are accompanied by the risk of gaseous nitrogen(N) loss in an agroecosystem remains unknown. A soil column experiment with a fully factorial design was conducted using three levels of vermicompost(no dose, low dose(1%, weight:weight), and high dose(3%, weight:weight)) without or with biochar(1%, weight:weight) to investigate their effects on rice growth and gaseous N loss across the crop growing season. Our results demonstrated that synergistic interactions existed between vermicompost and biochar in promoting crop yield. Compared with biochar amendment alone, biochar combined with vermicompost significantly(P < 0.01) increased rice yield by 26.5%–35.3%. However,high dose of vermicompost significantly(P < 0.01) increased the cumulative ammonia(NH_3) and nitrous oxide(N_2O) emissions. In the presence of vermicompost, the incorporation of biochar amendment significantly(P < 0.01) decreased the cumulative N_2O emission by 14.1%–18.6%. The lowest emission factor value of NH_3 and N_2O was achieved using biochar in combination with low dose of vermicompost. This study revealed that the combination of biochar and moderate dose of vermicompost offers a novel approach to promote crop productivity while reducing the environmental risk.