Responses of maize yield, nitrogen and phosphorus runoff losses and soil properties to biochar and organic fertilizer application in a light-loamy fluvo-aquic soil

Nitrogen (N) and phosphorus (P) are the primary nutrients to the promoting of crop yield, however, the losses of N and P by runoff dominated the non-point pollution. In the context of maintaining high farmland productivity and mitigating negative impacts on the environment, it is important to understand how biochar and organic fertilizer application influence maize yield, N and P use efficiency and losses by runoff, as well as soil quality. To address this, the current study was conducted based on a three-year field experiment that includes five fertilized treatments: No fertilizer (CK), chemical fertilizer (CF), CF + biochar (CFB), 20% chemical N was replaced by organic fertilizer (OF) and OF + biochar (OFB). The amendments of biochar and organic fertilizer significantly increased maize yield, N and P use efficiency, and meanwhile, decreased the N and P losses by runoff. From 2017 to 2019, the yield of OFB treatment was 4.4–161.9% higher than that of other treatments, The N and P use efficiencies of OFB treatment was 3.0–83.7% and 9.9–195.1% higher than that of other treatments respectively. N losses by runoff were decreased by 35.1–59.7% in OFB than CF, and −0.6–42.0% in OFB than other fertilized treatments. P losses by runoff were decreased by 39.9–48.8% in OFB than CF, and 5.6–32.0% in OFB than other fertilized treatments in 2018 and 2019. Moreover, biochar amendment significantly improved soil aggregate stability, and increased extracellular urease and acid phosphatase activities. Soil alkaline hydrolysable nitrogen and available potassium contents were significantly increased by the biochar amendment, but no significant impact on soil available P. These findings indicate that the integrated use of chemical fertilizer, organic fertilizer and biochar has the potential to maintain high grain yield with mitigating environmental impact.