Decreased Soil Nitrification Rate with Addition of Biochar to the Acid Soils

This study aimed to investigate the effects of mixed biochar on the nitrification rate in acidic soils. A 15N tracer experiment with (15NH4)2SO4 was conducted to determine the nitrification rates of four acidic agricultural soils with pH 4.03–6.02 in Yunnan Province, Southern China. The accumulation of 15N-NO3− and nitrification rates decreased with the addition of biochar at the end of incubation, suggesting that biochar could be a nitrification inhibitor in acidic fertilized soil. Nitrification rates in soil with pH 4.03 were evidently lower than those in soil with pH 4.81–6.02 with or without biochar. Decreased nitrification rates were detected in the acidic soils with biochar. Soil pH controlled nitrification more than biochar in certain strongly acidic soils.