[Effect of Biochar on Ammonia Volatilization from Soils of Different Surface Conditions]

In order to explore the effect of biochar on the volatilization of ammonia in different surface soils, through the field test method, the responsiveness changes of ammonia volatilization, ammonium nitrogen, and urease were studied under the influence of biochar and crop cultivation. The study set six treatments:CK+, BC0.5+, and BC4.5+ (the biochar applied at 0, 0.5, 4.5 kg·(m²·a)^-1, respectively, under the condition of crop cultivation), and CK-, BC0.5-, and BC4.5- (the biochar applied at 0, 0.5, 4.5 kg·(m²·a)^-1, respectively, under the condition of bare land). The results showed that under the condition of crop cultivation, the ammonia volatilization of the BC4.5+ and BC0.5+ treatments increased in 4 days, then significantly decreased by 9.95%-61.80% and 7.97%-50.52% (P<0.05), respectively, with respect to CK+. However, compared with CK-, the ammonia volatilization of the BC4.5- and BC0.5- treatments increased by 40.02%-93.15% and 28.09%-57.45% (P<0.05), respectively. For the same amount of biochar application, the ammonia volatilization of the crop-planting soil was significantly lower than that of the bare land, and BC4.5+ and BC0.5+ declined by 27.10%-92.10% and 13.17%-83.45%(P<0.05), respectively, compared with the BC4.5- and BC0.5-, and there was no significant difference between CK+ and CK-. The above results indicated that biochar-mediated soil ammonia volatilization was inhibited by the surface cover. Moreover, with respect to CK+, the maximum increase rates of the contents of ammonium nitrogen and urease in the BC4.5+ and BC0.5+ treatments were orderly at 69.25% and 72.73% and 93.61% and 90.56% (P<0.05), but the soil ammonia volatilization decreased in the same period. The biggest decline of the soil NH₄⁺-N and urease content of BC4.5- and BC0.5- were 63.78% and 95.70% and 78.38% and 92.64% (P<0.05), respectively. Simultaneously, the soil ammonia volatilization rose in the bare land compared with CK-. Therefore, the soil ammonia volatilization was inversely related to soil NH₄⁺-N and urease under the influence of biochar, and the effect of crop planting was more profound.