Effects of Byproduct Amendments and Nitrogen on Carbon Mineralization and Soil Enzyme Activities in Acidic Brown Soil from Jiaodong Peninsula of China.

It has been proposed strategy that acidic soil quality can be improved by addition of alkaline byproduct amendments containing silicon, calcium, magnesium and potassium. The effects of amendments and three different forms of nitrogen [(NH2)2CO, NaNO3 and NH4Cl] on quality of acidic soil were investigated in Jiaodong Peninsula of China. A 120-day incubation test was carried out to assess the effect of amendments and nitrogen on soil physicochemical properties, soil carbon (C) mineralization and enzyme activities. The results showed that the addition of alkaline amendments can increase soil pH from 5.93 to 6.99 at the beginning of cultivation, while when amendments combined with urea or NH4Cl, soil pH decreased with incubation time. The response of C mineralization was inversely proportional to soil pH value. The addition of amendments could improve soil C content via decreasing soil C-CO2 emissions, and the mineralization rate was reduced by 26%. Addition of amendments in combination with urea or NH4Cl, which could decrease soil pH, stimulated soil C mineralization and increased soil microbial biomass carbon (MBC) and dissolved organic carbon (DOC) fractions in acidic brown soil. However, when amendments were applied with NaNO3, the soil C mineralization could be inhibited. The addition of amendments or combination of amendments and nitrogen increased the soil invertase and phenol oxidase activities, and inhibited soil urease activity. Therefore, the chemical and biological properties of the acidic brown soil in Jiaodong Peninsula of China might be better improved by combination of amendments and NaNO3. [ABSTRACT FROM AUTHOR]