Effects of long-term inorganic fertilizer combined with organic manure on microbial biomass C、N and enzyme activity in cinnamon soil

The soil of long-term experimental field（0-20 cm and 20-40 cm）was collected and analyzed in Shouyang county, Shanxi province. The changes of microbial biomass C, N and soil enzyme activity in cinnamon soil and the correlation among them were both explored. The results were as follows: The changes of microbial biomass C, N in cinnamon soil were basically consistent. The amount of BC and BN in cinnamon soil both decreased from 0-20 cm layer to 20-40 cm layer. BC and BN in cinnamon soil could both increased through long term application of organic fertilizer only, inorganic fertilizer combined with organic manure in a right way. BC and BN in cinnamon soil could not both be observed to increase through long term application of different dosage of inorganic fertilizer only. The activity of Urease and Alkaline phosphatase in cinnamon soil both decreased from 0-20 cm to 20-40 cm layer, too. Urease and Alkaline phosphatase activity in cinnamon soil could also be increased by long-term application of organic fertilizer or inorganic fertilizer combined with organic manure in a right way. Urease activity in cinnamon soil tended to increase with long term application of inorganic fertilizer; however, the changing tendency of Alkaline phosphatase activity was just opposite to Urease’s. The apparent positive correlation was found between the contents of organic matter and the four kinds of soil quality indicators—microbial biomass C, microbial biomass N, Alkaline phosphatase and nitrate reductase, which was also found to be positively correlated with total N content. The contents of organic matter and total N could be estimated using microbial biomass C, N and soil enzyme activity, which could be used as biological indices in the evaluation of soil fertility, and provided the basis of how to improve soil fertility.