Abstract:

【Objective】 Soil microorganisms are involved in various biochemical processes and play a vital role in maintaining soil fertility and plant yields. The impacts of different long-term fertilization treatments on soil microbial community structure were studied to clarify the relationship between them. 【Method】 Soil samples were collected from long-term fertilization experimental plots receiving no fertilization, chemical fertilization, chemical fertilization as normally applied by local farmers, harvested residue return, 60% organic manure plus chemical fertilization and 30% organic manure plus chemical fertilizer. Total microbial biomass carbon was determined by chloroform- fumigation-extraction. Phospholipid fatty acid (PLFA) profiles for each treatment were used to characterize the microbial community structure and were analyzed by principle component analysis. 【Result】 Compared with the unfertilized control, all fertilization treatments showed significant increases in total microbial biomass carbon and PLFAs. The iC15:0 fatty acids significantly increased under long-term application of chemical fertilizer but decreased under both organic manure and residue return fertilization. In contrast, under organic manure and residue return, the aC15:0 fatty acids increased. Principal component analyses of the 21 PLFAs detected in the six treatments showed that 87.6 % of the total variance of the individual PFLAs could be explained by two principal components. All unsaturated and cyclopropyl PLFAs except C12:0 and C15:0 were highly weighted on the first principal component. The first and the second principal components could also explain 89.8% of the total variance of fertilization treatment. There was a very little different between the chemical fertilizer treatment and the treatment receiving chemical fertilizer as typically applied by local farmers. There was also almost no difference between the treatment that received residue return and the treatment that received 60% organic manure plus chemical fertilizer. 【Conclusion】 Long-term fertilization can significantly impact soil microbial biomass carbon and influence microbial community structure. PLFAs reflect soil microbial community structure and can be used to detect shifts in response to fertilization.

Key words: red soil, fertilization, microbial biomass carbon, phospholipid fatty acid (PLFA)