Differences of soil biological characteristics and bacterial diversity of sugarcane fields in red soil region affected by long-term single chemical fertilization and chemical organic combined application

【Objectives】 Study on the soil biological characteristics and bacterial diversity of soils affected by long-term fertilization will provide support for the sustainable development of sugarcane industry in Guangxi Province, 【Methods】 Long-term experiment started since 1995 in Laibin county, Guangxi Province. Three treatments include no fertilization (CK), chemical fertilizer only (NPK) and chemical fertilizer plus organic fertilizer (NPKM). Soil microorganisms were analyzed by using PCR-DGGE and dilution plate methods. 【Results】 The soil pH shows decreasing in the three treatments, particularly in the NPK treatment. The numbers of bacteria, fungi and actinomycetes were the highest in the NPKM treatment, which were significant higher than in the NPK and CK treatments. The number of cultivable actinomycetes in NPK treatment was significantly lower than in the CK, and there was no significant difference in numbers of bacteria and fungi between the NPK and CK. The activities of soil β-Glucosidase, phosphatase and protease were the highest in the NPKM treatment, and its biomass C and biomass N showed the highest as well. The activities of protease and phosphatase, and the biomass N in the NPK treatment were all lower than in CK. The bacterial diversity index, richness and evenness were all higher in the NPKM treatment. 【Conclusions】 The soil pH is easily declined by the input of fertilizers, particularly under the long-term single chemical fertilizer use. The long-term chemical fertilization may also result in low biodiversity and low activities of nutrient supply related enzymes in soil, leading to soil fertility decline and soil degradation. Conversely, the long-term combination use of chemical fertilizer and manure is effective in slowing the soil pH decline, improving soil fertility and ecological quality in sugarcane fields of red soil regions in Guangxi Province, China.