Effect Of Long-term Fertilization On Microbial Community In A Brown Soil Under Crop-rotation System

Soil microorganism is not only "source"and"stock" of soil nutrient, but also extremely important and the most active part of the soil ecosystem. It links the ecological system of underground and overground ecosystem and supports the soil fertility. On the basis of existing long-term fertilization on brown soil, this study aims to reveal influence of different fertilizing pattern on microbial communities and the interaction between soil properties and seasonal variation of microbial commnuties. We analyzed physicochemical properties of soil, and influence of different fertilizing pattern on microbial communities and the interaction between soil microbial communities and soil properties, the results were as follows:(1) Long-term fertilization significantly changed soil chemical properties. Fertilization increased the amount of soil total N, organic C and Alkali-hydrolyzable N. Except for the N treatment, fertilization significantly increased soil total P and available P. Compared with mineral fertilizers, organic manures had significantly greater impact on soil chemical properties. Mineral fertilizer decreased soil pH while organic fertilizer increased soil pH.(2) Long-term fertilization significantly changed the soil microbial community structure and activity. Except forN treatment, fertilizer significantly improved the SMBC content and soil dehydrogenase activity. Compared with mineral fertilizers, organic manures had significantly greater impact on the SMBC content and dehydrogenase activity.Fertilization significantly increased the brown soil bacterial and fungal diversity, phosphate fertilizer input can significantly increase the bacterial diversity. Overall, organic manures had significantly greater impact on bacterial diversity compared with mineral fertilizers. Unlike bacteria, organic fertilizer and chemical fertilizer had a similar impact on fungal diversity.By the cluster analysis of soil bacterial and fungal community structure of different fertilizer treatments, the study found that long-term fertilization divided the brown soil bacterial community into two groups, Cluster Ⅰ consisted of all soil samples obtained from organic fertilizer treatments, and Cluster II contained the soil samples collected in mineral fertilizer treatments as compared to control (CK) while the brown soil fungal community was divided into three groups, Cluster Ⅰ contained the soil samples obtained from manure (M) treatment, Cluster Ⅱ consisted of the soil samples obtained from treatments of manure applied with mineral fertilizers, and Cluster Ⅲ contained the soil samples collected in mineral fertilizer treatments and CK. Compared with mineral fertilizers, organic manures had significantly greater impact on bacterial and fungal community structure.(3) According to the size of brown soil stable bacteria, the sequence was Proteobacteria＞Acidobacteria＞Firmicutes＞Gemmatimonadetes. a-proteobacteria and β-proteobacteria were dominant community in Proteobacteria. According to the size of brown soil stable fungi, the sequence was Ascomycota and Zygomycota＞Chytridiomycota and Basidiomycota.(4) The seasonal variation of the brown soil microbial was significant. The varied trend of SMBC for all treatments were that SMBC increased rapidly in seedling stage, decreased sharply in jointing stage, then increased in tasseling stage, and then slow down. The content was equal to the level of seedling stage in mature stage. The varied trend of bacterial diversity for all treatments were that Shannon index increased rapidly in seedling stage, decreased greatly in jointing stage, then varied slightly. The varied trend of fungal diversity for all treatments were that Shannon index increased rapidly in seedling stage, greatly decresed in jointing stage, then increased sharply until milk stage, and then decresed slightly in mature stage.(5) Redundancy analysis and canonical correspondence analysis of soil physicochemical properties and microbial community structure demonstrated that the main factors influencing the SMBC and dehydrogenase activity were TN, SOC, TP, AP and AHN. The main factors influencing brown soil bacterial and fungal community diversity were TN, SOC, TP, AP and AHN. The main factors influencing soil bacterial and fungal types were TN, TP, AP, SOC and TN, SOC, AP, AHN, respectively. The main factors influencing seasonal variation of SMBC were DOC, AK, AHN, AP and pH, while the main factors influencing seasonal variation of bacterial and fungal diversity were DOC, AK, AHN and soil moisture content.