Soil Bacterial Diversity And Soil Enzyme Activities As Affected By Ginger Cropping Mode In The Downstream Of Minjiang River

Soil microorganisms and soil enzymes are important components of the agricultural system, which play an important role in the cycle of material and energy in the agricultural ecosystem. Studies have shown that unreasonable rotation cropping and interplanting, long-term continuous cropping caused the decreasement of soil enzyme activity, the loss of soil microbial diversity and alterment of soil microbial community structure significantly. And different types of plants have different tillages, and different types of plants could regulate composition of soil microbial community and soil enzyme through their litters, secretions and their character of prefering resource, etc. Ginger is a cash crop which prohibiting continuous cropping and has allelopathy strongly. It can alter the number of soil microorganisms and activities of soil enzyme, structure of the microbial community, is bad for the stability of soil ecosystem. In addition, with the differentces of combination of crops, tillage and fertilizer management, leading to the different characteristics of soil microorganisms and soil enzymes in soils of different cropping modes. Therefore, to understand the effects of ginger cropping system on soil microbial community and soil enzyme activities under different cropping modes, variations of soil bacterial diversity, enzyme activities and microbial biomass were studied by analyzing, PCR-DGGE fingerprints and DNA sequence in plain soil area and purple soil area of Minjiang River in this paper. Three typical cropping modes (corn-lettuce rotation cropping, continuous cropping of lettuce, rice-lettuce rotation cropping) in plain region and Four typical cropping modes (interplanting of corn + sweet potato, mono-cropping of soybean, continuous cropping of ginger, and rice-milk vetch rotation cropping) in purple region were selected for the study. The main result as these:(1) Ginger cropping mode significantly decreased the dynamics of soil microbial biomass C, N, P, significantly increased the value of soil microbial biomass C/N, soil microbial biomass C/P, soil microbial biomass N/P in soils in different cropping background, and the obvious differences among different cropping background, those results indicated accumulation and distribution of soil microbial biomass were affected strongly by cropping modes. Among the seven cropping patterns, the effects were the least in the one of rice-lettuce rotation cropping in the plain and rice-milk vetch rotation cropping in the hill. In addition, all kinds of residues in ginger rotation cropping have the obvious differences of trends and extents on changing of soil microbial biomass under seven different cropping modes. Cultivation of garlic significantly decrease the dynamics of soil microbial biomass C, the value of soil microbial biomass C/N and soil microbial biomass C/P, howere cultivation of lettuce significantly decrease the dynamics of soil microbial biomass C, value of soil microbial biomass C/N and soil microbial biomass C/P.(2) Ginger cropping mode significantly reduced richness and Shannon-Wiener index of soil bacteria in soils in different cropping background, howere the obvious differences of richness and Shannon-Wiener index among different cropping background. Among the seven cropping patterns, the effects were the least in the one of rice-lettuce rotation cropping in the plain and interplanting of corn and sweet potato in the hill, besides cultivation of gingers made the soils under three different cropping modes in plain and four different cropping modes in hill tend to be similar in structure of bacterial community.(3) Ginger cropping mode obviously altered structure of the bacterial community in soils under different cropping background, but the obvious differences among different cropping background. In plain area, rotation cropping of ginger-garlic-lettuce brought about disappearance of Proteobacteria group in the soil under the mode of continuous cropping of lettuce and rice-lettuce rotation cropping, and disappearance of Caulobacter group in the soil under the mode of corn-lettuce rotation cropping, Stenotrophomonas group in the soil under the mode of under rice-lettuce rotation cropping as well. In hill area, rotation cropping of ginger-mustard brought about disappearance of Nitrospira group, the disappearance of Chloroflexi group in the soil under the mode of under interplanting of corn+sweet potato and mono-cropping of soybean, Bacteriodetes group in the soil under the mode of under rice-milk vetch rotation cropping as well. In addition, all kinds of residues in ginger rotation cropping have the obvious differences of structure of the bacterial community under seven different cropping modes.(4) Ginger cropping mode significantly altered activities of hydrolase in plain and hill soils in different cropping background, especially activities of invertase and alkaline phosphatase, the obvious differences of trends and extent of changes of activities of hydrolase among different cropping background. Ginger cropping system significantly increased activities of invertase, decreased activities of alkaline phosphatase in plain and hilly soils in different cropping background, Among different cropping background, the effects were the most significant of activities of invertase in the one of continuous cropping of lettuce in and rice-milk vetch rotation cropping, and the least in the one of rice-lettuce rotation cropping and mono-cropping of soybean. the most significant of activities of alkaline phosphatase in the one of rice-lettuce rotation cropping and interplanting of corn and sweet potato, the least in the one of corn-lettuce rotation cropping and continuous cropping of ginger. In addition, under seven different cropping modes, all kinds of residues in ginger rotation cropping have the obvious differences trends and extent of changes of activities of hydrolase.The results from this study indicated that ginger cropping altered structure of the bacterial community and activities of soil enzyme in the downstream of Minjiang river, but variations of soil microbial biomass enzyme activities, bacterial community are obvious different in different cropping modes and all kinds of residues in ginger rotation cropping. The results suggested that ginger cropping could seriously influence soil bacterial diversity and soil enzyme activities. Compared to the other cropping mode, the trend of deceased is the most in one of the continuous cropping of ginger in hill area. Corn-lettuce rotation cropping and interplanting of corn+sweet potato could maintain the hightest diversity of soil bacterial community and activities of soil invertase and urease, it may be a reasonable ginger rotation model. those results provided efficient scientific data to maintain the healthy of agriculture ecosystem through chosing legitimately crop mode, optimizating the method of cultivation, strengthening management and so on.