| Soil microbes play key roles in the agroecological system and influence a large number of important agroecological system processes, such as nutrient cycling and soil formation. Moreover, soil microbes represent the unseen majority in agroecological system. However, while it is widely recognized that microbes play crucial roles in agricultural production, the impact of microbial community structures on plant productivity is still poorly understood. In this study, we combined the different chemical properties of typical agricultural soils from different regions with their microbial connunities by the method of sterilization and reinoculation to explore the impact of the microbial community on nutrient cycling and plant productivity in our typical farmland. The major results are presented as follows:1. In this study, we used the sterile black soil from Gongzhuling as research materials, and selected the non sterilized black soil from Gongzhuling, fluvo-aquic soil from Dezhou, gray desert soil from Shihezi and red soil from Qiyang as the inoculated soils, respectively, to conduct the pot experiment with maize. Our research results found the content of soil available nutrients (except the ammonium nitrogen) was higher in the treatment inoculated with black soil microbes than in the treatment inoculated with fluvo-aquic soil microbes; the nitrate content was the lowest in the treatments inoculated with gray desert soil and red soil microbes. The highest activity of soil β-1,4-glucosidase and acid phosphatase closely related to soil biochemical processes was found in the sterile black soil inoculated with red soil; The β-1,4-glucosidase activity was significantly higher in the sterile black soil inoculated with red soil than in the sterile black soil inoculated with black and grey desert soil, and the treatment inoculated with fluvo-aquic soil had also significantly higherβ-1,4-glucosidase activity than that inoculated with black soil. The activity of acid phosphatase of the treatment inoculated with red soil was significantly higher than that of other three treatments, and significant differences existed among these three treatments. However, the activity of polyphenol oxidase showed no significant difference among the treatments. By analyzing the microbial community structure of soil in every treatment, we found that soil microbial diversity index (e.g. Shannon index and Simpson index) reached the highest value (2.03 and 0.83, respectively) in the treatment inoculated with black soil, while the lowest value was observed in the treatment inoculated with fluvo-aquic soil. Treatments inoculated with black soil and fluvo-aquic soil had a similar microbial community structure, but others showed great difference. Different soil inoculations had a significant effect on plant productivity in the sterile black soil, and the plant biomass in the treatments inoculated with gray desert soil and red soil was significantly higher than that in the treatments inoculated with black soil and fluvo-aquic soil. Correlation analysis showed that plant biomass was negatively correlated with soil available nutrients (except phosphorus), but was not significantly related to soil enzyme activity. The plant biomass was positively correlated with Cytophagia population in the soil, but negatively correlated with Thermoleophilia, Chloracidobacteria or Acidobacteria populations.2. We used the sterile gray desert soil collected from Shihezi as research materials, and selected the non sterilized soils mentioned above as inoculums to conduct the pot experiment with maize. Our research results showed that the content of available nutrients (Moisture content, NO3--N, Olsen-P and DON) of the grey desert soil inoculated with black soil was higher value than that inoculated with other soils, while the content of NH4+-N and DOC showed no significant difference between the treatments. Significantly higher moisture content was noted in the treatments inoculated with black soil and fluvo-aquic soil than in the treatments inoculated with red soil or grey desert soil. The content of NO3--N and DON showed a similar trend, with the treatment inoculated with black soil showing significantly higher than the treatment inoculated with red soil. The content of Olsen-P in the treatment inoculated with black soil was significantly higher than that of the treatments inoculated with gray desert soil and fluvo-aquic soil. Soil β-1,4-glucosidase, L-leucine aminopeptidase and acid phosphatase showed the highest activity in the treatment inoculated with red soil. The activity of L-leucine aminopeptidase and acid phosphatase in the treatment inoculated with red soil was significantly higher than that of other three treatments, and only the activity of L-leucine aminopeptidase was significantly higher in the treatment inoculated with gray desert soil than in the treatment inoculated with black soil. The activity of polyphenol oxidase showed the highest content in the treatment inoculated with fluvo-aquic soil, and was significantly higher than in other treatments. By analyzing the soil microbial community structure, we found that soil microbial diversity index (e.g. Shannon index and Simpson index) reached the highest value (2.07 and 0.84, respectively) in the treatment inoculated with gray desert soil, while the lowest value was observed in the treatment inoculated with fluvo-aquic soil. Treatments inoculated with black soil and fluvo-aquic soil had a similar microbial community structure, but others showed great difference. Different soil inoculation treatments had a significant effect on plant productivity in the gray desert soil tested, and the plant biomass in the treatments inoculated with gray desert soil and red soil was significantly higher than that in the treatments inoculated with black soil and fluvo-aquic soil. The correlation analysis showed that plant biomass was negatively correlated with moisture content, Olsen-P content, β-1,4-glucosidase activity and polyphenol oxidase activity. The plant biomass was positively correlated with Sva0725, Sphingobacteriia, Acidobacteria and Saprospirae population in the soil, but negatively correlated with Gammaproteobacteria and Chloracidobacteriad populations.3. We used the sterile red soil from Qiyang as research materials, and selected the non sterilized soils mentioned above as inoculums to conduct the pot experiment with maize. Our research results showed that only the content of NH4+-N and Olsen-P showed significant differences between the treatments. The content of NH4+-N in the treatment innoculated with black soil was significantly higher than that in the treatment inoculated with gray desert soil or red soil, whereas the content of Olsen-P in the treatments inoculated with fluvo-aqci soil and gray desert soil were significantly higher than that of other two treatments. Soil L-leucine aminopeptidase and acid phosphatase showed the significant differences between the treatments. The activity of L-leucine aminopeptidase in the treatment inoculated with black soil was significantly lower than that of other three treatments, and the activity of acid phosphatase in the treatment inoculated with black soil was significantly higher than that of the treatment inoculated with gray desert soil. We analyzed the microbial community structure of soil and found that soil microbial diversity index (e.g. Shannon index and Simpson index) reached the highest value in the treatment inoculated with gray desert soil. Treatments inoculated with red soil and fluvo-aquic soil had a similar microbial community structure, but others showed great difference. Different soil inoculation treatments had a significant effect on plant productivity in the treatment inoculated with gray desert soil, and the plant biomass in the treatment inoculated with gray desert soil was significantly higher than that of the treatment inoculatwd with black soil or fluvo-aquic soil. The correlation analysis showed that plant biomass was negatively correlated with the content of NH4+-N and NO3--N. The plant biomass was positively correlated with Acidobacteria and Rubrobacteria populations in the soil, but negatively correlated with Alphaproteobacteria and Bacilli population in the soil.In summary, the soil microbial communities not only sensitively reflected the soil fertility, but also affected the plant productivity. The results of the present study show that the sterilized soils (including black soil, gray desert soil and red soil distributed in different regions) inoculated with gray desert soil and red soil can produce higher maize biomass, with the highest plant biomass produced in the gray desert soil noculated with itself. In this study clearly shows that the soil microbial cummunity has a significant effect on the growth of crops in the case of non pathogenic, and the degree of influence in this experimental condition can be comparable with the influence from the content of soil samples. Therefore, explaining the mechanism of how the farmland microbes affect the crop growth deeply will have a very important significance. |
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