| The microbial diversity and biogeochemical potential associated with agronomic management, crop rotation which boosts yeilds and improve the environment. Crop rotation and tillage systems play as a proactive strategy in the control of fungal soiiborne diseases. The physical and chemical soil properties is influenced by different crops, as well as the different combinations of time and order with crops on carbon emissions. The study designed focuses on 6 rotation patterns crop rotations over 5 years, with the aim being to assess the impact of rotation on soil physical and chemical properties, soil respiration and the soil microoganism organic carbon. S1-potatoes 1 yr-alfalfa 2 yr-oats 2 yr; S2-oats 1 yr-alfalfa 2 yr-potatoes 2 yr; S3-oats and alfalfa mixed cropping 1 yr-alfalfa 1 yr-oats 1 yr-potaioes 2 yr; S4-oats and alfalfa mixed cropping 1 yr-alfalfa 1 yr-potatoes 3 yr; S5-oats 2 yr-alfalfa 3 yr; S6-potatoes 2 yr-alfalfa 3 yr. Based on 16S rDNA sequence diversity by using an Illumina MiSeq next-generation sequencer, valuable phylogenetic information for the comparison of microbial diversity in environmental samples is more accurate. Here, we used high-throughput sequencing platform to appraise the diversity and composition of both bacterial and fungal communities characterized by pyrosequencing of 16S rDNA and ITS.1. S2 and S3 significanty increase the capacity of retaining soil moisture after winter that in these treatments after the autumn harvest soil moisture could reach 8%-10%. while the others dropped down to below 5% during the winter. At the same time, S2 and S3 kept the soil moisture of different depths at a higher level, uniform and stable, by contrast, others lost greatly.2. The soil surface temperature peak was in early August. S3’s s surface temperature (25 ℃) was significantly lower than other treatments (30-35 ℃), but at 50 cm soil depth was higher than the others. The stability of the temperature was showed not only between the soil depth, but also throughout whole growth period, with no dramatic ups and downs with the summer climate changing.3. The order, soil respiration (soil microbial and plant root respiration) of these treatments throughout the year, is S9<S2<S3<S4<S8<S10<S1＜S5<S6<S7. Crop rotation treatment can reduce the surface soil organic carbon mineralization and losses significantiy. S3 which is 324mg/kg is seen as the best in after harvest and S4 distinctly increased the microbial biomass-C, comparing with continuous cropping. The statistics also demonstrated that soil respiration and soil surface temperature had a quadratic relationship.4. Sucrase, pH. macroaggregate and urease were relatively more closely related to the microbio comunities. But without P values which was less than 0.01. the sum of X and Y axis contributing ratio was low from the PC A. Results of this principal coordinate analysis showed that the samples can be clustered into 4 groups: ①S1, S2, S3. S4; ②S6, S7. S9. S10:d,③S5 and ④S8. The analysis of Pearson correlation coefficient dropt down to about 60% between S5. or S8, and other patterns. S4 soil bacterial communities were not clustered together with other rotations. Heat map cluster analysis showed two distinct clusters, which confirmed the difference between the bacterial communities of 3 crops rotations and other soils. Bacillus were found mostly in S5 and S8 soils suggesting favorable conditions for the proliferation and activity of specific microbial taxa. S6 and S10 had hardly any Chirinophaga. Ramlibacter, Lysobacter, Rhodanobacter and Nonomuraea in S4 were highest, and a variety of bacteria distribution was relatively uniform. S4 increased the content of cellulose-decomposting bacteria, free living nitrogen fixing bacteria, and associate nitrogen-fixing bacteria these 3 functional bacteria; while S5 and S8 enriched ammonifying bacteria. Bacteria structure were dominated by different crop rotations. Proteobacteria was enriched significantly.5. A canonical correspondence analysis (CCA) revealed that fungal communities in bulk soils were influenced by the crop rotation systems, x and y-axis contributed rate of the CCA (CCA1 (28.2%), CCA2 (17.5%)) were higher than the bacteria that was accounted for the physical and chemical factors on the crucial positions overall. The two-dimensional coordinate axis could explaine 49.23% of reasons.. However, the primary factors influencing each community was that fungal communities were influenced most strongly by soil properties (especially carbon content, followed by temperature, moisture, sucrase and urease). To elucidate factors that may cause differences in crop rhizosphere microbial communities. Our present study indicates that the microbial communities in bulk could be managed by crop rotation systems. The samples were divided into three groups:①S1 S3. S4, S7, S9; ②S6, S5, S8, S5, S10; ③S2. And S7 in a critical position, could be divided into the second group. Under the phlym level, more than 90% was known including Ascomycota, Glomeromycota, Chytridiomycota, Basidiomycota; and Ascomycota is the most abundant (52.88-86.09%). Eurotiomycetes was significantly increased in S3 (43.64%) which was much higher than other tratments. Sordariomyceies was dominant in Ascomycetes (25%-50%). Basidiomycota, Tremellomycetes and Agaricomycetes were the main component of Basidiomycetes which influenced the decomposition of organic matter.In conclusion, the rotational pattern suggested of oats-alfalfa intercropping 1 year, alfalfa 1 year, oats 1 year and potato 2 years and oats-alfalfa intercropping 1 year, alfalfa 1 year, and potato 3 years could effectively increase the ability of soil carbon sequestration, improve soil properties and microbial activities. That has been proven to be suitable in this case, causing considerable enhancement in beneficial soil microbe, that Oats planted before alfalfa could increase microbial species diversity and increasing nitrogen fixing bacteria than continuous cropping alfalfa. More differences, species diversification, could better protect against climate changes. |
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