Effect Of Adding Corn-straw On Soil Organic Matter And Microbial Communities

Decomposition of organic material into the soil is an important part of ecosystems, the function of microbial decomposition determines the accumulation or release of soil organic matter(SOM). The unity of soil-microorganisms-organic material controls the material and energy circulation, mutual influence and constraints, determine the supply of soil nutrients together. A series of biological changes occurred during the processes of organic material degradation, to study the mechanism of microbial degradation of organic material is important for enhancing the soil fertility. In this study, indoor simulation, analysis the microbiological characteristics after corn stalk adding to soils which collected in different habitats with SOM content change. 85 soils which collected from different environments mixed with corn straw, then treat this systerm as our research objects to study SOM dynamics characteristics, total nutrient and available nutrient changes, cultured microbial quantity characteristics; by classified the soil moisture, initial content of SOM and soil land use patterns, to explore the elements of changes to SOM; making comparison between different SOM change soils PLFA microorganisms characteristics and use of high-throughput sequencing methods to find differences between the microbial diversity, to explore the dynamics of SOM and microbial community interaction mechanism, results were as follows:1. Soil relative change rate of SOM content and its initial SOM content had significantly negatively correlated, both had a good logarithmic relationship; soil moisture content increased, soils mount of cumulative and consumption both decreased gradually; arable lands relative rate of SOM change increased besides three soil samples, paddy’s SOM were all reduced, woodland and vegetable SOM both had increases and decreases samples; soil samples initial cultured bacteria was significantly higher than that of fungi and actinomycetes(p<0.01), after adding straw all microbial’s number increased, increasing proportion of paddy field>woodland> vegetable> arable land, fungi> actinomycetes> bacteria.2. After 90 d culture of soil-corn mix, according to the different between the treated SOM and the original soil samples SOM(I). 63.5% samples SOM have accumulated, which had a higherdegree of increase(I>12.05g/kg) was 39% samples, a lower degree of increase(0.25g/kg<I <9.00g/kg) was 61% samples. In addition, 36.5% of soil samples SOM decreased, the range was-112.30g/kg<I<-0.30g/kg.3. SOM net cumulative amount(I) as a standard for distinguish the soil group: I1 group was SOM accumulation significantly increase, I2 group was SOM accumulation not significantly increase, I3 group was SOM reduction samples. Selecting 10 soil samples was studied in each group. In addition to samples HUB-1, GZ-2 and HEN-13,soil nitrogen in all groups showed a different degrees of increase, amount of increasing I1> I2> I3, total phosphorus content,in addition to nine soil samples reducing, the rest are increasing, decreasing samples are appeaered in all three groups, total potassium content also increased significantly, the average increasing amount of I1, I2 and I3 group were 90.34,61.76 and 99.60g/kg respectively; most of three groups soil available nitrogen content increased, the increasing trend consistent with the trend of total nitrogen and organic matter, both I1> I2> I3 group, available phosphorus content also increased significantly, the average content of I3> I1> I2, I2 lower than I1 and I3 32%, 38% respectively, potassium content also increased significantly, the sample GS-1 belong to I2 group had the top increase amount of 2500g/kg, the lowest increment in I3 group soil CQ-3 also reached 88g/kg, no significant difference between the three groups of soil, I2 was slightly larger than I3 and I1 group.4. No matter treatment, three groups soil bacteria, fungi and actinomycetes were significantly increased, the increment of fungi>actinomycetes>bacteria. I3 group original soil culturable bacteria was significantly higher than group I1 and I2, mean number of bacteria in I3 was higher than I1 and I2 28.3%, 23.1% respectively. All three groups soils exisited the amount of original soil culturable bacteria inverse to microbial increment after treatment, such as I1 group SC-3, I2 group HEN-6, HUB-6 and I3 group AH-2, HUB-3, GS-4, HEB-2, HEN-13, HEN-2, especially obvious in I3 group.5. Due to the low nutrient of original soil in I2 group, limit the PLFA content and types remained consistent with the original soil; Although both I1 and I3 had the same high content of original SOM, but after adding fresh carbon I1 group caused true priming effect(TPE)by soil microbes, eight kinds of fungi, actinomycetes and G- bacteria which had carbon fixation function were stimulated, and accompanied 10 kinds of unknown bacterial populations disappeared which had carbon restrictions function. The value of bacterial/fungal significantly reduced, all lead to increscent of soil organic matter; Adding fresh carbon source in I3 group could promote 10 kinds of fungi, actinomycetes and G+ bacteria which could only use such carbon sources and lack the ability of degrading organic substance, finally caused false priming effect(FPE). The value of bacterial/fungal although declined significantly, but the cumber of bacteria far morethan the number of fungi, original soil nutrient mineralization terribly, soil organic matter content decreased.6. According to High-throughput sequencing results, I1 group SC-2 treatment samples bacterial abundance was no significant difference than original content, fungal abundance had a significant increase, I3 group HUB-3 samples abundance of bacterial and fungal both decreased significantly, two treatment soils diversity index were significantly lower than original samples; 4 soil samples were detected 24 fungi in genus level, the treated soil SC-2 groups compared with the original soil sequence proportion of the total, reduction sequence were 14 kinds of fungi, fungi increase in the proportion of the total sequence only six and all belong to genus of fungi, particularly fungi of unknown Sordariales increament up to 20%. HUB-3 treatment sample compared with the original sample sequence only seven fungus reduced, the proportion of increase fungi was 17, the dominant grouphad a single type of soil, but the proportion of low-abundance distribution flora in most of the treated soil had a slight increase. Corn straw treatment on SC-2 samples bacterial community had little effect on the species and aboundance of dominant bacteria groups before and after treatment, only Proteobacteria and Actinobacteria bacterial populations decline. But corn straw adding greatly changed the abundance of bacterial in HUB-3 samples, in addition to the advantages of bacterial flora Proteobacteria increased, others had a different degrees of decline.7. In SC-2 and HUB-3 examples, both from the paddy fields, with the similar original climate and decomposition conditions, SC-2 increased soil organic matter after the addition of straw, mainly due to the original soil microbial community composition and background control of physical and chemical indicators. CCA results showed that SC-2 and HUB-3 original soil have different microbial community composition, and known by the high-throughput analysis, SC-2 dominant bacteria in the original sample mainly Proteobacteria、chloroflexi and another 5 phylums, the dominant fungus including Verticillium 、 Coniochaetaceae and another four species,and HUB-3 in the original sample, the advantages of fungis include Microascaceae, Coniochaetaceae and Verticillium, bacterias include Proteobacteria, Actinomycetes and another six species.The process of degradation of organic material, two microbial groups changed after the SC-2 culture, the most obvious change are the bacterial groups, and after the end of the HUB-3 cultured, most microbial population changed are fungi(from CCA result), where in the SC-2 microbial flora is mainly affected by soil organic matter, total nitrogen, available phosphorus and nitrogen, but high potassium, p H and G+/G-would inhibit microbial decomposition efficiency. HUB-3 changes in microorganisms may be associated with the original organic matter mineralization and the mineralization process, the microbialcommunity composition and abundance of p H, total potassium and G+/G-value was positively correlated with organic matter, total nitrogen, available phosphorus and nitrogen were negatively correlated. 2 soil in the process microbial decomposition of organic materials controlled by different physical and chemical factors, but the specific mechanism needs further study.