Effect Of Long-term Different Fertilization And Plastic Mulching On Organic Fractions And Microbial Diversity In Brown Earth

Soil organic carbon play a crucial role in the cycling of almost all the major plant nutrients, which keeps stability of aggregate and improves abilities on keeping water and cushion to sustain cultivation. Soil microorganism is the critical resource and pool of soil nutrients and soil microbial community is an important measure of sustainable land use and is sensitive to changes in the soil as the alarm signal and sensitive index. Recently, studies in home and abroad almost focus on organic fractions and microbiological characters and diversity respectively. The systemic and comprehensive studies about union between organic fractions and microbial diversity combining with dynamic monitor have been lack . Based on 20-years-old located brown earth experiment site at Shengyang Agricultural University, this paper adopt the methods of organic fractions and PLFA and PCR-DGGE to determine the change of organic fractions and microbial diversity in the long-time fertilization and plastic mulching soil in order to explore the effect on their inter-relation between soil organic fractions and microbial diversity. In order to develop soil health and microbial diversity it will provide scientific basis for setting up farm management measures for persistent resources.The main results were as follows:(1)The effect of 20-years-old fertilizations on organic fractions of soil: M4, M4N2P1>CK>N4. Thecontents of total organic carbon in treatments of M4 and M4N2P1 were 25.1% and 35.4% higher thantreatment of CK, respectively, while thoes of treatment of N4 was 1.7% lower than treatment of CK. Theproportion of labile organic carbon in the total organic carbon in treatment of M4 was 62.5% higher thantreatment of CK, while that in treatments of M4N2P1 and N4 were 12.5 % and 59.1 % lower than treatmentof CK, respectively. The proportion of dissolved organic carbon in the total organic carbon in treatments ofN4, M4 and M4N2P1 were 28.4%> 27.6% and 37.9% lower than treatment of CK, respectively. Theproportions of microbial biomass carbon in the total organic carbon in treatments of M4 and M4N2P1 were118.1 % and 5.6 % higher than treatment of CK, respectively. The proportion of particulated organiccarbon in the total organic carbon in treatments of M4 and M4N2P1 were 65.3%and 4.8% higher thantreatment of CK, while that of treatment ofN4 was 21.8%lower than treatment of CK.(2) After 20 year plastic mulching, the contents of total organic carbon and organic fractions weredecreased. The content of total organic carbon in covered treatment of N4 was higher than that ofuncovered soil signifigantly. The content of labile organic carbon in covered treatment of CK was higherthan that of uncovered soil signifigantly. While the content of dissolved organic carbon in coveredtreatment of CK was lower than that of uncovered soil signifigantly. The content of microbial biomasscarbon in covered treatments of CK,N4 and M4 was lower than that of uncovered soil signifigantly, whilethere was no significant difference in particulated organic carbon between covered and uncovered.(3) After 20 year long term cultivation, changing trend of total content of PLFA was M4N2P1 >M4>N4>CK. Soil microbial community changed obviously because of different fertilization. The bacteriacommunity structures were changed by different fertilizarions. Soil community structures were similar between M4 and M4N2P1 and between covered treatment of CK and uncovered treatment of CK. Application of manure could increase bactieral diversity, while single application of nitrogen could decrease it. There was no signifigant effect of long -term plastic mulching on the total content of PLFA. The microbial community structure in soil of different fertilization trend identical development despite of different fertilization treatments. The bacteria diversity in teatments of N4 and M4 was decrease by pastic mulching, while that of treatment of CK was opposite.(4) There are some intimate relations between shannon-wiener, total organic carbon and labile organic carbon, microbial biomass carbon and particulated organic carbon. The organic fractions could be indicative index to soil health. The microbial diversity of soil was also the indication of change on active organic fractions of soil and soil fertility.(5) It is tested that application of manure or co-application of manure and chemical fertilizers take advantage of enhance on soil fertility as scientific management and single application of nitrogen reverse the treatment of plastic mulching can hold back bad-behaved development of soil fertility by application of single application of nitrogen. In virtue of sensitive response to farm management treatments, particulated organic carbon and microbial biomass carbon in soil can be of indication and character used to evaluate the effects of farm management treatments.