| Low-yield yellow clayey soil，with the restrictive factor of poor soil maturation degree, waswidely distributed in southern China The application of organic fertilizers were an important measurefor improving yellow clayey soil. In order to investigate the mechanism of fertility under differentorganic fertilizers application in low-yield yellow clayey soil, five treatments was carried out in a fieldexperiments:(1) no fertilizer (CK),(2) Chemical fertilizer (NPK),(3) NPK plus green manure（NPKG）,(4) NPK plus pig manure（NPKM）,(5) NPK plus straw（NPKS）. In this research, rice yield, soilphysical and chemical properties, soil organic carbon fractions, soil enzyme activities, phospholipidfatty acid composition and soil microbial community diversity were detected. The main progress asfollows:1. Rice yield was significantly improved after the application of organic manure. After two yearsfield experiments, the rice yield of chemical fertilizers plus organic manures treatments weresignificantly higher and more stable than CK treatment. Among all of the treatments plus organicmanures, pig manure treatment had the best effect on increasing rice yield, followed by green manureand straw. Green manure treatment trended to increase the yield production with years of trials.2. Soil structure and nutrient content were improved by the application of organic manure. Organicfertilizer decreased soil bulk density, increased the content of more than0.25mm large aggregate waterstability, pig manure and straw contributed to increase soil aggregate stability. NPKG/NPKM/NPKStreatments significantly increased soil nutrient content over CK and NPK treatments. Soil availablenutrients increased rapidly, while soil total nitrogen and organic matter content increased slowly. Strawapplication can effectively increased soil available potassium content, and pig manure applicationsignificantly increased the soil available phosphrous content.3. Soil organic carbon fractions were changed by the application of organic manure. Straw and pigmanure could improve the total organic carbon content, and the effect of different organic fertilizers onorganic carbon accumulation in soil was: straw> manure> green manure. After application of organicmanures, the proportion of steady-combined carbon and tight-combined carbon were improved in heavyfraction organic carbon, where compositions of combined formations of humus was also changed.Meanwhile, all the organic fertilizers treatments showed higher contents of humic acid (HA), fulvic acid(FA) and humin in different degrees. Chemical fertilizers treatment decreased the HA/FA ratio in topsoil,but straw treatment tended to increase the ratio and improve soil maturation degree of the yellow clayeysoil.4. Soil enzyme activities were significantly changed after the application of organic manure. Pigmanure treatment increased the enzymes of decomposition carbohydrates including β-glucosidase,β-cellobiosidase, N-acetyl-glucosamidase and sulfatase, urease activities, all of them were enhanced bysoil available phosphrous content, CEC and pH. Straw manure treatment significantly increasedα-glucosidase activity, which was positively correlated with soil C/N, soil total nitrogen, soil organic matter, soil available potassium. Howerer, there was a negative correlation between activities ofphosphatase, aminopeptidases, peroxidase, phenol oxidase and soil nutrients, CEC, pH. As a result, theactivities of phosphatase, aminopeptidases, peroxidase and phenol oxidase were inhibited inNPKG/NPKM/NPKS treatments.5. The microbial community structure of yellow clayey soil was affected by the application oforganic manure. Effect of fertilization on fungi was larger than bacteria and actinomycetes. Chemicalfertilizers reduced the amount of bacteria, fungi and actinomycetes in different degrees. Pig manureimproved molar percentage content of fungal and significantly reduced the bacterial/fungal ratio. Strawand green manure significantly reduces the actinomycetes molar percentage content. Principalcomponent analysis showed that the effect of green manure and pig manure treatments on microbialcommunity structure was similar.6. Soil microbial diversity was affected by the application of organic manure. The results of thestudy of bacteria and fungi microorganism genetic diversity by PCR-DGGE technique in yellow clayeysoil showed that the effect of fertilization on bacteria was larger than fungi. Soil bulk density wassignificantly associated with the change of soil bacterial genetic diversity. Soil nutrients had a greatinfluence on fungal genetic diversity, among which soil available potassium was significantlyassociated with the change of soil fungal genetic diversity(P﹤0.05）. Sequencing of PCR productsseparated in DGGE showed that Sphingomonas was dominant bacteria and Mortierella elongate andTalaromyces was dominant fungi in yellow clayey soil. Chemical fertilizer reduced bacteria and fungidiversity. Green manure and straw reduced the bacterial diversity, while were benefit to improve thediversity of fungi. |
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