The Effects Of Straw Returning On Soil Nutrients And Biological Characteristics

In this paper, the effects of straw returning on soil nutrients, soil enzyme activities, soil microbial biomasses and the soil fungal diversity were studied by long term experiment in wheat-corn double cropping systems. The aim was to provide a basis for exploring the development of low carbon agriculture, building a resource-conserving and environment friendly agriculture, and realizing the sustainable development of grain production.The main results showed as bellow:Straw returning increased the content of soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium. Straw returning cooperated with fertilization could slow down the decrease rates of soil nutrient and maintain the demand of the crop’s growth.Soil enzyme activities were affected by temperature and rainfall. Soil Urease, invertase, and acid phosphatase activity changed with the crop growth. From the wheat seeding to maize harvest stage, the soil urease activities of the treatment (wheat and maize straw returning but no fertilizing) compared with CK treatment were separately increased21.93%,4.92%,35.88%,4.71%,21.79%,0.99%,31.52%,21.77%,8.52%,3.74%and12.89%; the soil invertase activity of the treatment was increased52.7%averagely. The soil acid phosphatase activity (from wheat seeding to maize harvest stage) showed a wave change, and it rose at first and then fell down and rose again. The soil acid phosphatase activity of the treatment (wheat and maize straw returning with fertilizing) was signally higher than other treatments. The soil cellulase activity was stabile in the maize growth period, and it fluctuated in a custom range. The soil cellulase activity of wheat and maize straw returning treatment compared with CK during the period of maize growth separately increased by113.1%、24.2%、63.3%、128.2%、99.3%, with a significant difference.Compared with CK treatment, the treatment (wheat and maize straw returning with fertilizing) could markedly increase the content of the soil microbial biomass C, N, P, separately by164.6%,19.3%and609.1%.Total DNA was directly extracted and amplified with the ITS-1F and ITS-2primers targeting ITS1between5.8S rDNA and18S rDNA. The amplified fragments were analyzed by perpendicular DGGE. Seventeen DGGE bands recovered were re-amplified, sequenced and aligned with Blast. Phylogentic relationship of the representative banding were identified three groups. Ascomycota, Glomeromycota and uncultured fungus account for23.5%,11.7%and5.8%among them. The Shannon-Weaver index(H’) fluctuated from1.540to2.547. Clustering analysis and PCA analysis showed that the straw returning of maize made a great contribution to the diversity of the fungal communities. It suggested that Nested PCR and DGGE technique have a better priority in analyzing the community of soil fungal.