Effects Of Straw Incorporation On Soil Enzyme Activities,Microbial Biomass And Functional Diversity Of Communities

Straw is an important biological resource that is rich in nitrogen,phosphorus,potassium and trace elements.The reasonable straw incorporation provides a rich carbon source for the soil microbial community and stimulates soil microbes and various enzyme activities,which are beneficial to the improvement of the soil quality and productivity.Many researchers have done a lot of work about the effect of straw incorporation on soil enzyme activity and microbial functional diversity,also obtained corresponding research results.At present,a comprehensive study about straw amount,burial depth and length and its interaction has not been reported.Based on the previous researches,two-years straw incorporation with a quadratic orthogonal rotation design was carried out.Taking straw length,amount,and burial depth as three factors,the changes of soil enzyme activities and microbial indicators under different patterns were explored.Moreover,a regression model was constructed between the soil microbiological comprehensive index values and the three factors.The single-factor and two-factor interactions were analyzed to find out the optimal combination of straw incorporation for the improvement of soil microbial functional diversity and enzyme activity,which will provide a scientific basis for the rational utilization of straw resources and the promotion of soil fertility.The main conclusions of this study were as follows:(1)After two years of experiment,the soil urease,invertase,acid phosphatase,catalase and soil microbial biomass carbon,nitrogen showed increased firstly then decreased in 2016.The change of soil FDA hydrolase and dehydrogenase in the period of two years showed the same trend.Overall,straw length was 5-10 cm,straw amount was 4800-6800 kg/hm~2,and buried depth was10-25 cm,which was more conducive to the improvement of soil enzyme activity and soil microbial biomass carbon,nitrogen.(2)Straw length,amount and burial depth had different effects on Shannon-Weave,Shannon evenness and McIntosh index except Simpson diversity.Overall,soil microbial community diversity index was high when the straw amount was 6800-8000 kg/hm~2,the burial depth was10-20 cm and straw length was 5-10 cm.Straw incorporation can effectively improved the utilization of different carbon ratio by soil microorganisms,the main type of carbon source was carbohydrate,amino acids and polymers,with the extension of time,the use of various carbon sources was more balanced.(3)The single weight of soil enzyme activity and microbic was determined by the AHP,entropy weighting method,and game theory,the result indicated that the soil microbiological indicators have a higher criteria weight than soil enzyme activity indicators.The comprehensive index value constructed by the TOPSIS method had a strong correlation with the measured value of a single index and it could well evaluate the soil microbial characteristics.A regression equation was established for the relationship between three factors and comprehensive index.The results showed the interaction between the two factors had certain interactions,soil microbial functional diversity and enzyme activity decreased with an excess input of them.The optimal combination for the improvement of soil microbial functional diversity and enzyme activity was a straw length of5-10 cm,burial depth of 10-20 cm and straw amount of 4400-6500 kg/hm~2.