Influence Of External Factors And Determination Of Key Indexes In Composting Sludge And Sandy Soil Mixed System

It is necessary to properly and effectively deal with it.At present,the land use of sludge is the most potential disposal method.On the one hand,sludge can be used as a resource to improve the sandy soil.O n the other hand,it can effectively alleviate the severe land degradation problem faced by C hina,and enhance the arable ability of barren land.In this paper,the influence of three external factors,compaction,dry wet cycle and freeze-thaw,on the properties of composite soil is studied.The results show that:(1)compaction can increase the compactness of soil samples and significantly reduce the water stability of sand soil aggregates.The content of water stable large aggregates in sandy soil decreases by 27.3% compared with the control after 100 times of compaction.Adding sludge increases the content of water stable large aggregates,but after compaction,it was still lower than the control.The addition of sludge also improved the decrease of water holding capacity of sandy soil after compaction;(2)the porosity,aggregate water stability and water holding capacity of sandy soil were not significantly affected by the dry wet cycle.The porosity and water stability of the composite soil after adding sludge were higher than those of the sandy soil.With the increase of the cycle times,the porosity increased,and the content of water stable large aggregates decreased;(3)the content of water stable large aggregates in sandy soil decreased by 11.9% compared with the control after 8 cycles.The water holding capacity of sandy soil was also significantly reduced by freeze-thaw.Adding sludge can improve the decrease of water stable large aggregates content and water holding capacity of sandy soil after freeze-thaw.Compaction and freeze-thaw can reduce the water holding capacity of sandy soil and increase the risk of soil erosion.The composite soil with sludge has a certain ability to resist external erosion,which is conducive to soil and water conservation and plant growth.The sludge was mixed with 6 kinds of sandy soil in different regions at the ratio of 10% and 20%.The results showed that with the increase of sludge dosage,the content of clay and silt increased,the content of sand decreased,the bulk density decreased,capillary porosity and maximum water content increased,the content of water stable aggregates increased,the electrical conductivity increased significantly,the content of organic matter,hydrolyzed nitrogen,available phosphorus and available potassium increased significantly with the increase of sludge addition Increase.The results show that the addition of sludge can reduce the compactness of sandy so il,increase the porosity of sandy soil,improve the stability of aggregate,and increase the organic matter and nutrient content of sandy soil,so that the sandy soil is more suitable for plant growth.Taking 18 kinds of soil samples(6 kinds of sandy soil and 12 kinds of composite soil)as the research object,13 physical and chemical indexes of soil were screened by correlation analysis,principal component analysis and Norm value calculation,and the most representative indexes were found out,and the minimum data set for quality evaluation of sludge improved sandy soil was established.The results show that the minimum data set for quality evaluation of composite soil is composed of clay,silt,water stable aggregate,permeability coefficient,p H and available potassium,which can reflect the effective information of composite soil quality.