The Effect Of External Organic Matter Addition On The Formation Of Tidal Flat Soil Aggregates And Its Mechanism

The tidal flat along the east coast of China can be used as an important reserve cultivated land resource.However,the poor physical structure,high salinity,high pH and low nutrient content of soil in mudflat restrict its rapid utilization.On the basis of reducing salinity,adding exogenous organic matter to drive the formation of soil aggregates in the saline-alkali land of tidal flat is the premise of restraining the salt return of tidal flat soil,improving the soil fertility and promoting the transformation of tidal flat soil into agricultural soil.In this study,field experiments were carried out to study the effects of different application amounts(0,20,50,125,250 t ha^-1)of sewage sludge,dairy manure and vermicompost on the formation of soil aggregates in tidal flat.The effects of different amounts of glucose?0.5%,1%,1.5%,2%?,chitosan,microcrystalline cellulose,chitin and egg globulin on the formation of soil aggregates in tidal flat were studied in laboratory culture experiments.The results show that:?1?Under field test conditions,the application of sewage sludge,dairy manure and vermicompost increased the content of>0.25 mm and 0.106-0.25 mm aggregates in the beach soil,and the content of aggregates gradually increased with the increase of the application amount of organic matter.18 months after the application of organic compounds,the>0.25 mm aggregate content in the soil of each treatment was significantly higher than that of the control group.The>0.25 mm aggregate content in each treatment of sewage sludge(0,20,50,125,250 t ha^-1)was 91.8%.138.5%,182.1%and 276.8%higher than that of the control group,respectively.The application of cow manure increased by 58.2%,116.6%,197.8%and 277.6%,respectively.The treatments of earthworm manure increased by 65.9%,122.0%,193.2%and 258.4%,respectively?2?Under indoor culture conditions,the application of sewage sludge,dairy manure and vermicompost also promoted the increase of>0.25 mm and 0.106-0.25 mm aggregate contents in the tidal flat soil.After 9 months of culture,the content of>0.25 mm aggregates in soil treated with various organics was significantly higher than that of the control group.With the increase of culture time,the content of 0.25 mm and 0.106-0.25 mm aggregates in the tidal flat soil showed an increasing trend.The analysis of functional groups in the humus of each treatment showed that the increase of functional groups in the humus of earthworm manure was higher than that of the corresponding treatment of sewage sludge and cow manure?3?Under the condition of indoor culture,the effect of applying pure organic matter with equal carbon amount on the formation of soil aggregates in tidal flat is significantly different.At 3 months of culture,the application of glucose and chitin significantly promoted the increase of>0.25 mm and 0.106-0.25 mm aggregates in soil.With the advancement of culture,>0.25 mm and 0.106-0.25 mm aggregates formed by glucose,chitosan and egg globulin showed a decreasing trend.The amount of chitosan treated aggregates did not change significantly.The application of microcrystalline cellulose showed an increasing trend.The analysis of functional groups in the humus of the treated aggregates showed that the content of functional groups in>0.25 mm aggregates increased the most when microcrystalline cellulose and chitosan were applied.When glucose was applied,the functional group content in the 0.106-0.25 mm aggregates increased the most.