Study On Topsoil Structure And Organic Carbon Accumulation Characteristics Of Farmland In South Bank Of Dianchi Lake

Due to the strong human disturbance and the high intensity of cultivation,How to maintain the soil quality of facilities farmland is the key to maintaining the stability of its productivity and ecological functions.It is generally believed that the structural stability of farmland soil is closely related to the cultivation strength and the accumulation of organic matter.In order to explore the effects of high-intensity cultivation methods on soil structural stability and organic matter accumulation,the study select the facility farmland soils with different facilities for cultivation years and soil types in the Chaihe Reservoir to the lakeside area as the research object,thoroughly analyzes the water stability of soil aggregates and organic carbon content variation characteristics,it provide a reference for local farmers to choose reasonable soil management measures.The main findings of this research are stated as follows:1.Effects of different land use methods on surface soil structure and organic carbon accumulation on the southern coast of Dianchi Lake(1)In general,the water stability of the lakeside reclaimed wetland and adjacent farmland soil(all are Gleysols)structure on the south bank of Dianchi Lake is higher,and the content of > 0.25 mm water stable aggregates is between 78% and 80%.Although there is no significant difference in the amount of >0.25 mm water stable macroaggregates in the soils of the wetland and adjacent farmland,but in the 0-5 cm and 5-10 cm soil layers,the content of >2 mm water stable aggregates in wetland soil is significantly higher than that in adjacent farmland soil.This shows that reclamation significantly improves the water stability of the soil structure.(2)In the 0-5 cm soil layer,the organic carbon content(35.47 g/kg)of the soil in the wetland was significantly higher than that of the adjacent farmland soil(24.99 g/kg).However in the 0-5 cm or 5-10 cm soil layer,there is no significant difference in organic carbon content in the same particle size aggregates between the adjacentfarmland and the wetland soil.The analysis shows that there is a significant positive correlation between > 2 mm water-stable aggregates and the organic carbon in the0-5cm soil layer of Dianchi Lakeside.It shows that the soil organic carbon content is closely related to >2 mm aggregates.2.Structure and organic carbon accumulation characteristics of different soil types in the south shore of Dianchi Lake(1)Gleysols is located in the estuary area of the Chai River,the content of >0.25 mm water-stable aggregates in the 0-5 cm soil layer is significantly higher than that in the Ferrisols.However,the difference in the 5-10 cm soil layer is not significant.In the middle area of the Chai River,there is no significant difference in the content of >0.25 mm water-stable aggregates between 0-5 cm and 5-10 cm in the Gleysols and Ferrisols.(2)No matter in 0-5 cm or 5-10 cm soil layer,Gleysols is located in the estuary area of the Chai River,the content of soil organic carbon and organic carbon content in> 2 mm and 2-0.25 mm aggregates are significantly higher than those in Ferrisols.However,there is no significant difference in soil organic carbon and organic carbon content in various particle size aggregates in the Gleysols and Ferrisols in the middle reaches of the Chai River area.The analysis shows that there is a significant positive correlation between >2 mm water-stable aggregates and the soil organic carbon in the0-5 cm soil layer of the Gleysols,indicating that the soil organic content of the Gleysols has a close relationship with >2 mm aggregates,so Gleysols structure stability is better.But there is no correlation between > 2 mm water-stable aggregates and the soil organic of the Ferrisols.3.Effects of facility cultivation time on surface soil structure and organic carbon accumulation(1)The length of cultivation time of the facility has a great influence on the structural stability of farmland surface soil.Long-term facility tillage(> 20 years)significantly increased the content of >0.25 mm water-stable macroaggregates in 0-5cm and 5-10 cm soil layers compared with soil with shorter cultivation time(< 10years).It shows that long-term facility cultivation will not cause damage to the stabilityof the soil structure.(2)Regardless of soil type or soil layer,the organic carbon content of the long-term facility cultivation is significantly higher than that of the shorter of the facility cultivation.At the same time,the organic carbon content in the same particle size aggregates of the long-term facility cultivation is significantly higher than that of the shorter of the facility cultivation.The correlation analysis show that there is a significant positive correlation between > 2 mm aggregates and the organic carbon content in the 0-5 cm soil layer.This is mainly due to the long-term,large-scale application of organic fertilizers,The soil structural stability and organic carbon accumulation in farmland on the south bank of Dianchi Lake increased significantly with the extension of cultivation time.4.Kinetics of soil aggregate stability and clay-to-carbon ratio(1)Compared with the wet sieving for 5 min,the wet sieving for 160 min has no significant effect on the content of water stable aggregates >2 mm and <0.25 mm in the 0-5 cm soil layer of the reclaimed wetland soil.However,the content of water-stable aggregates > 2 mm in farmland soil are significantly reduced,and the content of microaggregates(0.25-0.05 mm)and the sum of clay+silt(< 0.05 mm)are also significantly increased.This indicates that the surface soil structure of farmland is vulnerable to damage during flooding.On the other hand,there is no significant difference in the organic carbon content in the large water-stable macroaggregates at different sieving times.(2)The clay-to-carbon ratio in the study area is between 7-35.The clay-to-carbon ratio of Ferrisols in the same sampling area is significantly higher than that in the Gleysols.At the same time,there is a significant negative correlation between the number of >2 mm aggregates and the the clay-to-carbon ratio.The analysis found that The clay-to-carbon ratio n = 7 should be used as an indicator of soil organic carbon and structure management in the southern shore of Dianchi Lake.