Study On Differences Of Soil Water Conservation In Paddy Fields With Different Cultivation Years In Liaohe Delta

Based on the loss of the main components of the soil due to the perennial cultivation of the paddy field and the reduced yield and quality of the paddy field,as well as the water conservation function of the paddy field as a constructed wetland.Years(delta area of Dawa District)and 20 years(Yanghuan area of Panshan County)were the research objects.Through the determination of soil physical and chemical properties and the analysis of preferential flow characteristics,the water conservation function of rice fields with different cultivation years in the 3 experimental areas were integrated.The evaluation provides a theoretical reference for continuous farming and management of rice fields.The main research results obtained are as follows:(1)Analysis of the mechanical composition of the soil in different paddy fields(0～100 cm)showed that the content of coarse powder was the highest,followed by fine sand,medium powder,and fine powder,followed by the least clay.The soil bulk density of paddy fields cultivated for 80 years,50 years,and 20 years is the largest in the germinated layer.In each soil layer of each farming period,the composition of mechanical aggregates is analyzed,and the aggregates of 1～2 mm are the most.In terms of water-stable aggregates,in the soil of the paddy field cultivated for 80 years,50 years,and 20 years,the aggregates with particle size of 0.25～1mm are the most,followed by <0.25 mm.Regarding the content of soil organic carbon,the paddy field soils of all tillage years showed surface aggregation,which decreased with the depth of the soil layer.The capillary porosity and total porosity of the soil show a decreasing trend as the soil layer deepens,and the non-capillary porosity is lower than the capillary porosity.The soil water content is the largest in the paddy field soil of 80 years of cultivation,followed by 50 years of cultivation,and the smallest of 20 years of cultivation.As the soil layer deepens,the soil moisture content decreases,and the soil moisture content of each farming year is significantly different among the tillage layer,plow bottom,subsoil layer,and gley layer.(2)The maximum water storage capacity,maximum retention water storage capacity,and saturated water storage capacity of the soil in the occurrence layer of each paddy field with different tillage years show a trend of first decreasing,then increasing and then decreasing as the soil layer deepens.The saturated hydraulic conductivity of different soil layers is the highest in the tillage layer of paddy field soil for 80 years and 50 years of tillage,and the highest in the gley layer after 20 years of tillage.The saturated hydraulic conductivity of the soil generally decreases with the increase of tillage years.(3)The soil dyeing area ratio of paddy fields with different tillage years decreases as the soil layer deepens,and the overall dyeing area ratio is 20 years of tillage> 50 years> 80 years.Correlation analysis shows that the dyeing area ratio has a very significant relationship with capillary porosity,total porosity,and organic matter,and a negative relationship with the maximum water storage capacity.(4)As the farming years increase,the water conservation index increases and the water conservation capacity increases.From the perspective of soil depth,the water conservation function index decreases with the increase of soil depth.The paper has 17 pictures,8 tables,and 111 references.