Study On Physical And Chemical Properties Of Wetland Soil In Daling Village With Different Retirement Years

According to field investigation, a comprehensive analysis of topography, parent material, climate, vegetation and human disturbance in a soil factors, according to soil genesis principle of soil samples were collected. Taking the wetland soil physical and chemical properties as the main research, the process and the status of the restoration of the ecological function of the wetland soil in the mountain of the mountain of Yunnan were compared and analyzed.. After a lot of investigations, according to the typical and representative principle, select the natural wetland soil plots, plots of 4a, farmland 10 a restoration and still growing turnip vegetable for research object, the natural wetland soil and vegetable for reference sample. Set of soil samples in each sample, each sample point set of 10 m * 10 m temporary quadrat. Within each quadrat randomly selected five point acquisition mixed samples, respectively, the soil surface of 0 ~ 10 cm, subsurface 10 ~ 20 cm and the lower layer 20 ~ 40 cm soil physical and chemical properties were analyzed. The results show that:1. Soil bulk density with years of returning farmland to forests decreased. By the vegetable soil and natural soil, soil bulk density by 1.02g·cm-3reduced to 0.47g·cm-3 changes in soil physical properties. The soil moisture content increased gradually from the farmland to gradually(the topsoil increased from 46.95% to 159.34%).. Soil mechanical composition in returning farmland to wet, fine sand and clay content increases(surface soil from 1.35% increase to 7.52%) and sand content decreased(surface soil from 4.76% reduced to 1.44%).2. The change of soil chemical properties was: the soil pH value was between 4.40 ~ 6.0, acid, and the longer the year of the project, the greater the acidity(the topsoil pH decreased from 5.68 to 4.62). The content of organic matter in soil increased with the increase of the years of returning to the years(the topsoil increased from 78.76g·kg-1to 255.46g·kg-1), especially the increase of the increase after returning farmland to 10 a. The contents of total phosphorus and available phosphorus fluctuated from the years of returning to grain, and the total phosphorus content of topsoil increased from 0.246g·kg-1 to 0.338g·kg-1. After returning the contents of total nitrogen and alkali solution nitrogen variation in the content of basic consistent, but total amplitude larger, alkali solution nitrogen of small amplitude, surface soil by vegetable to farmland 10 a to natural soil, total nitrogen content by 18.92g·kg-1reduced to 15.13g·kg-1, and increased to 28.24g·kg-1. Soil total potassium content tended to decrease the fluctuation trend; available K content decreased at the beginning of the farmland, farmland 4 ~ 10 a amplitude is smaller. After returning farmland 10 a and quickly increased, surface soil by vegetable to farmland 4a to natural soil, available potassium content by 118.0mg·kg-1 reduced to 40.7mg·kg-1, and increased to 103.0mg·kg-1; slow potassium content in early abandoned cropland increased slowly, since the conversion of farmland to 4a decreases rapidly. Exchange potassium and magnesium content changing trend of exchange, returning the early exchange of potassium and magnesium content decreased rapidly, the conversion between 4 ~ 10 a increased slowly, 10 a farmland increased rapidly after; exchangeable sodium content in farmland at the beginning of the amplitude is small, 10 a of returning farmland to forests increased rapidly after; exchange calcium content decreased rapidly in the early stage of restoration, after returning farmland 4a and increased quickly. Wetland soil cation exchange capacity decreased, but amplitude is smaller, the surface soil cation exchange amount of farmland by 28.46 cmol mg-kg-1 gradually reduced to farmland 10 a of the 25.65 cmol mg·kg-1, to the natural soil and rise to 42.81 cmol mg·kg-1. The correlation analysis showed that the wetland soil pH had a significantly negative correlation with total potassium content(P<0.01). Moisture content and total nitrogen, alkaline hydrolysis nitrogen content had a significant positive correlation, soil clay content and total phosphorus content was significantly negatively correlated, organic matter and total nitrogen, alkali solution nitrogen content was significantly and positively correlated, total phosphorus content and exchangeable calcium, exchange of magnesium ion content was significantly negatively related to total N and alkali solution nitrogen content showed a significant positive correlation, and exchange sodium and cation exchange capacity was significant negative correlation(P<0.05).3. The change of soil trace elements: after returning farmland to wetlands, soil total Cu and total Zn content and the content of available Mn showed to decrease the fluctuation trend, the available copper content is gradually increased trend(from 4.08mg·kg-1 increased to 6.62mg·kg-1). Surface soil available Zn from soils to farmland 10 a to natural soil and content by 0.81mg·kg-1 reduced to 0.28mg·kg-1), and increased to 1.69mg·kg-1. After returning farmland to soil, the effective iron content of the topsoil was decreased from 85140mg·kg-1 to 43851mg·kg-1, the Mn content decreased from 637mg·kg-1 to 145mg·kg-1. From the point of view of soil depth, soil available Cu, Zn and Mn in the surface than subsurface, has to soil surface enrichment phenomenon, the effective iron content of sub surface above the surface, obviously to the deep soil enrichment phenomenon. Exchange and correlation analysis showed that soil total copper content of calcium was significantly negative correlation, the effective copper and total N, available N content showed a significant negative correlation(P<0.05); total zinc and total phosphorus content was significantly positively correlated with exchangeable sodium and cation exchange capacity was significantly negatively correlated; effective zinc and total potassium content was extremely significant positive correlation(P<0.01), and exchangeable sodium and cation exchange capacity was significantly negative correlation, the iron content and total N, alkali hydrolyzable nitrogen content showed significant positive correlation(P<0.05), and exchangeable magnesium content was extremely significant negative correlation(P<0.01); effective iron and clay content was significantly and positively related to available Mn and alkali hydrolyzable nitrogen content showed a significant negative correlation. Soil total Cu and Zn content in full amount showed a significant positive correlation, available Cu and total Zn and available Zn content showed a significant negative correlation(P<0.05), Zn and total iron content was extremely significant positive correlation(P<0.01).4. After returning farmland to wet soil, especially the years of returning farmland, the content of wetland soil ecological function is close to the content of natural soil. The implementation of the returning farmland to wet measures is beneficial to the ecological evolution of the wetland soil to the wetland. The nature of the conversion of the natural process after the conversion of farmland to the disturbance of other factors, such as the change of the wetland soil physical and chemical properties.