Effect Of Cotton Planting On Physical Characteristics And Water-salt Dynamic Of Clay Solonchak

In order to research the effect of cotton planting on soil physical characteristics and water-salt dynamic of coastal saline clay, field experiments were conducted under two different treatment of planting cotton continuous for three years, planting cotton for a year and saline wasteland in Yellow River Delta to study the improvement of clay coastal solonchak from April 2012 to June 2013. Through the experiment, the effect of cotton planting on soil bulk density, saturated hydraulic conductivity, porosity and pore composition,and water-salt dynamic in different conditions were studied. The results showed that :(1)Cotton planting can reduce soil bulk density significantlyCotton planting can reduce soil bulk density of clayey saline soil significantly and improve the soil structure as well as soil aeration condition. This effect becomes more apparent especially on the 0-20 cm surface soil while the soil bulk density reduction of 20-40 cm soil layer is not obvious. The soil bulk density decreased gradually with the increase in cotton planting years.(2)Soil saturated hydraulic conductivity significantly increasedCotton planting can enhance the soil saturated hydraulic conductivity significantly and improve the permeability of soil, which makes the soil salt rapidly leached out of soil tillage layer even with the smaller 20 mm of rainfall. The improvement of saturated hydraulic conductivity caused by cotton planting only happened in the 0-20 cm surface soil, while in the20-40 cm soil layer, the saturated hydraulic conductivity had no significant change. The increasment of soil saturated hydraulic conductivity is more obvious with the increase of the time of cotton planting.(3)Total soil porosity increased, soil pore condition improvedCotton planting can significantly increase the soil porosity in 0-20 cm soil layer, improve the porosity. With the extension of cotton planting time, soil porosity showed an increasing trend. Soil pore situation of the soil layer below 20 cm did not change significantly.(4)Soil salinity in plough layer reduced generally during all the cotton growth periodCotton planting reduced the soil salinity in plough layer generally. After planting cotton for one year, soil salinity in plough layer reduced to 5 g/kg or less in each cotton growth period, while after planting cotton for three years, it reduced to 3 g/kg or less, which met the requirements of cotton on soil salt during all the cotton growth period.(5)Soil planting suppressd salt accumulation under the condition of evaporationCotton planting can significantly reduce soil salinity especially under strong evaporation conditions. The soil salinity in 0-100 cm each soil layer reduced significantly, while desalting effect in 0-80 cm soil layer is extremly significant(P<0.01).(6)Increased salt leaching speed under leaching conditionsCotton planting increased the leaching of soil salt caused by rainfull. In the 0-20 cm top soil, the reduction in soil salinity of 3a treatment is the most. In the soil layer below 20 cm,soil salinity decreased gradually with the increase of soil depth and extension of planting years. A small amount of rainfall had no obvious effect on salt leaching of saline wasteland,but it had obvious effect on salt leaching under cotton planting condition.(7)After three years of cotton planting, the soil can grow wheatUnder conditions of adequate water, if planting cotton continuously for 3 years, the soil salinity reduced to the range which can meet the normal growth of wheat.