Research On The Transport Law And Numerical Simulation Of Soil Water And Moisture During The Freezing And Thawing Period In Drip Irrigation Cotton Field

Xinjiang belongs to the seasonal freezing and thawing of the region, from the beginning of November to the end of each year in early April the following year, the soil through the process of freezing and thawing. In this process, water and salt migration changes occur, the formation of a salt accumulation phenomenon occurs easily result in farmland soil salinization, to sustainable development in Xinjiang oasis agriculture has brought significant risks. Therefore the choice of multiple perennial drip irrigation cotton field, through the analysis of freeze-thaw salt transport characteristics of drip irrigation and the availability of water and salt in cotton by Drip Irrigation snow cover changes under conditions of drip irrigation water and salt to explore thaw migration law; combining theory and thawing autumn poured salt Movement Law of drip irrigation, using Hydrus-3D simulation model to determine the suitability of Autumn Irrigation Norm, for sustainable development and salinization of governance by Drip Irrigation Cotton Field providing scientific theories and reliable basis.The main findings are as follows:(1)the presence or absence in the winter snow cover changes on soil salt has a certain influence. Similar bare(with snow cover) and covered ground(no snow cover) changes of water salinity changes due to coating of soil in freezing fronts salting effect weakened. In the thawing period, due to the film, there is no snow infiltration recharge, along with enhanced surface evaporation, surface moisture declining, salt is dissolved in water, the water is evaporated on the move, so the salt along with the move, exacerbated by soil salinization.(2)Different Planting Years in Cotton Field under Drip Irrigation under freeze-thaw conditions, water content and salinity rates have shown a temporal variability. Freezing and thawing of the entire water content and temporal variability of salinity rates moderate weak soil layers are strong individual variability. 0-80 cm soil moisture temporal variability strong, 80-150 cm soil moisture changes in the relative weakening of variability divided 0-80 cm to freeze moisture and salinity rate changes in key area, 80-150 cm as freeze moisture and salt from the area threatened rate. Drip irrigation plots of different planting years of soil moisture and salinity rate temporal variability, no significant difference.(3)years of Drip Irrigation under different planting cotton field soil salinity changes in the situation is different in the freeze-thaw conditions. The average salt content of soil has increased, and a large increase in surface salinity. With increasing planting years, affected by freeze-thaw action, 0-140 cm soil salinity increase in volume and value-added gradually reduced, but the salinity increases growth rate it is increased planting years.(4)Different Planting Years soil moisture change by Drip Irrigation in Cotton Field case also affected by freeze-thaw action, lower water potential topsoil moisture to the surface gathering, while some of the higher initial moisture content of the region, due to low soil water potential, Moisture will form agglomeration in this area. Forming a moisture content of the "big- small- big" distribution pattern. Using the same method for each planting years of freezing and thawing drip irrigation water migration analysis, found that the moisture content variation among different planting years no significant changes of drip irrigation, which is closely related to the initial moisture content.(5)years of Drip Irrigation under different planting cotton field soil profile salinity due to the impact of freezing and thawing, and the salt has dissolved in water, soil moisture forced migration, it also will be the migration of salt. Surface salinity has increased in the freeze, in the ablation period, due to the snow melting and thawing frozen layer, resulting in a downward leaching of salt, the salt has decreased. In a certain depth of soil salinity rate maxima all occur, due to the range caused by the accumulation of soil moisture. Change range Different Planting Years plots of different salinity rate freeze period, indicating that the thaw period with the increase in cotton drip irrigation under mulch planting period, the degree of change in soil salinity migration weakened.(6)After the earth were, first field soil particle analysis, obtain soil particles, on behalf of the RETC soil water movement parameter calculated using Hydrus-3D model to calculate the impact of different autumn irrigation on soil salt changes in quotas, combined with freezing and thawing theory finalization of Autumn Irrigation Norm is 2250m3/ha is the most appropriate.