Research For Simulation Of Soil Water And Salt Transport In Perennial Under Drip Irrigation Of Cotton Fields In Arid Areas

In1996, after the drip irrigation under film for success in Shihezi city of Xinjiangprovince121farm cotton under film drip irrigation, planting area has been increased year byyear, obtained the fast development. Although the drip irrigation under mulch reduced the soilevaporation, saving irrigation water, put an end to the water deep, to avoid the increase ofgroundwater level, but not the salinity of the earth’s surface exclusion of farmland, a lot of saltaccumulation in the root, the threat of crop growth, easily make farmland soil secondarysalinization, sustainable development the oasis agriculture brings great hidden danger.Although the drip irrigation under mulch reduced the soil evaporation, saving irrigation water,put an end to the water deep, to avoid the increase of groundwater level, but not the salinity ofthe earth’s surface exclusion of farmland, a lot of salt accumulation in the root, the threat ofcrop growth, easily make farmland soil secondary salinization, sustainable development theoasis agriculture brings great hidden danger. Therefore, this paper selects a plurality ofperennial under film drip irrigation cotton field, through the analysis of growth period, notaffect fertility period movement of water and salt in cotton fields and different factors on themovement of soil water, salt, heat, summarizes the accumulation characteristics of differentdrip irrigation of cotton salt.The research of this paper are as follows:(1) Observations through the whole year, low, medium, and high salinity3layers ofcotton field soil moisture distribution difference accumulation of salt is characterized by lowsalinity cotton fields salt concentration of120～150cm reach7～8months, salinity cottonfields salt concentration of90～120cm, the highest in6～7months, cotton fields salinity andhigh salinity is concentrated in the0～50cm With irrigation desalination., three cotton fieldsoil salinity significantly lower end of fertilityinterspersed has a good effect of irrigation on soil salinity leaching. Therefore, adjust the irrigation system should be based on their cottonfields salt.(2) snow melt water was significantly increased at0～50cm soil moisture content, has animportant role in the regulation and control of soil moisture, and soil moisture, there is nogreater impact on salinity, soil salinity, only a limited control without fundamentallysalinityon the shift can not be suppressed.(3) freeze-thaw conditions, the temperature of the soil temperature, with the increase insoil depth and decreasing lag time constantly extended soil ablation faster than the freezingrate, faster than the lower layer of the upper soil ablation. In the reproductive period, thepositive correlation between the soil and air temperature influence weakened, the lag time isextended as the depth increases with the increase of soil depth.(4) freeze-thaw conditions, permafrost changes in water and salt transport, remainedrelatively stable state, have a certain inhibitory effect on soil salinity. Attention after freezingand thawing of soil water and salt, with strong evaporation, the salt content of the set of saltarea as the water migrates upward, causing the upper layer of soil salinity increased, prone tospring back to salt.(5) With the rise in soil temperature, soil moisture diffusion rate increasing soil waterholding capacity to continue to lower, resulting in reduced5~60cm soil moisture at90~150cm soil moisture increased, leading to5cm and90~150cm soil salinity is relatively higher.Therefore, under the same conditions in the irrigation quota, relatively reduced irrigationquota of5,6months, the irrigation cycle relative decrease in July, August or increase irrigationquota, relatively reduced irrigation quota in September, so the crop to maintain good waterand salt environment, suppression of soil salinity on shift.(6) drip irrigation under mulch planting6years ago was desalted trend surface soilsalinity, soil salt and water environment is relatively good, the soil salt was leached below70cm. Drip irrigation under film sixth years after planting, the soil salinity migration changesare more active, and with the increase in age, to expand the area of set of salt, the salt accumulation is increasing, the influence of various factors, easy to move, normal growththreaten crops. Therefore, the cotton planting age6years should be irrigation, drip irrigationand the planting years longer cotton, should be reduced to4years or5years. If there is noirrigation condition, should be a higher amount of irrigation water in the irrigation withannual growth period, increase the inhibition of salt.(7) By soil moisture, salt analog value and the measured value, although some of thedepth of soil moisture content, salt content have some differences, but the basic changes withdepth migration consistent with the salinity of the soil moisture distribution with depthbasickeeps increasing distribution. Desalination trend by predicting the upper soil was lowersoil was set salt trend.