Soil Water-Salt Dynamic And Cotton Response To Salinity Under Drip Irrigation

Purposes: Serious soil salinization is one of the major problemS restricting the cottonproduction in Xinjiang. This research aimed to make sure soil water-salt migration changerule and the effects of different soil salinity on cotton growth and biomass of salinizationcotton field under drip irrigation, explore the adaptive response mechanism of drip irrigationcotton to soil salinity, establish cotton salt production function, determine the criticalthresholds of soil salinity in different growth stages of cotton. Therefor，providing theoreticalbasis for the rational development and utilization of salinity soil and good quality, high andstable yield of cotton in Xinjiang.Methods: Field test survey data and greenhouse simulation test verification werecombined in this research, sampling at regular intervals to determine soil water and salinitycontent, measure cotton growth indicators and estimate the predicted yield of cotton beforeharvest.Conclusions:1. Differences of0～60cm soil moisture content at the beginning of cotton emergencewere not significant, with the extension of cotton growth period, the differences increasedgradually and reached the maximum in cotton boll stage; Since then, with the development ofgrowth period, different salinity soil moisture content differences were decreased, and theaverage soil moisture content showed decline trend. With the increase of soil depth, soilmoisture content increased gradually; in the same soil depth, with the increase of soil salinitycontent, soil moisture content also presented a gradually increasing trend. Salinity content intopsoil was lower and in deep soil was higher in different growth stages of cotton, and saltcontent basically was also gradually increasing as the increase of soil depth. Variationcoefficient of soil salinity content gradually reduced with soil depth increased in cottongrowth and development stages. Soil salinity content and moisture content changementshowed better synchronized relationship.2. Soil saline ions content was low in the surface, there were less differences among theanions content overall, cations content changed with the increase of soil depth, and reachedthe maximum in40～80cm, then decreased. Principal component analysis results showed thatCa²⁺, Mg²⁺, SO₄^2-, Cl^-and Na⁺could be selected as characteristic factor to reflect thesalinization condition of the study area.3. Daily average evapotranspiration amount of different salinity soil reduced graduallywith soil salt content increase, and the biggest daily average evapotranspiration amountappeared in the blooming period. Along with the advancement of cotton growth period, drymatter accumulation was increasing. Single plant dry matter accumulation of cotton decreasedwith the increase of soil salt content. Appropriate soil salt content was beneficial to reduce water consumption of cotton growth period, and to improve water use efficiency （WUE） ofcotton without affecting cotton dry matter accumulation during the threshold.4. Salt sensitivity in different growth period of cotton was seedling-budding period,blooming period and boll-opening period respectively. Cotton salt tolerance ability isgradually enhanced from seedling-budding period to blooming period and then toboll-opening period. Cotton salt tolerance threshold of different growth stages:seedling-budding period was0.45～0.77mS·cm^-1, blooming period was0.61～0.93mS·cm^-1,boll-opening period was0.92～1.66mS·cm^-1; Cotton salt tolerance limit of different growthstages: seedling-budding period was3.72～4.00mS·cm^-1, blooming period was4.86～5.51mS·cm^-1, boll-opening period was4.63～5.79mS·cm^-1; Overall, cotton salt tolerance criticalthreshold was between0.45～1.66mS·cm^-1, salt tolerance limit threshold was between3.73～5.79mS·cm^-1. Salt tolerance was between1.63～3.41mS·cm^-1, when cotton yieldreduced to50%.