Effects Of Brackish Water Winter Irrigation On Soil Hydrothermal Salt Transport And Crop Growth Law In Saline-alkali Land

Ordos Ordos is located in the southwest of Inner Mongolia,its saline-alkali land area accounts for 14.01%of the total saline-alkali land area in the region,soil salinization problem seriously restricts the efficient and green development of agriculture in the region,the use of Yellow River water for autumn watering and melting salt washing salt is the more commonly used saline-alkali land improvement method in the region,the use of fresh water resources in the area is limited,but the salt water reserves are abundant,the use of salt water instead of the Yellow River water for leaching salt washing salt is of great significance,therefore,It is particularly important to explore the effects of saltwater icing irrigation on soil hydrothermal salt dynamic migration and crop growth in Ordos area.On the basis of fully drawing on the existing achievements at home and abroad,this study carried out in situ freeze-thaw experiments in field communities in Dalat Banner,Ordos City,Inner Mongolia for two consecutive years,and set up four sets of irrigation gradients,the irrigation water volume was 140 mm(S1),180 mm(S2),220 mm(S3)and no irrigation control(CK),and the salinity of irrigation water was 3～5 g/L.By measuring the soil physicochemical properties and crop growth indexes during the experimental period,the dynamic migration law of soil hydrothermal salt and the growth and development of crops during the growth period under reasonable saltwater icing irrigation water were explored.The main conclusions are as follows:(1)Brackish water icing irrigation can significantly reduce soil bulk density,and with the increase of salt water irrigation,the more significant the decrease in soil bulk density in the cultivated layer,the highest reduction is 6.01%.After the end of the ablation period,the irrigation amount of 180 mm significantly reduced soil p H and EC,and the maximum decreases were 34.35%and 13.61%,respectively.(2)Brackish water icing irrigation enhances soil water storage capacity and improves heat preservation effect.The temperature variation of deep soil decreased with the increase of irrigation water,the highest decrease was 32.10%,and the freeze-thaw duration decreased by 13 days,but the temperature variation of surface soil increased.(3)The soil salt and ion content were significantly different under different saltwater icing irrigation amounts.The irrigation amount of 180 mm can reduce soil salinity,and the salt rejection rate can reach up to 59.62%after the end of the ablation period,but the excessive amount of saltwater irrigation increases the soil salinity.Appropriate amount of saltwater icing irrigation reduced the main ion content and SAR content of soil during the freeze-thaw period,among which the soil SAR content was the lowest with irrigation water of 180 mm,and excessive saltwater icing irrigation increased the alkalinization degree of soil.(4)An appropriate amount of saltwater icing irrigation can promote the fertility indicators of sunflower in the later stage(seedling emergence rate,plant height,stem thickness,dry matter accumulation,100-grain weight,setting rate,yield),and excessive saltwater freezing irrigation inhibits the growth and development of sunflower.Under 180mm,the seedling emergence rate was 91.22%,and the yield was 3028.14 kg/hm~2.