Study Of Rules Of Salt Leaching And Autumn Irrigation Norm Of Cotton In Alar Irrigation District

Problems of soil salinization and Soil Secondary Salinization that caused by applying irrigation water are the main obstacle which restrict agricultural development in arid area, that is also an Important Factor of eco-environment and protection of oasis stability. salinization of soil always is strategy issue of sustainable agriculture development and improve environmental quality in arid area.The alar irrigation district that locate upstream of Tarim river is one of important national cotton base, problems of soil salinization are barrier factors with extension of irrigation agriculture. Therefore, autumn irrigation is a particular irrigation system designed to wash soil salt into deeper layers and retain a higher water content for the following spring crops in the Alar Irrigation District of Xinjiang. It involves problems of water & salt movement in saline-alkalization soil and growth of crops under salt stress .The aim in this paper is to pilot study these characteristics of coupled movement of soil water and salt and these rules of cotton growth by way of combining laboratory tests with field tests under different irrigation norm. The main results are as follows:1.The results indicate that the Kostiakov modelcan describe the cumulated infiltration well. The power function may be used to describe the relationships among the wetting front distance, the infiltration rate and the infiltration duration respectively. In same infiltration duration, the wetting front distance increase as the initial water content increases.2.In one-demension salt movement, with different irrigation quotas, there are good exponential relationship between salt content, salt concentration and soil depth;the larger is irrigation quota, the thicker Cl-concentration was leached,and Cl-concentration increase as the soil depth increases.3.Under the same irrigation quota, the depth of desaltification zone increase as the initial water content increases; the peak of the salt content , the peak of the salt concentration , the peak of the Cl-concentration and the peak of the ratio of Sf/S increase with decrease as the initial water content increases.4. Test results show that different irrigation quota treatment cause various results of salt content of cotton root zone,as a result,it affect growth of cotton seedling.When irrigation quota treatment is 3500m3/hm2, cotton seedling in this treatment are superior to other treatments in plant height, dried material weight, specific leaf area, seedling rate and growth of upper part of cotton.5.In diferent treatments discrict, there are the greater differences of cotton in plant height, the number of bolls and fruit branches, boll weight ,lint percentage and lint yield. Among them, there was significant difference in the number of bolls and fruit branches and lint yield.The results show that lint yield is the maximum when irrigation quota is 3500m3/hm2.6. Through analysis of salt tolerance in upland cotton, when salt content of 0~20cm soil layer under 0.5%, cotton yield does not be influenced;when salt content of 0~20cm soil layer is 0.25%~0.42%, cotton yield was not obviously reduced; salt content of 0~20cm soil laye was over 0.42%, the cotton yield was decreased significantly.