| Aimed at the soil secondary salinization in cotton field by drip irrigation under plastic film, through two aspects as variation during the year and interannual, analyzed the soil salt evolving characteristics in typical oasis region in Xinjiang. The results indicated that: During the year, the soil salt content assumed a decreasing tendency along with growing season. Among them in early May(seedling stage), middle July(blossom and boll-forming stages), middle September(harvest time), the soil salt presented an accumulated trend. There was a stable salt accumulated layer about 60～150 cm soil depth in cotton field by drip irrigation under plastic film for 4～12 years, the soil salt content in this layer was basically kept in 0.6% more or less. In 0～60cm soil layer was basically kept a desalination status, the soil salt content in this layer was kept in about 0.2%～0.4%, which can be treated as non saline soil. For the cotton field by drip irrigation under plastic film lasting 15 years, the soil salt presented a large rangeability along with growing stage, and assumed a characteristic of moderate soil salinization. During the interannual, at the beginning 1～6 years by drip irrigation under plastic film, the soil salt assumed a continual decreasing trend, particularly for the layer of 0～20 cm soil depth, the desalination was rather obvious. Implemented drip irrigation under plastic film for 6～7 years, the change of soil salt trended a stable status, each cotton field appeared a stable salt accumulation layer, which was in 80～100 cm soil depth and the salt value was kept about 0.25%, which belongs to non saline soil. |