Change characteristic of soil salinity on long-term drip irrigation under plastic film in Xinjiang cotton field

With the increase in application period of drip irrigation under plastic film, a change trend is caused. Eight cotton field blocks were applied continuous drip irrigation under plastic film 2-16 years in Xinjiang Shihezi 121 group. These plots were similar in all respects, salinity change was monitored with three consecutive years at fixed point. The results show that the salinity of farmland with drip irrigation under plastic film was migrated by drip water into the area between the membrane and gathered in the surface region, the natural distribution status of soil salinity was altered significantly by drip irrigation under plastic film in the early growth period, salt was migrated and accumulated to the deep soil and the area between the membrane year by year. The soil salinity of the root growth region and salt aggregation area was decreased with years increasing, and the salt of the root growth zone decreased to the appropriate range after four years of drip irrigation. The salt of surface layer within six years of the drip irrigation was relatively higher in the end of growth period, salinity was lower in general with more than eight years of drip irrigation. The trend of average salt content for soil layer of 0-40 and 0-100 cm was first fast and then slow. Soil salinity in 0-40 cm soil layer decreased to 0.5% after 5.7 years of drip irrigation applications time. Soil salinity in 0-100 cm soil layer decreased to 0.5% after 6.9 years of drip irrigation application, salt and water control of drip irrigation farmland are needed to increase drip irrigation for seven years.