Study On Salt Leaching Ration And Simulation Of Drainage Of Cotton Field With Drip Irrigation Under Film In Non-growth Period

Drip irrigation under membrane technology has applied in cotton field for many years in Xinjiang, which not only has saved water resources and brought the comprehensive benefits of economy, ecology and society, but also led to the accumulation of salt in a layer of soil. It is easy to form secondary salinization of the soil. In order to prevent this phenomenon, irrigation by flooding has been applied to against the phenomenon during the spring in southern Xinjiang, but irrigation requirement is random, which is not conducive to the conservation of water resources and the leaching efficiency, so the suitable salt leaching ration has a certain significance. In this paper, a field experiment was carried out in March of 2013 and 2014 in Korla Bazhou’s irrigation experiment station, analyzing the influence of quantity, time and frequency of irrigation respectively on soil salinity, put forward the most suitable salt leaching ration for local area. Using the DRAINMOD model, simulating groundwater level and salinity, verified the applicability of the model with the experiment data, and use the model to simulate the change of displacement changes of soil salinity under different irrigation amount, drain depth and spacing of drainage ditches to put the suitable size. The main research results are as follows:(1)Through different row spacing, and the influence of the effect of different irrigation water for salt-leaching analysis,the results show that: In 0 ~ 60 cm soil layer, desalination effects vary from different row spacing, narrow line and width line. Under 60 cm soil layer, irrigation water has no effect on salinity of different row spacing. Among three different irrigation water, of 1350 m3 / hm2, 1800 m3 / hm2 and 2250 m3 / hm2, 1800 m3 / hm2 irrigation water leaching effect is best.(2)By analyzing the effects of different times and frequency of irrigation salinity, the result shows: The annual spring irrigation time should be after the March 20, while the whole permafrost melted. Although the soil salinity accumulation of two-time irrigation is less than the accumulation of one-time irrigation, considering irrigation time and cotton planting time, one-time irrigation should be chosen.(3)Verify the applicability of the DRAINMOD model in arid areas through the test data. Using DRAINMOD model to simulate the salinity situation, the results show: Among three different volumes of 1350m3/hm2,1800mm3/hm2,2250m3/hm2 of irrigation:, 1800m3/hm2 has the best effects on washing the salt. According to the influence of different drain depth and spacing of displacement, comes the conclusion that, the deeper and the more narrow spacing of the drain, the displacement is more. The 3-meters depth drain with 125-meters drain spacing is the most suitable size of the drain.