Water and salt transport and desalination effect of halophytes intercropped cotton field with drip irrigation under film

Abstract: Improvement of saline-alkali soil by halophyte is one of the most effective methods, which has good application prospect such as low cost, high efficiency and environment friendliness. Large amounts of saline-alkali soils and severe drought significantly restricts sustainable development of irrigated agriculture in the Xinjiang region. However, long-term application of the irrigation method will face the potential risk of salinization. Thus, the paper's aim was to explore the characteristics of water and salt transport in field soil and halophytes's desalinization effect in saline-alkali soil under the intercropped cotton systems under the drip irrigation with film. The experiment was carried in field and water balance spot. In the field experiment, the groundwater depth was not adjusted and 3 kinds of halophytes (alfalfa, Suaeda and cumin) were used. The treatment without halophytes was considered as the control. In the water balance spot experiment, the Suaeda was intercropped with cotton and 4 kinds of groundwater depths (1.5, 2.0, 2.5 and 3.0 m) were designed. The soil moisture, salinity, sodium and chloride ion content, cotton yield and groundwater recharge were determined. The results showed that halophytes intercropped with cotton could significantly increase the average soil moisture at 0-30 cm depth between the film and inside film during the growth stage of cotton in field, and the treatment with intercropping Suaeda was the most effective. The average soil desalinization rate of intercropping alfalfa, Suaeda, cumin and the treatment of no intercropping in soil at 0-100 cm depth was 55.97%, ?18.77%, ?21.43% and ?307.52%, respectively. The treatment with intercropping alfalfa was the most effective to remove salt from soil. The desalination rate in the narrow rows was the highest and that between the film was the lowest; Intercropping halophytes could decrease the content of sodium ions and chloride ions to a certain extent in soil at 0-100 cm depth, and increase the cotton seed yield and water use efficiency. Among the treatments, intercropping alfalfa was the best for decreasing sodium ions and chloride ions content of the field soil. The trial of water balance spot showed that the smaller the groundwater depth was, the higher the average soil moisture was, and the smaller the moisture difference inside film and between films in soil at 100 cm depth under intercropping conditions was. Compared with no intercropping, the intercropping treatments could effectively reduce soil salinity, increase the soil moisture, increase the cotton yield and improve the water use efficiency. In addition, the intercropping treatments increased the groundwater recharge ratio. Among all the treatments, the intercropping Suaeda and alfalfa had the best effect. We suggested to improve saline soil by intercropping Suaeda with cotton under the drip irrigation with film since the intercropping Suaeda with cotton had the better inhibition effect for sodium ion accumulation than the intercropping alfalfa treatment. These results will provide the support for saline alkali soil improvement with drip irrigation under film and the sustainable application for the irrigation method in saline alkali soil and arid region.