| As is well known,agriculture is a prerequisite for the rapid development of the national economy and a foundation for human survival.Therefore,it is particularly crucial to develop appropriate irrigation systems for farmland.Due to its unique natural climate and complex agricultural management measures,the Hetao Irrigation District has been mainly irrigated through traditional flooding for many years,and the problem of soil salinization urgently needs to be solved;In addition,the increasing pollution of agricultural non-point sources had led to an increase in the nitrogen content of groundwater in irrigation areas in recent years.For the Hetao irrigation area,the irrigation water volume and film covering on farmland had a profound impact on the regulation of soil water,fertilizer,and salt transport.In this study,six field experimental treatments were designed,namely,enhanced membrane treatment(D1Y,76 mm)with high irrigation amount under film drip irrigation,enhanced membrane treatment(D2Y,60mm)with low irrigation amount under film drip irrigation,degradable membrane treatment(D1N,76 mm)with high irrigation amount under film drip irrigation,degradable membrane treatment(D2N,60 mm)with low irrigation amount under film drip irrigation,and traditional enhanced membrane treatment(M1Y,76 mm)with high irrigation amount under film drip irrigation and traditional enhanced membrane treatment(M2Y,60 mm)with low irrigation amount under film drip irrigation,To explore the variation pattern of soil water,salt and fertilizer movement under diverse irrigation treatments in Hetao Irrigation Area,and then use the HYDRUS-2D model to simulate the change of soil water,salt and fertilizer in different soil layers of Hetao Irrigation Area with the growth period,and further analyze and predict the impact of irrigation volume on the local water,fertilizer and salt movement.The main conclusions of this study were as follows:(1)The soil moisture content rapidly increased after irrigation with different treatments at different growth stages,and the increase in high irrigation treatment was higher than that in low irrigation treatment,and it remained at a high level in the soil layer of 40～60 cm.After irrigation,soil ammonium and nitrate nitrogen decreased with the increase of soil depth,while soil nitrogen remained at a relatively low level in the later stages of growth.Under film drip irrigation was more prone to soil salt accumulation at the surface layer of 0～20 cm compared to traditional flood irrigation treatment;After water redistribution,salt migrated with water to a soil layer of 20～60 cm,and all treatments showed a rebound trend.(2)With the development of growth period,the nitrate accumulation of each treatment showed a decreasing trend,and slightly increased in the later growth period,while the treatment of high irrigation water volume will accelerate the leaching of soil nitrate nitrogen.The accumulation amount of salt outside the film in 0～40 cm soil layer and 0～100 cm soil layer of drip irrigation under film in different growth periods was higher than that in the film.Each process(D1Y,D2Y,D1N,D2N)0～100 cm soil total salt content changes of drip irrigation under mulch was 755.69 kg/hm~2,6433.84 kg/hm~2,6405.79 kg/hm~2,1702.21 kg/hm~2,respectively.D1Y treatment had the smallest change of total salt content and the best leaching effect.(3)The results of variance analysis showed that the variation of salt accumulation in 0～100cm soil layer after irrigation at the early stage of growth was 0.02(p<0.05),reaching a significant level among different types of film mulching;The variation of nitrate nitrogen accumulation in 0～100 cm soil layer after irrigation at the early stage of growth was 0.01(p<0.05),reaching a significant level between different irrigation amounts and types of plastic film mulching.(4)The evaluation indexes of the simulated and measured values of HYDRUS-2D model showed that the R~2 of soil moisture content,soil salinity and soil nitrogen(ammonium nitrogen and nitrate nitrogen)in each soil layer were 0.82,0.71,0.88 and 0.93,respectively.The RMSE and d of other statistical parameters were within the acceptable range,and the model agreement was high.The model can be used to study the transport law of soil water,fertilizer and salt in Hetao irrigation area.(5)The simulation scenario of the HYDRUS-2D model showed that with the increase of irrigation volume and drip irrigation times,the soil salt in the film had a good leaching effect on the 0～40 cm soil layer,and the salt content in the 40～60 cm soil layer rised slightly.Water was helpful to the leaching of nitrogen in 0～60 cm soil layer,and the nitrate nitrogen decreased with the increase of irrigation amount.On the basis of the field irrigation system,the amount of irrigation and the number of drip irrigation should be appropriately increased.When the irrigation quota of 120 mm is set during the maize growth period,the accumulation of nitrate nitrogen in 0～60 cm soil layer is effectively reduced,and the accumulation of nitrate nitrogen in 60～100 cm soil layer is inhibited. |
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