| In the hilly and gully region of the Loess Plateau,the climate is arid and the rainfall is insufficient,and the soil desiccation becomes increasingly serious.Moreover,it is extremely difficult to restore the soil moisture in the deep layer,which seriously restricts the vegetation restoration and agricultural sustainable development in this region.In this study,white film covering(WF),black film covering(BF)and bare field control(CK)tests were carried out in qinggen horizontal terraces in Mizhi County,northern Shaanxi province for 5 years.The water content,temperature and electrical conductivity of 1.5m soil profile were monitored by GS3 sensor,and the spatial and temporal distribution characteristics of soil moisture,heat and salt were studied after years of one-dimension film covering in furrows.Through the filling water of straw material of rainwater harvesting drain,combined with several typical ground cover conditions,on the depth of 3 m within the scope of soil moisture dynamic monitoring analysis of last 1 year,poly ditch rainwater harvesting is studied combined with dynamic dried layer of soil moisture under different coverage measures and different coverage measures combining together hydrating effect of ditch rainwater harvesting.The purpose of this study was to explore the feasibility of long-term and multi-year film mulching measures to improve soil moisture,heat and salt status,and to compare the difference of bamboo joint gully combined with different surface mulching measures in the regulation and repair of dry soil water.The main results are as follows:(1)After five consecutive years of film mulching,the average soil moisture content and water storage in 0-150 cm soil layer still increased to a certain extent compared with the bare soil.The soil water storage capacity of black film treatment was higher than that of white film and bare land,showing a good effect of water replenishment and moisture conservation.The highest and lowest soil temperatures were 2.2℃ and 0.9℃ higher than those of the bare soil,respectively.The thermal insulation effect of white film was better than that of bare soil.With the increase of soil depth,the thawing time of the lower soil was earlier and the freezing time was later than that of the upper soil.(2)During freezing-thawing stage,soil salt rapidly migrates and accumulates to the frozen layer,and in summer,soil salt content in all soil layers shows a sudden increase period.The salt accumulation effect of white film treatment in 0-100 cm was more obvious,But in general,long-term film mulching does not cause soil secondary salinization.There was a significant positive correlation between soil water content and salt content in all treatments in the transitional and replenishment stages of soil water content(P < 0.01).There was a significant correlation between water and heat in different periods(P < 0.01).Due to the great difference of soil moisture,heat and salt status in tillage layer in different periods and the influence of other complex factors,the correlation between soil heat and salt in different periods of different treatments is very different.(3)In the case of dry year during the experiment,the soil water content of each gathering ditch combined with different mulching measures still increased significantly in the depth range of 3m.The compensation degree of soil water storage deficit of different measures was in the order of covered gully > bare gully,and covered gully > bare land.Among them,the average compensation degree of water stored in 50 ～ 300 cm mulch ditch was 42.1%,showing obvious water replenishment advantage,followed by straw ditch,22.62%.The soil water replenishment advantage of gully combined with mulching on horizontal terrace was mainly reflected in the depth range of 120-280 cm.The restoration depth of soil water in different measures was plastic film ditch(> 3m),branch ditch(> 3m),straw ditch(≥2.8m),pebble ditch(2.8m),bare ditch(2.6m)and bare ground(2.6m).The above research results can provide a theoretical basis for dryland agriculture in the hilly region of the Loess Plateau to regulate soil moisture,heat and salt conditions through long-term ridge raising and film mulching.The pattern of collecting rain and preserving moisture by gathering ditches combined with surface mulching can provide a reference for realizing efficient utilization of horizontal level rainfall resources and developing forest and fruit cultivation in mountainous areas. |
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