Influence Of Brackish Water Heterogeneous Soil Structure Of Sand Cave On Soil Water-Salt Transport And Tomato Growth

Soil salinization has become a resource and environmental problem faced by human beings all over the world.Agricultural land represented by Hangjinhou Banner in Hetao Irrigation District of Inner Mongolia is seriously salinization.The shortage of freshwater resources seriously restricts the sustainable development of agriculture in the irrigation district.At present,"drip irrigation + sand cave " is a new planting structure model for improving saline-alkali soil.However,there are few studies on the improvement of saline-alkali soil in Hetao irrigation area,and the applicable improvement technology and feasibility of different soil texture and salinity brackish water irrigation need further discussion.Therefore,this thesis takes the representative saline soil of Hangjinhou Banner in Hetao irrigation area as the research object,and sets the "drip irrigation + sand cave " structure as the precondition.The indoor infiltration test is carried out to analyze the influence of salinity of brackish water(0?2.0?3.0?4.0g/L)on soil infiltration characteristics and spatial distribution of water and salt.Combined with outdoor infiltration test,the migration law of water,and salt in saline soil of different textures(sandy loam,silty loam,clay loam)in the irrigation area,the water dissipation characteristics of processed tomato,growth and development,yield and quality are discussed.The optimal salinity level of brackish water drip irrigation with sand cave structure is obtained,and the most suitable saline soil texture for planting sand cave structure is clarified,which provides theoretical basis for the feasibility of brackish water implementation and the applicability of improving saline soil quality.The main conclusions are as follows :(1)The wetting front ratio of sandy soil is less than 1,and the vertical water infiltration is dominant.The influence of clay loam infiltration salinity on the wetting body area was significantly higher than that of silt loam.Compared with distilled water,the infiltration conditions of 3.0 g / L and 4.0 g / L increased by 32.51 % and55.42 %.3.0 g / L increased the instantaneous water infiltration rate and infiltration range at the sand-clay soil interface in the vertical direction.The advancing distance and velocity in the range of saline soil showed a significant power relationship with infiltration time.Based on the double change factors of salinity and infiltration time of brackish water,the horizontal and vertical wetting front advancing distances in silt loam and clay loam with sand hole structure were established.(2)The soil moisture of sand-pit structure was mainly concentrated at the junction of heterogeneous soil,and the water content of silt soil and clay soil under3.0 g / L treatment was the most significantly increased compared with that under distilled water treatment,with the increase rates of 12.3 % and 23.39 %.The soil salinity was concentrated from the deep junction of heterogeneous soil to the edge of wetting front,and the desalination range was mainly distributed at the junction of heterogeneous soil.When the salinity of infiltration water was higher than 3.0 g / L,the soil moisture content increased significantly,indicating that 3.0 g / L brackish water irrigation was the best.(3)Sand hole planting structure can significantly improve the distribution of soil moisture in clay loam,and the maximum increase is 5.92 % ? 9.14 % below the boundary of heterogeneous soil.The improvement effect on water holding capacity of sandy loam and silty loam soil is not ideal.Sand hole structure improves the salt leaching effect of silty loam and clay loam soil,and the relative desalination rates of undisturbed soil are 34.74 % ? 58.17 % and 46.81 % ? 79.16 %,respectively.(4)During the growth period of tomato,the daily water consumption intensity increased first and then decreased,and reached the peak at the fruit-setting and ripening stage.Sand hole structure had a promoting effect on the growth of plant height and stem diameter under clay loam planting,which increased by 8.79 % ?11.44 % and 47.57 % ? 59.60 %,respectively.At the same time,it significantly increased fruit yield.The yield per plant increased by 0.97 ? 1.10 times,and the soil water use efficiency increased by 54.24 ? 61.17 %.Sand hole structure had the most significant inhibitory effect on the growth of plant height and stem diameter and the improvement of fruit quality under silty loam planting,followed by the effect on the growth and fruit yield and quality of tomato under clay loam planting,and the fruit quality under clay loam planting was greatly improved.In summary,brackish water played a promoting role in soil water infiltration of sand cave structure.3.0 g / L brackish water could improve the moisture content at the interface depth of silty soil and clay loam heterogeneous soil under sand cave structure and increase the range of desalination area.Sand hole structure can effectively improve the hydrothermal and salt environment of tomato in the root soil of clay loam in Hetao Irrigation District,promote the growth and development of tomato,and achieve the purpose of increasing production and improving quality.The results showed that the saline water and sand point drip irrigation heterogeneous soil could effectively improve the root water and salt environment and regulate the growth response of tomato,which had positive significance for agricultural economic development and agricultural ecological protection in Hetao irrigation area.