Effects Of Soil Matrix Potential On Soil Water And Salt Distribution And Yield And Fruit Quality Of Watermelon In Gravel-Mulched Field

The shortage of water resources in the arid regions of central Ningxia,the use of local underground brackish water is an important way to alleviate water shortages in the region.The brackish water drip irrigation technology has been applied to a large area of water-pressed watermelon,but the distribution law of soil water and salt under this condition is not clear.Understand the distribution law of soil water and salt under the brackish water irrigation condition,and master the correct water and salt regulation method is the key to rationally utilize the brackish water drip irrigation.Regulating soil matrix potential in crop root zone is an important method to regulate soil water and salt distribution under salty drip irrigation conditions.In this paper,the spatial and temporal distribution of soil water and salt in the saline soil under different soil matrix potentials and the effects on the growth,yield and quality of watermelon were studied by field experiment.The distribution characteristics and salinity of soil water and salt in sandy soil under salty drip irrigation were determined.Accumulating the law,and then determining the appropriate soil matrix potential control threshold for watermelon in the sand-pressing gravel-mulched field,providing a scientific basis for the establishment of a reasonable brackish drip irrigation system for the watermelon in the sand,and providing a theoretical basis for the safe and sustainable use of brackish water.The research results arc as follows:(1)Under the condition of brackish water drip irrigation,the soil moisture change in the 0-100 cm soil layer is mainly manifested as:in different growth stages,the moisture content in the 20-40 cm soil layer is reduced,and the moisture content in the 40-60 cm soil layer is increased,60 The soil layer of-100cm is basically unchanged and the water condition is good.During the whole growth period,the soil moisture gradually stabilizes with the increase of soil depth,and the soil moisture content of 0-20cm soil layer increases continuously,with an increase of 6.6l%to 32.61%;20-30cm soil layer soil moisture content decreased,the reduction ranged from 0.33%to 25.8%,and the soil moisture content increased in 30-100cm soil layer.In terms of spatial variation:the lower moisture content is mainly concentrated in the horizontal direction from the dripper 15-25cm,the vertical direction 20-40cm,and as the growth period changes,the center of the low water region continues to approach the head.The water consumption of watermelon decreases with the decrease of soil matrix potential.Overall,the soil treated with-10KPa and-20KPa has better moisture and provides sufficient moisture for the growth of watermelon.(2)The content of salt in the 0-40 cm soil layer gradually decreased in each matrix treatment,and the decrease in salt content in the 20-40 cm soil layer was more obvious than that in the 0-20 cm soil layer,and the impairment was 0.07-0.17 mS/cm.In the 40-100 cm soil layer,with the increase of soil depth,the salt content increased continuously.As the soil matrix potential decreases,the ability of salt to migrate to deeper layers decreases.In the 0-100cm soil layer,the salt concentration decreased by 6.61%during the whole growth period of-10KPa,and decreased by 1.03%when treated with-20KPa;the treatment of-10KPa and-20KPa had a certain leaching effect on soil salinity.Each substrate potential treatment forms a desalting zone near the dripper.The desalting zone is mainly located in the horizontal direction from 0-20 cm in the dripper and 0-35 cm in the vertical direction.With the decrease of the matrix potential,the area of the desalting zone is continuously reduced,small.As the depth of the soil increases,the soil pH increases first and then decreases.(3)The treatments of-10KPa and-20KPa promoted the main vine length,stem diameter,leaf number and leaf area of watermelon plants;the smaller the matrix potential value,the higher the value of SPAD.The content of soluble solids in melon and melon(yin and yang)of watermelon increased with the decrease of matrix potential treatment value,and the difference between treatments was not significant;total acidity,soluble sugar content,pH value of melon juice,The values of the transverse diameter and the hardness of the melon skin are lowered as the matrix potential value is lowered.Under the treatment of each substrate potential,the yield of watermelon treated with-10KP was the highest,which was increased by 5.59%-20.43%compared with other treatments.