Study On The Mechanism Of Lycium Barbarum’s Salt Tolerance And Microbial-Fertilizer Salt Regulation Based On Osmotic-Photosynthetic Feedback Under Brackish Water In Hetao Irrigation Area

Aiming at serious soil salinization,low water utilization rate,low crop yield and urgent improvement of soil microbial-ecological environment in the Hetao irrigation district,this study carried out field experiments on the effects of optimal improvement measures and brackish water-microbial fertilizer irrigation on soil environment and physiological characteristics of Lycium barbarum based on moderate saline soil,systematically revealing the regulation mechanism of microbial fertilizer on saline soil under brackish water irrigation.The mechanism of Lycium barbarum osmosis,and photosynthesis response under brackish water stress were clarified.Based on the simulation of soil and Lycium barbarum characteristic indexes and the prediction of the HYDRUS model,the optimal brackish water irrigation quota and the appropriate microbial fertilizer application amount of saline soil were proposed.The main innovation of this study is to explore the mutual feeding relationship between microorganisms and salt in salinized soil and to clarify the regulation path of the process chain of"water and fertilizer-soil water and salt-soil microbes-soil nutrients-Lycium barbarum osmosis and photosynthesis-yield"with the goal of Lycium barbarum yield.The research results aim to enrich the theory of Lycium barbarum resistance in saline-alkali land,which has important scientific value and practical significance for long-term green control of saline-alkali land,safe utilization of brackish water,ecological health maintenance and economic development in irrigated areas.The main results of this thesis are as follows:1.Compared with the traditional tillage mode,the combined improvement of phosphogypsum and Suaeda salsa under brackish water irrigation significantly increased the soil moisture content in topsoil during the growth period（except the early flowering period）（P<0.05）,decreased the soil p H value and electrical conductivity,and the desalting rate was as high as 40.73%.Combined modification and phosphogypsum modification significantly increased the content of organic matter and available phosphorus on the soil surface.They increased the diversity index by 6.10%and the richness index by 26.92%compared with the traditional tillage at the initial improvement stage.The combined modification of phosphogypsum with Suaeda salsa and phosphogypsum increased the yield of Lycium barbarum by 31.49%～64.38%and the water use efficiency by 29.80%～73.97%.2.Soil moisture content and p H value increased by 2.25%-10.43%and0.60%-2.85%,respectively,with the brackish water irrigation quota increase.The Bu Er Jun Tan microbial fertilizer increased soil moisture content by 5.38%～9.60%on average and decreased soil p H by 0.71%～2.11%.Soil moisture content and p H value increased first and then decreased with the application rate of the microbial fertilizer.Compared with no application of microbial fertilizer,soil organic matter,alkali-hydrolyzed nitrogen and available phosphorus increased by 82.02%,116.33%and83.15%.Soil Na⁺,K⁺,Ca²⁺,Mg²⁺,Cl^-and SO₄^2-decreased first and then increased with the increased brackish water irrigation quota.When the irrigation quota was 240mm,the contents of all ions were low,HCO₃^-increased with the increase of brackish water irrigation quota,and soil salt ions decreased with the increase of microbial-fertilizer application.The Bu Er Jun Tan microbial fertilizer had a better absorption effect on soil salt ions,and the dominant bacteria,such as Sphingobacter,were added.The relative abundance of chitin decomposition and chloroplast function of soil bacteria increased by44.98%and 178.46%on average.Soil moisture content,Na⁺and organic matter were important factors affecting bacterial community composition under microbial fertilizer.Organic matter has an important effect on the composition of soil salt ions and bacterial communities.Soil K⁺and bacterial community richness index have higher indirect inhibition on organic matter.3.Lycium barbarum betaine,soluble sugar,proline,Na⁺and Cl^-decreased first and then increased with the increase of brackish water irrigation quota,reached a low value when the irrigation quota was 240mm,and decreased with the increase of microbial fertilizer application rate.The variation trend of Lycium barbarum K⁺with brackish water and microbial-fertilizer was opposite to that of betaine.The net photosynthetic rate,transpiration rate and stomatal conduction of Lycium barbarum increased first and then decreased with the increase of brackish water irrigation quota and microbial fertilizer application rate,and reached the highest value when the irrigation quota was 240mm and fertilizer application rate was 5kg/mu.Under the same condition,the yield and hundred fresh grain weight of Lycium barbarum were significantly higher than those of other treatments（3.47%-73.76%and 17.04%-74.78%）.Based on the structural equation model,the soluble sugar,betaine,proline,Na⁺,and intercellular CO₂concentration significantly inhibited the yield of Lycium barbarum,and K⁺,net photosynthetic rate,transpiration rate,and stomatal conductivity could positively promote the yield of Lycium barbarum.The total effects of soil-Lycium barbarum comprehensive characteristics on yield were as follows:organic matter,net photosynthetic rate,bacterial community richness index,p H value,soil K⁺,soil moisture content,Lycium barbarum K⁺,stomatal conductance and soluble sugar.4.The optimal brackish water irrigation quota based on the characteristic indexes of Lycium barbarum was 190.8～246.6mm,and the microbial fertilizer rate was5.43～6.90kg/mu.Based on the comprehensive soil quality index,the optimum microbial-fertilizer application amount was between 3.83 and 6.60kg/mu.Considering the above factors,it is suggested that the brackish water irrigation quota of Lycium barbarum should be 190.8～246.6mm,and the microbial fertilizer application rate should be 3.83～6.60kg/mu.5.The tested Hydraus-1D model is accurate and can simulate soil water and salt in the study area.The simulation results showed that under the condition of suitable microbial fertilizer,when the brackish water irrigation quota was 230～245mm,the average total salt content of crop root layer soil was 3.53g/kg,and the salt accumulation rate was lower than 56.75%of other irrigation quotas.In conclusion,the optimal improvement mode under the planting conditions of Lycium barbarum in the Hetao irrigation area is phosphogypsum-Suaeda salsa comprehensive improvement and phosphogypsum improvement,the optimal brackish water irrigation quota is 230～245mm.The appropriate microbial fertilizer type is Bu Er Jun Tan microbial,which is rich in humic acid,and the optimal application amount is 3.83～6.60kg/mu.