Effects Of Strip Interlayer On Distribution Of Water,Salt And Fertilizer And Root Growth Of Cynodon Dactylon In Coastal Saline Soil

Due to the shallow groundwater burial in the coastal saline areas of the Yellow River Delta,the high salt content and nutrient poverty of the soil have caused a wide area of saline land in the region,which seriously restricts the sustainable development of agriculture.The use of barrier layers is an effective method to improve saline-alkali soil by cutting off the evaporation channel of groundwater at a suitable depth underground,thereby reducing the accumulation of salt in the crop root zone.However,the current method of barrier layer installation uses full coverage,which requires a relatively high amount of material and is not conducive to large-scale promotion.Therefore,this study proposes a partially covered（striped）barrier layer addition method to improve coastal saline-alkali soil.It is assumed that reducing the width of the barrier layer can also achieve good water retention,salt inhibition,and yield-increasing effects.Through soil box experiments,different coverage ratios（50%,70%,100%）and different barrier layer materials（peat,straw,biochar）were set to analyze the effect of striped barrier layer addition on the water-fertilizer-salt distribution of coastal saline-alkali soil and the growth of Cynodon dactylon,in order to determine the optimal barrier layer material and coverage ratio for improving coastal saline-alkali soil and promoting the application of barrier layers in soil improvement.The main results and conclusions are as follows:（1）Compared with different barrier layer materials,the addition of barrier layers significantly reduced the electrical conductivity（EC）,p H,Na⁺,Cl^-,and SO₄^2-ion content of the surface 0-20 cm soil,among which the salt inhibition effect of peat and straw barrier layer treatments was better.However,the straw barrier layer treatment significantly reduced the soil moisture content of the surface soil by 19.67%,which is not conducive to normal plant growth.The peat barrier layer treatment significantly increased the soil moisture content of the upper soil layer by 4%while reducing the soil p H by 6.96%,showing good water retention and salt inhibition effects.（2）Adding different barrier layer materials significantly increased the soil organic matter（SOM）,available phosphorus（AP）,nitrate nitrogen（NO₃^--N）,ammonium nitrogen（NH₄⁺-N）,and nutrient elements of K⁺,Ca²⁺,and Mg²⁺in the 0-20 cm soil layer,and the AP content of the soil increased significantly by 34.7%-44.73%;the NH₄⁺-N and NO₃^--N content were 1.04-1.96 times that of the control group.The o SOM of the peat barrier layer treatment increased significantly,showing an increase of122.65%compared with the control group;K⁺,Ca²⁺,and Mg²⁺ions increased significantly by 0.73 times,2.59 times,and 2.05 times,respectively.（3）Compared with the control treatment,adding different barrier layer materials significantly increased the total biomass of Cynodon dactylon,among which the peat barrier layer treatment was the most significant,showing an increase of 1.27 times compared with the control group.Adding peat and straw barrier layer treatments significantly increased the total root length and root surface area of Cynodon dactylon by 1.44-1.58 times.Considering the soil physical and chemical properties and plant growth,peat has the best effect on improving coastal saline-alkali soil.（4）Based on the optimal barrier layer material（peat）obtained from the experiment,different barrier layer coverage ratios were studied,and it was found that with the increase of peat coverage ratio,SOC,AP,NH₄⁺-N,NO₃^--N,and K⁺,Ca²⁺,and Mg²⁺ion content of the 0-20 cm soil layer gradually increased,while the EC,p H,and Na⁺,Cl^-,and SO₄^2-ions gradually decreased.Compared with the control group,the electrical conductivity of the soil above the 50%coverage ratio barrier layer decreased by 21.79%,and the electrical conductivity of the 70%and 100%coverage ratio treatments decreased significantly by 36.02%-49.57%.The SOC above the 50%coverage ratio barrier layer increased by 14.33%,and the 70%and 100%coverage ratio treatments increased significantly by 38.02%-43.45%.（5）Compared with the control group,the 50%peat coverage ratio addition had no significant effect on the plant height and root system of Cynodon dactylon,and only when the coverage ratio reached 70%and 100%,the parameters such as plant height,total root length,and total biomass of Cynodon dactylon increased significantly.The increase in plant height was 1.44 and 1.60 times for the 70%and 100%coverage ratio treatments,respectively;the increase in total root length was 43.81%and 67.60%,respectively;the increase in total biomass was 1.12 and 1.27 times,respectively.Through differential analysis,it was found that there was no significant difference in plant height,total root length,and total biomass between the 70%and 100%peat coverage ratio treatments.In summary,the addition of striped barrier layers can effectively inhibit groundwater evaporation,reduce soil salinization in the plow layer,increase soil nutrient content,promote plant root growth,and improve plant biomass.To promote large-scale application and save improvement costs,this study believes that adding a70%peat coverage ratio is a more suitable deployment method,which can provide a theoretical basis for the application of barrier layers in improving coastal saline-alkali soil.