Improvement Effect Of Straw Returning With Inorganic Improver On Coastal Saline Soil

Saline land in Yellow River Delta is the reserve land resource with the cultivation conditions for agricultural development and utilization in China at current stage,but the high soil salinity and low soil fertility in this area have seriously restricted the ecological protection and high-quality agricultural development.Straw returning is an important technology of amelioration soil salinity,and is utilized worldwidely.Straw returning can increase the soil organic carbon,improve the soil water and fertilizer retention capacity,and achieve soil reform and fertilization.Calcium silicate and magnesium sulfate can effectively lower soil pH,reduce soil alkalinity,increase soil infiltration coefficient,enhance soil permeability,and significantly improve the effective soil nitrogen,phosphorus and potassium contents.In present study,moderate salinity soil in Yellow River Delta was employed as experiment material,and seven treatments of straw mulch return(S),straw buried return(P),straw mulch+buried return(SP),inorganic improver alone(I),straw buried return+inorganic improver(PI),straw mulch+buried return+inorganic improver(SPI)were set for soil column test.After irrigation leaching,maize was then planted.The effects on soil salt transport,maize growth and soil physicochemical properties of different straw returning methods and its combine application with inorganic improver were studied,and the effect on salt reduction and soil modification were also clarified.The main research results were as follows.(1)Straw mulch or buried returning combine with inorganic improver(PI,SPI)treatments can more effectively promoted the downward transport of soil salts with water and accumulate in the leaching solution,the total salt content in the leaching solution of PI and SPI treatment significantly increased by 67.32%and 90.12%compared with CK,except for HCO₃^-,the content of each salt-based ion in the leaching solution showed a pattern of straw mulch or buried returning combine with inorganic improver(PI,SPI)>inorganic amendment treatment(I)>straw return treatment(S,P,SP).(2)Straw mulch or buried returning combine with inorganic improver(PI,SPI)treatments significantly promoted maize growth,and the plant height,stalk thickness and dry matter yield in all periods were higher than the other treatments,with 15.40%-68.58%(plant height),15.27%-55.14%(stem diameter)and 13.20%-87.41%(dry matter yield)increment compared with CK respectively,the uptake of N and P by maize in different straw return methods or with the application of inorganic improver could promote the uptake of N and P.The uptake of nutrients by maize in each improved treatment increased by 32.27%-73.8%compared to CK;the basic order of uptake of soluble salt-based ions(K⁺,Ca²⁺,Mg²⁺)in all parts of maize was leaf>stem>root,which was repulsive to Na⁺that inhibited growth,with the highest content in root.The content of Ca²⁺and Mg²⁺in all parts of the plant was significantly higher than the other treatments and the content of Na⁺was significantly lower than the other treatments in the combined treatment of straw mulch or buried returning combine with inorganic improver(PI,SPI).(3)The salt content of the soil was decreased in different ways of straw returning or application inorganic improver treatment than before the start of the experiment,and the salt content was also decreased with the increasing of soil depth,and the desalination rate of each treatment ranged from 52.61%-83.94%(0-20 cm),61.84%-71.61%(20-40 cm)and 41.94%-60.86%(40-60 cm).Furthermore,the highest desalination rate was found in each soil layer of straw mulch or buried returning combine with inorganic improver(PI,SPI),which increased by 14.44%-59.55%compared to CK.The K⁺,Na⁺,Cl^-and HCO₃^-contents as well as the total salt content in the soil of straw mulch or buried returning combine with inorganic improver(PI,SPI)treatments were lower than that of CK and straw return treatment(S,P,SP).(4)Straw buried return(P),straw mulch+buried return(SP),straw mulch or buried returning combine with inorganic improver(PI,SPI)improved significantly,the soil organic matter in the 0-40 cm soil layer increased by 10.96%-22.15%,available potassium content increased by 18.72%-45.61%,available phosphorus content increased by 39.36%-66.96%,nitrate N content increased by 14.83%-18.66%,ammonium N content increased by 18.06%-27.99%;moreover the percentage of 0.25mm-2mm water-stable agglomerates increased by 32.67%-63.95%,and the percentage of<0.25mm microagglomerates decreased by 13.06%-19.92%.