Enhancing Salt Leaching Efficiency Of Saline-sodic Coastal Soil By Rice Straw And Gypsum Amendments In Coastal Area Of Jiangsu,China

High salinity-sodicity affects large areas of newly-reclaimed land in many coastal regions that need proper leaching before they become productive.However,poor soil properties make the saltleaching process ineffective.In this study,a laboratory experiment was conducted to explore the usefulness of applying inexpensive chemical and organic amendments(gypsum and rice straw)through percolation columns in improving leaching efficiency in Dongtai coastal area-JiangsuChina.Four treatments,control(CT),rice straw(RS),gypsum(GPS),gypsum,and rice straw(GPS+RS),with two replicates,each were tested to find the optimal combination.The experiments were conducted during the winter season of 2020-2021,and were continued for six months.Soils were leached to six pore-volumes(PV)of water passed.Soil property changes after leaching were measured as well as cumulative dissolved cations(Ca2+,Mg2+,K+,Na+),sodium adsorption ratio(SAR)electrical conductivity(EC),hydraulic conductivity(HC),and soil reaction(pH)in leachate.The results indicate that application of GPS+RS subsequent with leaching more effective and better-reducing ECe,SAR,and ESP values compared to other treatments.The final ECe,SAR,and ESP in GPS+RS dropped to 3.61%,5.04%,and 8.14%,respectively,of their respective initial values,and they have lowered close to the safe limit of salinity and sodicity of(ECe?4 dS m-1,SAR?13 mmolc Kg-1,ESP?15%)for rice production.Gypsum treatment increased the electrolyte concentration of the leaching solution and therefore helped to increase the soil HC.Gypsum addition to organic amendments significantly increased(P<0.05)their soil HC compared to those soils that received only organic materials.The pH in GPS and GPS+RS treatments did not record any noticeable increase compared with CT treatment.The final soil pH values in all the treatments were still higher than the optimal range of agricultural crops(6.0-6.8).In addition,GPS+RS treatment is more effective in replacing Na+ from the exchangeable sites.In contrast with CT and RS treatments,exchangeable Ca2+ increases significantly in GPS+RS and GPS treatments.Moreover,the concentrations of K+ and Mg2+decreased significantly(P?0.05)in all treatments compared with their respective initial values.On the other hand,cumulative dissolved cations K+,Na+,Ca2+,and Mg2+in leachate were the highest,then reduced for the subsequent leaching processes.Among all treatments,it was accomplished that the GPS+RS and GPS treatment had a more substantial influence on raising the accumulative dissolved Na+ and Ca2+ in leachate and also had a higher impact on increasing the leachate EC.The cumulative dissolved Mg2+ increased significantly over leaching in all the treatments,and CT and RS treatments were significantly(P?0.05)higher than GPS treated.The final results showed that salt leaching efficiency improvement in all the treatments was in the order of GPS+RS>GPS>RS>CT.The outcome from this research may provide a technical reference for reclamation and enhancing the salt leaching efficiency for saline-sodic soils in the study region or areas with similar soil properties.