Effects of Different Washing Reagents on Removal of Soil Salt Salinity for Coastal Reclamation Zones
[Objective]The effectiveness of washing reagents in removing soil salinity was evaluated to provide theoretical guidance for soil amendments in coastal reclamation zones.[Methods]Slightly and heavily saline soils of paddy fields from the Chongming coastal reclamation zones in Shanghai City were selected as the research objects,and the effects of five types of washing reagent(potassium nitrate,iron nitrate,calcium nitrate,magnesium nitrate,and ammonium bicarbonate)concentrations and extraction times on soil salinity(Na+,K+,Ca2+,Mg2+,CO32-,HCO3-,Cl,and SO2)removal efficiency were compared and analyzed.[Results]The five washing reagents promoted the removal of Na+and Cl-in the slightly saline soils,and the effect of potassium nitrate on Na+removal efficiency was the most obvious,because the Na+concentration in the eluate was increased by 9.9％-25.9％compared with that in the control.However,Cl-was more easily removed by ammonium bicarbonate,and the increase ratio was approximately 9.6％-21.2％compared with the control.Potassium nitrate(3.0 mmol/L)showed the best results,considering the removal of soil salt ions and the loss of soil nutrients(K+,Ca2+,and Mg2+).The Na+,Cl,SO42-,and Ca2+concentrations in the eluate of the second washing by potassium nitrate were markedly lower than those after the first time,whereas it was not the case for HCO3-and Mg2+.In this experiment,the five washing reagents showed negligible effects on the removal efficiency of Na+and Cl-in the heavily saline soils because the applied concentration was much lower than the salt ion content in the soils,and the increase rates of the two ions were 0.10％-1.0％and 0.01％--4.40％,respectively,compared with the control.[Conclusion]The types,concentrations and times of washing reagents should be determined according to the types and contents of soil salt ions when improves soil in coastal reclamation zones.The application of washing reagents could be combined with irrigation measures.
saline soilswashing reagentssalt ionsremovecoastal reclamation zones
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