Improvement Of Soda Saline-sodic Soils Using Copperas

Several million hectares of saline-sodic soils in the Songnen Plain, northeastChina, are difficult to be ameliorated and utilized due to their poor soil properties. Theby-product of titanium dioxide (copperas) production is huge and difficult to dispose.It would be of great significance to use it in improving saline-sodic soils for resourcereuse and agriculture development. Effects of copperas on soil salinity, pH,exchangeable sodium/calcium/magnesium, exchangeable sodium percentage (ESP)and chemical forms of Fe were studied. The results showed that:(1) soil salinity, pH,exchangeable sodium and ESP decreased with the increment of copperas, theydecreased from14.54dS·m-1,10.58,15.75cmol·kg-1and81.95%in the control to7.92dS·m-1,9.56,8.38cmol·kg-1and42.29%, respectively, when the application rateof copperas was2.0%.(2) soil salinity exchangeable Ca and Mg increased with theincrement of copperas. They increased from7.86cmol·kg-1and0.45cmol·kg-1in thecontrol to10.56cmol·kg-1and0.76cmol·kg-1, respectively, when the application rateof copperas was2.0%.(3) the application of copperas also changed the proportion ofchemical forms of Fe to total Fe in soil, the proportion of reducible Fe, which isbeneficial to improvement of soil properties, increased from4.41%to17.22%.(4) soilphysical and chemical properties such as water permeability, salinity, pH,exchangeable sodium and ESP got improved in different degrees with the applicationof copperas, gypsum, polymeric aluminum ferric sulfate (PAFS) and polymeric ferricsulfate (PFS). In general, the improvement effect of PAFS and PFS was much higherthan copperas and gypsum, the difference between the latter two was not that much.However, PAFS and PFS are very expensive, copperas is the cheapest.Therefore, copperas is effective for amending saline sodic soils, and copperas ingeneral saline soil improvement has practical popularization value for alternatinggypsum. However, as to the improvement of some hard saline-sodic soils, polymermodifier such as PAFS and PFS would be more suitable.