Time monitoring of leachate quality during reclamation process of saline-sodic soil using soil column

Soil salinity and sodicity are serious challenges related to soil management and sustainable production in arid and semi-arid regions. This study investigates different methods of calcareous saline-sodic soil amelioration which emphasized on time variability of leachate quality. The experiment was factorial based on CRD using 6 soil treatments consist of control, cattle manure, pistachio residue, gypsum, and their combination; 2 leaching treatments (with and without sulfuric acid) and 3 replicates, which was conducted in laboratory conditions using soil column. Four intermittent leaching steps with one month interval and one pore volume were applied. The results showed that in the calcareous soil, application of gypsum led to -3 to -35 percent reductions in sodium leaching, while in presence of sulfuric acid, this gypsum efficiency raised to 10-34 percent. Because of higher decomposition rate of cattle manure than pistachio residue, more sodium removed out of soil column. Among four studied cations, potassium showed the lowest variations of change (CP) with time. In this regard, pistachio residue released higher potassium amounts into soil solution. Moreover, the efficiency of amendments in removing calcium out of soil profile was reduced for the subsequent leaching steps. This finding was attributed to some reduction in organic matter decomposition and resultant organic acids, which caused an increase of pH. Time variations of CP for potassium were similar to that of the calcium. Without application of sulfuric acid, the highest CP values of EC and SAR were observed for cattle manure+gypsum and cattle manure treatments with amounts of 305 and 163 percent, respectively. The findings of this research reveal that gypsum alone can not be applied for ameliorating calcareous saline-sodic soils.