Impacts of Different Amendments and Water Qualities on Soluble and Exchangeable Phases and Hydraulic Conductivity of a Calcareous Soil

This study aimed to evaluate the effect of nanoclay (NC), zeolite (Z), biochar (B), municipal waste compost (MWC), and farmyard manure (FYM) at two application levels of 1% and 3% (w/w) on the saturated hydraulic conductivity (K_S) and sodification process of a calcareous soil under leaching by waters with different electrical conductivity (EC) and sodium absorption ratio (SAR) values. Columns containing control and amended soils were washed in three separate experiments using 20 pore volumes of three solutions classified in C3S1, C4S3, and C4S4 classes. The incorporation of the amendments led to a significant decrease in soil sodification because of decreasing exchangeable sodium and increasing exchangeable calcium. The exchangeable sodium percentage (ESP) of soils after leaching by solutions C3S1, C4S3, and C4S4 varied in the ranges of 1.80–5.79%, 2.78–7.85%, and 3.66–15.6%, respectively. The highest and lowest ESP values were obtained for control and 3% FYM treatment, respectively. For each leaching solution, the K_S was significantly higher in the control compared to the amended soils (P ≤ 0.05). The lowest value of K_S was obtained for the 3% B treatment. Furthermore, K_S values increased with an increase in SAR of water. This was likely due to the simultaneous increase in EC and concentration of divalent cations (calcium and magnesium). The most effective amendments in controlling soil sodification were FYM, B, and MWC at the application level of 3%.