Evaluating the relative contribution of physiochemical and biological factors in ameliorating a saline-sodic soil amended with composts and biochar and leached with reclaimed water

- Unsterilized and pre-sterilized soil amendment mixtures were studied.
- Pre-sterilization significantly reduced aggregate stability of soil with composts.
- Pre-sterilization did not affect soil chemical properties significantly.
- Biological and physiochemical factors act synergistically when composts are used.
- Biological factors are not significant contributors of reclamation with biochar.

The mechanisms that assist in the reclamation of salt-affected soils in arid and semi-arid regions when treated with organic amendments have not been well characterized. In this experiment, the relative importance of biological and physiochemical mechanisms that aid in the reclamation of physical and chemical properties of a saline-sodic soil amended with composts and biochar were evaluated. Unsterilized and pre-sterilized soil and amendment mixtures were used to test the effects of biological and physiochemical factors. Soil and organic amendments were initially subjected to sterilization by autoclaving and gamma irradiation before incubation. Amendments were applied at a rate of 75 t ha− 1 and treated soils were incubated for a month and then leached with reclaimed water. Soil physical and chemical characteristics such as wet aggregate stability, hydraulic conductivity, cumulative Na+, Ca2 +, and Mg2 + leached, soil pH, SAR, ECe, and ESP were analyzed. Results indicate that pre-sterilization significantly affected soil physical properties such as aggregate stability and hydraulic conductivity only in compost-treated soils. Unsterilized compost-treated soils had significantly higher soil aggregate stability and saturated hydraulic conductivity than pre-sterilized soils. Soil pH was significantly lower in unsterilized soils that received composts, but other chemical properties were not affected by pre-sterilization. No significant effect of initial sterilization was observed in biochar treated soils in remediating their physical and chemical properties. Irrespective of sterilization, composts and biochar successfully remediated a saline-sodic soil leached with reclaimed water. It appears that the mode of action of biochar is physiochemical while composts provide a comprehensive reclamation when biological and physiochemical factors act together.