Comparison of Vegetative Bioremediation and Chemical Amendments for Non-calcareous Highly Saline-Sodic Soil Remediation

Abstract

Salt-affected soils cover a wide area, limiting agricultural production worldwide. Several remediation options are available and include chemical and vegetative remediation, but several aspects of each process are not yet fully understood. Therefore, the goal of this work was to study the application of both techniques in a highly saline scenario and provide insights into the limits of the application of this technology. Two chemical amendments (CaSO4 and CaCl2) and two plant species (Juncus maritimus Lam. and Spartina maritima (Curtis) Fernald) were tested to remediate a non-calcareous soil with an electrical conductivity of 20 dS m−1 (EC) and a sodium adsorption ratio (SAR) of 45. Vegetative bioremediation experiments were performed under non-leaching conditions. As such, salts were redistributed and increased at the surface and decreased in depth due to capillary rise. In such conditions, there was no clear positive effect of plants on soil parameters. However, tested plants grew, accumulated, and excreted salts and sodium comparably to other research in the literature. Regardless, the obtained results suggest that plant salt uptake alone may not be sufficient for soil remediation, and therefore, other mechanisms may also play a significant role. As to chemical amendments, both chemicals used proved to be effective and reduced non-calcareous saline soil parameters to below threshold values of 4 dS m−1 for EC and 7 for SAR. However, CaCl2 was more effective and faster to remediate than CaSO4, likely due to higher solubility. Therefore, CaCl2 may be a viable, yet less tested, option for faster remediation processes.