Organic amendments improved the chemical–nutritional quality of saline-sodic soils

Soil salinity/sodicity is among the major threats to sustainable agriculture and plant production throughout the world. The damage caused by such threats can be reduced by developing efficient and suitable organic reclamation practices. We investigated the impact of organic amendments including biochar (BC) and vermicompost (VC) versus chemical treatments including gypsum (G) and elemental sulfur (S), versus combined approaches, vermicompost plus gypsum (VC + G) and elemental sulfur (VC + S) on the remediation of saline-sodic soils. Treatment effects were quantified and compared using two variants of soil quality index (SQI), including integrated quality index (IQI) and Nemoro quality index (NQI). Amendments varied in soil pH reduction by 0.75 to 0.95 units, exchangeable Na by 4.8–64.8%), and exchange sodium percentage by 5–63.7%. Organic and combined approaches significantly improved soil nutritional quality which is characterized by higher available P and K as well as bioavailable Fe, Mn, Zn, and Cu. VC alone and in combination with G and S resulted in the greatest overall improvement in soil chemical remediation and nutritional quality. Given both IQI and NQI models, the highest values of SQI were obtained for VC + G/S remediation treatments. Overall magnitude of soil quality index (IQI and NQI) was primarily determined by exchangeable sodium percentage (ESP), pH, and available P. Our results indicate not only the high potential of VC to improve soil nutritional quality, also signifies the role of VC in enhanced effectiveness of gypsum and sulfur in saline-sodic soils reclamation. Here we show that organic amendments can be as effective as chemical treatments in remediation of saline-sodic soils. Additionally, organic–chemical amendment combination can be an environmentally more sustainable alternative to sole chemical remediation practices while obtaining comparable efficacy.