Reclamation of degraded saline-alkali soils of the northwestern region of India through microbial amendments

Salt-affected soils of semi-arid northern India severely limit ecosystem functioning and agroforestry productivity through elevated salinity, low organic carbon, restricted phosphorus availability, and alkaline pH. Eleven amendment treatments comprising enriched charcoal (Ench) and enriched soil (EnS) substrates co-inoculated with four indigenously characterised plant growth-promoting rhizobacteria (PGPR: Klebsiella aerogenes , Lysinibacillus acetophenoni , Pseudomonas stutzeri , and Pseudomonas mosselii ) were evaluated across three soil depth intervals (0–30, 30–60, and 60–90 cm) in a randomised split-plot design at three sites (Hisar, Karnal, Bhiwani) in Haryana. Soil pH, electrical conductivity (EC), organic carbon (OC), available nitrogen (N), phosphorus (P), and potassium (K) were analysed using split-plot linear mixed-effects models (LMMs). Ten amendments significantly reduced EC, with nine achieving significant reductions across all three depth intervals and the largest reductions reaching 0.31 dS m⁻ 1 (67% of baseline) at the surface. Eight treatments increased OC significantly at 0–30 cm (83–109% above baseline); only T11 (EnS + four-strain consortium) extended this effect to 60–90 cm (+ 0.262%, p = 0.014). Multiple treatments significantly increased phosphorus availability at all three depths. pH, N, and K were unresponsive within the study period. Marginal R 2 values ranged from 0.074 to 0.569 across the six soil properties, while conditional R 2 values ranged from 0.634 to 0.881 for models with estimable random-effect variance, indicating that the hierarchical model structure accounted for substantial additional variation beyond treatment and depth. A PCA-derived Soil Quality Index showed the highest mean SQI for T2 (Ench + K. aerogenes ) and T5 (Ench + P. mosselii ), whereas T9 (EnS + P. stutzeri ) showed the lowest coefficient of variation across the three soil-depth intervals. These responses indicate that selected organic-microbial amendments have potential to improve specific dimensions of soil quality under the conditions tested, while their persistence and broader applicability require validation across additional seasons and sites.