Impact of Microbial Inoculants on Soil Exchangeable Cations in Salinity-Affected Dryland Soils

Abstract

A laboratory incubation study was conducted at Tamil Nadu Agricultural University, Coimbatore (2021-2022), to evaluate the efficacy of salt-tolerant microbial inoculants for the biological remediation of saline soils with an electrical conductivity (EC) of 4.03, 5.01, and 6.02 dS m-1 under dry land conditions (75 % field capacity). Two microbial consortia CSR-GROW-SURE [contained halo-tolerant strains including Lysinibacillus fusiformis (CSR-A-11), Lysinibacillus sphaericus (CSR-A-16), and Bacillus licheniformis (CSR-M-16)] and the TNAU culture (Bacillus subtilis) were applied at three dosage levels: 1, 2, and 3 L ha-1. Soil samples were collected at 30, 60, and 90 days after incubation (DAI) to assess changes in soil exchangeable cations. The application of CSR-GROW-SURE at 3 L ha-1 significantly reduced the levels of exchangeable calcium (Ca2+), magnesium (Mg2+), and sodium (Na⁺) in saline soils with EC levels of 4.03, 5.01, and 6.02 dS m-1 at 90 days after incubation (DAI), compared to the control. The percentage reductions observed were (8.11, 4.27 and 5.69%) for Ca2+; (8.01%, 4.29%, and 5.59%) for Mg2+; and (26.45, 26.04 and 25.64%) for Na+, respectively. In contrast, exchangeable potassium (K⁺) showed the highest percentage increase of (15.44, 17.03, and 14.72%) at the same EC levels. These results were statistically on par with those recorded for the TNAU culture applied at 3 L ha-1 at the same incubation period, indicating similar efficacy in improving soil chemical properties under similar salinity levels. These findings suggest that halo-tolerant microbial inoculants, particularly CSR-GROW-SURE and TNAU culture with 3 L ha-1, hold considerable potential for the reclamation of saline soils. Their application enhances nutrient mobilisation, mitigates salinity-induced stress, and contributes to sustaining soil health in salt-affected dry land ecosystems.