Sustainable utilization of coal combustion fly ash in the management of hydro-physical properties and productivity of reclaimed sodic soil

Purpose Poor hydro-physical properties associated with sodic soil despite intervention of reclamation technologies have become emerging issues for sustainable crop production. Coal combustion fly ash (FA), from thermal power stations, is also posing environmental hazards. The objective of the study was to resolve hydro-physical problems of reclaimed sodic soil using FA and green manure (GM) with wider impact on least limiting water range (LLWR), plant-available water capacity (PAWC), and crop productivity with safe FA disposal. Materials and methods A field experiment was conducted with seven treatments on sodic soils which had been reclaimed 15 years back, but crop productivity was low due to its poor hydro-physical properties. The treatments were as follows: control (reclaimed sodic soil); 1% v/v FA; 1% v/v FA + sesbania as GM; 2%v/v FA; 2% v/v FA + GM; 3% v/v FA; and 3% v/v FA + GM. Soil hydro-physico-chemical analysis was carried out to study changes in soil properties under the treatments. Results The results indicated a decreased bulk density, exchangeable sodium percentage, and dispersion ratio with increasing dose of FA alone and with GM. Saturated hydraulic conductivity was found maximum (0.258 cm h −1 ) in 2%v/v FA + GM. The wider differences of least limiting water range between control and treated plots (7.45–18.12% v/v) in comparison to plant-available water capacity (PAWC; 20.24–26.48%v/v) indicated sensitiveness of LLWR towards small changes in soil physical properties. The maximum grain yield of rice (5.2 t ha −1 ) and wheat (3.6 t ha −1 ) was harvested in 3% v/v FA + GM, which was on par with 2% v/v FA and 3%v/v FA. Toxic elements like Cr, Cd, and Pb in soil were found within the permissible limits as a result of FA application. Conclusion The results of the study suggested that addition of FA alone or in combination with GM may help in the improvement of hydro-physical environment of reclaimed sodic soil, with respect to hydraulic conductivity, infiltration rate, dispersion ratio, percentage of soil aggregate size, LLWR, and PAWC. Thus, 2% v/v FA could safely be used to improve hydro-physico-chemical properties of soil and provide a sustainable and effective strategic approach for FA disposal and crop productivity enhancement.