Managing Saline Irrigation and Soil Microbiome Using Coalchar-Derived Graphene Oxide

Soil salinity and declining soil biological health are major constraints to sustainable crop production, particularly under the intensifying impacts of climate change. This review examined the emerging role of graphene oxide derived from refractory coal char as a multifunctional material for improving soil health, engineering soil microbiome, and ameliorating saline irrigation water. Refractory coalchar, an industrial by-product, can be transformed into graphene oxide through oxidation–exfoliation processes, producing a material with high surface area and abundant oxygen-containing functional groups. These properties enable efficient adsorption of sodium ions and dissolved salts, thereby reducing electrical conductivity and sodium adsorption ratio of poor-quality irrigation water. Beyond water treatment, graphene oxide influences soil physicochemical and biological properties. Its application enhances soil organic carbon, cation exchange capacity, and nutrient availability while reducing salinity stress. Importantly, graphene oxide acts as a supportive matrix for microbial colonisation, leading to improved microbial biomass, enzyme activities, and functional diversity. Evidence from incubation and field studies indicates that the combined effects of improved water quality and enhanced soil biological activity translate into significant gains in crop growth and productivity under saline conditions. The graphene oxide derived from coalchar into agricultural systems represents a circular and climate-resilient approach, converting industrial waste into a value-added resource for sustainable farming. This review aimed at ensuring sustainable crop production in salt-affected and climate-stressed agroecosystems.