Acidulated composts govern the soil solution nutrient composition through changes in key functional bacterial community of alkaline soils

Soil chemical degradation is an important concern for sustainable crop production in arid and semi–arid regions worldwide. This study evaluated the soil alkalinity stress alleviation potential of rapid acidulated compost developed from the elemental S (S°), consortia of S°–oxidizers, and composts in surface soil (0 − 15 cm) depth of high pH belongs family of Typic Natrustalf. The acidified compost decreased the total alkalinity, [CO₃²⁻ + HCO₃⁻]/[Cl⁻ + SO₄²⁻] and [Na⁺] / [Cl⁻ + SO₄²⁻] ratio. The concentration of NH₄⁺, NO₃⁻, total nitrogen, Ca²⁺, Mg²⁺, dissolved reactive P, and total P was greater in the soil solution of the acidified compost–treated soils. The acidulated compost also increased the S (CaCl₂–extractable and water–soluble) and P (water–soluble and calcium–bound) pools. Besides, C, N, P, and S associated with microbial biomass, the soil enzymes such as fluorescein diacetate, dehydrogenase, alkaline phosphatase, and β–glucosidase were increased appreciably after acidulated compost application. While the arylsulphatase activity declined after compost application. The acidulated compost reshaped the bacterial assemblage by an appreciable decline in nirK and nosZ abundance. The nosZ abundance was greater than nirK. It also improved the biota harbouring nifH, phoD, and soxB genes. It altered the microbial assemblage of the N cycle by a twofold decline in amoB and a 1.6 times increase in amoA gene abundance. The compost–induced changes in microbial population explained about 50 % variability in the mustard yield. This study concluded that the acidulation of compost before application in the field using S° and consortia of S°–oxidizers can be an effective strategy to alleviate the alkalinity stress, manage nitrous oxide emission with improved soil health in alkaline soils and alkali irrigated agro–ecologies.