<p>Fortification of cattle manure, and city waste compost was carried out with addition of Reliance formulated S (RFS) and groups of halo–alkaliphilic microbes. The acidulated composts produced were evaluated to offset soil alkalinity and facilitate soil nutrient accessibility, productivity benefit and quality improvement of sorghum [<i>Sorghum bicolor</i> (L.)] and mustard (<i>Brassica juncea</i>) for two years under field lysimeter conditions. Sorghum and mustard production increased due to the application of acidified composts before sorghum sowing each year. Application of compost increased the protein content by 1%, while a decrease in 4% erucic acid content was recorded in mustard grain with compost addition compared to the control. The acid detergent lignin content decreased by 10% in the sorghum biomass upon applying the RFS. The acidified compost application lower down the soil pH_s (1.3–6.3%) and alkalinity (18–28%) than control. The fortified compost solubilized the inherent CaCO₃, with an associated increase in the amounts of Ca²⁺, Mg²⁺, SO₄^2–, total N, and P in the soil saturation paste. Different fortified composts enhanced the S addition, increased the microbial biomass carbon (21–50%), phosphorous (16–118%), sulphur (80–104%) and dehydrogenase (50–58%), <i>β</i>–glucosidase (10–29%), fluorescein diacetate (6–13%), and alkaline phosphatase (79–80%) activities as compared to the control. The acidulation of manure and compost can be an effective option for the recycling and reuse of waste, neutralization of soil alkalinity, and crop production improvement.</p>