Impact of Sugarcane Residue-based Amendments on Soil Organic Carbon Stock and Yield of Black Gram (Vigna mungo L.) under Natural Farming Protocols

Declining soil organic carbon and increasing reliance on synthetic fertilizers are important constraints to sustainable crop production. The present field experiment was conducted during the kharif season at Surat, Gujarat, India, to evaluate the influence of sugarcane residue-based amendments and natural farming practices on soil properties, nutrient uptake, soil organic carbon stock, and yield of black gram (Vigna mungo L.). The experiment was laid out in a randomized block design with six treatments and three replications. The treatments consisted of control, sugarcane trash mulching, sugarcane bagasse compost, press mud application, natural farming with biochar, and recommended dose of fertilizers. Soil samples were collected before sowing and after harvest for analysis of soil organic carbon, pH, electrical conductivity, available nitrogen, available phosphorus, available potassium, and bulk density. Plant samples were analyzed for nitrogen, phosphorus, and potassium uptake at harvest. The results showed that sugarcane residue-based amendments improved soil organic carbon, nutrient availability, bulk density, nutrient uptake, and crop yield compared with the untreated control. Among the treatments, natural farming with biochar recorded the highest soil organic carbon content (0.68%), grain yield (1328 kg ha⁻¹), and biomass yield (3025 kg ha⁻¹). The same treatment also recorded the highest final soil organic carbon stock (13.36 t C ha⁻¹) and carbon accumulation (4.04 t C ha⁻¹). Press mud application also showed improvement in soil organic carbon and carbon stock. The findings indicate that recycling sugarcane residues through organic amendments, particularly when combined with biochar-based natural farming inputs, can improve soil health and support black gram productivity under the tested conditions. However, longer-term evaluation is needed to confirm the persistence of these effects across seasons and soil types.