Valorization of sorghum residues through vermicomposting and biochar production and their physico chemical characterization

Sorghum residues utility as a livestock feed is rapidly waning and thus is available for alternates uses especially value-added products (valorization). Rabi sorghum mega variety ‘M-35-1’ residues conversion into vermicompost and biochar and their physico-chemical characterization was assessed at ICAR-Indian Institute of Millets Research, Rajandra nagar, Hyderabad, India during 2022. Results indicate that sorghum residues have higher biochar conversion ratio (37.2%) than vermicompost (33%), however, vermicompost has moderately alkaline pH (8.41) while biochar has alkaline pH (9.73). Though both products fell into moderately saline category, EC of vermicompost is higher than biochar (3.76 v 2.61 dSm^-1). Bulk density & particle density (g cm^-3), porosity and moisture holding capacity (%) has increased by 14.2, 16.2, 1.42 and 1.89 times (vermicompost) and 2.16, 4.27, 1.99 and 10.9 times (biochar) as compared to sorghum residues. Carbon concentration is reduced by 25.7% in vermicompost production but increased by 43.8% in biochar production and biochar falls into Class 2 as per International Biochar Initiative (IBA). Elemental composition indicates that vermicompost is enriched by 468, 100, 42.9, 24.4, 32.3, 147, 13.7, 44.8 and 103% for N, P, K, Ca, Mg, S, Cu, Mn and Na while biochar in N, K, Ca, Mg, Fe, Zn, Cu, and Mn by 144, 24.2, 80.0, 8.82, 246, 790, 662, and 36.2%. However, there is reduction in Fe & Zn (81.6 and 34.5%) and P and S contents (48.3 and 53.3%) in vermicompost and biochar as compared to sorghum residues. Sorghum residues (₹ 3000/ ton) valorization into vermicompost and biochar involve additional expenditure of ₹ 4350 and 2500/ ton and a selling price of ₹ 9.2 and 8.1 per kg is cane be marketing price and an agro-industry can thrive on it. Vermicompost can be used in organic nourishment of crops while biochar in enhancing soil moisture storage in dry lands and in long-term C sequestration.