Production of a Composite Organomineral Fertilizer Based on Plant Residue and Phosphorite Raw Material

Abstract

Background: Mineralized mass (MM), a low-grade by-product of phosphorite beneficiation, contains phosphorus with low laboratory solubility. Aims: To characterise the physicochemical composition of a composite organomineral fertiliser obtained by processing mineralized mass (MM), a by-product of phosphorite ore beneficiation, with plant residue (PR) oxidised by hydrogen peroxide in the presence of sulfuric acid, and to determine the optimal component ratios. Study Design: Laboratory experimental study; six MM:PR mass ratios were tested at four H2O2:H2SO4 molar ratios (24 experimental points, each in triplicate). Place and Duration of Study: Institute of General and Inorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Uzbekistan, 2025–2026. Methodology: PR was oxidised with 10% H2O2 in the presence of H2SO4 (H2O2:H2SO4 molar ratios 1:0.1, 1:0.2, 1:0.4 and 1:0.5) and mixed with MM at MM:PR mass ratios from 100:40 to 100:200. The product was neutralised with ammonia water, dried and granulated. The composition was determined by gravimetric and titrimetric analysis (n = 3; SD ≤ 0.5%). Trilon B-soluble P2O5 (% of total P2O5) was used as an operational laboratory index of phosphorus solubility. Results: MM contained 14.43% P2O5, of which only 9.11% was Trilon B-soluble. As the PR share increased, the organic matter content of the product rose from 26.08 to 55.97%, the humic acid content from 3.94 to 17.62% and Trilon B-soluble P2O5 from 38.78 to 86.65% of total P2O5, while total P2O5 fell owing to dilution. A higher H2SO4 share increased this index at every MM:PR ratio. At the recommended ratio (MM:PR = 100:150; H2O2:H2SO4 = 1:0.5) the product contained 4.22% total P2O5 (72.51% Trilon B-soluble), 49.94% organic matter and 13.18% humic acids. Conclusion: Oxidised plant residue combined with sulfuric acid increased the Trilon B-soluble fraction of phosphorus in substandard mineralized mass; however, in the present design the effect of the organic component cannot be separated from that of the acid. To our knowledge, this is the first systematic data set of this kind for mineralized mass. The recommended ratio is a screening-level choice; control experiments, contaminant analysis (F, Cd, Pb, As) and pot and field trials are required before any agronomic claim.