The effect of different organic manure blends in the chemical and microbial properties of Bokashi biofertilizer.

Abstract

This study investigates how different organic manure blends affect the chemical composition, nutrient availability, and microbial biomass of Bokashi biofertilizers. Recognizing the growing demand for sustainable farming practices and the environmental challenges posed by synthetic fertilizers, the research focuses on three primary manure sources poultry manure, cow dung, and pig manure as well as a blend composed of 50% poultry, 30% cow dung, and 20% pig manure. Laboratory-based experiments were conducted at the Fambidzanai Permaculture Centre under controlled fermentation conditions. Fermentation maintained source pH trends: poultry (9.19→9.07), cattle (8.09→8.05), pig (9.06→9.01), and blend (8.07→8.06). Organic matter soared from 1.3–1.8% in raw manures to 16.2–22.8% in Bokashi, while C:N ratios rose from ~11–12 to 14.5–24.8. Available nitrogen peaked at 12.65% in the blend (11.72% poultry; 12.08% cattle; 11.40% pig), with phosphorus and potassium highest in the blend (1.82% P) and cattle Bokashi (2.11% K). A strong positive correlation was observed between pH and total N (r = 0.839) and between C:N ratio and organic matter (r = 0.875). Microbial analysis revealed that cattle-based Bokashi achieved the highest total viable counts (TVC) of 900,000 CFU/g, whereas poultry-based Bokashi registered the lowest (52,000 CFU/g). Notably, mould counts were undetected in the blended and poultry treatments, indicating microbial suppression potential. These results demonstrate that optimizing manure blends enhances nutrient stabilization and microbial quality while preserving pH balance, offering a viable path toward more effective, sustainable soil amendments. The study underscores the potential of manure blending in Bokashi formulations and offers practical insights for farmers, fertilizer producers, and policy makers invested in regenerative agriculture.