Evaluation of Phytotoxicity of Manure-derived Fertilisers Using Seed Germination and Root Elongation Bioassays

This study evaluated the phytotoxicity of poultry manure-derived fertilizers. Four composting treatments were obtained from fresh poultry droppings at different initial C/N ratios (12 and 30, P and M, respectively) and oxygenation levels: static pile (S) and forced aeration (A). Acute toxicity tests were performed on seeds of three plant species (Helianthus annuus, Vigna radiata, and Sinapis alba) using elutriates of fresh poultry droppings (FPDs) and composts (1:10 w/v) at different concentrations (25, 50, 75 and 100% v/v). Seeds were disinfected, exposed to elutriates, and monitored for germination and root elongation over 4 days. Relative growth and germination indexes were calculated (RGI and GI, respectively). Toxicity/inhibition thresholds for GI and ICR were <80% (high), 80–100% (low), and >100% (none). Sunflower showed low toxicity effects with composted treatments, either static (MS,PS) or aerated ones (MA, PA), with a mean RGI of 1.07±0.22 and GI of 99.5±18.26 for all concentrations studied. Mungbeans showed high sensitivity to most composting treatments, particularly PA (RGI:0.7±0.25; GI:74±23.54) and MS (RGI:0.62±0.36; GI:64.24±38.84), while only PS showed low toxicity (RGI:0.94±0.15; GI:94.18±13.23). For both sunflower and mungbeans, FPD decreased germination and radicle growth below 70, showing high toxicity in both indexes. Mustard had variable responses, no sensitivity to PS and MA treatments, with average RGI of 1.5 and GI of 147.32, while MS and FPD caused slightly low toxicity, and PA had high toxicity. Root elongation (RGI) was more robust than germination (GI) for detecting phytotoxicity. In general, it was observed that composting poultry droppings, regardless of the aeration or initial C/N, reduced in sensitive species, making it suitable for its use as fertilizer.