Evaluation of phytotoxic effects of integrated nutrient management techniques on soil nutrient availability and maize germination

Nutrient management, which strategically combines two or more nutrient sources (organic, inorganic, and mineral amendments), aims to enhance crop resilience and sustain soil fertility under climatic variability. However, the early-stage phytotoxin effects and nutrient-release dynamics of different NM formulations require clarification for maize production systems in Nigeria. A laboratory bioassay was conducted using eight NM treatments: control (no amendment), cow dung (CD), NPK 15:15:15 fertiliser (NPK), agricultural lime (AL), and their combinations (CD+NPK, CD+AL, NPK+AL, CD+NPK+AL). Water extracts of each treatment (1:10 and 1:1 w/v) were incubated for 24 h at 25 ± 2 °C, centrifuged, and filtered before phytotoxicity testing with maize (Zea mays L.) seeds. Germination percentage, root and shoot length, and germination index (GI) were measured. Extract pH, EC, and nutrient composition were analysed. Data were subjected to one-way ANOVA, and means were separated with Tukey’s HSD at p ≤ 0.05. The extract pH ranged from 6.2 to 8.0. Single-mineral treatments (NPK, AL) exhibited moderate phytotoxicity (GI = 45–62%), while cow-dung-based combinations (CD+AL, CD+NPK, CD+NPK+AL) achieved higher GI ≥ 80%, indicating non-inhibition. The synergistic effect of organic inputs moderated extracted salinity and improved nutrient equilibrium. Enhanced early root vigour under combined CD-based treatments implies improved nutrient release and reduced osmotic stress. Combining cow dung with mineral fertilisers and lime effectively reduced phytotoxicity while improving nutrient balance, supporting precision and climate-smart integrated nutrient management adoption for maize systems in Nigeria.