E.T. AKHIHIERO

This study focused on the optimization of organic fertilizer production from Chromolaena odorata (Siam weed) with the aim of determining the most suitable drying conditions for nutrient preservation and evaluating its effects on soil fertility and maize (Zea mays) growth performance. Fresh C. odorata leaves were collected, air-dried, and oven-dried under varying temperature (30–85 °C) and time (30–120 min) conditions. The effects of these parameters on nutrient composition (particularly nitrogen (N), phosphorus (P), and potassium (K)) were analyzed using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The optimized fertilizer product was applied to soil samples to assess changes in nutrient levels before and after maize cultivation. Results revealed that both drying temperature and time significantly influenced the nutrient composition of C. odorata. Nitrogen and phosphorus contents decreased with increasing temperature, whereas potassium concentration increased due to moisture reduction and mineral concentration effects. The optimal drying condition was found to be approximately 55 °C for 90 minutes, which preserved the highest levels of essential nutrients. Post-sowing soil analysis indicated improved macronutrient and micronutrient concentrations following the application of the optimized organic fertilizer. Maize plants grown in treated soil exhibited superior vegetative growth compared to the control, with notable increases in plant height, stem diameter, and dry biomass yield. The findings demonstrate that Chromolaena odorata can serve as an effective and sustainable source of organic fertilizer. Its utilization not only enhances soil fertility and crop productivity but also provides an environmentally friendly means of managing this invasive weed species.