Effect of nitrogen and potassium fertilizers on the growth and yield of watermelon in Ibadan, Nigeria

Abstract

Watermelon (Citrullus lanatus Thunb) is a widely cultivated and consumed fruit crop, though limited information exists on the nitrogen (N) and potassium (K) influence on its growth, yield, and fruit quality. This study evaluated the effects of N (urea) and K (muriate of potash) fertilizer rates on the growth and yield of watermelon under field conditions at Akerele Village, Ibadan, Oyo State, Nigeria. Three N levels (0, 30, and 60 kg ha⁻¹) and three K levels (0, 30, and 60 kg ha⁻¹) were arranged in a 3 × 3 factorial experiment using a split-plot design with three replications, giving nine treatment combinations. Data collected were subjected to analysis of variance (ANOVA), and significantly different treatment means were separated using Duncan’s Multiple Range Test at p < 0.05. Nitrogen significantly increased the number of branches at 60 kg N ha⁻¹ but had no significant effect on vine length, number of leaves, weight of vine, or fruit weight. Potassium significantly increased vine length and fruit weight, with 30 and 60 kg K ha⁻¹ giving the highest fruit weight, but had no significant effect on the number of leaves or weight of the vine. The N × K interaction significantly affected vine length, vine weight, and fruit weight, with N₀K₂ and N₂K₂ giving the longest vines, N₁K₀ the highest vine weight, and N₀K₁ the highest fruit weight. Fertilizer application therefore produced only limited, parameter-specific improvements over the control. Soil nutrient analysis before fertilizer application is recommended to ensure efficient nutrient management and optimum watermelon production.