Effects of nitrogen and phosphorus nutrition on growth, yield, yield components and fruit quality of watermelon (Citrullus lanatus Thumb)

Abstract

An experiment was conducted in the Botswana College of Agriculture, Notwane farm in Gaborone North to evaluate the effect of nitrogen and phosphorus on growth, yield, yield components and quality of watermelon (Citrullus lanatus thumb var. Crimson Sweet). Five levels of nitrogen (0,50, 100, 150 and 200) and four levels of phosphorus (0,25,50 and 75) were laid in a split-plot design with five replications. There was no interaction between nitrogen and phosphorus fertilizer applications on all the dependent variables determined. Application of nitrogen at 50, 100 and 150 N kg/h increased vegetative growth, fruit yield, yield components and fruit quality. Application of N beyond 150 kg/ha decreased all the above dependent variables. Phosphorus application at 25 and 50 kg/ha increased vegetative growth, yield and yield components of watermelons. The positive response of watermelon plants to N and P was attributed to the role of N and P on growth, development, and efficient utilization of carbohydrates to form protoplasm and more cells, and the increase in dry matter, It was concluded that in order to optimize watermelon fruit yield and quantity, N and P should be applied at 150 and 50 kg/ha, respectively. The author recommends that for wider application of these fertilizer rates in Botswana N and P trials be undertaken in various parts of the country under different soil types, irrigation regimes and rain-fed agriculture to confirm the current findings.