Effects of Organic and Inorganic Fertilizer on Soil Chemical Properties, Growth and Yield Performances of Watermelon in Humid Rain Forest South Western Nigeria.

One of the major draw backs of sustainable crop production in Nigeria is the inherent low soil fertility and unfavourable soil physical properties. The effects of different fertilizer sources (organic and inorganic) were assessed on the growth and yield of watermelon in Ikorodu, Lagos, Nigeria in Randomized Complete Block Design (RCBD) with four treatments replicated three times. The fertilizer sources were: 25 t/ha-1 (22.5kg/plot) cow dung, 250 kg/ha-1 (0.225 kg/plot) compost, 200kg/ha-1 (0.018kg/plot) NPK 15-15-15 and control (no fertilizer). The growth and yield parameters evaluated were number of leaves, vine length, stem/vine girth at 4, 6 and 8 weeks after sowing (WAS), number of days to 50% flowering, number of fruits per plot, fruit circumference and fruit weight. Application of organic and inorganic fertilizer significantly influence growth parameters; watermelon grown on soil incorporated with cow dung significantly (P<0.05) produced plants with the longest vine length and stout stem girth followed by compost manure at 6 and 8 weeks after sowing (WAS). However, nutrient sources did not significantly affects the number of leaves produced but cow dung and compost manure still produce the highest number of leaves. Similar trend was equally observed in number of days to 50% flowering. Yield attributes were significantly influenced by nutrient sources, watermelon fertilized with cow dung produced the highest number of harvested fruits and fruits weight, followed by NPK 15-15-15 and compost manure, while fertilizer sources did not affects the fruits circumference. Post soil analysis shows that all the treatments reduced calcium, sodium, available phosphorus and soil pH from 6.20 to a range between 5.56-5.86; pH level required for watermelon cultivation. Application of cow dung and compost increased potassium magnesium, organic carbon, total nitrogen and CEC in the experimental soil. The results clearly showed that watermelon grown in the study area responded positively to the soil fertility amended compared to control with cow dung showing significant growth and yield performances. Therefore, it is advocated that resource-poor farmers should utilized cow dung for optimum watermelon growth and yield as cow dung would supply required nutrients for sustainable watermelon cultivation and as well improved soil physio chemical properties.