Effect of plants density and nitrogen source on watermelon (Citrullus lanatus) performance under Gezira Conditions)

This study was carried out to evaluate the effect of different planting densities and mixing organic and inorganic sources of nitrogen on growth, productivity and quality of watermelon (planted on 3 m-wide raised beds). Two experiments separately were conducted at the Gezira Research Farm of the Agricultural Research Corporation, Sudan, for two consecutive seasons, winter 2009/10 and kharif 2010. The first experiment was performed to study the effect of plant density on watermelon growth, yield and quality. Nine treatments, three intra-row spacing, 50, 70 and 90 cm and three numbers of plants per hill, 1, 2 and 3 were evaluated in a factorial experiment fitted in Randomize Complete Block Design (RCBD) with three replications. Results of growth parameters indicated significant differences among treatments in number of branches/plant in the two seasons. While no significant differences were observed in plant length and number of leaves/plant in winter season but in kharif season significant differences were observed in number of leaves/plant. Results of yield components indicated no significant differences among treatments in number of fruits per hectare, highly significant differences in the two seasons in marketable fruits yield, significant and highly significant differences for Total Soluble Soled (TSS %) in winter and kharif seasons, respectively. The results indicated that 70 cm intra-row spacing with one plant/hole gave the optimum plant density for watermelon, since it resulted in optimum growth and the highest marketable yield and quality. The second experiment was conducted to study the effect of combining organic and inorganic sources of Nitrogen on watermelon fertilization. It contained six combination of various ratios of farmyard manure and urea to supply a total amount of 86 kg N/ha. The percentages of N to be provided by farmyard manure and urea were as follows 0:100, 25:75, 50:50, 75:25, 100: O. An untreated control treatment (without N fertilizer) was added to the experiment. Results of growth parameters indicated highly significant differences among treatments for plant length and no significant differences for number of branches/plant and number of leaves/plant except in kharif season, where highly significant differences were detected for number of leaves/plant. Significant differences and highly significant differences were detected for number of marketable fruits/ha in winter and kharif seasons, respectively. Highly significant differences for marketable fruits yield (tons/ha) were detected in the two seasons. Significant differences among treatments were also observed for TSS% and plant tissues nitrogen content in the two seasons. Significant differences in number of marketable fruits/ha were found only in the kharif season. Highly significant differences were detected among treatments for soil nitrogen content (%). Results indicated that the combination 25% N from farmyard manure and 75% N from urea (25: 75) is the best combination of the two fertilizers to give optimum growth and highest marketable yield and quality of watermelon. The results of this study indicated that the best plant population of watermelon sown on 3 m-wide beds is provided by sowing at 70 cm intra-row spacing and keeping one plant/hole. The study also indicated that, the use of fermented farmyard manure at the rate of 1.67 tons/ha to give 25% of the recommended nitrogen dose that completed by 150 kg urea/ha to give 75% N was the best combination for the fertilization of watermelon