EFFECT OF N-FERTILIZATION ON YIELD COMPONENTS OF NIGHTSHADE

Nightshades (Solanum L. section Solanum, e.g., S. scabrum, S. tarderomotum, S. villosum, S. americanum and S. grossidentatum) are widely cultivated in East and West Africa due to their potential nutritional and economic benefits, but little is known about production practices in cultivating nightshades. This study was carried out at AVRDC-The World Vegetable Center in Arusha, Tanzania to evaluate the yield response of nightshade to N-fertilization. Eleven promising accessions, representing genetic diversity in 103 nightshade accessions conserved at AVRDC-RCA in Arusha, were selected and evaluated over two seasons in years 2004 and 2005. The experiments were conducted in the field in plots measuring 6×2 m and laid-out in 4×11 factorial randomized complete block design with three replications at a spacing of 50×50 cm. Four rates of urea fertilizer, i.e., control (= no urea added), 60, 90 and 120 kg/ha were used as treatments. The urea fertilizer was applied as side-dressing in two equal splits two and six weeks after transplanting. Data on leaf, fruit and seed yield were collected at a two-week interval beginning six weeks after transplanting and subjected to ANOVA using CoStat software. Results revealed that fruit and seed yields increased significantly (P≤0.05) with an increase in application of urea N but differences in leaf yield between the N-rates used were non-significant (P≤0.05). Significant differences were observed in leaf, fruit and seed yield components between the accessions evaluated. Line BG 16 recorded the best leaf and seed yields at 24.17 and 6.86 t/ha respectively, while the highest fruit yield was recorded with line IP20 which gave 119.59 t/ha. It is recommended that N fertilizer should be applied at lower rates (60 kg/ha) for leaf production of nightshade while higher rates of up to 120 kg/ha should be applied for fruit and seed production.