摘要: Optimum nitrogen (N) fertilizer rates and application timing have not been clearly established for papaya plants in north central Florida. Annual N application rates vary from 160 to 500 kg'ha-1 and papaya growers in Florida often... 展开 Optimum nitrogen (N) fertilizer rates and application timing have not been clearly established for papaya plants in north central Florida. Annual N application rates vary from 160 to 500 kg'ha-1 and papaya growers in Florida often band fertilizer within the row before and after planting. ‘Red Lady’ papaya (Carica papaya L.) seedlings were transplanted to the field in Gainesville, Florida. For the N rate study, granular fertilizer was applied to the soil. Nitrogen was applied at 50,100, 200, or 300kg/treated ha per year to determine the N rate for optimum papaya growth and yields. A second set of experiments compared the effects of various application timings on papaya growth and yields. Treatments consisted of all fertilizer (N at 223 kg-ha~(-1))applied prior to planting (preplant); 2/3 preplant and 1/3 applied after planting (post-plant); 1/3 preplant and 2/3 post-plant; and all fertilizer applied post-plant three times per year. Total plant vegetative fresh weights increased linearly from the50 to the 300 kg/treated ha annual N rate in both years and stem diameter also increased linearly with time but independent of treatment. Total fruit yield per plant, fruit weight, and fruit number increased, reaching a maximum level at the 223 kg/treated ha rate. In the fertilizer application timing study, there were no significant treatment effects on growth of any plant part except root fresh weight. Root fresh weight was lowest when fertilizer was applied entirely pre-plant in 2005. Application timing generally had no effect on growth, yields, or petiole N content. 收起