Effect of N-Fertilizer Rates and Timing on Grain Yield andComponents of Sunflower

This experiment was conducted to determine the effects of time and rate of nitrogen fertilizer (urea) application on yield and yield components and quality of sunflower (Helianthus annuus L.)cv.Euroflor. A field experiment was carried out at College of Agriculture, Shiraz University during Summer 2009. The experimental design was a factorial based on a randomized complete block design with 3 replications. Five nitrogen rates (0, 50, 100, 150, 200 kilograms N per hectare) and four split application of nitrogen fertilizer (T1 “1/3 before planting, 1/3 V4, 1/3 R1”, “T2 1/3 before planting, 1/3 V4, 1/3R5.8”, T3 “1/3 before planting, 1/3R2, 1/3 R5.8”, T4 “1/3 V4, 1/3 R1, 1/3 R8”) were used. Chlorophyll content, head diameter, plant height, number of grains per head, thousand grain weight, dry matter yield, harvest index and grain yield were determined after harvesting. There was a significant difference within various rate of nitrogen application. Significantly highest plant length, leaf area index, total dry weight, chlorophyll content, head diameter, number of grains per head, thousand grain weights, grain yield and dry matter yield were recorded at 200 kilogram N per hectare followed by 150 kilogram N per hectare. However, there was no significant difference between 150 and 200 kg/ha N. Split application of nitrogen had no significant effect on plant characteristics except on grain yield, the highest grain yield was obtained from T1 (1/3 before planting, 1/3 V4, 1/3 R1) treatment.