Study of various levels of nitrogen fertilizer and plant density on grain yield, rate and effective grain filling period sunflower (Helianthus annus L.) cultivars in Ardabil region

In order to investigate the effects of plant densities and nitrogen levels on grain yield، rate and effective grain filling period sunflower (Helianthus annus L.) cultivars in Ardabil region، an experiment was carried out as split plot factorial based on randomized complete block design with three replications in experimental field of University of Mohaghegh Ardabili in 2009. Nitrogen fertilizer in three levels (0، 75 and 150 kg N/ha as urea) were assigned to the main plots and the combination of plant density (8، 10 and 12 plant m-2) with two sunflower cultivars (Urofelor and Armavirisky) were factorially assigned to the subplots. The results showed maximum grain weight، rate and effective grain filling period belonged in low plant densities and high nitrogen rates. Means comparison showed that maximum of grain weight were obtained in Armavirisky cultivar × 8 plants/m2 with application of 150 kg N/ha and minimum of it was obtained in Urofelor cultivar × 12 plants/m2 without application of nitrogen fertilizer. The highest grain yield was obtained in application of 150 Kg N. ha-1×Armavirisky cultivar and the least of it was obtained in Urofelor cultivar without nitrogen fertilizer. It seems that in order to increasing the grain yield، rate and effective grain filling period can be suggested that 150 Kg N. ha-1 with Armavirisky cultivar be applied in conditions of Ardabil climate.