effects of different amounts of nitrogen and plant density on yield, yield components and seed oil percentage of pumpkin (cucurbita pepo l.)

in order to study the effects of different amounts of nitrogen and plant density on yield, yield components and seed oil percentage of pumpkin (cucurbita pepo l.) an experiment was conducted as split plot based on randomized complete block design with two factors and three replications at agricultural research field station of ferdowsi university of mashhad, iran, during growing season 2010-2011, the main factor nitrogen fertilizer included three levels 150, 250 and 350 kg.ha-1and the subfactor plant density, included three levels 2.5, 1.25 and 0.62 plant.m-2.test results showed that nitrogen fertilizer had no significant effect on fruit yield and 1000-seed weight, but plant density had significant effect on pumpkin yield. between different densities 2.5 plant.m-2 was significantly increased seed yield and fruit yield. the interaction results showed that 250 kg of nitrogen /ha in density 2.5 plant.m-2 achieved the highest seed yield. also the highest oil percentage and oil yield was in density 1.25 plant.m-2. these results indicated that, the optimal amount of fertilizer was 250 kg of n.ha, which achieved the highest seed and oil yield in pumpkin. plant density lower than 1 plant.m-2 did not had significant effect on yield improvement.