Investigating the effect of planting date and Nitrogen fertilizer on pod formation in Soybean (DPX cv.) in Golestan province

In Iran, soybean (Glycin max L.) is usually grown in Golestan and Mazandaran provinces due to its special ecological demands. About 60,000 to 70,000 hectares of the lands in Golestan province are used to cultivate this crop each year. Given that the identification of factors that improve the agronomic conditions can be influential in improving the production of this oil crop, a split-plot experiment including two factors and 12 treatments was carried out with four replications. It followed a randomized complete blocks design and was conducted in Ali Abad Katool region (Kamalan Zone) in 2010. The main factor included the planting date at six levels (2th, 12st, and 22nd of July and 1st, 11th, and 21st of August) and the second factor included nitrogen fertilizer at 2 levels (0 and 25 kg/ha pure nitrogen). The results indicated that the number of healthy pods in the whole plant, the main stem, and the secondary branch was influenced by the planting date. The 2nd of July was the best planting date in comparison to the other times due to the average grain yield amounting to 3941 kg per hectare. In addition, nitrogen had a significant positive effect on grain yield. The results revealed that all the traits except for the number of seeds per pod decreased with a delay in cultivation. The interaction effect of the planting date and nitrogen was significant for the total number of healthy pods in the whole plant, the main stem, and the secondary branches. Generally speaking, considering the best time of cultivation can improve grain yield due to its appropriate growth period and an increase in yield component. In addition, applying nitrogen fertilizer, at least one time, can have a positive effect on soybean grain yield.