عنوان مقاله [English]
نویسندگان [English]چکیده [English]
To investigate the relationship of plant density and grain yield of two pinto bean cultivars at four different sowing dates, a split plot factorial experiment based on randomized complete block design (RCBD) with four replications was conducted in Faculty of Agricultural Sciences, the University of Guilan in 2009- 2010. Two pinto bean cultivars (seed coat with black and red mottles) were sown at four different sowing dates (20 August, 30 August, 9 September, and 19 Sept.) and three plant densities (15, 25, and 35 plants/m2). Pods and seeds per plant, plant height, pod weight, and grain yield were significantly affected by sowing date and plant density. The interaction effects of sowing date and cultivar were also significant for pod length, pods per plant and pod weight but interaction effects of sowing date and plant density were only significant for pods per plant and grain yield. All these traits were decreased with delaying in sowing date. Number of sub branch, number of node brunch and pods per plant decreased, but pod weight and grain yield per unit area increased, with increasing plant density. The results indicated that delayed sowings reduced grain yield of low densities more than that of high densities. Consequently, estimated optimum economic densities for delayed sowings were more than those for early sowings. Therefore, it is necessary to increase seeding rate at delayed sowings, in order to prevent or to reduce the yield loss.