Effect of plant densities and weed competition on yield and yield components of Red-bean genotypes

Weed management in red-bean (Phaseolus vulgaris L.) is very important because of relatively high reduction of crop growth and yield, in weedy condition. Therefore, focusing on variation of bean genotypes and plant densities may clue to solve the problem. In this study, the effects of plant densities of three red-bean genotypes in the case of weed infestation on growth, yield and yield components were evaluated.

This experiment was conducted as split plot based on a randomized complete block design with three replications in Research Farm of University of Guilan in 2017. The main plots included red-bean genotypes (Darakhshan and Sayyad cultivars and D81083 line), and the sub-plots were planting densities of 15, 25 and 35 plants.m-2 in weedy conditions, and 25 plants.m-2 in weed free condition.

The plant height and yield were affected by the genotypes and the plant densities of red-bean in weedy and weed-free condition, but the harvest index was not. Biological yield, number of pods per plant, number of seeds per pod and the dry weight of 100 seeds varied based on genotypes and plant densities. The highest plant height was seen in Sayyad, D81083 and Darakhshan genotypes respectively. Plants height in treatments with the density of 25 plants.m-2 did not show significant differences in weedy and weed free conditions; while the densities of 35 and 15 plants.m-2 of plants in weedy treatments had the highest and the lowest heights, respectively. The highest amount of seed yield, biological yield, number of pods per plant, number of seeds per pod, and 100 seeds weight, of all three genotypes were found on weed free conditions. In all plant densities, the highest amount of seed yield was belonged to line D81083 and the lowest amount was belonged to Seyyad, while there were no significant differences between seed yield of both and Darakhshan cltivar. Among weedy treatments, the highest amount of biological yield and number of pods per plant were found in cultivar of Derakhshan with 25 plants.m-2. For Sayyad cultivar, the highest amount of biological yield, and for line D81083, the highest amount of biological yield, number of seed per pod and 100 seed weight were observed in densities of 25 and 35 plants.m-2. For Sayyad cultivar, there were no significant differences among plant densities on number of pod per plant, and 100 seed weight. The lowest number of pod per plant of darakhshan cultivar was found in 35 and 15 plants.m-2 in weedy condition, but in line D81083 it was seen in 15 plants.m-2. There were no significant differences for number of seeds per pods and 100 seed weight of Darakhshan cultivar between density of 25 plants.m2 and weedy condition, and also for number of seeds per pods of Sayyad cultivar and line D81083 between density of 25 and 35 plants.m2 and weedy conditions with density of 25 plants.m2 and weed-free treatments. The lowest seed per pod for all genotypes were found in 15 plants.m-2 in weedy conditions. There were no significant differences between Darakhshan cultivar and line D81083 for indices of competition, ability withstand competition and yield loss, whereas competitive ability of Sayyad cultivar was lower than two other genotypes.

Generally, it would be concluded that regardless of some differences exist in weed competition effects on yield component, all three red bean genotypes were sensitive to weed infestation during growing season and showed considerable seed and biological yield reduction, especially in low plant densities (15 plants.m-2).