در سردگان )PHASEOLUS VULGARIS( دوره بحراني مهار علفهاي هرز لوبياچيتي

The Critical Period of Weed Control of Colorado Bean (Phaseolus Vlgaris) in Lordegan

In order to ermine the critical period of weed control of Colorado bean (Phaseolus vulgaris L., Talash cultivar) in Lordegan region, an experiment was conducted in 2001 and 2002. The experiment was arranged in Rndomized Cmplete Block design with 4 replications, Treatments included weed free and weed-infested period with ten days interval after bean emergence. First group of treatments consisted of weed control from bean emergence to 10, 20, 30, 40 and 50 days after emergence. In the second group of treatments, weeds were allowed to interfere from emergence time to the aforementioned stages of bean growth. Meanwhile, two additional treatments were arranged in control plots as weed free (full season control) and weed-infested (full season competition) respectively. Gompertz and Logistic equations were used to determine the critical period of weed free and weed-infested period, respectively. Results showed that bean yield loss increased with increasing duration of weed interference, and decreased with increasing duration of weed control. Critical period of weed interference in Colorado bean with 5% accepted yield loss occurred between 24 days to 38 days after bean emergence (2 weeks period). This period was the same with the V3 and before RI (flowering stage) respectively. Due to higher impact of weeds, critical period in the second year was longer than the first year, in such a way that it occurred between 18 and 44 days after bean emergence (a 26- day- period). Pod number per plant was correlated more with bean yield than other yield components. This character was severely reduced by increasing duration of weed interference after bean emergence.