Improving the harvestability of dry beans with gibberellic acid
Currently beans (Phaseolus vulagris L.) are commercially harvested in several operations. Initially mature plants are cut below the soil surface by a bean puller, swaths are later windrowed, then picked up and threshed. Attempts to improve the efficiency of bean harvesting, using straight cut harvesters have been problematic due and the proximity of the pods to the ground. Yield losses during straight cut harvesting can range from 25-90%. Increasing stem length, thereby increasing the distance of pods from the ground, will permit the direct harvest of dry beans and reduce yield losses. The effects of gibberellic acid (GA) on the canopy structure and harvestability of three cuitivars (Othello, UI 906, and Aztec ( 1995 only)) were examined in the field. Trials were conducted at two locations in 1994 and 1995. Five rates of GA (0, 12.5, 25, 37.5, and 50 ppm) were applied at three growth stages ( 1 st, 2nd, and 3rd trifoliolate leaf stages). Mechanically harvested yields were compared to hand harvested yields to determine if treatments improved the percentage yield recovery with straight cut harvesters. Some cultivars were found to be more sensitive to GA treatment than others. Gibberellic acid stimulated internode elongation in all cultivars, stem length increases of 10% to 200% over control plants were recorded. One cultivar’s (Othello) harvestability was improved by very high concentrations of GA.
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