INFLUENCE OF THRESHING METHODS AND HARVESTING TIME ON THE PHYSICAL AND PHYSIOLOGICAL QUALITY OF DRY BEAN SEEDS

Abstract

An experiment was carried out to evaluate the proportion of physical damage in three dry bean varieties (Flor de Durazno, Bayomex and Negro Perla) harvested at 110, 115, 120, and 125 days after planting, and threshed with four different methods (manual, beating-in-sack, tractor wheel crushing, and mechanical thresher). Physical damage was evaluated by the chlorine test, while physiological quality was determined by standard germination test. Results showed that the threshing method and the harvesting time influenced greatly the quantity of physical damage. The highest number of damaged seeds was produced by threshing mechanically (34%), followed by tractor wheel crushing (11%), and beating-in-sack (9%), in contrast, the lowest proportion was attained in the manual threshing method (5%). Differential rates of physical seed damage in the tested varieties were observed at the different harvesting dates, for instance, Flor de Durazno showed from 14.5 to 17.9%; in Bayomex such rate was from 17.6 to 30%; and Negro Perla had from 5.2 to 7.7% of damaged seeds. The most frequent seed-coat damage in Flor de Durazno and Negro Perla was 25%; in Bayomex, the most frequent categories of damage were 50 and 75%. The highest germination ratio was observed in manually threshed seeds (>80%), in contrast, the lowest ratio was obtained from the mechanically threshed seeds. The best germination ability was produced by Bayomex seeds in most of the threshing methods.