Our program focus at Washington State University is to provide small-scale growers with cost effective and scale-appropriate technologies that enable them to produce and market dry beans. Our program uses small-scale technologies to dry, thresh and clean dry beans.
Bean plants must be sufficiently dry to thresh (separate beans from pod) or they will bind up threshing equipment. Harvest whole bean plants or only bean pods, as you choose. Your choice is likely dependent on available equipment and/or desired market product. Harvest mature beans before pods begin to shatter in the field or the pods will split open, spilling beans onto the ground.
Drying beans completely in the field in western Washington is possible if weather permits. For WSU’s small-scale bean project, three days of hot, sunny weather was sufficient to dry the pile of whole plants pictured below (Figure 1) We turned the plants 1–2 times each day to facilitate drying throughout the pile.
If weather is cool or moist, beans can be further dried inside using a box fan (Figure 2) as we also did in our project. Bean plants can also dry on greenhouse shelves with clean tarps beneath the shelves to catch beans that have been expelled from shattering pods. Turn piles over once a day to prevent moisture accumulation at bottom of piles. Beans are sufficiently dry if the pods shatter, but are too dry if beans split.
Hebblethawaite, P.D.; Hawtin, G.C., Dantuma, G. 1983. The Faba Bean (Vicia faba L.) Grain and whole-crop harvesting, drying and storage. Butterworths (printed at University Press, Cambridge). pp 525-533.
Phaseolus Bean: Post-harvest Operations. Chapter 4 discusses numerous processes in bean production, including natural and artificial ways of drying beans, for small scale bean producers by the Food & Agriculture Organization of United Nations (FAO)/Rural Infrastructure & Agro-Industries Division (AGS).
Threshing is the process of removing the bean grain/seed from the pod and can be done either by machine or hand.
For WSU’s small-scale bean project, we threshed beans in a converted chipper-mulcher (Figure 3). Whole bean plants or pods were placed in the thresher chute at the top of the machine. Beans, crushed pods, stems and leaves fell out the bottom of the thresher into the collection box. Beans tended to fall to the bottom of the collection box while plant debris tended to be on top. We scooped plant debris from the bottom of the collection box and discarded it. It took approximately 5 minutes to thresh 100 plants with this technique.
After beans are harvested and threshed, they need to be cleaned, removing unwanted plant material, weed seeds, soil and stones. This too can be achieved through manual or mechanical means.
For our WSU small-scale bean project, beans were cleaned by putting them, along with the fine plant debris, into the top chute of the cleaner (pictured to the left in Figure 3). The beans quickly fell into another collection box at the bottom, while the remnants blew away. Small rocks and dirt clods that fell into the collection box with the beans were removed by hand.
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