Dry Edible Beans: Harvest and Storage

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Pub 811: Agronomy Guide > Dry Edible Beans > Harvest and Storage

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Producing beans that are clean, bright and whole is the ultimate goal. Dry edible beans are sold to consumers on eye appeal. This is why quality and colour are so important. It is important to recognize the two important factors in the grading of beans - dockage and pick.

Dockage is anything foreign that is removed through the screening process. Some items can only be partly removed through screening, such as corn, soybeans, weeds or other crop types. Items that can cause a load to be refused include metal, glass, etc., and severe staining. Corn in a sample can also result in the rejection of a load, because it may be assumed the corn is GMO.

Pick refers to the percentage (weight basis) of defective beans including splits, checked seed coats, discoloured beans, mishappen, contrasting types and foreign material that remains after dockage. The dollar charge for pick is double; equal to the weight loss from picked beans plus the cost to remove this type of damage.

Dry edible beans can be a sensitive crop to harvest. Weather conditions in the fall can cause some bean types to deteriorate in quality much quicker than others. Kidney, dutch brown and black beans tend to withstand more adverse weather at maturity than the white navy, cranberry and white kidney types. Larger seeded coloured beans tend to absorb more moisture after a rain, requiring more time to dry down. It is therefore important to know the quality standards for the crop's market class.

The recommended range of moisture for harvest is 16%-20%. Harvesting outside this range will greatly reduce quality. Low moisture contents will increase the levels of split seeds and cracked seed coats. Wet or immature beans will become stained from the leaves, stems and dirt.

There are two common methods of harvesting dry edible beans: pulling followed by windrowing, and direct-combining.

Pulling, Windrowing, Combining

Beans planted in wide rows are usually harvested after pulling, which cuts the plants 3-5 cm (11/4 in.) below the soil surface and pulls plants from two or more rows into a single row with a windrower. Beans are pulled when 90% of pods have matured and turned buckskin brown. To prevent pod drop and shattering losses, pull beans early in the morning when the plants are tough and damp with dew. Beans are harvested later the same day with an edible bean or conventional combine equipped with a windrow pick-up attachment. Since prolonged exposure of the mature crop to excessive moisture will result in reduced quality, it is important to harvest the crop as soon after pulling as possible. Larger-seeded bean types require specialized combining in order to meet quality standards set by the market. Under good conditions, seed losses of 3%-5% are normal during harvest (i.e., 1% loss pulling and windrowing, 1% at combine pick-up, and 1%-2% cleaning and threshing).

Direct Combining

Bean types most suited to direct harvest include white beans with upright plant type, adzuki beans, black beans and pinto beans. Larger-seeded bean types require specialized combines in order to meet the quality standards of the market.

¹ Includes only those trials where equipment was operating as intended.

Combine enhancements help reduce harvest losses and minimize dirt, splits and damage to the beans. The cleaning and threshing characteristics of the crop will change throughout the day as moisture content changes. Combine set-up should include:

• Knives kept sharp to minimize shatter losses.
• Cylinders run only fast enough to thresh the crop. Run as much material as possible through the cylinder to minimize seed damage. Cylinder speeds on many combines do not go below 250 rpm, which can be too fast for easily threshed beans. Cylinder slow-down kits, which include a smaller diameter drive pulley and a belt, are available.
• Unloading augers run slow and full to minimize seed damage. The short vertical auger on the combine (turret auger) that takes seed from the bottom of the tank to the main unloading auger is a point of high seed damage. Some bean growers have changed unloading augers to conveyer belt systems.
• Combine ground speed set about two-thirds the speed used for harvesting soybeans.
• Vine lifters raising low hanging pods before the plant is cut. This can be one of the greatest benefits when harvesting varieties without a strong upright plant type.
• Flexible floating cutter bar adjusted to clip the bean plants as close to the ground as possible. This will help minimize the cutting of low-hanging pods and associated seed loss. The knife must cut cleanly and quickly to avoid shaking the plants, splitting pods and shattering beans. Most losses that occur are shatter loss. Ontario studies have shown that a flexible floating cutter bar can reduce losses by 25% compared to a conventional floating header. In addition a "quick-cut" sicklebar reduced loss by up to 40% compared to a standard sicklebar. Table 5-7, Average White Bean Harvest Loss, displays the results from harvest loss comparisons made between four harvest methods on several farms in Michigan in 1990 and 1991.
• An air reel used to significantly improve intake of plants into the combine and reduce losses at the knife. The air blast keeps weeds and bean plants off the knife, offering better cutter bar visibility without shoving stones into the header. The biggest benefit of the air reel is demonstrated under difficult harvest conditions, when the crop is lodged or the volume of crop is reduced. Under good conditions, harvest losses may be as low as 3%, regardless of whether an air reel is used. Late in the day, as pods dry, header losses can reach more than 20% with a standard pick-up reel, while losses with an air reel are only 10%.
• A modified harvest pattern to improve yield and quality. Travelling against the direction of lodging allows the harvest of leaning branches and low-hanging pods and can reduce stubble losses. In an unevenly maturing or weedy crop, delay harvest in the affected areas until they are mature or they can be treated with a desiccant.

Quality Preservation at Harvest

Occasionally, the crop may be ready to harvest but the field or part of the field may still be green or weedy. Harvesting when green stems or green weeds are present may result in stained beans. Products are available for harvest aid to burn down weeds and desiccate the crop. See OMAFRA Publication 75, Guide to Weed Control, for more information. Similarly, weeds such as Eastern black nightshade and American pokeweed can cause severe staining. Where direct harvest is intended, a desiccant should be applied to dry the remaining green tissue.

Secondary growth can occur as plants begin to mature, particularly when rainfall follows an extended dry period. Special effort should be taken to maintain seed quality. Before harvesting, the combine should be cleaned of any residual seed of previously harvested crops. If on-farm storage is necessary, store individual varieties of beans in separate bins that are free from other grains and oilseeds. Harvested beans should be kept free of stones, glass and other seed-size contaminants. Failure to maintain the purity of the crop can result in lost value.

Figure 5-1. Dry Edible Bean Scouting Calendar