Dry edible beans are sensitive to damage at harvest. Beans are sold based on eye appeal so seed coat quality and colour are important. Producing beans that are clean, bright and whole is the ultimate goal and timely harvest is paramount to maintaining quality. Know the quality standards for the crop’s market class. The ideal moisture range for harvest is 16%–20%. Harvesting outside this range will reduce quality. Low moisture content at harvest will increase the amount of split seeds and cracked seed coats.
Weather conditions in the fall can cause some bean types to deteriorate in quality much more quickly than others. Some differences in classes are as follows:
- Kidney, Dutch brown and black beans tend to withstand more adverse weather at maturity than the white navy, cranberry, otebo and white kidney types.
- Cranberry beans are susceptible to darkening of seed coat following maturity, lowering their value, so prompt harvest is important.
- Larger seeded coloured beans tend to absorb more moisture after a rain, requiring more time to dry down.
- Adzuki beans are strongly upright, quite resistant to weathering and their hard seed coat resists absorption of moisture after maturity.
Each bean type has unique quality standards that buyers look for. It is important to know these prior to harvest. White beans must be clean and free of dirt tag (smearing) and staining. Seed size and colour are important in cranberry and adzuki beans, while a low level of cracked seed coats in kidney beans is an important quality factor.
Dockage and Pick
Dockage is anything foreign that is removed from the beans through a screening process. Some items can only be partly removed through screening, such as weed seed, corn, soybeans or other crop types. Severe bean staining from weeds or green material can cause a load to be refused, and quality will be reduced if there is dirt on the beans. Other items that can cause a load to be rejected include metal and glass. It is critical that bean deliveries are free of soybeans, corn or other bean classes. Soybeans or corn in a sample can result in the rejection of a load because it will be assumed they are genetically modified, which is not tolerated by some importing countries. Allergens such as wheat and soybean can also be a concern, and processing may not be able to remove all contaminants. Before harvesting, clean the combine of any residual seed from previously harvested crops.
Pick refers to the percentage by weight of defective beans, including cracked seed coats and discoloured and misshapen beans that remain after dockage is removed. The dollar charge for pick is double; equal to the weight loss from picked beans plus the cost of removal.
There are two common methods of harvesting dry edible beans: pulling followed by windrowing, and direct-combining.
Pulling, Windrowing, Combining
Larger-seeded beans and beans planted in wide rows are usually pulled and placed in windrows at harvest. Pulling refers to cutting the plants 3–5 cm (1.25 in.) below the soil surface and merging several of the planted rows into a single swath or windrow. 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 moisture will result in reduced quality, harvest the crop as soon as possible after pulling. This specialized harvesting is required to meet quality standards set by the market for larger-seeded bean types. 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. Some larger-seeded types can be successfully direct harvested when grown in narrow row widths and harvested at appropriate seed moisture to reduce seed damage.
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, meaning that adjustments to the combine should be conducted throughout the day.
Combine set-up considerations are:
- Keep knives sharp to minimize shatter losses.
- Run cylinders only fast enough to thresh the crop. Run as much plant 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.
- Run unloading augers slow and full to minimize seed damage. The short vertical auger on the combine (turret auger), which takes seed from the bottom of the tank to the main unloading auger, is a point of high potential seed damage. Some bean producers have changed unloading augers to conveyer belt systems.
- Set combine ground speed to about two-thirds the speed used for harvesting soybeans.
- Use vine crop lifters which raise 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. Direct harvesting at an angle to the row distributes the flow of bean plants across the knife.
- Adjust the flexible floating cutter bar 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” sickle bar can reduce loss by up to 40% compared to a standard sickle bar.
- Use an air reel 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. As pods dry late in the day, header losses can reach more than 20% with a standard pick-up reel, while losses with an air reel are only 10%.
- Follow 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 field, delay harvest in the affected areas until they are mature.
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. Similarly, weeds with purple berries, such as Eastern black nightshade and American pokeweed, can cause severe staining. Also, secondary growth of beans can occur as plants begin to mature, particularly when rainfall follows an extended dry period. Where direct harvest is intended, apply a desiccant to dry the remaining green tissue. Harvest aid products are available to burn down weeds and desiccate the crop. For more information see OMAFA Crop Protection Hub. There may be different application timings for different products, so refer to and follow all product labels. There may also be restrictions on use of certain products for dry edible beans exported to specific markets. Check with the bean dealer on restrictions.
If on-farm storage is necessary, store individual varieties of dry edible beans in separate bins that are free from other grains and oilseeds. Keep harvested beans free of stones, glass and other seed-size contaminants. Failure to maintain the purity of the crop can result in lost value.