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Dry Bean Harvesting

Harvest Timing

Bean crops must be cut at the proper stage of maturity. The ideal time to cut bean plants is when 60 to 70 per cent of the pods have turned a buckskin color. Cutting earlier may result in unnecessary shrinkage and wrinkling of the seed coat. Cutting later may result in excessive harvest losses due to pod shelling and the loss of whole pods. Other harvest tips include:

  • keep some green vegetation on the plant so that windrows will not be moved by strong winds while the curing process is taking place
  • bean crops cut at the proper stage require approximately 7 to 10 days of good drying weather before they are ready for combining
  • dry bean will not store in boxes if the moisture content is 18 per cent or higher – the moisture content must be 15 per cent or less if the intended storage is bulk storage
  • if bean seed becomes too dry, the percentage of splits and cracks will increase during harvest and post-harvest handling
  • the ideal moisture content for combining and storage is between 13 and 15 per cent

Harvest Systems

System options tend to revolve around two basic concepts: 1) undercut the crop and then use a pick-up header to feed the material into the combine, or 2) straight cut Black and Navy types.

Undercutting

  • bean cutters are designed to cut the crop at approximately 3/4 of an inch below the soil surface
  • proper completion of the hilling operation during the growing season will definitely make it easier to cut the crop
  • the blades on most cutters can be set at two different angles and may be shimmed to alter the angle at which they enter the ground – soil texture, compaction and soil moisture will all be determining factors for the preferred cutter settings
  • if a proper cutting edge is not maintained, a poor cutting job will cause heavy harvest losses – it’s essential to periodically check the performance of the bean cutter in case it requires re-adjustment
  • the use of a rod to lift the roots out of the soil after undercutting is a common harvest practice – the rod ensures that no plants are left uncut or are held tightly by the soil
  • a rod may be used either at the same time as cutting or immediately before combining, but a rod application should not be used at the same time as undercutting if the crop is overripe, as the crop will be at high risk of blowing – under these conditions, the rod should be used just ahead of the combine
  • although windrowing is not a preferred operation in harvesting a bean crop, windrowing may be necessary depending on the type of harvest equipment used:
    • windrowing may be done by using a conventional windrower or a side delivery rake
    • some growers windrow at the same time as undercutting, and others just prior to combining
    • if the crop is to be windrowed just prior to combining, it should be done when the crop is tough to reduce shattering
    • do not windrow any more than can be combined in one day because wind will move the bean swath
  • two popular types of combine pick-ups are “Sund” and “Rake-Up”
  • pick-up speed should not exceed the ground speed of the combine, to reduce shelling and pod loss
  • a number of harvest equipment combinations are:
  1. Cut and rod in the same operation at 70 per cent buckskin pod colour. Pick-up and combine. For normal row crop production of dry bean, this option results in the lowest harvest cost per acre while doing a good job of minimizing harvest losses.
  2. Cut the crop at 70 per cent buckskin pod colour. Rod just prior to combining. Pick-up and combine.
  3. Cut at 70 per cent buckskin pod colour. Rod just prior to windrowing. Windrow just prior to combing. Pick-up and combine.
  4. Desiccate solid seeded upright/bush bean at 85 to 95 per cent buckskin pod colour. Straight combine. This option is only viable for upright or bush types grown in a solid seeded field. A flexible header on the combine is necessary for this method of harvest, and lifter guards are also recommended for straight cut operations.
  • for normal row crop production of dry bean, option 1 results in the lowest harvest cost per acre while doing a good job of minimizing harvest losses
  • option 4 is only viable for upright or bush types grown in a solid seeded field – a flexible header on the combine is necessary for this method of harvest, and lifter guards are also recommended for straight cut operations
  • solid seeded bean crops require smooth, level fields, and fields should be rolled shortly after seeding (use empty rollers only)
  • vine type varieties (most often grown in southern Alberta) do not straight cut well, as pods often touch the ground, resulting in excessively high harvest losses

Combine Settings and Operation

  • combines may either be specialized units designed specifically for harvesting dry bean or conventional units with either a cylinder or rotor threshing system
  • dry bean is very susceptible to splitting and cracking, so the rpm of the cylinder and the clean grain elevators should be reduced as much as possible – cylinder speeds between 170 and 350 rpm are satisfactory for most threshing conditions
  • clearances between the cylinder and concave, and between the wires in the concave, must allow the seed to pass through freely
  • the use of perforated sheet metal (3/16 round) and slotted screens in the feeder housing or screening on the combine table will help eliminate dirt from the grain – and save wear and tear on the equipment
  • the unloading auger should run at an idle speed to prevent damage to the seed – if you see evidence of seed damage or splitting, make immediate adjustments

Handling and Storage

Proper dry bean storage management is important to prevent a grade decrease. Dry bean must be dried slowly using low temperatures for heated air dryers and optimum relative humidity for natural air drying systems. Over-drying increases the chance of splitting, cracking, and handling damage, while drying too slowly increases the risk of mold and insect invasion.

  • Box storage can be safely undertaken at 17 per cent seed moisture or less
  • If the crop is going into bulk storage, 15 per cent seed moisture or less is required
  • Handle the crop as gently as possible if on-farm storage is used, storing on shop floors, quonsets, etc. and moving with front end loaders is a typical storage and handling method – if dry bean is stored in these types of facilities, ensure floors have not been stained with oil, grease, diesel fuel, pesticides, etc. as the seed will readily absorb odors from these products and become unsaleable (also make sure the area is free of birds, cats, dogs and mice)