Correct desiccation, harvest and storage is key to maximising bean quality, explains PGRO.
1) If the bean crop is infested with green weedy material or has a few late set pods that are still green, application of a desiccant will aid combining.
2) The most widely used material is diquat, still approved for use for 2019 harvest. A non-ionic surfactant can be added (but before spraying consult the processor in the case of crops grown for human consumption). It can be used on crops for animal feed, human consumption and seed.
3) Apply when 90 per cent of field bean pods are dry and black and most of the seed is dry. At this stage most of the leaves have senesced and fallen but the stems are still green. The contact action is fast, and harvesting can be carried out 4-7 days later.
4) Glyphosate is not a true desiccant but can be used as a pre-harvest treatment to control perennial weeds. It must not be used on crops destined for seed.
5) PGRO, with other organisations, is continuing to evaluate the efficacy of alternative desiccants to diquat. The final use date for all products containing diquat is February 4, 2020.
1) Beans are often perceived as being able to withstand harvest delays long after other crops such as cereals have been harvested.
2) However, once beans are ready to harvest the quality will begin to deteriorate. If pods split and beans are exposed to light this will cause the seed coat to darken and increase the amount of crop loss during harvesting.
3) When mature, cycles of wet and dry weather increase the chances of staining if they are not harvested. Quality is key to achieve the human consumption premium.
1) The quality standard for beans is usually 14 per cent moisture content (MC) with two per cent impurities, or a combination of the two that should not exceed 16 per cent.
2) Drying can be more difficult with beans than with cereals due to seed size, and while damaged produce is acceptable for compounding, mouldy produce is not.
3) The large size of bean seeds makes drying difficult as they have a low resistance to air flow. It takes time to move moisture from the inside to the outside hence slow, gentle drying with ambient air is best.
4) Beans should not be over-dried and rapid drying at higher temperatures may affect texture and colour and seeds may split.
5) Most types of dryer may be used for beans, but those operating at low temperatures are safer.
6) Floor-ventilated bins are easy and relatively safe to operate. When the initial moisture content is high, the transfer of the produce from bin to bin and the use of warmed air together with adequate ventilation may be necessary to avoid mould developing in the upper layers.
7) Radially-ventilated bins allow faster drying than floor-ventilated bins, but care must be taken not to overheat beans.
8) On-floor drying using ambient or warmed air can be used. Care must be taken not to load beans too deep if moisture content is high and if lateral ducts are spaced wider than one metre.
9) Storage in dark areas is recommended for beans destined for the human consumption market to delay the development of tannins which cause beans to discolour. Beans must be dried down to 14 per cent MC for long-term storage in bulk - this is important since beans are often stored for some time before they are sold.
Product % MC Max drying temperature
Seed >24% 34 - 38°C
Seed <24% 38 - 43°C
Human consumption 43 - 49°C