Faba beans mature in 100 to 130 days, depending on moisture conditions. As the crop matures, the lower leaves darken and drop, and the pods dry and turn black, starting at the bottom of the plant. In some places, faba beans are commonly desiccated and straight-cut. However, in Saskatchewan, swathing and then combining the crop is more common.
Pre-Harvest Aids and Desiccants
Products registered for use as pre-harvest aids or desiccants in faba beans include diquat and glyphosate.
Glyphosate is registered for pre-harvest weed control in faba beans—it is not registered as a desiccant. It may be used to control perennial weeds such as quack grass, Canada thistle, sow thistle, common milkweed, toadflax, and dandelion. Glyphosate can be applied when the seed moisture content is less than 30%. At this stage, faba bean stems are green to brown, pods are yellow to brown, and 80–90% of the leaves have dropped. Since glyphosate use is registered under the User Requested Minor Use Label Expansion (URMULE) program, the manufacturer assumes no responsibility for herbicide performance. Those who apply glyphosate on faba beans do so at their own risk.
Diquat is a registered desiccant for faba beans. Desiccants are used to achieve a uniformly dry crop that goes through the combine easily at harvest. Diquat should be applied when most plants are ripe and dry. At this stage, the pods are filled, and the bottom pods will be tan or black. Always read and follow label directions before applying.
Growers should communicate with buyers before applying pre-harvest aids and/or desiccants to ensure which products are accepted by their specific buyer, and to ensure they comply with maximum residue limits.
Swathing
Faba beans may shatter if left standing until full maturity, so swathing before this is common. The crop should be swathed when the lowest few pods on the plants are darkening in colour in about 25% of the crop. By this time, the upper pods should be fully developed with a moisture content around 40%, and the middle pods will be turning light green with about 60% moisture. A light, narrow swath should be used, as the crop may take up to three weeks to dry once cut.
Combine when the seed moisture content is 18–20%. Combining in the early morning may reduce seed damage if the moisture content is lower than 18–20%. Combines should be set with maximum concave clearance, high fan speed, and reduced cylinder or rotor speed (300–400 rpm). Augers should be operated at low speeds to avoid splitting. To reduce seed coat cracking, minimize drop distances when moving faba bean seed. Harvested seed should be aerated to 16% moisture for safe storage.
It is not advisable to straight-cut faba beans without desiccation, as this is likely to result in significant shattering losses.
Make every effort to harvest your faba bean crop in the fall. Overwintered faba beans left in the swath are prone to developing toxic moulds and are unsuitable for sale, even as livestock feed.
Storage
Faba bean seeds often respire or sweat after they are placed in storage. Extra care should be taken to monitor the grain inside the bin for moisture build-up or spoilage. Aeration fans can be used to cool the grain in the fall and warm it in the spring, and to reduce condensation in the bin. Seed is more susceptible to cracking and peeling if handled at temperatures below -20°C.
If heat drying is necessary, a maximum temperature of 32°C is recommended. Dry in two stages, with a day between operations, if more than 5% moisture is to be removed. The maximum seed moisture recommended for safe storage is 16%.
Most varieties of faba bean seed that contain tannins will darken over time and should not be stored for two summers.
