Timely harvest is extremely important for maintaining food grade quality, seed coat colour and seed viability. Price declines occur rapidly as quality worsens.
Harvest losses can be as high as 40 per cent in narrow-row dry bean and extra care must be taken by the grower to prevent loss. Crop development stages must be very closely monitored to determine the best time to harvest, especially for determinate types. Successful weed control is critical for swathing or straight cutting dry bean. Bean plants in the wheel tracks of sprayers often are delayed and may still be green when the rest of the crop is ready to be harvested. Over-ripe pods are prone to shattering and seeds are lost if harvest is delayed.
The buckskin stage of dry bean occurs when pods turn yellow and flexible, and is an important crop stage to become familiar with when determining harvest timing.
Many producers in Saskatchewan and western Manitoba, growing determinate dry bean varieties in the narrow-row production system, are choosing to cut their crop using a swather. The choice of swather model is a very important harvest decision. Some models are able to cut dry bean with very little loss.
A swather equipped with vine-lifters and a pick-up reel allows the crop to be cut when the majority of the field is in the proper stage, even though some lower areas or wheel tracks are less mature. Immature plants will dry down in the swath, and harvest losses due to shattering and earth tag are reduced.
Varieties with a high pod clearance rating must be grown in order to be successful using a swather.
Swath when about 50-70per cent of the pods are in the buckskin stage, when the pods have turned from green to yellow and are still flexible. At this stage, many of the leaves are yellow and approximately half the leaves will have dropped from the plants. Swathing when some leaves still remain on the plant may be beneficial for varieties with determinate growth habit and short stature.
If stems are moist, the swather knife may gum up, requiring periodic cleaning. Swaths are prone to wind damage for the first few days. Plants will rot in the swath if excessive moisture occurs after swathing. If pod moisture is too low, excessive shattering can occur during swathing. If these conditions occur, swathing should be delayed until early morning or late evening.
Combine when the seed moisture content reaches approximately 18 per cent. Seed is easily damaged during harvest and handling. Cylinders or rotors should be run only fast enough to thresh the crop, and as much material as possible should be run through the cylinder to minimize damage. New rub bars and concaves should be "worn" before harvesting dry bean. Concave wires can be removed to allow the flow of large seeds. The clean grain, return and unloading augers should be checked and properly adjusted to reduce sharp edges. Unloading augers should be operated full and slowly.
Straight-cut harvesting of dry bean is feasible as long as the crop is evenly mature and the pods are high enough above the soil surface to allow the cutter bar to pass under them. Headers can be modified with vine lifters or pod lifters designed for direct harvesting of dry bean. Choose a header size that closely matches the combine capacity for even flow through the machine with minimum damage to the seed.
Straight cutting should begin when approximately 75 per cent of the pods are hard and dry with the remainder in the buckskin stage. The crop can be left standing until a killing frost dries the crop and remaining immature weeds. Excessive harvest losses can be avoided by selecting crop varieties with a high pod clearance rating.
After the crop matures past the buckskin stage, it is subject to fluctuations in moisture content depending on the time of day and weather conditions. Keep checking the sample throughout the day and adjust the combine accordingly.
On hot, dry days, the pod moisture can decrease rapidly leading to increased pod shattering. If seed moisture falls below 13 per cent, excessive seed damage can occur. Low pod moisture conditions are indicated by the presence of open pods on the cutter bar. If this occurs, it may be advantageous to wait until the pod moisture content increases.
Pod moisture may be too high in early morning or late evening, causing difficulty in threshing the seed from the pod. High moisture conditions can also lead to increased soil sticking to the seed - referred to as earth tag.
Storage and handling
Steel flighting augers are not recommended for dry bean. The use of a belt conveyor will greatly reduce seed damage while moving the seed in and out of storage. The installation of a bean ladder within the grain bin allows it to be filled without damaging the seed.
Some bean marketing companies prefer to take delivery of the crop immediately from the combine to reduce mechanical damage to the seed.
Dry bean is often stored at 17 per cent moisture. However, 16 per cent is considered dry.
For long-term storage, moisture content should be lowered to 15 per cent. Bins equipped with aeration fans are required to cool and dry the sample and reduce losses due to spoilage. Weed seeds and other dockage should be removed to avoid spoilage and down-grading of the crop. Bean seed should not be handled at temperatures below -20ºC or when the seed moisture content is below 14 per cent to avoid mechanical damage. Supplemental heat drying temperatures should be restricted to a maximum of 38ºC to avoid germination loss.
Dry bean grading is done by the Canadian Grain Commission. Factors such as damaged or heated seeds, foreign material, disease, seed uniformity and the presence of off-types are considered when establishing a grade.