Monitor soybeans regularly once they begin to mature. Soybeans are at full maturity (R8) when the crop is tan-brown in colour, 95% of the pods are brown, seeds rattle in the pod and all leaves have dropped. The crop is ready to harvest 5-10 days after R8 is reached when seed moisture is <14%. Refer to MPSG’s Soybean Maturity Guide to help time your harvest.
Preharvest Weed Control and Desiccation
If considering preharvest weed control or desiccation, apply when seed moisture is <30% in the least mature part of the field. At this stage, you will see 80-90% leaf drop, pods will be brown and seeds will rattle within pods.
When selecting late-season herbicides, it is important to choose the right product for the intended outcome. Desiccants are contact herbicides that even up the dry-down of plant material across a field (within 1-3 days) to advance harvest. Preharvest weed control often involves a systemic herbicide like glyphosate for the purpose of controlling perennial weeds.
To avoid market risks associated with maximum residue level (MRL) violations:
- only use registered products applied at the labelled rate and timing,
- regularly consult with your buyer to keep tabs on product limitations, and
- consider avoiding late-season herbicide altogether.
Note that if a buyer does not accept preharvest glyphosate, that applies to tank-mixing as well.
Soybeans can be direct combined (straight cut) or swathed. However, direct combining is the preferred harvest method. If soybeans are swathed, they should be combined shortly after to avoid seed quality loss. Soybeans are easily damaged by precipitation if left in windrows.
Direct combine soybeans with a flex header when seed moisture is <14%. At this stage, pods will be dry and seeds will be hard and rattle within pods. Note that soybeans can be combined when seed moisture is below 20%, but soybean seed must be stored at <14%. Avoid harvesting at <12% seed moisture to prevent cracking and splitting of seed. Carefully adjust cylinder speed and concave clearance to minimize seed damage.
Over 80% of soybean harvest losses occur at the header. Measure seed loss periodically during harvest to optimize your combine settings and protect yield. The Bean App Harvest Loss Assessor calculates yield loss based on seed counts. This includes loose seeds on the ground and seeds that remain in pods on cut stubble or on plants that did not feed properly into the combine.
There are several tactics to reduce header loss:
- Type of header – A draper header, when properly adjusted (i.e., to the bean setting), can reduce yield loss by 0.5-1 bu/ac compared to an auger header.
- Angle setting of the header – Spend the time adjusting the header angle settings between crops to minimize losses, regardless of the header type. Getting the knife positioned between the ground and lower tip of the bottom pod is key.
- Use of an air system – Losses can be reduced by 0.5-1 bu/ac, on average, when using an air system on either a draper or auger header. At a price of $10/bu, this can provide a savings of $5 to 10/ac. To determine if an air system is worth the investment, consider that the payback area for an air system with an average capital cost of $16,500 would be 1,650 to 3,300 acres. This indicates that using an air system can provide substantial benefit in reducing losses.
- Ground speed – The effect of ground speed needs to be weighed against the urgency of harvest. Combine speeds of 3-4 mph have been shown to reduce losses compared to higher speeds of 5-7 mph (average difference of 0.5 bu/ac).
Harvest Header Losses in Soybeans – Pulse Beat Article by Charley Sprenger, Prairie Agricultural Machinery Institute
Preventing Soybean Harvest Loss – Pulse Beat Article by Cassandra Tkachuk, Manitoba Pulse & Soybean Growers
Optimizing combine efficiency while harvesting soybeans in Manitoba – PAMI Research Report