Pictured Above: Deep ruts created by harvesting soybeans in wet soil conditions. Photo by Mike Staton, MSU Extension.
According to the United States Department of Agriculture National Agricultural Statistics Service, 43% of the Michigan soybean crop was still in the field as of Nov. 4, 2019. Given the calendar date and the projection for above-normal precipitation and below normal temperatures in the 6-10 day weather outlook, harvesting these fields will be challenging. The following recommendations from Michigan State University Extension will help producers overcome these challenges.
Try to wait until the soil is dry or frozen enough to support the combine to avoid cutting deep ruts like those shown in the picture, as these will fill with water and delay future field operations. Soil compaction associated with wet harvest conditions can also reduce crop yields for several years. Modifying the combine by adding tracks or flotation tires may help improve flotation and traction and reduce soil compaction in wet conditions. Regardless of the tire configuration, using the minimum air pressure recommended by the manufacturer for the loaded combine is an effective way to reduce soil compaction.
The plants will be tough and difficult to cut, so it is critical to have the cutter bar in top condition. All knife sections and guards should be sharp and tight and all guards should be properly aligned to ensure optimum cutting. The gap between the sickle and the hold downs should be about the thickness of a business card. Reducing your ground speed will also improve cutting and provide more uniform feeding into the combine. Harvesting on an angle to the rows should also improve feeding in row spacings of 15 inches or wider.
The moisture content of the seed will also be high. In theory, soybeans can be harvested when the seed moisture is below 20%. Moisture testers and yield monitors are usually accurate when measuring soybean moisture. However, when soybeans are wet, Charles Hurburgh and Meaghan Andersen, Iowa State University Extension specialists, recommend checking your yield monitor or hand-held moisture meter against your grain buyer’s meter on at least three samples, as they tend to underestimate the grain moisture content by one to two points.
Threshing and cleaning high moisture soybeans is challenging. Achieving uniform feeding and keeping the threshing cylinder/rotor full are the first steps to improving threshing. Draper heads and air-assisted reels will improve the uniformity of feeding. If threshing is not satisfactory, try reducing the concave clearance first. This may increase plugging problems at the cylinder/rotor if the straw is tough. If plugging is a problem or unacceptable threshing occurs, increase the speed of the cylinder or rotor. Make incremental adjustments and check threshing performance and grain quality after each adjustment. It can be a balancing act to find the correct cylinder/rotor speed and concave clearance settings that provide acceptable threshing without causing excessive split or crushed beans.
I usually encourage producers to check for gathering losses at the head because under normal conditions, 80% of all harvest losses occur at the head. However, when harvesting soybeans this late, the tough stems and pods and softer seed will probably increase threshing and cleaning losses, so checking your losses behind the combine becomes equally important. For every four beans per square foot found on the ground, one bushel per acre of yield is lost.
The wet beans will need to be dried or aerated immediately after harvest. Please see the MSU Extension article on drying and storing wet soybeans for recommendations. Producers planning to deliver wet soybeans directly to the elevator should determine the elevator’s maximum allowable moisture content prior to delivery.
The bottom line is harvest what you can when you can, as there is greater potential for soybean quality to decrease and field losses to increase as we approach the end of the year. If weather conditions don't improve, some producers may consider leaving the beans in the field over the winter and harvesting them in the spring. This is a risky practice. Wet, heavy snows can flatten the plants, making harvest very difficult. The risk of experiencing seed damage due to phomopsis is also increased with delayed harvest. The presence of phomopsis is confirmed if linear rows of black specks occur on the stem. If you see these signs and the pods are infected, damage to the seed can potentially occur. The good news is that the risk of soybeans sprouting in the pods is low when the pods are intact and not open.
Producers that consistently harvest soybeans in November should consider planting earlier maturing soybean varieties. Please see the MSU Extension article, "Should you plant earlier maturing soybean varieties?" for more information.
This article was produced by the SMaRT project (Soybean Management and Research Technology). The SMaRT project was developed to help Michigan producers increase soybean yields and farm profitability. Funding for the SMaRT project is provided by MSU Extension and the Michigan Soybean Checkoff program.