Harvesting drought-stressed soybeans for forage -

Value of soybean grain versus value of soybean forage
Estimating the potential grain yield of drought-stressed soybeans is very difficult. This is because plants that have retained more than 50 percent of their leaves have the potential to produce a good grain yield as long as significant rain occurs before they stop producing flowers (early August).

Mike Staton

Be patient and assess the grain yield potential in mid-August. At this time, if more than 50 percent of the leaves have been lost, the plants have stopped producing flowers and few pods are present, grain yield will be very low.

A reasonable estimate of the dry matter yield for drought-stressed soybean forage would be 1.5 tons per acre. According to the feed tables in the Nutrient Requirements of Dairy Cattle, soybean silage harvested at early maturity contains 17.4 percent crude protein (equivalent to mature alfalfa hay), 1.29 NEL 3X Mcal/Kg (equivalent to mid-maturity alfalfa hay), 46.6 percent NDF (equivalent to mature alfalfa hay) and 5.7 percent ether extract or oil content (about 2.5 times the amount in alfalfa hay).

These values will change with the development stage of the crop. This is especially true for the ether extract or oil content. Because the oil is in the seeds, larger, more mature seeds will increase the oil content.

Impacts on crop insurance
The key message here is communicate closely with your crop insurance agent before taking any actions such as harvesting the crop for forage (including grazing) or destroying the crop and planting an alternative forage crop. Failure to communicate with your agent prior to these actions will result in a loss of indemnity payments.

USDA program eligibility
Contact your local USDA Farm Service Agency office to determine how harvesting the field for forage or replanting to an alterative forage crop will affect USDA program eligibility.

Pesticide feeding restrictions
Soybeans treated with the following herbicides can be harvested as feed and fed to livestock:
• Boundry
• Dual II Magnum/Parallel
• First Rate
• IntRRo/Microtech
• Prowl H2O/Prowl
• Sencor
• Sharpen
• Trifluralin
• Basagran
• Glyphosate
• Poast/Poast Plus

Always read and follow information listed on these product labels regarding feeding treated crops. The Poast/Poast Plus labels are a good example of why this is important because they state that treated soybeans can be harvested for hay, but not for silage. Soybeans treated with herbicides other than those listed above cannot be harvested as feed and fed to livestock.

Soybeans treated with the insecticides listed below can be harvested as feed and fed to livestock. Soybeans treated with insecticides other than those listed below cannot be harvested as feed and fed to livestock. As always, carefully check and follow the product label.

• Product: Baythroid XL
Active ingredient: cyfluthrin
Forage and hay pre-harvest interval (PHI): 15 days for dry vines (hay) and green forage

• Product: Bifenture EC
Active ingredient: bifenthrin
Forage and hay pre-harvest interval (PHI): No specific statement on label

• Product: Brigade 2EC
Active ingredient: bifenthrin
Forage and hay pre-harvest interval (PHI): No specific statement on label

• Product: Dimethoate
Active ingredient: dimethoate
Forage and hay pre-harvest interval (PHI): Some formulations - do not graze within five days of last application. Other formulations list no specific statement on label.

• Product: Intrepid
Active ingredient: methoxyfenozide
Forage and hay pre-harvest interval (PHI): 7 days for hay or forage

• Product: Lannate LV & SP
Active ingredient: methomyl
Forage and hay pre-harvest interval (PHI): 3 days for forage, 12 days for dry hay

• Product: Leverage 2.7
Active ingredient: imidacloprid/cyfluthrin
Forage and hay pre-harvest interval (PHI): 45 days for dry vines (hay), 15 days for green forage

• Product: Leverage 360
Active ingredient: imidacloprid/cyfluthrin
Forage and hay pre-harvest interval (PHI): 15 days for dry vines (hay) and green forage

• Product: Radiant SC
Active ingredient: spintoram
Forage and hay pre-harvest interval (PHI): No specific statement on label

• Product: Sevin
Active ingredient: carbaryl
Forage and hay pre-harvest interval (PHI): 14 days for grazing or harvest for forage

Soybeans treated with the fungicides listed below can be harvested as feed and fed to livestock. Soybeans treated with fungicides other than those listed below may not be harvested as feed and fed to livestock. As always, carefully check and follow the product label.

• Product: Alto 100 SL
Active ingredient: cyproconazole
Forage and hay pre-harvest interval (PHI): 14 days for grazing forage (no information on hay)

• Product: Headline
Active ingredient: pyraclostrobin
Forage and hay pre-harvest interval (PHI): 21 days for hay and 14 days for forage

• Product: Headline SC
Active ingredient: pyraclostrobin
Forage and hay pre-harvest interval (PHI): 21 days for hay and 14 days for forage

• Product: Priaxor
Active ingredient: fluxapyroxad + pyraclostrobin
Forage and hay pre-harvest interval (PHI): 21 days for hay and 14 days for forage

• Product: Quadris
Active ingredient: azoxystrobin
Forage and hay pre-harvest interval (PHI): 0 days for hay and forage

• Product: Quadris Xtra
Active ingredient: azoxystrobin + cyproconazole
Forage and hay pre-harvest interval (PHI): 14 days for hay and 14 days for forage (when 6.8 fl. oz. per acre or less has been applied)

• Product: Quilt
Active ingredient: azoxystrobin
Forage and hay pre-harvest interval (PHI): 0 days for hay and forage

Harvesting for hay
Harvesting soybean forage for silage is preferred over baling it as dry hay because ensiling retains more dry matter during harvest and storage. However, it is possible to make high-quality hay from soybeans in the R3 to R5 growth stages. There are lots of leaves at these stages and the pods are less likely to shatter during mowing and raking operations.

Use a roller-type mower conditioner set to lay the hay in a wide swath and leave about 4 inches of stubble. When dry, slowly and gently rake the swath into a windrow in the morning when humidity levels are higher to avoid leaf loss. Invert the windrows after several hours of good drying conditions and bale in the early evening to avoid further leaf loss.

Harvesting for silage
The crop can be harvested from R3 to R6. Soybeans harvested at R3 to R5 will produce high quality forage and have lower oil content than those harvested at R6. The higher oil content may cause fermentation problems. However, soybeans harvested at R6 will produce more dry matter.

Mow the crop with a mower conditioner equipped with roller crimpers. Experience from Wisconsin indicated that flail conditioners cause more damage and dry matter loss than roller conditioners. As with alfalfa, soybeans should be allowed to wilt in the field to 65 percent moisture before chopping.

Determining the whole plant moisture content is critical to achieving proper fermentation.

Collect representative samples from the chopper and use the microwave method to determine whole plant moisture levels before chopping each field. Adjust the chopper to produce a 3/8-inch cut to improve packing.

Feeding soybean hay
Soybean hay has a tendency to cause bloat in cattle, so it should be fed carefully. Mix the soybean hay with grass hay or fill the cattle up on grass hay prior to feeding soybean hay.

Horses can safely consume soybean hay if it is baled and stored properly.

Feeding soybean silage
Feed quality of soybean silage is equivalent to alfalfa haylage. Soybean silage is less palatable than haylage or corn silage. However, it can make up 15 to 20 percent of a dairy ration without impeding animal intake or milk production. The exception is when the soybeans are harvested after the R6 stage is reached as more seed (higher oil content) is present, which can affect fermentation and palatability.

Harvesting soybeans for forage is an individual decision and should be given careful consideration. Be patient and wait until early to mid-August to make the final decision as soybeans can recover from drought stress if significant rainfall occurs before August. FG

References omitted but are available upon request.

—From Michigan State University Extension