Originally published 13 September 1996

Considerations When Using Soybeans as a Forage

Late planting of soybeans coupled with below average hay and pasture yields are forcing soybean and ruminant livestock producers to consider harvesting the soybeans as a forage. There are several items that must be considered before soybeans should be harvested as a forage.

• Developmental Stage and Potential Grain Yield?
• Timing of Soybean Forage Harvest?
• How to Harvest Soybean Forage?
• Herbicide Legalities?
• Custom Rates for Forage Harvest?

Developmental Stage and Potential Grain Yield?

What is the current maturity stage of the soybeans and what is the potential grain yield? Ellsworth Christmas, Purdue University Soybean Specialist, in mid-September provided the following information in Table 1 that may be helpful as you assess whether late-planted soybeans have an opportunity to reach physiological maturity. Farmers should assess individual soybean fields as there may be maturity stage and yield differences due to variety and/or rainfall received.

Soybeans that won't reach physiological maturity before a killing freeze do have value as a forage as stored winter feed supplies are going to be lower than average and if the soybean crop can be harvested as forage at the proper stage of maturity. Current hay prices in Indiana have a wide range with low and superior quality hay selling for approximately $40 and $170 per ton, respectively, at northern Indiana auctions.

Timing of Soybean Forage Harvest?

When should soybeans be harvested as a forage? Feed composition tables provide an estimation of what the quality of soybeans harvested as a forage might be at a given maturity stage. Table 2 provides quality estimates for several soybean maturity stages. Testing the forage with a commercial feedstuff testing laboratory is recommended as results will more accurately reflect true forage quality and result in properly balanced rations.

The measure of energy found in the table, total digestible nutrients (TDN), doesn't follow the typical decline in energy found with commonly used perennial grasses and legumes. This difference, undoubtedly, reflects the contribution that the grain is making to harvested forage.

Since soybeans were commonly used in the early twentieth century as a forage, I searched the archives for recommendations regarding harvest stage. Unfortunately, no clear recommendation on time of harvest was apparent from reviewing this literature. One common theme was that the crop should be harvested as a forage before leaves begin to drop and before any pods begin to change to a non-green color. This is reflected in Table 2, too, as the mature crop had the poorest quality.

How to Harvest Soybean Forage?

How should soybeans be harvested? To reduce leaf loss, grain loss, and potential for rain damage, the soybeans should be made as silage rather than as hay. Soybeans should be wilted to a moisture that works best for the specific silo structure being used. The moisture should be 60 - 70 % for soybeans ensiled in a trench, bunker, concrete stave or bag-type silo. If an oxygen-limiting silo is used, moisture level can be 50 - 60 %.

Of the harvested soybean forage, stems will have the lowest quality. If chopped and ensiled, livestock will not be able to sort out the lower quality stem as compared to when soybeans are made and fed as long-stemmed hay. If harvested as hay, a mower-conditioner should be used and a longer curing time expected as compared to alfalfa.

Making hay of any type in late September and October is "easier said than done" because of cooler and shorter days as compared to summer time. If quality is good, protection from weather damage during storage is recommended. In my opinion, grazing soybean forage is risky because it is difficult to control selective grazing of immature grain. Founder and off-feed problems could result if over-consumption of the seed occurs.

Herbicide Legalities?

What herbicides were applied? Unfortunately, most of the herbicides utilized on soybeans have not been registered for use when the soybeans are fed as a forage and not harvested as grain. Dan Childs, Purdue University Weed Specialist, provided the information in Table 3 that indicates whether soybeans can or cannot be legally harvested as a forage.

Custom Rates for Forage Harvest?

What are custom rates for forage harvest? In many cases, the cash grain farmer's soybeans will be harvested by a livestock producer that will ultimately feed the soybean forage to his livestock or the soybeans will be harvested on a custom-rate basis. Extension publication EC-130, Indiana Custom Rates for Power Operated Farm Machines, 1994, provides some basis as to cost associated with forage harvest operations.

Average prices charged in 1994 for cutting and conditioning, raking, making small square bales (58 lb. twine tied), and making large round bales (1269 lb.) were $9.72 per acre, $4.33 per acre, $.38 per bale and $7.42 per bale, respectively. The point is, assuming the soybean forage would be of similar quality, soybean hay will command a higher price per ton than a standing crop to be made into hay because of the harvest cost already incurred with the soybeans in storage.

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