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Hay, Silage, Grain, Green Manure: Non-Human-Food Uses for Soybean Crops

By Dr. Harold Willis

Although most soybean producers strictly grow their beans to sell on the market, high quality soybeans are a valuable source of animal food. It is always better to feed crops you have grown to your animals than to risk buying feed of uncertain origin and quality. There are other uses as well outside of just food.

Soybean Forage

During the 1930s and 1940s, soybeans were widely grown in the United States for forage and hay. Even though largely superceded by alfalfa, soybeans are an excellent, high protein source of animal feed. Any variety may be grown, but taller indeterminate varieties are best.

If planted for forage or pasture, use a high seeding rate, about 4 to 6 plants per foot in rows about 8 inches apart. Soybeans may also be interplanted with grasses for grazing or with corn or sorghum for a ready-mixed chopped feed. The soybeans are valuable as a soil builder.

soybean hay
Soybean hay. Courtesy How to Grow Super Soybeans.

Soybean Hay

For maximum yield, soybeans for hay should be cut when the seeds have begun to set but before the leaves turn yellow. Cut on a sunny day after the dew is off. Let lie until the leaves are wilted but not brittle (usually the next day). Rake into windrows and let cure for 4 to 5 days. Soybean hay takes longer to cure than other hays, but it is less susceptible to rain damage and can be stored for long periods without nutrient loss. When baling or handling soybean hay, use care to avoid leaf loss.

Soybean hay is similar to alfalfa in nutrient content. It is slightly laxative, and limited amounts should be fed for the first few weeks (it can be mixed with grass hay to reduce amounts). There may be some animal refusal of the hay. Soybean hay should not be available to the animal all the time.

Soybean Silage

Soybean plants make a palatable component of silage, at a ratio of two parts corn to one part soybeans. The two crops can be interplanted to facilitate chopping or they can be grown separately and mixed. If interplanted, the seeds can be mixed in the planter and planted at about 20 pounds per acre in corn-width rows. If planted separately, the soybeans should be allowed to wilt after cutting to about 70% moisture. Harvest when the plants are green and succulent.

Other silage seed mixtures that work well are:

  • 3 parts corn or: 3 parts corn
  • 1 part sorghum 1 part sunflowers
  • 1 part soybeans 1 part soybeans

Soybean Feed Grain

Raw soybean seeds are difficult to digest because they contain what is called an anti-trypsin factor, a substance that inhibits protein digestion. Also, raw soybeans contain urease, an enzyme that breaks down urea into the more toxic substance ammonia. Both of these are destroyed by heat, so cooked or roasted soybeans are easily digested. One-stomach animals such as pigs, horses, poultry and rabbits must eat cooked soybeans. However, ruminant ani­mals (cattle, sheep and goats) can digest raw soybeans without difficulty, and one-stomach animals can be fed grain mixtures with up to 10% raw soybeans. All animals prefer the taste of cooked soybeans.

The most ready source of processed soybeans for animal feed is the soybean meal that results from beans being processed to extract the oil. Currently, soy­bean meal is the most commonly used source of protein supplement in animal feed. Heat used in processing destroys most of the anti-nutritional factors. Stan­dard meal is 44% crude protein meal, with the hulls being included as fiber. Since poultry do not digest the hulls, a 48% meal is also available. For use in poultry feed mixtures, soybean meal should be toasted to eliminate all of the anti-nutritional factors. Since soybean protein is low in the amino acid methio­nine, poultry feed mixtures need a source of it. The amount of soybean meal used in the feed depends on the animal’s stage of growth and protein needs for lactation. Vitamin and mineral supplements are often added. Soybean oil is also used in feed mixtures, but generally only if economically feasible.

Whole cooked or roasted soybeans can be a valuable addition to animal feeds. Relatively inexpensive cookers or roasters can be obtained for large batches. For small amounts, you can cook them in the kitchen (simmer fresh beans in a small amount of water for 15 to 20 minutes, or until tender; dried beans must be soaked in cold water 24 hours and simmered 4 to 5 hours). Use them within a few hours or refrigerate. To roast soybeans, put in a 300 degree F. oven until light brown (they may be stored in a closed container for a long time).

Soybean Green Manure

Soybeans tilled into the soil when they are green and lush make an excellent green manure. Besides the nitrogen from the root nodules, the rest of the plant adds organic matter and various nutrients to the soil. As mentioned earlier, increased organic matter improves soil structure, water holding capacity, drainage, and has other beneficial aspects. An acre of soybeans can add 175 pounds of nitrogen, 95 pounds of potassium and 20 pounds of phosphorus—and you can use seed you grow yourself.

Soybeans can be planted in late summer or early fall after another crop has been removed. High plant populations are best. Don’t worry about weed control. When plants are green but before pods form, till into the upper several inches of soil. If the weather is still warm, they will decompose within six weeks. If a green manure crop is incorpo­rated into the soil in the spring, wait several weeks (until it decompos­es) before planting another crop, since the decomposing organic matter temporarily ties up nutrients.

Source: How to Grow Super Soybeans