Salvaging Green Soybeans for Forage or Green Manure

Salvaging Green Soybeans for Forage or Green Manure

October 3, 2008

Late planted beans may not mature before frost, but all is not lost. There are several salvage options for these beans. One of the better options is to use these beans as a forage. After all, when soybeans were first introduced to the United States they were used as forage. Today they still can be used effectively for grazing, hay, or silage.

Forage Options

Grazing. Usually grazing is the simplest option. Since cattle don't normally graze beans, it will take a while for them to adapt, but once they do, they will perform well on bean pasture. Soybeans have a low risk of causing bloat. However, if pods filled very much, animals could get too much fat or oil from the seeds. Consumption of more than four to five pounds of beans per day can reduce fiber digestibility and cause other digestive disturbances. To reduce this risk, provide some good, palatable grass hay in the soybean pasture to try and reduce the amount of soybeans in the diet. Strip graze soybeans by allocating a fresh strip to animals every couple of days. This will reduce selective grazing of pods by forcing animals to consume more of the whole plant and also greatly reduce trampling losses.

Hay. Soybean hay can be similar to alfalfa hay in nutritional value, but it's hard to make. Stems are quite woody and dry slowly. To hasten stem drying, be sure to condition or crimp the hay. Leaves dry quickly and crumble easily, further complicating the drying process. There's a tendency to want to rake in order to hasten drying of the stems on the bottom of the windrow, but that could cause many dry leaves to crumble and fall away, leaving just the bean sticks for hay. There are two options for addressing these problems.

  1. Leave the windrow alone while it dries unbearably slowly, hoping that it doesn't rain before it's fit to bale. This may be your best option if weather cooperates.
  2. Rake soy hay within one day of cutting, before leaves on top have dried enough to crumble. This may be your only option if raking is necessary to put two or more windrows together for satisfactory baling.

Silage. Making good soy silage is less risky, if you have silage equipment and do it right. Start by making sure the moisture content of the chopped forage is between 60% and 70%. When possible, I prefer mixing bean with corn or sorghum as they are being ensiled. A ratio of one ton soybean silage to three or four tons of corn or sorghum silage will improve fermentation of the soybean silage and increase protein content of the corn or sorghum silage by two to three points.

For straight soybean silage, chop when leaves first start to turn yellow. Be sure to get a good, clean chop. Uniformly add a silage inoculant designed for legumes like alfalfa. In addition, add about one bushel of rolled corn or fifty pounds of molasses to each ton of wet silage to aid fermentation. Pack the soybean silage especially well.

Green Manure

If making forage from green beans is not a good option, don't forget that bean plants that include all the beans, pods, leaves, and stems will contain about 3% nitrogen, or about 60 pounds of nitrogen per dry ton of bean biomass. Most fields will have between one and two tons of dry biomass so more than 60 pounds of nitrogen per acre can be made available to your next crop if you incorporate the green plants into the soil as a green manure. This also will return other minerals and organic matter to the soil.

Bruce Anderson
Extension Forage Specialist