Soybeans as forage: New varieties rival alfalfa for quality

By Loretta Sorensen, For Minnesota Farm Guide
Thursday, June 18, 2009 11:50 AM CDT

The introduction of soybeans to the United States was as a forage rather than grain crop. New forage varieties released by the USDA in 1997 have been tested since then to determine if soybeans could be grown as a valuable forage crop.

Southern Illinois researcher and assistant professor Rebecca Atkinson says the renewed concept of soybeans as a forage crop has been “quietly growing” since 1997. Her research with winter turnips to extend the grazing season led her to forage soybean testing to determine their value to the beef industry.

“Roundup Ready varieties Large Lad and Big Fellow have potential to produce nine tons of dry matter per acre and up to 28 percent protein,” Atkinson says. “Some plots with these varieties grew up to six foot high. That's probably too high for cattle to graze and walk through. The crop should be strip grazed at three feet. If it's not grazed below 10 inches there's great potential to graze it twice.”

Eagle Seeds in Weiner, Ark., has cultivated award-winning Roundup Ready, conventional, specialty and forage soybeans, conducting studies in over 25 locations that simulate conditions in a variety of geographic locations. In 2008, tested varieties were grown at Southern Illinois University, the LSU Ag Center in Louisiana and Oklahoma's Noble Foundation. Plans for 2009 testing include plots at the University of Nebraska and North Dakota State University.

Analysis of Large Lad and Big Fellow's nutrient qualities about 10 weeks after planting at nearly three-foot heights tested better than alfalfa, with 23.5 percent to 27 percent crude protein in freshly clipped plants with fairly soluble protein.

“NDF (neutral detergent fiber) was a little high for fresh forage, about 38 to 39 percent, similar to alfalfa in the late vegetative or early bloom stage,” Atkinson says. “ADF (acid detergent fiber) was 28 percent, which is also similar to alfalfa.”

Atkinson's research process also investigated digestibility of each variety and found it to be in the range of 69 to 71 percent. Net energy content scored well at .65 for maintenance and .39 for gain but is less than alfalfa. TDN (total digestible nutrient) was similar to alfalfa at 61 percent.

“That's very comparable to alfalfa,” she says. “Determining whether there's more value in soybean or alfalfa forage depends on a producer's geographic location. One benefit of soybeans is ability to rotate crops and not tie up a field with alfalfa for three to five years. Alternatively, you plant alfalfa once in about five years. Forage soybeans would be planted every year.”

Depending on location, forage soybeans need between a 90-day and 120-day growing season. Beef producers using them for forage would have to balance soybean forage with pasture or other types of hay to prevent nitrates from reaching dangerous levels.

“Depending on soil nutrient level and rainfall amounts, nitrate levels could become high,” Atkinson says. “They wouldn't be toxic, but it wouldn't be healthy for cattle.”

Since news of her research was released, Atkinson has heard from beef producers considering or planning to use soybeans as a forage or haylage crop.

“One Indiana producer is considering a 10-acre test plot for grazing,” Atkinson says. “If he goes ahead with that, it would be the end of June before he could put cows on it. An Ohio producer is considering using it for hay, and another Kansas producer is looking at 100 acres to make silage for feedyards.”

In testing forage soybeans for hay, researchers will consider how to rake and dry soybean forage and how much moisture to retain to maintain nutritional value of the hay.

Atkinson is waiting for funding before continuing her 2009 research. With Illinois' strong dairy industry, she plans to include dairy cattle in coming projects. She also plans to test planting patterns of forage soybeans and corn silage to increase corn silage quality.

“You want to harvest the beans before the seed gets hard,” she says. “We harvested test plots when pods were full and seeds were still soft, about an R5 stage. One of our challenges intercropping with corn will be the soybean's tendency to vine. I think you could get at least two cuttings of hay from these varieties, but I won't know for certain until testing is completed.”

The economic contrast between soybean forage and other types of hay and silage wasn't reviewed in any of the current research projects. Atkinson says existing data would allow researchers to provide economic comparisons.

“There are a lot of elements to consider and geographic location would be an economic factor,” Atkinson says. “We know if you're using soybean forage for stocker cattle, you should be able to cut back on other protein sources and may not need another protein source. You'd have to really look at details, like seedbed prep, how much time is invested in planting, herbicide and insecticide costs. The economic information does need to be reviewed.”

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