Source: South Dakota State University Extension
Dairy producers dealing with drought conditions can consider soybeans and sunflowers as forages.
SDSU Extension Dairy Specialist Alvaro Garcia said soybeans and sunflowers provide an option if dry conditions have shrunk the crop's potential yield below the economic threshold for seed harvest, or if producers face a shortage of roughage.
"How producers harvest alternate crops for forage depends on the crop and its stage of maturity," Garcia said. He added that it's important to observe any herbicide restrictions when using soybeans for forage.
Baled soybeans: Soybeans can be comparable to early-bloom alfalfa in nutritional value. Producers should bale when pods are almost full of seeds and lower leaves are just starting to turn yellow, but are not falling off. The stems tend to dry slowly. Conditioning will bring total moisture below 25%. Producers should rake no more than necessary since leaves and pods tend to easily shatter.
Soybean silage: Moisture content is important if producers choose to ensile; they should keep it similar to that of alfalfa silage. For soybeans, ideal time to make silage is just before the pods are full. Waiting until complete maturity results in forage of lower digestibility and can lead to fermentation problems due to high oil content. Mixing one-third corn silage with the soybean silage can help producers avoid these problems, since the soluble sugars in corn speed up fermentation and dilute the fat content of the soybeans.
Sunflower silage: On a dry matter basis, sunflower silage contains slightly more crude protein (12.5%), considerably more fat (7.1 to 10.7%, depending on the variety), and more calcium than corn silage. On the negative side, sunflower silage contains 1.5 to 2 times more fiber and up to 3 times as much indigestible lignin compared to corn silage. Due to this lower energy content, it is important to feed sunflower silage to lower-producing dairy cows, dry cows, or growing heifers.
Sunflower stalks contain abundant water, and producers should wait, in some cases up to two or three weeks, after the first killing frost before ensiling. At this point the leaves should be quite dry (bottom leaves will be yellowish in color) and the flowers should be bending over. At this stage of maturity, the silage will contain approximately 30% dry matter.
Milk production decreased by 8 percent in dairy cows fed sunflower silage in substitution for corn silage, according to research conducted at South Dakota State University, but milk fat was 12T higher.
Garcia said more drought management information is available at iGrow.org in the Livestock and Agronomy communities.