Ensiling Sunflowers

Although sunflowers are generally planted for seed production, they can be used as a source of forage. Since the seeds represent only about 1/3 of the plant dry matter, stressed sunflowers with little potential for seed production can be profitable if utilized as forage.

Does variety make a difference - Confectionary or Oil type?

Most of the literature suggests that confectionary types are most often used for silage. Typically seeding rates are 3-5 lbs/ac (20-30,000 plants/ac) and row widths @ 24”. This is not far off from what we are commonly seeding in Manitoba. However, forage yields of sunflowers are generally less than corn when a full growing season is available.

What to think about before harvesting

As with producers wondering about making grain or silage, many decisions of whether or not to ensile your sunflowers will be left to the last minute (after the frost). Consider your options well in advance.

Moisture

One of the main limitations of producing sunflowers for silage is the high level of moisture within the plant at the time of harvest. The thick stalks make for a slow dry down. The moisture content of sunflowers at maturity can be between 80 to 90%, and would require wilting before ensiling to reach the desired 60-70%. As many growers are aware, even when heads are brown, dried up and seeds are ready for harvest, the plant moisture can still be as high as 80%. These high moisture levels can still be evident two weeks after a killing frost. Therefore careful consideration is required when deciding to harvest your sunflowers for silage. You may want to consider swathing your sunflowers to quicken drydown.

Buffering Capacity

Optimum harvest dates are especially important, much like soybeans, since the high fat content of sunflowers also gives the plant an ability to buffer against ensiling. However, the relatively high levels of water soluble carbohydrates in the stem improve its ensiling properties. Generally, their buffering capacity is just about equal to silage corn that is nearly past its optimum harvest date.

Harvesting

When chopping for silage, harvesting procedures are the same whether the crop is immature or mature. The only difference is in the quality produced. Immature sunflowers will produce silage with lower lignin contents, higher protein levels, lower fat contents, and moisture levels greater than 70%. Keeping in mind your target moisture for ensiling is between 60-70%.

Sunflowers destined for silage should be harvested when the backs of the heads turn yellow and the bracts around the head turn brown, but before the bottom leaves drop off. Since moisture levels may still be around 80%, some producers will wait a couple of weeks after the first killing frost before ensiling. At this point the leaves should be pretty dry (bottom leaves will be yellowish in color) and the flowers should be bending over. However, waiting this long may increase leaf and other dry matter losses. Considering the coarseness of the stems, a fine chop is recommended to achieve the desired pack density.

Nutrient Values

Generally speaking, the feeding value of sunflower is about 80% of the value of corn silage. More specifically, sunflower silage is lower in energy than corn silage on a dry matter basis (60-65% TDN), slightly higher in crude protein (12.5%) and considerably higher fat (7.1 to 10.7% depending on the variety) (See Table 1). However, sunflower silage contains 1.5 to 2 times more fiber and up to 3 times as much lignin (indigestible) compared to corn silage. Due to this lower energy content and higher fiber, sunflower silage is generally recognized as adequate for dry cows, steers, growing heifers and low milk producers.

At a study at South Dakota State University (SDSU), milk production decreased by 8% in dairy cows fed sunflower silage in substitution for corn silage, but milk fat was 12% higher. At the University of Wisconsin, for cows producing 60 lbs milk, the substitution of corn silage with up to 66% sunflower silage did not affect milk and protein yields. Partial replacement of corn silage with sunflower silage could be a viable option for lactating cows of moderate milk production.

Forage quality could be improved by supplementing with other forage alternatives such as corn silage, haylage, or hay.

Table 1: Nutritional quality of sunflower, immature corn, and mature corn silage, alfalfa hay (harvested in early bloom) and timothy hay (harvested in late vegetative stage) in South Dakota.1

¹Data from Miller, Oplinger and Collins, 1986.

²In vitro dry matter disappearance. 

References

• Alternative Field Crops Manual
• SUNFLOWER SILAGE