Harvesting Sunflowers for Silage

This page was adapted from the article, "Harvesting Sunflowers for Silage," which appeared in Crop & Pest Report on September 8, 2021.

In years when a sunflower crop may not make it to grain harvest, producers may wonder if they should salvage the crop and harvest it as forage. The decision to harvest sunflowers as forage, particularly silage, requires careful consideration of several factors. Sunflower silage can make a suitable feed for beef cows, sunflower silage is about 80% of the feeding value of corn silage. Still, the challenge is getting it put up, because sunflowers typically do not dry down well. Consequently, dry feed must be added to the silage pile to reduce the moisture level to a point where seepage is not a major problem.

The moisture problem in sunflower silage can be corrected by several means. Former NDSU animal science specialist, LaDon Johnson, suggested blending corn and sunflower silages when packing as one method. The blending ratio should be one load of sunflower silage to three to four loads of corn silage. Waiting seven to 10 days following a killing frost will facilitate dry down. Some varieties may take longer and waiting longer, also increases the risk of wind damage to the crop and greater dry matter losses. It is also suggested to blend dry forage into the silage pile to reduce the moisture content.

Optimal moisture content in sunflower silage appears to be 60% to 72% or 28% to 40% dry matter. To minimize effluent seepage problems, the moisture level will likely need to be below 65%. Silage that is too wet will also result in undesirable clostridial fermentation, reducing the forage quality and may limit voluntary intake due to palatability. Keep in mind the target moisture of 60% to 72%; harvesting immature sunflowers can produce silage with lower fiber, lignin and fat content, possibly improving the forage quality.

Sunflower silage is lower in energy at 61% to 66% total digestible nutrients (TDN), variety dependent, than corn silage at 68% TDN. The lower energy of sunflower silage is mainly due to the greater fiber content of sunflower silage which is approximately one-third more than corn silage and three times the amount of lignin, the indigestible portion of the fiber.

However, confectionery and oil-type sunflowers can make silages that contain more protein (11.1% to 12.5% versus 8.2% crude protein, respectively), fat (7.1% to 10.7% versus 3.3%, respectively), calcium (0.8% to 1.5% versus 0.24%, respectively) than corn silage at 100% dry matter.

Due to the fat content of sunflower silage, the forage should be limited to one-half or less of the diet dry matter basis. In forage-based diets, dietary fat content exceeding 6% will reduce the intake and digestibility of forages. Likewise, the high fiber content of sunflower silage may reduce intake by slowing down the rate of passage in the rumen.

As with making any silage, allow 28 days for the ensiling process to occur before feeding or exposing the forage to oxygen. Pricing silages can be complex. Factors that may influence the value of sunflower silage include substitute feed costs, fertilizer costs, harvesting costs, removal of residue and nutrients from the field, storage costs, harvest and storage losses or shrink, and energy, protein and fiber content of the sunflower silage. Analyze the sunflower for nutrient content, and use these values to better understand the forage quality, and determine the pricing based on forages with similar nutritive value, such as medium quality hay.

For sunflower covered by insurance, be sure to contact your crop insurance agent before harvesting. Likewise, check any herbicide and insecticide labels applied to the sunflower and follow the pre-harvest time restrictions before harvesting for silage.

Many drought-stressed plants accumulate nitrates. Before feeding, test your drought-stress sunflower silage for nitrates. Although proper ensiling will reduce nitrates, it does not guarantee the forage will contain ‘safe’ levels of nitrates.

See the NDSU Extension publication “Nitrate Poisoning of Livestock,” for more information about elevated concentrations of nitrates in feedstuffs.

Zac Carlson 
Extension beef cattle specialist

Miranda Meehan
Extension livestock environmental stewardship specialist

Hans Kandel
Extension Agronomist, Broadleaf Crops