Cover Crops to Support Forage Diets

By: Farm Journal Content Services for Drovers online

Interested in pairing up a cover crop with corn silage? A key is to consider harvest timing – usually mid- to late May for boot stage – to ensure the cover crop forage is of the quality needed for lactating cows.  If targeting forage for heifers, harvest a bit later at heading stage to increase tonnage and fiber content.

Popular cover crop options include winter cereals, like winter rye and triticale.

“Winter rye is growing in popularity because it has rapid growth, especially in the spring, and will mature earlier in the spring,” said Matt Akins, University of Wisconsin–Madison dairy management specialist. “Agronomists say it tends to overwinter a little better than triticale. However, a drawback to rye is that it matures very quickly in the spring, so a weather delay can cause harvesting issues. Triticale matures more slowly in spring and may reduce some weather risk at harvest. Wheat is another option, but it tends to mature slowly in the spring, which causes issues with the subsequent crop.”

Soil Health Benefits

Cover crops can help increase organic matter over time by breaking down residue above and below ground. Cover crops can also reduce soil erosion by 60 to 90% and improve water quality. They can also improve soil tilth by building a more robust soil biome through the excretions of fungus, microbacteria and earthworms, which help hold the soil together better. Some cover crops, like legumes, are planted due to their ability to fix and hold nitrogen in place.

“If you have a really wet spring like this past year, cover crops can pull some of the moisture out of the soil as it is actively growing,” noted Akins. “In a dry year, the cover crop may cause lower soil moisture conditions, potentially causing issues for the next crop.”

Harvesting Cover Crops

“A lot of producers are harvesting their cover crop as a silage crop; many are larger dairies attempting to build back up their feed supply,” said Akins. “They’ll cut and wilt it, letting it dry for a day or so to get the moisture content down, then come back and chop it.”

When harvesting to feed lactating cows, the ideal time to harvest is boot stage – just before the head is going to emerge from the stem. If weather might delay harvest, Akins says to harvest early rather than late.

“If you have weather coming, producers should err on the side of taking the crop off a little early,” he said. “If you plan to feed the crop to pregnant heifers, it’s OK if it’s a little later. Packing can be an issue when harvesting later, so chop more finely to improve packing.”

As the crop matures from boot stage to heading, the fiber content increases and the digestibility of the fiber goes down. The protein and sugar content are also decreasing as the crop matures, but the tonnage goes up.

Harvesting Tips

  • When cutting the crop for wilting, lay it out in a wide swath so it dries as quickly as possible, especially when temperatures are cooler.
  • When ensiling a cover crop, some producers decide to bag it so it’s separate from other silage crops because it will have a different nutrient profile and will need to be fed out differently.
  • For moisture content, target 30 to 40% dry matter for silage forage use. If it’s harvested later and is stemmy, chop it finer to help ensure a good pack.

Yield Expectations

“Typical tonnage at boot stage is 1 to 2 tons, and at heading stage it can be two to four times that, depending upon the year,” Akins explained. “If you have a really cool, wet year, yield will be on the low side – it’s just not going to yield as well.”

Akins says a 2-ton yield is often the tipping point for growing an economically profitable crop based on input costs and estimates of harvesting costs. Experts recommend that even if it’s a low-tonnage year, it’s usually beneficial to harvest because you might have a poor summer crop and may need every bit of yield you can get.


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