Sometimes you get what you pay for, and one expert suggests variety not stated (VNS) seed in cover crops isn’t sufficient. Instead, Chris Reberg-Horton, associate professor and organic cropping specialist at North Carolina State University, says you should invest in a cultivar that’s backed by research.
“We use [VNS] as a check and it varies so much year over year,” Reberg-Horton says. With variability, you don’t know what to expect and a bad seed lot could leave you with a poor taste for cover crops.
These differences in VNS of the same species could be a result of where the seed was grown, age of the seed or storage conditions. Altogether, the differences mean you don’t know what the cover crop will look like, what it will yield or how it responds in your environment.
It could also help avoid spreading invasive weed species because certified seed tests don’t allow them. For example, farmers in Minnesota are learning a hard lesson.
The Minnesota Department of Agriculture found instances in which Palmer amaranth was in conservation seed mixes. The mixes were mislabeled with low germination rates and inaccurate information on the contents of the mix—all a violation of the law.
Minnesota isn’t the only state having issues with Palmer amaranth and other weeds sneaking into conservation seed mixes. Palmer amaranth seed in CRP planting mixes has been found in Illinois, Indiana, Iowa and Ohio. It could be in other states, too, just not identified yet.
In addition, VNS might mean the latest genetics aren’t included, which could decrease your stand. Seed companies are researching what it takes to make a better cover crop, providing the maximum benefit of planting instead of rolling the dice with VNS.
Public and private entities are finally investing in cover crop breeding.
“[For example] Dixie variety crimson clover was first introduced in 1951 and is still the most favored variety on the market,” Reberg-Horton says. “Would we do that with corn? No. We want innovation. We are far from maximizing the benefits of cover crops.”
If you’re investing in cover crops, make sure your investment pays by picking the right seed. Consider certified seed so you can set realistic expectations for the crop.
Get Carbon-to-Nitrogen Ratios Right When Selecting Crops
The optimum diet for soil microorganisms is a 24:1 carbon-to-nitrogen (C:N) ratio, according to USDA Natural Resources Conservation Services. Microorganisms use 16 units of carbon for energy and the other eight parts for maintenance.
When selecting cover crops, consider their C:N ratio, as well as residues from previous crops or other common plants. Multispecies mixes can help you strike the balance of C:N ratios. (Note: The lower the ratio, the more nitrogen available to crops.)
Since 2008, farmers have increased their use of cover crops by 13% each year, according to a survey from the Sustainable Agriculture Research Education program. In 2017, farmers planted about 17 million acres of cover crops. Of those acres, nearly 50% were in cereal rye, with oats at 26% and radishes at 23%.