NCSHC May Meeting Recap - Keith Berns, Green Cover Seed
The NC Soil Health Coalition was joined by Keith Berns for our monthly meeting on May 2nd. Keith responded to questions that were submitted by Coalition members prior to the meeting and provided a vast amount of valuable information to the farmers in attendance. Keith is the Co-Founder and Co-Owner of Green Cover Seed, which is a leading cover crop and forage seed supplier based in Bladen, Nebraska. Keith and his brother have been no-till farming in Nebraska for decades and began experimenting with cover crops in the mid to late 2000s. They started Green Cover Seed in 2009 to address the lack of seed availability in their area, and Green Cover has since grown to sell enough seed to cover over one million acres each year.
A summary of each topic that Keith covered is provided below, in addition to the website links that Keith mentioned. For further information, Keith can be reached at keith@greencoverseed.com and the representatives from Green Cover are happy to assist farmers with cover crop selection and questions regarding any of their products.
What are the benefits of planting cover crops at the recommended seeding rate and how do those benefits offset higher seeding costs per acre?
When possible, planting cover crops earlier in the fall will usually require lower seeding rates and still achieve the same benefits as higher seeding rates planted later in the year. Planting earlier provides cover crops the opportunity to tiller, which provides greater soil coverage and biomass.
Another consideration is that proper seeding rates provide better weed control due to increased competition and biomass from the cover crops. This can lead to lower herbicide usage for weed control, thus offsetting the cost for higher seeding rates, and providing additional benefits from the cover crop. One benefit is reduced soil erosion. Sufficient cover crop stands significantly reduce erosion by holding soil in place with the root biomass and by absorbing the energy from raindrops before they reach the soil surface. Adding legumes to a cover crop mix can provide the additional benefit of nitrogen fixation, which has increased in value in recent years as synthetic nitrogen costs have gone up. Lastly, thicker cover crop stands offer improved spread and coverage throughout the soil profile with the plant root systems. This is particularly valuable for healing heavily tilled soils because it improves soil aggregation and biological activity within the soil by offering a source of carbon for the soil microbes.
What are the most important considerations for using a roller crimper for cover crop termination?
Three things must be correct to successfully use a roller crimper for cover crop termination. You need (1) the right equipment, (2) the right plant species, and (3) the right timing. When roller crimping works poorly, at least one of these items is usually missing.
Roller crimpers can be purchased or fabricated using various designs, and it is important that the roller crimper has the ability to both roll the plant down and crimp the plant stem. The plant should not be cut, so the blades used for a roller crimper should not be sharpened. Crimping the plant stem breaks the vascular system of the plant and prevents it from transferring water and nutrients from the root system. This terminates the plant but leaves the biomass in place and attached to the root system. The blueprints for the roller crimper design developed by the Rodale Institute are available for free on their website: https://rodaleinstitute.org/education/resources/roller-crimper-blueprints/. In general, a roller crimper consists of a 24” to 36” hollow drum that can be filled with water to increase the weight. Flat bars are welded to the drum in a chevron pattern. This pattern is used to avoid the hop and bounce that is created from welding the bars in a straight pattern across the drum. More bars can be added to the drum to increase the number of times each plant is crimped to improve termination. Small roller crimper planter attachments are available, but generally don’t work as well as larger roller crimpers due to reduced down pressure and fewer blades for crimping.
When selecting plant species that will be terminated with roller crimping, look for taller plants that have larger, hollow stems. Cereal rye is one of the most commonly used cover crops with roller crimping for this reason. Unlike cereal rye, plants like annual ryegrass that have many small, short stems and extensive root systems will not be killed with roller crimping. Other plant species that crimp well include peas, hairy vetch, and other cereals.
Roller crimping must be done at the correct stage of plant growth to be effective. This means plant species that reach maturity at approximately the same time should be used in cover crop mixes that will be terminated with roller crimping. Plants are most susceptible to crimping at anthesis (during flowering). Roller crimping is sometimes used twice in one season if plant species are not flowering at the same time. A light herbicide application can also be used to supplement roller crimping. Herbicide rates can be reduced significantly because the plant has already been damaged through the roller crimping. There are increasing efforts to develop improved varieties of hairy vetch, crimson clover, and peas that may lead to earlier maturing varieties that can be crimped ahead of early planted crops such as corn. Keith’s recommendation for a cover crop mix of cereal rye, crimson clover, and hairy vetch is to crimp the crop when the rye is mature because it is the most difficult to kill. A second pass may be required to terminate the clover and vetch. Triticale and wheat can be used to provide a later maturing cover crop and are generally easier to crimp than rye because the stems are larger.
How do you select the correct seeding rate for cover crop blends when a specific ratio of different plant types is desired, such as 70% grasses and 30% legumes?
There is not a consistent answer to this question among cover crop and soil health experts, however, Keith did share how Green Cover Seed approaches this question. The SmartMix Calculator provided on Green Cover’s website provides the recommended full seeding rate for specific cover crop species for the zip code you enter into the calculator. The calculator also gives you the lbs/acre, the percentage of the full rate, the percentage of the total weight, and the percentage of the total seeds for each species in a cover crop blend. To determine the effect each plant species will have on the cover crop blend, Green Cover uses a value called “percent effectiveness.” The percent effectiveness is calculated by averaging the percentage of the total weight and the percentage of the total seeds for each plant species in a mix.
For example, a cover crop blend may be 8% by weight and 49% by number of seeds proso millet. By averaging 8% and 49%, the percent effectiveness is 29%. Similarly, if the same blend is 11% by weight and 8% by number of seeds sun hemp, the percent effectiveness for sun hemp is 10%. The remaining seeds in the blend will make up the remaining percent effectiveness so it equals 100%. The percent effectiveness can be used as a guide for determining the overall impact of specific species on a cover crop blend. As Keith shared in the meeting, there is no “right” answer to this question, and there are many factors to consider when selecting seeding rates for different species.
The SmartMix Calculator also provides other metrics for the cover crop blend such as C:N ratio, drought tolerance, frost and winter tolerance, diversity, and grazing effectiveness. Green Cover usually recommends using 125% of the full rate for cover crop blends. The SmartMix Calculator is available for free on Green Cover’s website: https://smartmix.greencoverseed.com/.
Can shipping costs be reduced by shipping multiple orders to one farm, then allowing other farmers to pick up their orders from there?
Yes, because it is cheaper per pound to ship more seeds to one location. This means that it could be cheaper for multiple farms in an area to coordinate when they order seeds and have them shipped to one location. Depending on the distance and cost required for picking up seed from another farm, this may be cheaper than shipping directly to your farm. For example, as of early May 2023, to ship 2,000 lbs to Mount Olive, the cost would be $0.17/lb. The cost would be $0.12/lb for 5,000 lbs, $0.10/lb for 10,000 lbs, and $0.07/lb for 44,000 lbs (a full semi load). Shipping to a commercial address will save $50-$70 per shipment. To be considered a commercial address, an unloading dock, a forklift, and business hours are usually required, so farms do not normally meet the qualifications.
Can you explain the basics of seed inoculants, including rhizobium for legumes, free-living soil microbes, and mycorrhizal fungi?
Legumes form an association with different rhizobia species to fix atmospheric nitrogen. This means that hairy vetch requires a different bacteria species than crimson clover which requires a different species than Austrian winter peas. Rhizobia is marketed and sold for specific plant species, so the correct bacteria species can be matched with the correct plant species to enable nitrogen fixation. In addition to using the correct species, the correct timing must be used when inoculating seeds with bacteria. Specific inoculants will include directions that indicate how long the bacteria are viable for once applied to the seed. The timing can range from a few weeks to a few months.
In addition to nitrogen-fixing rhizobium, there are also free-living bacteria species that fix nitrogen in the soil. These include Azospirillum, Azotobacter, and Gluconacetobacter. These organisms benefit non-legume plant species by making atmospheric nitrogen plant available in the soil. Other organisms are able to make mineral nutrients, such as phosphorus, plant available. These organisms require carbon compounds from the plant for energy and supply nutrients back to the plant in return.
There are many families of mycorrhizal fungi that associate with plant roots and effectively increase the ability of the plant to access water and nutrients. Mycorrhizal fungi are more expensive to apply per acre, generally $12 per acre, whereas rhizobia may be $0.75-$1.50 per acre. Fungal inoculants are more difficult to produce and therefore cost more to apply. There are also biological stimulants, such as fulvic acid, humic acid, kelp, chitosan, worm castings, and sugars that can be applied at seeding to further boost biological activity.
Green Cover Seed sells a variety of inoculants including rhizobia for various species of legumes and a diverse seed inoculant that contains arbuscular mycorrhizal fungi and free-living bacterial species that aid in nutrient availability. The price of inoculants will depend on the complexity and number of microbe species that are provided. Green Cover can apply inoculants to seed prior to shipment. Since biological stimulants do not contain living microbes, they can be applied at any time prior to seeding. Mycorrhizal fungi is hardy but should be applied no more than 9 to 12 months prior to planting. Rhizobia must be added much closer to planting, up to 60 days prior in warm weather and 90 days prior in cool weather. Some products must be added at planting time, particularly peat products containing rhizobium. All products have their own unique requirements that should be verified prior to using them to ensure the bacteria and fungi are able to survive and thrive in your soil.
For more on inoculants and biological amendments, check out this article on Green Cover’s website: https://greencover.com/inoculants-and-soil-amendments/.
Do you have experience selecting native plant species that are suitable for North Carolina?
In general, annuals can be used across a wide geography. The same annuals can be grown in California, South Dakota, and North Carolina, for example. Perennials require more specific growing conditions and are not as transferable across locations. All perennial species are not suitable across North Carolina. Native species are best sourced close to your area. Native species can be more difficult to establish and are much more expensive. Introduced perennials can be a cheaper alternative to native species and are still very productive. An introduced cool season blend that Green Cover recommends for certain areas is alfalfa, clovers, lespedeza, orchard grass, novel endophyte fescue, meadow brome, perennial ryegrass, chicory, plantain, and small burnet. This mix is viable for 5 to 7 years but generally needs to be reseeded after that. A native species blend may last for decades once established.
Would you like more information from Green Cover Seed?
Green Cover offers a variety of resources on their website, including videos, articles, and an annual Soil Health Resource Guide. The Guide is available for free and can be downloaded or mailed to your home by requesting a copy at this link: https://greencover.com/freeguides/.
Are you a farmer in North Carolina who is interested in learning more about soil health resources and joining a network of farmers across the State who are also implementing soil health practices? Join the NC Soil Health Coalition by completing the application form on our website. Sign up for membership and join us for our June meeting!
