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Soil Health Minute: Grazing cover crops

A Jan. 22 "Grazing Cover Crops" workshop in Rutland, N.D. brought in farmers and ranchers from hundreds of miles away, which led to excellent discussion for various conditions and systems. We had five sessions led by North Dakota State University specialists and researchers, so I'll highlight the top points from each session.

Kevin Sedivec discussed full- and late-season cover crop options for biomass production and quality while still being cost-effective. In general, at least 30 days of growth is needed to get money back on seed costs when grazing cover crops. With a fall-seeded cover crop, like cereal rye, winter triticale or winter wheat (seeded by Aug. 15), it's reasonable to get 30 days of grazing in fall and another 20-30 days of grazing in spring. For a full-season cover crop, there is the option to hay it (but don't use brassicas in the mix because water content is too high) and then graze the re-growth. In the fall-seeded mixes, Pasja turnip and radish are excellent with a small grain because of their cold tolerance.

Marisol Berti covered the importance of species and variety selection for forage biomass and quality. Some varieties have double the yield of other varieties, so always ask for the name of the variety and then compare it with information in the Grazing Cover Crops booklet (available online: ndsu.edu/soilhealth).

For example, purple top turnip will produce 1.8 tons per acre of biomass with total digestible nutrients of 71 percent, while the Winfred hybrid will put on significantly higher biomass of 2.5 tons per acre and total digestible nutrients of 78 percent when planted as a full-season cover crop. Purple top will not re-grow, whereas Winfred will because it was designed for grazing. When putting the biomass through livestock, getting extra tonnage of higher quality plus re-growth is likely worth the seed cost.

Greg Lardy focused on nutrition for livestock and spent time talking about what the rumen needs. His motto: "Feed the microbes in the rumen first." Microbes produce fatty acids through fermentation, and ruminants use these compounds for energy. Microbes also produce 80 to 100 percent of the protein needed by cattle, and a large portion of water soluble vitamins come from the microbes in the rumen. This is why the rumen and quality of forage available to feed the rumen is extremely important. Grazing cover crops in a vegetative stage is a priority because that is when quality is highest. The more mature the plant is, the more cellulose and lignin it has and the more difficult it is for the microbes to ferment.

Miranda Meehan's session focused on evaluating production and management — going into carry capacity and stocking rates. She went through the NDSU Grazing Calculator App which guides you through calculations to set the correct stocking rate using forage production and carrying capacity. Stocking rate is one of the most important grazing management decisions made by a farmer or rancher, and this app helps you get it right.

Mary Berg shared information on compost and manure applications. There are many benefits to grazing cover crops with livestock versus hauling in manure or compost, one being that there is no cost for hauling if you let the animals spread it themselves. Another benefit is that the urine is an extremely important source of nitrogen because it is readily available. Fencing and grazing strategies can be used to help spread the manure and urine evenly across the field.

More information on each of these topics can be found in the NDSU Grazing Cover Crops booklet posted on the NDSU Soil Health webpage (ndsu.edu/soilhealth).

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