BCRC: Cover Crops
Cover crops are typically diverse, annual crop mixtures planted with the intent to build and improve the soil. Cover crops may also include biennial or perennial species, depending on the end-use and goals of the producer. Cover crops may be grazed, baled, or used for silage, depending on the species that are seeded. Cover crops may also be used as a green manure or plough-down crop.
Cover crops, often called “cocktails,” consist of plants that will benefit the soil ecosystem and support a variety of soil microbes, fungi, and other biodiversity, such as earth worms. Cover crops can enable soils to have improved water infiltration, increased organic matter, and more efficient nutrient recycling. Some cocktail crop species may be useful in utilizing excess water in a field that would otherwise be water logged, while other species may be selected for their drought-tolerant qualities and their ability to make the most efficient use of existing moisture.
A mixture of cover crop species is usually recommended, and may include both cool season (i.e. C3) and warm season (i.e. C4) species, broad leaved species, legume species, Brassica species, and grassy species. Using a mix of cover crop species maximizes photosynthesis, allowing solar energy to be captured at different heights and angles. Different cover crop species will also have different rooting zones, therefore impacting soils at different depths.
Cover crops can be a valuable and quick-growing source of forage for livestock, and provide grazing in the same year the crop is seeded. Cover crops also allow cropland and pastures to be more efficient with water and nutrient cycling, and less reliant on costly inputs such as fertilizer.
From an animal standpoint, a forage cocktail also provides cattle with a diet that is nutritionally diverse. A mix may include species such as clover, a forage Brassica (i.e. turnip, radish), barley, or peas. Each plant species may reach maturity at slightly different times, therefore providing green forage continuously through the growing season. Using a combination of plants rather than a single forage species also helps to increase the overall yield potential of the crop. Producers will want to manage cover crops through grazing management strategies, such as temporary fencing, that allow appropriate and timely grazing that matches the species and their stage of growth.
If producers are planning on using cover crops for silage, greenfeed, grazing, or another controlled feeding methods, feed testing is required to identify any potential nutrient or anti-quality issues.
Depending on soil fertility conditions and species selection, some cover crop plants, such as Brassica species, can accumulate excess nitrates and sulfur so cattle producers should pay attention to their animals for those symptoms. Other species in a mix may cause grain overload if animals are allowed to selectively graze, so take steps to prevent that from occurring by only allowing a portion of the field to be accessed at a time.
Some species within a forage cocktail do not have a lot of fibre, particularly as species regrow following grazing. Cattle producers may want to include roughage in these grazing fields, even by providing straw bales or slough hay, to slow down the passage of forage through the digestive system and increase the nutrient uptake.
Producers are urged to pay attention to their cattle when grazing or feeding cover crops. Use common management practices, such as the following, to avoid problems:
- Turn cattle out onto new cover crops only when they are full (i.e. avoid early morning moves);
- Avoid moving cattle to a new cover crop during weather changes;
- Avoid moving cattle to a new cover crop following a major handling event (i.e. processing, preg-checking, following a long trailing event);
- Prevent animals from selectively grazing (i.e. choosing the “best, leaving the rest”) by allowing them to graze a portion of a field at a time and ensuring an appropriate stocking rate;
- Monitor animals for signs of reduced feed intake, incoordination, panting, or other signs of nutritional toxicity.
Producers may want to incorporate one or several legumes in their cocktail mix to build nitrogen in their soils. Different legumes can be selected to meet different grazing needs, whether you’re grazing in early spring, late fall or winter.
Seeding rates will vary according to the diversity of mix. Seeding rates also have a large impact on the cost, as does the number and variety of species. There are several seeding cost calculators available to producers, including this version available at: http://decision-tool.incovercrops.ca/
Seeding dates may be planned strategically. Some producers may opt to seed two crops in a season, where they silage the first crop and graze the second crop. Other producers sometimes seed fall or winter crops in the spring, for grazing later in the season and early in the next.
- Evaluate your goals for cover crops. What is your intended outcome and what specific issues are you trying to resolve? Do you need to build organic matter or improve water infiltration? Are you concerned about soil erosion? What is motivating you? How will this fit in with you current cropping and grazing management?
- Evaluate your existing infrastructure. What sort of water development, fencing, or other infrastructure may you need in order to graze cover crops? Do you have the seeding equipment necessary to plant a cocktail?
- Look for informational resources. Do you have experience seeding cover crops or grazing them? Do you have someone you can contact or resources available?
- Evaluate grazing conditions as the season progresses. Have you performed feed analyses? Are your cattle receiving all of the nutrients that they need to stay healthy? Do the nutrients match the stage and class that your cattle will be at during grazing?
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