Cover crops can help improve soil quality, save manure nitrogen or fix nitrogen for the following crop, supply rescue forage and can lead to improved ground and surface water quality. Cover crops have a host of benefits, but there isn't a single species that does it all. You need to determine what your goal is for your field and select a cover crop species that will do that. Secondly you need to plant it at the appropriate time so it has sufficient time to do what you intended it to do. Cover crops are just like cash crops, they respond well to moderate to high fertility and good available moisture; a field that has low fertility will have a marginal cover crop growth as well. Fields with a history of manure applications or planned applications are excellent locations for cover crops.
What's your goal?
- Nitrogen fixation (legumes)
- Nitrogen scavenging (grasses taking up and storing leftover N from soil)
- Soil Building (organic matter and soil structure improvement)
- Erosion Fighting (soil-holding ability of roots and vegetation)
- Weed Fighting
- Quick Growth
- Alleviate Compaction
- Reduce Nematodes
- Attract Beneficial Insects
What goals cover crops achieve?
(Annual ryegrass, Barley, Oats, Rye, Wheat, Buckwheat and Sorghum-sudan)
Roles: Most scavenge nitrogen, improve soil organic matter and soil structure, prevent erosion and provide forage. Grasses have relatively quick growth.
(Berseem clover, Cowpeas, Crimson clover, Field peas, Hairy vetch, Medics, Red clover, Subterranean clover, Sweet clovers, White clover and Woollypod vetch)
Roles: Fix nitrogen, improve soil organic matter and soil structure, prevent erosion and provide forage. Legumes typically have slower growth than grasses.
(Mustards, Radish and Rapeseed)
Roles: Prevent erosion, suppress weeds and soilborne pests, alleviate soil compaction and scavenge nutrients
What is a good Mixture?
You likely have heard that mixtures of different cover crop species are good, but what is a good mixture and how do you plant it?
Again it comes down to the time of the year and your location. Generally it is a good idea to plant at least one grass and one legume species and to have one of them survive the winter to provide the soil protection over winter with an actively growing crop come spring time. Also consider adding a brassica to the grass and legume mixture for more diversity. There are many premixed cover crop mixtures on the market. Some of them are listed below.
- Annual ryegrass and crimson clover
- Radish, crimson clover and annual ryegrass
- Radish and annual ryegrass
- Radish and crimson clover
- Radish and oats; oats
- Crimson clover and radish
- Red, ladino, and sweet clover
- Annual ryegrass, crimson clover, red clover, radish, sweet clover
- Hairy vetch and oats
- Cereal rye and hairy vetch
- Triticale and annual ryegrass
- Peas, oats and hairy vetch
Seed mixture of annual ryegrass, crimson clover, and forage radish.
Most species will have the best chance to germinate and survive if they are drilled into the soil, many smaller seeded species will do okay broadcasted if there is adequate moisture after seeding. Often larger seeded species will be planted in the large grain box on the grain drill and the small seeded species will be planted in the small seed box of the drill, however in a mixture depending on the size of the largest seed you may need to use the small grain box. As a general rule do not plant the seed deeper more than 2.5 times its diameter. It is okay to see a few small seeds on the surface of the soil; that means most of them are planted at the correct depth.
Remember that every year is different, what worked last year might not work this year. By planting multiple species of cover crops you spread out your risk of a crop failure and will likely have at least one of the cover crops growing successfully. Don't be afraid to try something new and different on a few acres; just don't plant the whole farm with one species on the same day if possible. Plant cover crops as soon as the primary crop is harvested to capture as much growing time as possible before winter arrives.