A lot of corn was chopped for corn silage last week and harvest continues this week. We are about a month ahead of last year’s corn silage harvest and this year’s earlier harvest provides an opportunity to get cover crops established on those acres. Earlier planting of cover crops is good. The touted benefits of cover crops are dependent upon the crop producing forage mass above ground and developing a root system below ground. More growth is generally equal to more benefits. In addition to protecting the soil against erosion, cover crops can improve soil quality, provide supplemental forage for grazing or mechanical harvest, can use excess nutrients in the soil, and can provide an option for manure application during late fall and winter periods. The expectation here is that we get some rain so that the cover crop can germinate and grow to take advantage of an earlier planting date.
Some cover crop grass options after corn silage include spring oats, spring and/or winter triticale, winter cereal rye, barley, and winter wheat. Note that winter wheat even if used only for a cover crop should still be planted after our hessian fly-free date. Legume options are more limited but include crimson clover and winter peas. Generally these would be included in a mix with one or more of the small grains. Legumes have the potential to produce some nitrogen for the next crop, but for that to happen they have to be planted as early as possible, preferably at least 4-6 weeks before frost, and make sure the seed is inoculated with the correct rhizobia bacteria. Winter peas planted early, probably before that mid-September time frame will most likely winter kill. When winter peas are planted late they often will overwinter. I have talked with farmers who have planted winter peas in the late September to early October time frame and had that crop overwinter. The downside is those late planting dates generally do not produce much fall growth so if soil cover is the goal, plant earlier.
With regard to the small grain crops, oats (or spring triticale) drilled immediately after corn silage by the end of the first week in September could provide 0.5 to 1.5 tons of dry matter before a killing frost depending upon moisture, fall temperatures, and days until that killing frost. Since oats and spring triticale winter kills spring termination management is not needed, but from a manure management perspective oats or spring triticale as a cover crop does not provide an option for a winter manure application to a living crop. Barley when grown for grain in the succeeding year is usually planted between September 15 and 30. Triticale is generally planted with timing similar to winter wheat and cereal rye for grain production is planted between September 15 and the end of October. With the exception of winter wheat, any of these crops can be planted earlier if the primary purpose is as a cover crop and supplemental forage. All of these small grains except oats and spring triticale will overwinter and begin growing again in the spring. The grower must have a plan for the spring forage growth and/or crop termination before planting corn or soybeans. Remember that both oats and spring triticale will produce more forage in the fall, so either of these crops plus a winter-hardy small grain like winter rye, winter triticale, winter wheat or barley can provide forage later in the fall and again next spring. It is worth mentioning that cereal rye begins growth early in the spring and it has a rapid maturation so the grower must be prepared to either utilize it as forage early or terminate it early.
Another cover crop and supplemental forage option after corn silage that I am a little reluctant to mention is annual ryegrass. The reluctance is because some growers have had problems terminating the annual ryegrass with herbicides in the spring. Growers who have taken a mechanical harvest off first with a later spring herbicide application have fared better. If the goal is provide cover and forage then variety selection for winter hardiness is important. Refer to the Ohio Forage Performance Trials for selecting varieties (http://hostedweb.cfaes.ohio-state.edu/perf/). Mark Sulc, OSU Extension forage specialist, has planted annual ryegrass in early September for several years, and says that one can expect 800 to 2000 lbs. of dry matter/acre by late November and early December, with yields of 3 to 5 tons of dry matter/acre the following year from improved varieties with good winter survival and with adequate nitrogen fertilization rates.
Another factor that needs to be considered with fall cover crop planting is potential herbicide residual in the soil. The residual activity of an herbicide in a soil is dependent upon a number of factors including soil type, soil pH, organic matter level, rainfall, and temperature. In addition, when a particular herbicide was applied in terms of time between application and the planting of a cover crop is important. Unfortunately most herbicide labels may not have information about potential residual effects on cover crops.
Purdue University has been evaluating the impact of commonly used residual herbicides on cover crop establishment and recently posted an article summarizing their results in the Purdue Pest and Crop Newsletter (http://extension.entm.purdue.edu/pestcrop/2015/Issue22/). Quoting from that article “As a general rule, residual herbicides that have activity on grass weeds can interfere with the establishment of some cover crop species, especially the smaller seeded ryegrass species. Residual herbicides from the group 2 (ALS), group 5 (triazine), group 14 (PPO), or group 27 (bleacher) can interfere with the establishment of some of the broad leaf cover crop species.”
Cover crops can provide a number of benefits when they have time to get established and grow sufficient biomass. A winter hardy cover crop may become part of a nutrient management plan and provide an additional option for manure application. This year’s early corn silage harvest is an opportunity to get some cover crops planted and established in a timely manner. For more information about cover crop timing, specific species recommendations, seeding rates, and potential forage yields and quality, contact a member of the OSU Extension Ag Crops Team.