I am frequently asked how late is too late to plant cover crops in the fall.
There is no decisive answer. But if you could tell me what the weather will be for the next six weeks, I would be confident in recommending the last date that would be worth the risk of establishing a cover crop.
It boils down to understanding the weather trends for your area and the amount of risk you may want to take, just like you do with your cash cropping decisions in the spring. If it’s mid-June and still too wet to plant corn, do you stay with corn or switch to beans? The decision is no different with how late is too late to plant cover crops.
Know Species Potential
It’s well known that cereal rye can be planted anytime in the fall and it will undoubtedly grow. You may not see it until spring, but it’ll be there. The question is, when do other species reach the end of a justifiable planting window. It is prudent to know that there are winter hardiness and late planting date variations within a given species.
For example, hairy vetch varieties or selections can vary widely in survivability as it relates to the planting date. Knowing how a specific species performs in your area can only be learned through personal experience or a trusted seed salesperson or consultant.
The Case for Mixes
Planting cover crop mixes has been popular for many reasons. Specifically, this practice has merit at the end of a given species planting window. For example, radishes might be questionable to be planted in the end of September in most regions. However, spending $4 an acre on two pounds of radish seed may be worth the risk during late fall where decent growth may be realized in the context of a mix that includes cereal rye or triticale. In addition, you could add a pound of inexpensive oilseed rape cover crop that will undoubtedly over-winter, even when planted in late October in most areas. Also, species that are more winter-hardy can protect more fragile species.
Get It in the Ground
Anytime you are planting late, be sure to get the seeds in the ground. Do not broadcast the seed on the soil surface as this potentially only adds delay to germination if wet weather is not experienced immediately. Soil temperatures are generally warm in the fall and seeds will sprout quickly, especially in a no-till situation where significant crop residue is present.
Use Weather Data
For those in the Northeast, Cornell University has developed the Winter Cover Crop Planning Scheduler, which is associated with their Climate Smart Farming Program. Simply type in your ZIP Code, enter the desired species you’d like to plant, and the model will tell you the probability of success on any given date. It uses historical weather data from the past 30 years but also allows you to see more recent weather patterns over the past 15 years. For those more comfortable managing late planning decisions with data, this tool is for you. It’s available at bit.ly/WinterCoverCrops
And Then There’s Cereal Rye
It’s never too late to plant cereal rye. You may not see it in the waning weeks of autumn or early winter, but it’ll pop up in early spring as soon as temps begin rising above 40 degrees. However, if you are planting late, you should use a higher seeding rate — up to 2 bushels, or even more if the strategy is specifically to use cereal rye for forage.
Risk Versus Reward
There are several guidelines you can utilize to make late planting decisions. Use them to determine your risk in making the most of your cover crop planting opportunity.