By: Heidi Reed & Sjoerd Willem Duiker
With the unseasonably warm weather we have had in the last several months, cover crops have been growing quickly. This is usually a good thing since we know that we get the most out of our cover crops when they're allowed to grow for as many days and as big as possible. More and more farmers are accomplishing this by planting green into living cover crops.
But, many counties have gotten about half as much precipitation as expected in an average year (Figure 1). Some rainfall is predicted in the next week, but it likely won't be enough to alleviate the preceding months of dryness. Despite a sharp drop in temperatures coming next week, which will slow cover crop growth, please keep an eye on your rain gauge and consider burning down cover crops early to lessen the risk of robbing moisture from your corn or soybeans.
Figure 1: 90 day mean precipitation and departure from average 1/11/2023 through 4/10/2023 Mid-Atlantic River Forecast Center, Accessed 4/11/2023.
Research from Penn State and other institutions shows that planting green significantly dries the top three inches in the soil profile compared to planting into cover crops killed a week or more pre-plant, because the growing cover crop transpires and draws water out of the root zone. A drier seedbed can be a great benefit in a wet spring but disastrous in a dry spring. Increased mulch cover after planting green conserves soil moisture in summer, but this benefit is outweighed by potential stand establishment issues (and related corn yield loss) caused by planting into overly-dry soil.
The beauty of planting green is that it's an adaptive management practice. Maybe you had plans to plant green when you seeded rye in the fall, but you can change those plans in response to the weather for the best possible outcome. On the other hand, if you have a field that sits wet, or you are lucky enough to get timely rain in the coming weeks, you can still plant green and benefit from moisture management, weed suppression, etc.
Your best options are always either planting into a dead, brown cover crop, or planting green - don't get stuck somewhere in between.
If you do decide to plant green this year, we have found the following to set farmers up for success:
- Soybeans are more adaptable to planting green than corn; get comfortable with soybeans first.
- Equipment must be well-maintained and calibrated
- Roll cover crops over 18 inches tall, especially if planting corn
- Use row cleaners to help warm soil in the furrow
- Planters work better for soybean establishment through thick cover than drills, due to better seed placement
- Check if you are planting deep enough; you must account for the cover crop thickness
- Put an extra 50 pounds per acre of N at corn planting to compensate for N-tie up by a cereal cover crop with the remainder of N needs applied at side-dress based on yield goals. PSNT and tissue sampling can help dial in N needs.
- Scout for early season pests and use IPM to manage pests.
- Minimize neonicotinoid seed treatments and "insurance" insecticide sprays that can kill predators of insect and slug pests, which are allies in pest control
- Consult with farmers in your area who have planted green successfully