Excess moisture plus cool temperatures in April delayed field work, including planned cover crop burndowns. Meanwhile, cover crops continue to grow, with rye heads emerging and crimson clover starting to bloom in the southeast.
Those who did have the chance to burn down cover crops may notice the dead residue insulating the soil. This is excellent for soil conservation, traps excess moisture and slows evaporation, so soil takes longer to dry enough to be suitable for corn and soybean planting.
According to the Penn State agronomy guide, optimum corn grain yield declines by about one bushel per acre per day of delay after the start of the ideal planting window, which ranges from mid-April to mid-May, depending on the region of the state.
Risk of delayed planting causing yield loss in soybeans is lower, as full-season soybeans can still reach full yield potential through mid-May.
Extension agronomist Heidi Reid explains that with the clock ticking on optimum planting time in the southeast and some more rain in the forecast, planting green could be a viable option for growers itching to get in the field who are concerned with the size and maturity of their cover crops.
Penn State research has shown that planting green into living cover crops provides a significantly drier seed bed compared to planting into cover crops killed a week or more pre-plant. Allowing the cover crop to grow until main crop planting means the plants continue transpiring, drawing water from the root zone and drying the soil. Planting green can also conserve more moisture later in the growing season compared to pre-plant killed cover crops, due to the higher biomass residue trapping moisture.
Some farmers choose to plant green for the first time because of time and weather constraints, or ineffective herbicide applications. So, even if you did not plan on planting green this spring, conditions are right to give it a try. As with any new management practice, it is best to do some homework before using it on all your acres.
Based on our three-year, five-site research project, we have come up with some suggestions for planting green success. This abridged list includes only those applicable now and throughout this growing season, although best management truly begins in the fall before cover crop planting.
Start planting green with soybeans instead of corn. Soybeans adapt to reduced populations from residue interference and cooler soils by branching, compared to corn which cannot adapt to reduced populations.
Consider how much cover crop biomass your equipment can handle, and rolling/crimping mature, high-biomass covers. Though every farmer uses different equipment and settings for planting green, and management varies farm-to-farm, all equipment should be well maintained and calibrated. We recommend rolling cover crops taller than 18 inches to reduce cover crop residue interference with the main crop.
Use aggressive row cleaners to start. This is often a matter of preference, but those new to the practice may appreciate more aggressive residue management for better sunlight penetration to help warm the furrow and improve emergence.
Use a planter rather than a drill for establishing soybeans. Greater precision with planters improved soybean performance compared to drills when we planted green.
Focus on optimum planting depth. Planting green can result in planting through significantly more biomass than usual. Make sure to adjust gauge wheels to account for the thickness of the extra residue.
Carefully attend to nitrogen management with corn, including at planting, and sidedress nitrogen as needed. To make sure the corn doesn’t suffer from the slow release of nitrogen from high C:N mature cover crops, an extra 50 pounds per acre of nitrogen at planting is advised, with the remainder applied at side-dress based on yield goals.
Scout for early season pests and use integrated pest management practices.
Avoid neonicotinoid seed treatments and preemptive insecticide sprays that can kill predators of insect and slug pests, which are allies in pest control. Some farmers have found that planting green reduces slug damage to their main crops. We found that reduced slug damage was not predictable in soybeans and found mixed results for corn, but promoting natural enemies has been shown in other studies to significantly reduce pests.
Finally, consult with farmers in your area who have planted green successfully. It is always best to learn from those nearby with similar soils and crop rotations who have done well with planting green. Do not be afraid to ask questions and learn from others’ mistakes.