More and more growers are interested in planting cover crops to improve their soil and increase soil productivity. It is also a good tool to reduce nutrient losses since covers scavenge up nutrients like nitrogen and phosphorus that contribute to hypoxia in surface waters.
Unfortunately it is not always timely to plant cover crops after corn and soybean harvest. There is usually not enough time left in the fall to get any growth if you drill or broadcast after combining—leading to disappointing results.
However some growers have chosen flying cover crop seed onto standing corn or beans in the late summer. In my experience aerial seeding is not always successful and requires a good rain immediately after seeding. It’s not all that easy to get a good stand of cover crops to become productive in a growing corn or bean field, and having moisture immediately available is critical.
Several factors limit success rates. Herbicide carryover can cause problems, particularly this year with delayed or prevented planting and late applications of herbicides. Also, time of seeding is critical so sunlight can penetrate down to new seedlings. Most covers aren’t particularly shade tolerant. For soybeans, aerial seed the beans just before leaves start to drop. In corn, some folks wait until leaves dry or drop below the ear. And the earlier that corn can be harvested, the better for cover crop growth.
If you have irrigation, don’t be cheap with moisture. Apply water to get the seed to germinate and seedlings to establish. Available moisture on the surface is pretty much the key to seeding success.
Cover crop selection is also important and if you aerial seed you probably gain at least a month on growth compared to seeding if you wait until after harvest. For aerial seeding use firm, dense seeds like spring barley, oats, wheat cereal rye, turnips and radishes, which don’t require much depth of seeding and quickly absorb moisture and germinate. Avoid larger seeded species like peas or expensive cocktails. If you want covers to winter kill, avoid winter species like winter wheat, rye or barley.
As soybeans move into R5 and R6 or pod fill and corn is in R2 (blister) or R3 (milk), begin to watch the crop to anticipate when light will begin penetrating through the canopy and when you can pull the trigger on aerial seeding. And watch the forecast and try to have seed flown on a day or two before half- to one-inch rain.
Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at firstname.lastname@example.org or by leaving a comment below.