Cover Crop Issues

Cover Crop Issues

A week of good weather has helped most farmers get crops planted. However, there are issues dealing with fast-growing cover crops (e.g., cereal rye). Due to a warm winter and spring, most crops, including wheat, are 2-3 weeks ahead in maturity. Fall-planted crops are all headed out and getting tall. How viable is the seed, and how do you manage those situations?

On seed viability, cereal rye seed is viable 30 days after heading and flowering. Some cereal rye has been headed out for 2 weeks, so it’s time to get it terminated. Some rye is 4 to 6 feet tall, so shading is becoming another issue to consider. Balansa clover seed can remain viable in the soil for 3 years and reseed itself. Balansa and Crimson clover seed is viable 30 days after blooming. Hairy vetch seed can remain viable for 5 years in the soil (hard seed) and starts to mature around July 10, which may be July 1st this year. For all cover crops, terminating cover crops once they are 10-20% blooming reduces the chance of reseeding. Some farmers might think they can save the cost of reseeding cover crops. Slugs and voles love the excess seed, creating both a potential weed problem and a pest (slug and vole) problem for many years!

Tall cover crops tend to shade the growing crop. Do you want to get it on the ground? Yes. First, the cover crop shades plants so crops grow better once the residue is on the ground. Second, crop residue breaks down faster on the ground, making nutrients crop-available in August or September. Soybeans take up about 2/3 of their nutrients after blooming. For corn, most nutrients (up to 60-75%) are needed once corn pollination starts. Third, cereal rye residue on the ground is allelopathic, meaning it suppresses weeds, with most of the chemical in the stem and leaves. Fourth, the residue mulches the soil, conserving soil moisture by reducing soil temperatures and also reducing soil erosion.

Next, how do you get the cover crop on the ground? Some farmers kill it early, but this year that was difficult with all the wet weather. If the cover crop is still alive, crimping can terminate the cover crop and also get it on the ground. On corn, crimp after emergence up to V3 or V4 (3-4 true leaves). Crimp in the same direction or parallel to the row. Do not crimp after V5 or V6, or the corn will die once the growing point emerges, and the corn gets too brittle. On soybeans, do not crimp when the cotyledons or first leaves emerge. On newly emerging soybeans, once the cotyledons are clipped off, the plant dies. Wait until at least the first set of trifoliate leaves emerge, all the way up to 4-5 inches tall soybeans before crimping. If you do not have a crimper, farmers can use a cultipacker or a rolling basket, but these implements do not kill the cover crop, and spraying will be required. If crimped at the right stage, cover crops will die, and you save the cost of the spray.

Rolling or crimping cover crops after they have been sprayed is more difficult. When cover crops, especially cereal rye, are actively growing, they are at full turgor pressure. When they are crimped or knocked down, it’s like busting a balloon full of water, destroying the internal vascular system. Once they start to die, the turgor pressure goes down, they turn yellow, and they are harder to knock down and keep down. This may require two passes in opposite directions (parallel) to the row to get the cover crop flat. Generally, at 8-10 mph, farmers can roll in acres whatever the width of the implement (e.g., 15 foot-15 acre/hr, 30 feet-30 acre/hr, etc.).

If you are getting intermittent rains, can you roll (cultipacker or rolling basket) or crimp cover crops? Cover crops have tons of roots per acre in the soil that cushion the soil. By moving fast (8-10 mph), you can cover the ground quickly with little soil damage. All the residue and roots keep the soil from compacting. The roots promote good soil structure, so you can get across the soil. As long as the mud is not flying or you are creating ruts, farmers can get cover crops on the ground fairly quickly without many problems. Most problems occur on the bare soil. Raise the equipment on the ends to turn to prevent soil gouging and ruts. Many local Ohio Soil & Water Conservation Districts (Putnam, Williams, Erie, Ashland, Muskingum) and Indiana (Allen County SWCD) have crimpers to rent cheaply.