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Cover Crop Problems – Ohio Ag Net

By James Hoorman, Hoorman Soil Health Care

A week of good weather has helped most farmers get their crops planted. However, there are problems with fast-growing cover crops (e.g. cereal rye). Due to a warm winter and spring, most crops, including wheat, mature 2-3 weeks earlier. Crops planted in the fall all go out and grow big. How viable is the seed and how do you deal with those situations?

As for seed viability, cereal rye seed is viable 30 days after heading and flowering. Some of the grain rye has been on the market for two weeks, so it’s time to end it. Some rye are four to six feet tall, so shade becomes 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 flowering. Hairy vetch seed can last for 5 years in the ground (hard seed) and starts to ripen around July 10, which could be July 1 this year. For all cover crops, terminating cover crops once they are 10-20% flowering reduces the chance of reseeding. Some farmers may think they can save the cost of reseeding cover crops? Slugs and voles love the excess seed and it creates both a potential weed problem and a pest problem (slug and vole) for years to come!

Tall cover crops tend to shade the growing crop. Want to get it on the ground? Yes. First, the cover crop shades the plants so crops grow better once the residue is on the ground. Second, crop residues break down more quickly on the soil, making nutrients available in August or September. Soybeans absorb about 2/3 of the nutrients after flowering. Corn requires most of its nutrients (up to 60-75%) once corn pollination begins. Third, grain rye residue on the ground is allelopathic, meaning it suppresses weeds, with most of the chemicals in the stem and leaves. Fourth, the residue mulches the soil, which conserves soil moisture by lowering soil temperatures and also reduces soil erosion.

How do you then get the cover crop on the ground? Some farmers kill it early, but this year it was difficult with all the wet weather. If the cover crop is still alive, shrinkage can end the cover crop and also get it to the ground. In maize, shrink to V3 or V4 (3-4 true leaves) after emergence. Shrink in the same direction or parallel to the row. Do not shrink after V5 or V6 or the corn will die as the growing point emerges and the corn becomes brittle. With soybeans, do not shrink when the cotyledons or first leaves appear. In newly emerging soybeans, the plant dies as soon as the cotyledons are cut. Wait until at least the first set of trifoliate leaves emerge all the way to 4-4 inch tall soybeans before crimping them. If you don’t have a crimper, farmers can use a cultipacker or rolling basket, but these implements will not kill the cover crop and spraying will be necessary. If it is shrunk at the right stage, the cover crops will die off and you will save the cost of the spray.

Rolling or shrinking 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 shrunk or toppled, it is like bursting a balloon full of water, destroying the internal vascular system. Once they start to die, turgor pressure decreases, they turn yellow and become harder to knock down and hold. This may require two passes, in opposite directions (parallel) to the row, to level the cover crop. In general, farmers can roll in acres at 8-10 mph regardless of implement width (e.g., 15 feet-15 acre/hour, 30 feet-30 acre/hour, etc.).

If you get occasional rain, can you roll (cultipacker or rolling basket) or shrink cover crops? Cover crops have tons of roots per acre in the soil that cushion the soil. By moving quickly (13-16 km/h) 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 that you can easily penetrate the soil. As long as the mud doesn’t fly around or cause ruts, farmers can get cover crops on the ground fairly quickly without much problem. Most problems occur on bare ground. Raise the equipment at the ends to turn to prevent the ground from sticking out and leaving marks. Many local Ohio Soil & Water Conservation Districts (Putnam, Williams, Erie, Ashland, Muskingham) and Indiana (Allan County SWCD) have crimpers that are cheap to rent.

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