Normally we think about cover crops for fall planting, but there are also options to plant cover crops in March/April.
If you have winter wheat or barley in the field, you can frost-seed medium red clover as soon as the snow melts and the soil thaws. The practice has proven viable for many of our growers, despite the disadvantage of not having good seed-to-soil contact. Freezing-and-thawing cycles tend to create a honey-comb effect which helps seeds to get contact with the soil. The recommended seeding rate for this practice is 10 to 12 pounds per acre. Make sure the seed is inoculated with a true clover rhizobium inoculum, especially if no clover has been grown in this field for a while. Check the width and uniformity of distribution of your spreader so you get even coverage.
Another method of seeding is by mixing the red clover with fertilizer during top-dressing time. Remember to remove any screens in the spray lines, have constant agitation, and don’t let the seed sit in the fertilizer solution for more than a few hours. After the small grain harvest the red clover will be growing in the stubble.
Interference of red clover with grain harvest is not common because the red clover is typically not very tall by this time. The clover can be harvested in the fall (up to 2 tons of dry matter per acre) or just let it go until the following year. If red clover is purely grown as a cover crop it can be terminated before a high-nitrogen demanding crop such as corn. It is common for a good red clover stand to provide 80 to 100 pounds per acre of nitrogen fertilizer equivalent. In addition, we have found that the cover crop gives a rotational benefit above and beyond the nitrogen value resulting in a 15- to 20-bushel-per-acre corn yield boost. More information can be found in this Penn State Fact Sheet.
Another option for cover crop planting is using cool season cover crops before a summer planting of corn, sorghum or sudangrass. This would be a practice that can be used in fields that lay fallow after corn or soybean harvest. Species that come to mind are oats and field peas. Field peas include spring peas and Austrian winter peas — the seeding rate of spring field peas is higher due to bigger seed size, but its forage yield is typically higher as well.
Oats and field peas can be planted anytime when soil conditions are fit (preferably when the frost is out of the subsoil). You can even plant these if the surface of the soil is frosted in the early morning, allowing you to enter a rather moist field without causing compaction. Recommended seeding rates are 2 bushels of oats per acre (70 pounds) and 40 pounds per acre of Austrian winter peas or 80 pounds per acre of spring peas. Plant 1 to 2 inches deep. Inoculate the peas with pea/vetch rhizobium inoculum.
Both oats and peas will grow when soil temperatures are 40 F. The oats/pea mix can be harvested in early summer or terminated before summer crop planting. The oats utilize soil nitrogen that is liable to loss in the spring, while the peas fix atmospheric nitrogen.