Small grain cover crops considered
With this year’s late planting and abundant moisture, corn silage may come off later than usual.
Therefore, cover crops may be established later, limiting options to small grains. Fortunately, there are a variety of winter-hardy small grains out there; however, there is often not enough attention paid to selecting the right species and seeding them at the right rate.
When planning for small grain cover crops, I suggest letting the intended use determine the optimum species and rate.
First, assess your needs. Cereal rye, a cover crop widely adopted because of its ability to be seeded late and rapidly grow in the spring, can mature too quickly as I saw this spring, with many having difficulties planting into tall, thick cover that couldn’t be terminated in time.
To avoid this, you can plant winter wheat, which provides a more manageable cover that matures later than rye. In addition to becoming the go-to cover crop for small grain silage, the rye-wheat hybrid of triticale can also be easier to plant if you are unable to chop it.
Barley can reach the boot stage sooner than rye but with less biomass, making it a good alternative for those who want to plant into rolled cover earlier in the spring. A good strategy for spreading risk is to plant more than one species, making for a wider maturity window for silage harvest or planting green.
Next, know your seeds per pound as it can vary widely between varieties. For instance, cereal rye varies from under 12,000 to over 33,000 seeds per pound. Assuming a seeding rate of 1.5 million viable seeds per acre and germination of 85 percent, seeding rates would vary from 53 to 147 pounds per acre, giving little credibility to the two bushels per acre rule of thumb.
Cover crop use can also affect seeding rates. If chopping for silage, a rate of
1.5 million viable seeds per acre should optimize biomass production. However, if you are utilizing a cover crop for suppressing winter annuals such as marestail, the goal is to achieve 100 percent ground cover early, meaning that seeding rates should be increased as more plants will canopy faster than a thinly seeded stand.
Conversely, if soil health and controlling erosion is your objective, higher rates may not be necessary.
Many of the veteran no-tillers I know reduced rates to around 1 million viable seeds per acre, citing quicker drying of soil in the spring due to improved light penetration and airflow, a more manageable level of biomass when planting green and reduced costs.
A lower rate may also be appropriate if you’re applying manure, as fall nutrient applications will promote tillering of plants. In fact, nutrient application can have a greater effect on cover crop biomass than seeding rate, meaning that good forage stands and weed control can be achieved when reducing seeding rates on cover crops that receive manure, which is good news for those looking to reduce your cover crop costs.