For years I have said that if the price of fertilizer doubled, there would not be enough cover crop seed in the world to meet demand. Unfortunately, that is exactly where we are today.
Cover crops and fertility
Cover crops perform four main functions with respect to soil fertility. The first is to retain nutrients in the soil, especially nitrogen, as it is an escape artist and can leave with the water, either by runoff or by leaching into the soil.
Second, legume cover crops can extract nitrogen from the air and store it in the soil for use by cash crops.
Third, they can extract nutrients deeper into the soil profile than the cash crop could accomplish and subsequently release those nutrients to the soil surface, making them available for the next crop. Deep rooted covers like radishes and annual ryegrass are some of the best examples.
Finally, cover crops can indirectly release nutrients that were not available, mainly due to the activation of biological life in the soil.
The perfect storm
Ironically, despite recent increased interest, seed for cover crops was already going to run out due to low yields due to excessive heat and limited humidity last summer in Oregon, where most seeds are grown.
Limited supply and increased demand will result in higher prices for cover crop seed, but will likely still favor the cover crop path at a cost per unit of fertility.
Can I plant a cover crop this spring?
Against the background of using cover crops to increase or compensate for purchased fertility, the options are limited for a spring cover planting.
A plausible idea is to plant peas as early as possible. Yes, I planted peas in January with good results. Adding a bushel or two of oats is beneficial in achieving some weed control.
To be effective, this strategy would be targeted on your last corn planting around the end of May. The peas can then provide up to 100 pounds of nitrogen.
Spreading manure on a growing cover crop is an ideal method of retaining applied nutrients in the field. Be careful not to smother the cover crop with heavy application.
The advantage of a live cover crop is that it will immediately take up available nitrogen and essentially store it until later. The timing of the release of these nutrients from the cover crop will be determined by maturity at the end.
Typically, cereal rye killed at the start-up stage or earlier will release most of its captured nitrogen during the summer.
If grain rye is controlled after the ear has emerged, most of the nitrogen will be blocked until it breaks down and likely not be available until the next cash crop is planted.
You should treat your cover crops like your cash crops. The benefit of cover crops is how you manage them, just like in cash crops.
Cover crop has gone from making fun of the local mad farmer who planted radishes as a cover crop to now featured in every print farm magazine. Farmers are being prepared like never before to use cover crops.
Those who just look at cover crops from an economic perspective now see the potential benefit in the ledger with nutrient assessment.
Closer to the coach
Talk to your cover crop seed supplier now and communicate your intentions for this fall.
In the spirit of treating your cover crops like your cash crops, you may now need to reserve your cover crop seeds months in advance in 2022 in order to get your preferred genetics.
The most frequently asked question over the past decade: “Do cover crops pay off? – can now have a clearer answer.