DYERSVILLE, Iowa – The key to a good stand of cover crops is early seeding and timely rain shortly thereafter. That’s according to Growmark Western Region Agronomy Business Director Nate Pierce, who observes that in many cases, cover crops can become a weed if they don’t germinate until the spring. Pierce talked to Iowa Agribusiness Radio Network reporter Ken Root about how cover crops performed through this unusual and persistently cold winter.
Some key takeaways:
– Pierce says cover crops can work well to limit soil erosion, and if seeded timely, can do well to capture nutrients like phosphorus and nitrogen that might otheriwse leave the farm.
– This winter, seeding time proved to be important: early seeding and rain created good stands that fixed nutrients in or near the root zone, and kept soil in place. Later seeding, or a lack of rainfall, resulted in cover crops which are only now germinating and have essentially become weeds.
– The seed industry has geared up to meet fall cover crop seed demand, but currently, this fall’s inventory of seed is mostly in the field. Pierce says that makes the cover crop industry susceptible to production losses, such as drought or excessive moisture.
– Pierce says the cover crop which Growmark sees headed to the most acres is cereal rye. It’s easy to establish, sow, and terminate. Its root system is particularly fibrous, which makes it great not just for holding the soil together, but also for capturing nutrients and keeping them in the root zone.
– Terminating cover crops is a new challenge not just for growers, but for custom applicators and retailers too, according to Pierce. When the stand is small, he says a simple application of glyphosate and 2, 4-D at appropriate rates will do the trick, but when growers are attempting to apply pre-emergent herbicides or liquid fertilizer simultaneously, he says the presence of cover crops obstructs herbicide. He suggests a separate burndown for cover crops, otherwise producers could be stuck with cover crops acting as a weed all summer long.
– Tillage may seem counterproductive at first blush, but Pierce says it doesn’t need to be. Winter peas or a legume will fix nitrogen; tilling those cover crops into the ground will put the nitrogen into the soil in the root zone. With rye and tillage radishes, Pierce says tilling them under produces escapes, which can then flourish in the same capacity as weeds. He suggests a burndown, or a pass with a cultivator, to get rid of them.
– Radishes need to be seeded early for early establishment and development of a deep taproot. The goal of a tillage radish is to break up the soil, but Pierce points out that the hole made by a decaying radish can go as deep as two feet. Subsequent application of fertilizer or manure can follow the channel made by the radish directly out of the root zone, and possibly into a tile line. Pierce also points out that when radishes are killed in the fall, they emit a penetrating and unpleasant odor, making them poor candidates for planting in fields near homes.