Considerations when Formulating Cover Crop Mixes

La Crosse Seed continues to witness an evolution in the cover crop industry, now that more growers are comfortable using cover crops. This time of year, we receive requests for many cover crop combinations.

While we encourage the use of our Soil First™ and Cover Crop Solutions™ branded mixes (these blends perform well across a wide range of environments) we understand the need for flexibility – growers have experience with different mixes and that confidence is important as acres grow across the country. In addition, NRCS & SWCD agencies continue promoting their own unique mixes. It makes sense to revisit basic principles to consider when formulating a custom cover crop mix:

  1. Goal: A well-defined goal may eliminate many unnecessary species that will alter the overall formulation. Concentrate on desired benefit/s and choose only those species that generate that service.
  2. Seed Size & Seeding Depth: Varying seed sizes alter how different species physically mix together and directly impacts seeding depth. Many species can tolerate some seed depth variability, but it’s easy to understand why some cover crop stands end up looking short a crop or two – usually due to seeds being buried too deep.
  3. Seeding Method: Much like factor #2, how seed is planted can greatly affect the final stand. Many drills and seeders offer flexibility for different seed sizes, but aerial, over-the-top, and broadcast applications don’t offer that luxury. If one species in a mix can’t tolerate less than ideal soil environments (where seed-to-soil contact is maximized), there’s a strong chance those will either not appear or will germinate much later than those that do.
  4. Time of Planting: We preach planting cover crops as early as possible in late summer or early fall – every growing degree day (GDD) matters. Don’t forget, it’s possible earlier plantings will ultimately look different than expectations when the formulation was first put together. For example, mixes containing brassicas should have a lighter ratio of those species when planted earlier in the seeding window vs. planting late. Brassicas respond to heat better than many other cool season crops, so decrease the ratio of these when the season allows for more growth. Increase those percentages late however, especially if small grains aren’t included that often help harbor smaller brassicas and legumes as they establish.
  5. Competition: Not all cover crops grow at the same speed or rate. For example, many brassicas grow faster than cool season legumes, and some clovers take much longer to establish than other legumes. It’s typical to see spring oats germinate in about half the time of cereal rye or winter wheat.
  6. Herbicide Interactions: The more complex the mix, the more at risk that combination could be for poor establishment due to herbicide carryover. Depending on the cash crop cycle and coinciding pesticide applications, it’s common to see germination issues or delays alter the final cover crop stand.

There may be some debate across the industry on the overall value of cover crop mixes vs. straight species plantings. Research shows many services from cover crops are equally achieved when planting a monoculture vs. a blend of many species. However,diversity is good for many things, including soil. It’s been proven that seeding multiple species create a healthier soil environment, where microbial advancements occur faster and beneficial organisms thrive. We suggest tempering the complexity of these mixes to a level where management and practical agronomy isn’t compromised.

Need help deciding which mix to plant? Check out our Soil First Cover Crop Mix Decision Tree here: http://bit.ly/2xF0Uvh