Consider your cover crop plan, before planting corn or beans!
As we near planting, most farmers are locking down their management decisions. One of the most important decisions to be made all year is choosing which hybrid or variety to use on each field (or part of the field). Many factors go into these important decisions (soil type, maturity, pest resistance, etc); however, very few farmers take their cover crop plan into consideration.
Few operations in the Midwest are using cover crops on 100% of their acres. Instead, farmers often prioritize fields that they feel would benefit most from cover crops, in order to maximize their ROI. Many experienced cover croppers know the value of planning ahead and keep in mind which fields will have covers in fall when selecting corn or soybean products.
One factor to consider for fields that will have cover crops is row crop maturity. Using shorter season hybrids or varieties allows an earlier planting window (especially important for crops like oats that will winter kill) to maximize cover crop growth and benefit. By using a 3.2 soybean instead of a 3.7 soybean, it is often possible to seed covers 10-14 days earlier. Seeding earlier allows more flexibility on which species can be used as many species including crimson clover, hairy vetch, peas, and radish, need 30-50 days to mature before a frost. Early season often results in more timely applications, as applicators are often less backlogged.
Many farmers are finding that cover crops are especially beneficial near the edges of fields. The outer few passes often have drainage issues from compaction, as well as more pest and weed concerns. Establishing a cover crop in the outer rows (either by having early harvested outer rows or using a high boy or airplane) can improve field harvestability through increased water holding capacity. Cover crops are also beneficial on fields that have grain storage bags, as they help to absorb water and allow activity sooner than fields without.
Another consideration for covers is herbicide management, as many covers can be very susceptible to herbicide injury. The use of residual herbicides has increased the last few years due to weed resistance. Residual herbicides persist from a few weeks up to several months in the soil, and may effect cover crop establishment. There are several factors that can lead to herbicide injury to the establishing cover crop, including the sensitivity of the cover crop being planted, rainfall amounts and timing, herbicide half-life, soil type, and application date and rate. Most herbicides do not have a specific section with restrictions for cover crops. Most will fall under the “other crops” category on a label and be subject to an 18-36 month plant back. There are usually specific instructions for hay or grazing restrictions. It is the applicator and grower’s responsibility to read and follow label directions.
For more information about herbicide - cover crop interactions check out the University of Wisconsin bulletin WCWS 201 describing rotation restrictions or the Iowa State University Integrated Crop Management newsletter that can be found at "https://crops.extension.iastate.edu/effect-residual-herbicides-cover-crop-establishment" that provides information on this topic also.