You may look at most small grains – oats, rye, wheat, triticale, barley, spelt – and think of either grain or forage. As it happens, small grains also make excellent cover crops. They are easy and economical to establish and grow, great at building soil, and helpful for uptaking excess nutrients. Get them in the ground on the early side in the fall (or spring, for oats, spring triticale, or spring barley) to get the most benefit. You don’t need a fancy mix or even a legume to reap many of the benefits that come with keeping soil covered. Diversity is a bonus, but usually not a necessity in basic cover cropping.
Small grain cover crops have more benefits than you think –
- They are cheap to plant. If you intend the crop only for cover crop use, you won’t need to use the full seeding rate typical of forage or even grain crops. Often at a third to half of the forage seeding rate (planted on time and managed correctly) many small grains tiller, fill out and provide excellent groundcover and root growth. This could be as little as $15-20/A in seed cost (Hint: the triticale market is very buyer-friendly this year).
- They’re easy to manage. The large seeds establish easily when planted at the right depth (1 inch is ideal), and grow quickly and tiller in the fall when planted on time.
- They’re easy to control. The threat of weediness is low if they are properly controlled in spring – whether with tillage, burndown, mowing, or even grazing.
- They are good at uptaking nutrients. Root masses penetrate downward and outward, scavenging nutrients from manure applications and leachate from the previous crop. They often make off-season manure applications possible.
- They are among the best sources of over-winter soil organic matter. Small grains are a better source of active carbon than legumes, which has many benefits for soil. Soil organic matter supports improved soil biological diversity, water infiltration, drainage, nutrient availability, and retention of water and nutrients.
- They can be a blank canvas on which to build a simple or complex mix. Small grains fit with almost any winter annual. However, the planting date needs to be adjusted to accommodate the other species. A brassica like radish or a legume like crimson clover or hairy vetch needs an earlier planting, usually at least 6-8 weeks prior to your frost date. Adjust the seeding rate as well. The small grain should be no more than 75% of full rate, and the smaller seeded companion can usually be 50% to full rate (it will often be slower growing, slower establishing, and need
a little more advantage against the small grain’s competition). Annual ryegrass also makes an excellent companion and works for planting into mid fall, but must be terminated properly. Annual ryegrass can persist unless plowed under or thoroughly sprayed. Each of these companions add digestible protein and energy to your small grain. At King’s, even our more complicated winter cover crop mixes are based on small grains, relying on triticale to anchor soil and shelter less cold-tolerant species. The small grains also provide bulk and substance if the mix is used for forage.
- They can be multi-purpose. Plant at a full rate, and the small grain stand can be grazed or harvested in fall or spring (provided there is enough time for a little regrowth before winter). Most small grains have high levels of fiber digestibility and protein if harvested before heading. Triticale is excellent in this regard. You’ll still get the benefits of ground cover, erosion control, some weed control, fertility retention, and more.
- They compensate for gaps. Small grains tiller and can even canopy in the fall if they are planted early enough (after about 6 inches of growth, however, you sacrifice some winter hardiness and risk matting and snow mold). Some small grains also close gaps by virtue of their specific growth tendencies. TriCal 815 Triticale, for example, has a more prostrate and spreading growth pattern that grows both out and up. The quick cool season growth outcompetes weeds, and small grains have the ability to keep growing even as temperatures dip (rye, the most winter-hardy grain, doesn’t go dormant until temperatures drop below 40 degrees F). Growth characteristics like these prove to be an advantage over weeds.
- They work hard right out of the gate. Small grains begin growth quickly, especially in early fall with late summer residual heat. Even a few weeks into their growth, soil infiltration is improved.
- They work with most rotations. Small grains are flexible. Most small grains can still be planted after corn silage harvest. In many cases, triticale and rye can still be planted after corn grain harvest. Oats can be planted in late summer and winterkill, in case soil needs to be ready to go first thing in the spring. And all small grains are valuable to break up a rotation with early or late season vegetables, anything from garlic to tomatoes to pumpkins, since they provide the break of grasses in a heavily broadleaf-based rotation.
- They buffer soil against extremes in temperature. Bare soil absorbs much more heat and cold than soil protected or insulated by crop residue or actively growing plants. This wreaks havoc on soil biology. Much of soil health depends on stewarding the life in your soil!
- There are few pests or diseases they host that will be a problem for the rotation as a whole – unless you have an exclusively small grain rotation (not advised).
What’s the exact contribution?
Small grains’ role in the nitrogen cycle is often debated. They uptake nitrogen as they grow, but how soon can it be made available to the next crops? Much of this depends on when the cover crop is terminated. More mature small grains take longer to decompose, and have a greater ratio of carbon to nitrogen, tying up the nitrogen for longer. Tying up nitrogen will impact yield unless you provide extra fertility. (Another way to offset this is to use a legume companion crop such as hairy vetch, crimson clover, or winter peas, helping to fix nitrogen and build the total amount of nitrogen in the soil.) Therefore, it’s better to err on the side of terminating the cover crop at an earlier stage of maturity. Incorporation will lead to faster decomposition and N mineralization than leaving the residue on the surface. Incorporating the crop before it reaches 18 inches tall is considered ideal, since lignin (carbon to nitrogen ratio) is increasing to structurally support a taller plant and grain head. If the crop is taken for forage, you’ll be less likely to run into this problem, since you will be leaving less material that will take much less time to break down.
In many situations, it’s better to sacrifice some cover crop yield and active organic matter contribution to preserve the yield potential of the following crop.
It’s difficult to quantify the nutrient contribution of the cover crop to your soil with all the possible variables left to account for – your existing soil fertility, your planting date, seeding rate, termination date, and all the possible rainfall, snowfall, and temperature conditions. We can say with confidence that an actively growing small grain cover crop greatly reduces nitrate leaching over the winter and therefore increases the nitrogen credits that will eventually be returned to the root growth zone of the soil. We also know that ultimately the total amount of nitrogen sequestered by the cover follows the total biomass produced (this goes for nitrogen fixation by legumes, as well) – so you fix or sequester more the longer you let it grow. The immediate effects on the next crop are unavoidable considerations, however, and there will usually be a trade-off in place.
If you are late in planting, increase the seeding rate, since you risk running out of good growing days fall to get the tillering that is ideal for winter survival and groundcover. Timely or slightly early planting is ideal, since it lets root and tiller growth get a head start.