When selecting cover crops, it is important to (1) identify a goal, and (2) think about the current and next crop in rotation. This determines what you put in the mix, seeding rates and timing of seeding.
Basing mixes around goals, keeping it simple and adding as you get more experience is a good path to follow. The decision on what grass to include in the cover crop mix is important because it influences the residue you plant into in the spring. Here are some tips on grasses that can be included based on what we've been learning and seeing.
Cereal rye is a great tool to achieve the goals of erosion control, fall and spring moisture management and weed control. Cereal rye will establish in the fall and provide cover to control erosion in the winter and spring. It will also use moisture in the fall, but the main benefit is in the spring when it grows rapidly.
It is excellent for controlling early season weeds because of competition and allelopathy. We are also seeing some late season control through residue. Seeding rates vary between 20 to 70 pounds per acre depending on soil type, timing and application method. Rates increase the later you seed.
Because cereal rye will over-winter and grow again in the spring, using it before a small grain crop is not recommended. Cereal rye should be terminated 10-14 days in advance of planting corn. Most farmers are planting cereal rye before soybeans, then planting directly into the living cereal rye (aka planting green); however, this practice does not comply with Risk Management Agency guidelines.
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Oats can be used to control erosion and manage moisture in the fall. Oats are also known for being mycorrhizal, which means it forms fungal associations that assist with phosphorous uptake. Using oats provides decent cover to control erosion and uses moisture after a short season crop, but it will not over winter and does not produce a stiff residue. This makes it easy to plant into the following spring. Farmers using 30 to 40 pounds per acre have been happy with the results.
Use oats before a wheat crop to have the option to control any volunteer oats in the cash crop with herbicides. It could be used before corn or soybeans as well.
Barley is typically used as a cover crop on saline ground. It can be used as a full season, spring-seeded or fall-seeded cover crop, and used as an indicator of salts and mulch before planting alfalfa on salt-affected areas.
It can be planted as a spring cover crop before soybeans in Iron Deficiency Chlorosis-prone areas as a management tool (but you may just use cereal rye instead). Most farmers opt for a different grass in the fall-seeded mixes because barley will grow rapidly, can produce a head and as a result, leaves some pretty stiff residue. Rates are generally between 30 and 40 pounds per acre, but that varies.
For more information, visit NDSU.edu/soilhealth or follow me on Twitter (@NDSUsoilhealth).
