Figure 1. Grass blend (left) and broadleaf blend (right) cover crop mixtures. Photo by Dr. Peter Sexton.
With small grain harvest wrapping up across the state, many growers are considering cover crop options. Mild to severe drought conditions across much of the state are causing many concerns including cover crop planting and establishment (SD Drought Monitor). Cover crops are planted for a variety of reasons across South Dakota but two of the most prominent purposes include long term soil health benefits and fall forage grazing opportunities.
Benefits and Risks
According to SARE, cover crops manage soil moisture, promote soil structure/increase soil fauna diversity, provide N for the following cash crop, enhance residue and nutrient cycling, increase organic matter, and suppress weed germination. Cover crops can offer many benefits to your overall production system, but as most farming practices do, the benefits come at a risk. Cover crops are merited with soil moisture management, but planting timing and specie selection are an essential part of accomplishing this, especially during a dry year.
Regardless of seed choice, some topsoil moisture is needed to enable germination of any crop. Smaller seeded cover crops shouldn’t be planted exceptionally deep, but generally require less moisture to germinate than larger seeds. Therefore, important selection factors include:
- Seed size
- Drought tolerance
- Intended purpose
If your intended 2017 cash crop is corn, a broadleaf cover crop mix should be considered; however, if you are planting soybean next year, grasses are ideal. With fall quickly approaching, a cool season blend may be more beneficial and provide more growth than warm season grasses.
Crops to Plant
Barley, wheat, and cereal rye are examples of some cool season, drought tolerant grasses; mustard and rapeseed are relatively drought tolerant cool season broadleaf crops, and field pea, vetch, and white clover may be good legume options- all appropriate for late dry July/August plantings when anticipating some improvement in topsoil moisture. For a full list of details see SARE- Cover Crops (Chart 3A).
Once plant establishment occurs, the soil is better protected from drying and erosion and the growing plants are conducive to a ‘living soil’ environment. In turn, water retention is often improved. However, remember that if moisture does not reach a planted seed, germination won’t occur, regardless of its drought tolerance abilities. The management lines are rarely black and white in production agriculture, and this decision is no exception, but proper research and decision making are key in making the best decision for your farm.