In many areas of South Dakota, the pasture acres are in short supply. The fact that at least so far in the growing season precipitation is below normal adds to those concerns. If those trends continue, finding additional feed resources will become a high priority for cow/calf producers.
Annual forages are viable options to consider in addressing those needs. The two broad categories of annual forages are cool-season and warm-season forages. The key difference between the two is when they are ready for harvest. Harvest options include grazing, haying, or silage, depending on the crop.
Cool-season forages are typically small grains planted either alone or in combination with a cool season legume such as field peas. These are planted in early spring and will be ready for harvest by early summer. Because they avoid the peak of summer heat, the moisture requirements are not as high as some longer season crops. If moisture conditions improve, warm-season annuals could be planted for a double-crop.
Warm-season annuals perform best during the warmest part of the summer. These crops are typically planted in June or July. The most common warm-season annual planted in the Northern Plains are the hay millets, pearl millet, sudangrass and sorghum-sudan hybrids, and forage sorghums. Each of these crops has advantages and disadvantages, depending on the environmental conditions and the planned usage.
- Hay Millets: As the name implies, these crops are best suited to be harvested as hay rather than grazed or cut for silage. These plants have finest stems and cure the easiest compared to other summer annuals. Hay millet is most drought-tolerant and can produce forage in as little as 8 weeks after planting.
- Pearl Millet: Pearl millet offers more production potential than do the hay millets. Pearl millet has the ability to re-grow, making it a better option for grazing or for multiple cuttings at any growth stage. Pearl millet has coarser stems than hay millet, making curing for baled hay more challenging. Unlike sudangrass, sorghum-sudangrass and forage sorghum, pearl millet doesn’t accumulate prussic acid, which means that cattle wouldn’t have to be temporarily removed because of an early frost.
- Sudangrass and Sorghum-Sudangrass Hybrids: Because of the thicker stems for these crops, they are much better suited to be harvested as silage compared to hay. These also work well as supplemental summer grazing. Prussic acid can be a concern when grazed. The greatest risk for prussic acid poisoning occurs under drought conditions, when plants are damaged by frost, or when livestock graze short regrowth. To minimize risk defer grazing until sudangrass is 18 to 20 inches tall and sorghum-sudangrass hybrids reach 24 to 30 inches. Remove livestock for 5 to 6 days if these plants are damaged by a killing frost so that the plants can dry out and the prussic acid can dissipate.
- Forage Sorghum: This crop is the latest maturing and has the most production potential. Forage sorghum is best suited for silage production.
- As with all forages, maturity at harvest determines quality. Harvesting earlier results in higher quality forage. Delaying harvest tends to increase dry matter yield.
- Consider prior crop history. Herbicide use history, especially for products such as atrazine can affect stand establishment. Soil sampling and testing is also important to determine proper fertilizer application rates.
- Before planting an annual forage crop, consult with a crop insurance advisor to avoid jeopardizing coverage.
- Be cautious when applying high levels of nitrogen fertilizer to a planned forage crop. Small grains are notorious accumulators of nitrates and excessive nitrate levels could render the forage useless.