With poor profitability projections on most row-crop budgets, planting summer annual forages and using forage mixes for grazing should be considered on marginal acres. Adding a different crop to the rotation and a more diverse plant population on traditional row-crop acres can have cascading effects in a good way. Planting summer annuals can also be a good addition to your drought management plan.
For grazing and summer haying, the primary options for farmers are sorghums and millets. For sacrifice areas that are subject to high grazing pressure and where the goal may just be to keep the ground covered, consider crabgrass. Forage sorghums have increased in popularity as an alternative silage. Teff is a consideration for those wanting to produce a high-quality, finer-leafed forage that can be dry baled.
Sorghum-sudangrass can handle wide ranges of soil fertility and can be planted in lower soil temperatures (approximately 60ºF). Millets perform well on fertile soils and should be planted in soil temperatures of 65ºF degrees or above. Planting depth should be approximately 0.75 inch to 1 inch in depth.
In most cases, these summer annuals will be ready to graze six to eight weeks after planting. Start grazing when plants are approximately 24 inches tall. Grazing should stop when a third of the plant height remains or before grazing under 8 inches, whichever is greater. For haying, plants should be allowed to reach flag leaf stage. Mowing heights should leave adequate height for regrowth if more than one cutting is desired. Leaving 8 inches of stubble height, plants grow back more quickly.
Summer annuals require management and planning. Potential hazards to animal health include prussic acid poisoning, also referred to as cyanide poisoning, and nitrate toxicity. Pearl millet is the safer option when it comes to prussic acid poisoning. When grazing sorghums, prussic acid poisoning is a concern. Concern elevates when the plant is stressed. Frost is the most commonly discussed stressor, but even overgrazing, especially of immature plants, can cause elevated concern for prussic acid poisoning.
High nitrogen rates or excess manure fertilization can cause increased risk for elevated nitrate levels. It is recommended that plants be tested for nitrates prior to grazing and that grazing heights are managed to leave the bottom third of the plant or an 8-inch stubble height, whichever is greater.
To minimize risk of bloating, don’t turn out hungry cattle. Make sure cattle have had plenty of feed and water prior to turning into summer annuals. Monitor cattle behavior attentively for the first 48 hours after turnout. Do not allow cattle to overgraze, as this increases the risk of nitrate poisoning and reduces forage regrowth. Diluting the diet with other feeds while grazing is good risk management.
