Beef cattle owners that are looking for supplemental forage options should consider summer annuals. June is the ideal time frame for planting a warm season summer annual crop. These forages thrive in summer heat, are drought tolerant, and can be used for either grazing or as a stored feed. Summer annuals include sorghum, sudangrass, sorghum x sudangrass hybrids, millet, teff, and corn. With adequate soil fertility and a minimum of moisture, these species are capable of producing three to five tons of dry matter over the summer months. Most of these species can provide two to three grazing passes or cuttings beginning 30 to 45 days after planting.
Plant summer annuals when the soil temperature is 60 to 65 degrees F. Plant forage sorghum at 12-15 pounds/ acre, millet, sudangrass and sorghum x sudangrass hybrids at 25 to 35 pounds/acre, teff grass at 4 to 5 pounds/acre and corn used as forage at about 80,000 kernels/acre and seeded with a grain drill. Soil pH should be in the 6.0 to 6.5 range, soil phosphorus should be at least 15 ppm and soil potassium in the 100 to 125 ppm range. All summer annuals respond to nitrogen and best yields will be obtained when 50 pounds of actual nitrogen/acre is applied before or at planting and then again following each cutting or grazing pass. Livestock owners that need to summer apply manure can utilize summer annuals for this purpose.
Summer annuals can be used as a double crop in situations where the previous crop is harvested by the end of June. Some examples include planting a summer annual after 1or 2 cuttings of alfalfa that needs to be rotated out of production, or perhaps after the harvest of barley.
In situations where the summer annual is going to be used for grazing, stagger plant the allotted acreage. Summer annuals grow fast and mature quickly. Forage quality is good at young vegetative growth stages but declines rapidly once the plant enters reproductive growth. A good strategy is to separate plantings by 14 days from the end of May through early July. Summer annuals best suited to grazing include millet, sudangrass and sorghum x sudangrass hybrids. The brown mid-rib (BMR) varieties of sudangrass and sorghum x sudangrass are recommended because they have superior digestibility compared to non-BMR varieties. Corn has also been used for grazing but only one grazing pass is possible since corn will not regrow.
Graze sudangrass and sorghum x sudangrass hybrids when plants are 18 to 30 inches tall. At this growth stage forage quality will be 17 to 19% crude protein, with a neutral detergent fiber (NFD) content of 58 to 60% and a net energy of lactation around 0.69 Mcal or a total digestible nutrient (TDN) content of 66 to 68%. Leave a 6 to 8 inch stubble to facilitate fast regrowth. Millet should be grazed beginning at 12 to 18 inches in height. Remove cattle to leave a 6 inch stubble. Millet forage quality will be equal to or slightly higher than sudangrass and sorghum x sudangrass hybrids when it is grazed in this fashion. Due to the rapid maturity of summer annuals, plan acreage based on what livestock can consume in about 10 days. If grazing was uneven and old stems remain, clip the stubble to a uniform 6 to 8 inches after the grazing pass.
All of the summer annual species can be mechanically harvested for stored feed. This is really the best option if forage sorghum or teff grass is planted. With the exception of teff grass, baleage and silage are the best harvest and storage options for summer annuals because they have a high moisture content and they are difficult to dry. Typically, forage sorghum, sorghum x sudangrass hybrids and sudangrass are harvested at 36 to 48 inches in height while millet and teff grass are harvested at the boot stage or approximately 36 inches in height.
One note of caution is that summer annual crops can accumulate nitrates in the lower portions of the stems under drought conditions. Reduce nitrogen fertilization and manage grazing to make sure livestock do not graze lower than 8 inches to reduce the risk of nitrate toxicity. In addition, sorghum, sorghum x sudangrass hybrids and sudangrass all have varying levels of potential for prussic acid poisoning if plants are consumed when they are under stress conditions.
Source: Rory Lewandowski, Extension Educator, Wayne County