Warm Season annual crops are planted mainly for temporary pastures or hay crop. These forages are relatively fast growing, are high forage producers, and managed properly, make excellent quality forages and hay. Management of these varieties are more intense than for perennial grasses. If managed properly, these varieties will produce excellent yield and top quality hay. Problems associated with these forages are an accumulation of nitrates and prussic acid, which can be deadly for all classes of livestock. Millets, forage sorghums and other sorghum type plants should be fed to cattle and wildlife. Caution should be exercised when feeding any sorghum species to horses. For horses millets are the animals forage of choice.
Planting Management of Warm Season Annual Forages
One disadvantage of planting warm season annual forages is that a seedbed must be prepared on an annual basis, and the crop must be planted every year.
Forage management is similar to those of warm season grasses: grazing must be controlled. For hay production stubble height needs to be carefully monitored to ensure proper re-growth.
With most annual forages, planting should not begin until soil temperatures are above 65O- 70O F . Many sorghum type forages are very sensitive to low soil temperatures and initial growth will be slow and germination may be reduced if planted to early. When planting, plant at proper planting depths, depending on variety. Plant larger seed (sorghum type forages) at a depth of 1-1 ½” deep, and smaller seed (Millets) at ¾ to 1″. Most millets are daylight sensitive and should not be planted until there are twelve hours of day light. Make sure there is adequate moisture, good seed to soil contact and firm ground around seed by rolling or packing. If rain is in the forecast, rolling or packing may not be necessary.
Drill planting ensures adequate seed placement as well as good seed to soil contact. Therefore, lower planting rates can be used. When drill planting annual forages it is beneficial to have a smooth weed free and clod free seedbed. If the drill does not have packer wheels, follow behind planter with a roller or packer.
Broadcast seeding of annual forages is sometimes blended with fertilizer and is broadcast over the top of the prepared ground. Broadcast applications do not ensure uniform ground coverage or proper planting depth. It is important to use higher seeding rates when broadcast seeding to ensure proper stand establishment and uniformity. After broadcasting seed over soil surface, light discing or harrowing will assist in covering the seed with soil. Firm seedbed after planting with a roller.
Seed Bed Preparation
For adequate growth and establishment, a firm, clean weed free seedbed is required. Seedbed preparation includes disking, chiseling, harrowing and rolling to firm seed bed and conserve moisture. Fertilizer should be applied and incorporated during this period.
Seedbed preparation is recommended in the late winter or early spring (January- March). This will allow enough time to intercept several spring rains to ensure adequate moisture in the lower soil profile before planting. A light cultivation may be needed prior to planting to remove any weeds that may have germinated since initial seedbed preparation.
Fertilizing Warm Season Annual Forages
Annual crops such as Haygrazer (Sorghum X Sudan), Forage Sorghums, Millets, Hegari and other warm season forages require different fertilizer methods than warm season grasses, and must be managed quite differently.
When fertilizing these crops, fertilizer application should be split in two applications. The first application should be applied during seed bed preparation, before planting. The second application after first hay cutting or graze down. The application rates on these forage should be monitored according to environmental conditions, as well as intended use of the crop.
Apply all required Phosphate (P205), Potash (K2O) and 2/3 Nitrogen (N) before planting. Incorporate fertilizer in to 6-8 inches of topsoil. Because these are annual crops, growth rate is much faster than perennial crops; therefore the actively growing plants will utilize the added nitrogen quite readily. Apply remaining 1/3 required nitrogen after 1st cutting or graze down to stimulate re-growth. When applying a topdress application, it is always recommended that the application be made when rain is in the forecast, and conditions are favorable for good growth. Under drought conditions, or heavy rainfall periods, where flooding may persist, the second application of Nitrogen fertilization is not recommended.
For hay production, if a third cutting of hay is desired, an additional 1/3 rate of required Nitrogen may be applied if moisture is adequate. (Optional).
Weed control is limited because of the quick growth and height of forage. Best weed control programs begins with a weed free seedbed. Because the value and the production expense associated with the crops are relatively high, weed control should be kept to a minimum.
Many producers, especially those who drill plant on wide rows as indicated for grazing, may shallow cultivate, if desired.
Under most situations many producers may elect to apply a herbicide after plants reach 12-15 inches. However, care should be taken, because many sorghum varieties are very sensitive to commonly used herbicides in the early growth stages.
When planted at higher seeding rates and under favorable conditions many weeds will be shaded out by the tall erect forages.
Managing Warm Season Annual Forages for Grazing
Annual forages intended for grazing purposes should be row planted for total utilization. Plant at a lower seeding rate. Many producers find that planting in row widths of 14-24″ provide satisfactory forage production and seeding cost can be reduced by as much as 50%.
Planting in rows 14-24″ wide, allows the cattle a place to walk, reduces trampling and waste as seen with broadcast applications. The forage should be grazed when plants are 24-30″ high. Graze forage to an 8-10″ stubble height.
All annual forages should be controlled grazed to utilize high forage quality and production. If conditions such as drought or excessive rains persist, caution must be taken to avoid Nitrate and Prussic acid poisoning. If grazing is necessary, supply plenty of dry forage or hay, and limit access to the field for only several hours a day.
Managing Annual Forage Crops for Hay Production.
If the crop is intended for hay production, higher planting rates are recommended. High planting rates ensure higher plant populations, which in turn result in finer stem hay.
Most annual forages should be cut and baled before boot stage. At this stage, protein values are around 10-16%, has 65-70% digestibility and the plant has not had time to form a hard joint or node (this is dependent on the variety and species planted). When cut at this stage, regrowth will be greater and an additional cutting can be expected. Another advantage is that during this stage the plant has not begun dropping its lower leaves.