Although forage sorghum is a warm-season annual, now is the time to think about options for planting and buying this summer’s seed. Consider forage sorghum for excessively well-drained shaley, sandy or slate soils, where it can be a more economical choice than corn. When moisture stress is severe, it has the unique ability to go dormant until the stress is relieved.
If you are trying forage sorghum for the first time, it is an excellent alternative forage to try and a way to diversify your rotation and your TMR, but there are a few critical planting and equipment details that have to be followed. Start small – perhaps enough to fill an Ag Bag, then increase acreage as you begin to get a feel for it. King’s Agronomist Tracy Neff recommends that you start with a dwarf variety (shorter with higher leaf-to-stem ratio) if you are new to sorghum. Dwarf sorghum is a little more forgiving – less prone to lodging in high populations, and fills out low populations with abundant tillers.
The gene 6 Brown Midrib (BMR) trait, found in most Alta Seeds sorghums we carry, also boasts more digestible fiber and less lignin, which gives it superior palatability. Before BMR genes, farmers often planted sorghum at higher rates to achieve a thinner (more digestible) stem. This was both more expensive and led to lodging, making harvest more difficult. BMR plants are already more digestible, so they don’t have to be planted like this to manipulate the stem size (and you don’t have to sacrifice standability).
Forage sorghum can provide an almost complete ration for animals with lower energy requirements, like dry cows or heifers, or in beef operations to feed stockers. In high-producing herds (80 + lbs of milk), it should be used as a complement to corn silage in the diet, allowing you to stretch your corn silage inventory. If you decide to do this, work with your nutritionist in replacing a few pounds of corn silage at a time, then gradually increase forage sorghum while monitoring productivity.
Moving further south, sorghum shows an increasing advantage over corn, thriving in hotter temperatures, drier conditions and shallow or poor soils. (Southern soils often dry out more quickly as well since organic matter deteriorates more rapidly.) The per-acre cost of growing it is economical (usually about $400/acre, including seed and other inputs), and it does well in areas with deer pressure (deer tend to leave it alone since it has no ear). This is not to say it should replace corn; it simply provides an alternative with unique advantages in some conditions.
It’s best to use a properly calibrated planter with sorghum cups. Plant in 30-inch rows if you are harvesting with a traditional row harvester or Kemper head. A Kemper head is also suitable for 15-inch rows. If you have never planted sorghum, check with the manufacturer of your planter to make sure you get the proper meter box and cups and plates. We highly recommend using a planter instead of a drill with some holes taped off, as this does not adequately control the spacing of seeds.
Forage sorghum yields can range from 15 to 25 tons/acre. For a good stand, make sure to plant deep enough and delay planting until soil temperatures are 60°F and rising for good germination. Target a seeding depth of 1 to 2” deep, placing the seed in adequate moisture for emergence. If the seed is planted too shallow, you run the risk of the soil drying out after the seed has absorbed moisture, which means it could swell up and dry out before it has a chance to emerge. After emergence, though, sorghum is usually quite drought-tolerant.
In most Mid-Atlantic states, yield can be maximized with a mid-May to early June planting. In Southeastern PA and to the north, plant around early June. Aim for 80,000-100,000 seeds per acre seeding rate, depending on the hybrid selected. In other words, for most types of forage sorghum that you will harvest at soft dough stage, the seed should be planted in 30-inch rows with 2-3 inches between plants, or 15-inch rows at 4-6 inches between plants.
You can often get away with planting into soils with surface dryness, but there is some controversy over planting into soil that is surface-dry enough that weight is needed. Do not plant into soil that has no moisture in the top two inches. Some types of soil are prone to crusting, though. In this case, weight will be needed to penetrate the crust even though there may be plenty of moisture at 1”. You will want to check in all cases that the seed is getting into the soil and that there is adequate moisture at the depth it is being planted to. Use your discretion about using extra weight to accomplish this, although it is usually advisable to wait until there is enough moisture.
Soil testing is critical, since sorghum removes large quantities of nutrients. Pests, though, are not much of a problem. Sorghum plants produce a substance that is toxic to corn rootworm larvae, so planting it in a corn rotation would break the rootworm cycle.
When harvesting sorghum for silage, remember that it will be wetter than corn silage – about 70-75 percent moisture. Letting the crop dry to a lower moisture is not recommended, as the grain will become hard and pass right through the cow. Because of its higher moisture, it’s best stored horizontally, in bags or bunks.
We always get questions about which herbicides are acceptable to use with sorghum. Remember that you need to consider not only the half-life of the herbicide you choose, but also the sensitivity of the following crop.
Our sorghum seed is sold both untreated (UT) and Concep (C) treated. UT sorghums can grown organically and cultivated like corn, or grown with atrazine, the easiest herbicide to use. With C treated sorghum, we often recommend a combination of Dual and atrazine (brand name Bicep). Combining atrazine with another herbicide helps cut heavy application and protect water quality – and it targets both grasses and broadleaf weeds.
You can also post-treat with other herbicides like2,4-D or dicamba for escaped broadleaves, just as with corn. Avoid planting sorghum into fields with johnsongrass; sorghum cannot tolerate any of the herbicides that are used to control johnsongrass.
There are many benefits of a forage sorghum crop, but keep in mind the planting depth, seeding rates, harvesting, weed control, and nutrition considerations that are critical to success and unique to a sorghum crop.
We encourage you to contact us if you would like more detail or have any questions.