Sorghum and its many variations are now appearing in fields across the United States with virtually no latitude or longitude limitations when hybrids are properly selected. Their ability to tolerate drought, generate substantial biomass and produce high quality forage makes sorghum species a valuable option in the forage toolbox.
In a recent Forage Forum webinar offered by Purdue University Extension, postdoctoral researcher Shelby Gruss discussed the flexibility of sorghum as silage, hay, and pasture.
For forage producers, the most widely used types of sorghum include single-cut, high-yielding forage sorghum hybrids and multi-cut sudangrass and sorghum-sorghum hybrids.
Forage sorghums are almost always harvested as silage, while moss sorghum and southern grass can be used as silage, green grass, hay, or for grazing. In much of the United States, making dry hay from sorghum species is difficult because the stalks are difficult to dry.
Gruss noted that none of the harvest method options should occur until the plants are at least 18 to 24 inches tall to avoid prussic acid issues. She also said green ground sorghum should be fed on the same day to avoid nitrite buildup in the feed.
When planning the incorporation of sorghum species into a crop rotation, it is essential to wait until the soil temperature reaches at least 60°F before planting. “Sorghum thrives in high temperatures and will continue to grow at temperatures up to 100°F, while corn will stop growing at around 85°F,” Gruss said. “Sorghum also requires less fertilizer and water than maize.”
It starts with dhurrin
“Although sorghums have many benefits, there are also concerns about cultivation,” Gruss said. “These are prussic acid poisonings and high nitrates, although the latter can also be a problem in many other types of forage crops.”
The researcher noted that a compound called dhurrin is the precursor to the formation of prussic acid (hydrocyanic acid) and is most prevalent in young plants or the tillers and leaf tissues of plants that are stressed in some way. or another, such as frost or drought. Like nitrates, dhurrin levels can also increase when a crop is over-fertilized with nitrogen.
To avoid prussic acid issues, Gruss suggested not harvesting or grazing plants under 2 feet tall, not harvesting plants under water stress, and waiting at least a week before harvesting plants. frosty plants. She also noted that growers can choose sorghum hybrids that have been bred for their low dhurrin content. For sorghums harvested as silage, fermentation will help reduce prussic acid levels.
One of the benefits for growers of sorghum species is that there are a plethora of traits available to suit an operation’s needs and growing plans. Those currently available are listed below, and some hybrids possess more than one of these traits:
- Sugar cane aphid tolerance
- Brown midrib
- Photoperiod Sensitivity
- Dry stem
- High leaf to stem ratio
- brachytic dwarf
- Herbicide resistance (non-transgenic)
Gruss pointed out that hybrids without dhurrin or without prussic acid will soon be on the market; these come from some of his research at Purdue. Dhurrin-free hybrids should be available within the next two to three years and have proven to be highly preferred by grazing cattle.
Additionally, during Purdue research, Gruss said he found that dhurrin content or potential for prussic acid poisoning was not reduced during the wilting period of sorghum forage after being cut. This means that prussic acid poisoning is always a risk for dry hay. This finding contrasts with previous reports.
In conclusion, Gruss said it’s important for growers to consider their growing and feeding goals to determine which traits will work best for their farms. For example, a photoperiod-sensitive hybrid can be a problem for silage harvesting because it will never reproduce in northern latitudes. As a result, it remains moist and requires freezing before drying. On the other hand, these types can be beneficial in a grazing situation.
To see Gruss’ presentation in its entirety, Click here.