Summer annual forages require planning

Producers who want to try their hand with summer annual forages should do some planning beforehand, according to a Texas Cooperative Extension agronomist.

“Summer annual forages can be a productive and profitable crop here on the Texas Plains,” said Calvin Trostle, Extension agronomist based at Lubbock. “But they require some planning. Fertility, irrigation, seeding rates, planting and harvest equipment, and harvest timing should be part of any production plan.

“Your choice of forages is also part of the equation. Conventional or brown midrib (BMR) hybrid sorghum sudans, hybrid pearl millet, forage sorghum, and photoperiod sensitive forages do well here. In our irrigated trials, these forages can produce more than 20 tons per acre on average.”

A soil test can help producers set a realistic yield-goal, based on available soil nutrients and their fertilizer strategy, he said.

“A 5 ton per acre dry weight yield will remove about 160 pounds of nitrogen, 30 pounds of phosphorus and 120 pounds of potassium from the soil,” Trostle said. “Pretty similar to an irrigated grain sorghum yield of 8,000 pounds per acre. So your baseline fertility plan should be close to what you would use for 8,000-pound grain sorghum.

“A good rule of thumb is to plan on applying 7 to 10 pounds of actual nitrogen per acre for each ton in your wet-weight yield-goal. Split applications of nitrogen are also a good idea.”

Dryland summer forage production is possible, though poor stands and drought can take their toll, Trostle said. Fortunately, irrigated forage sorghum, for example, typically requires 15 percent to 20 percent less water than corn silage, he added.

“Seeding rates for irrigated land are roughly one and one-half to two times higher than dryland seeding rates,” he said. “If you plan to graze it and cut it for hay or silage, you should plan to seed a little heavier than you would for dryland production.”

For example, a good drilled seeding rate for dryland sorghum-sudans is about 15 pounds per acre. A good rate for a similar irrigated field is about 25 pounds per acre. With hybrid pearl millet, a producer could seed dryland ground at 10 pounds per acre and irrigated land at 15 pounds per acre, the agronomist said.

Seed size can affect seeding rates, and may also affect a producer’s choice of planting equipment, he said.

“A higher planting rate is no guarantee of superior yields,” Trostle said. “Grain drills are adequate for planting, but a planter may be a better choice and can produce a better stand - particularly in dryland situations - if the drill is old and worn.

“If long-term grazing is part of your production plan, consider plugging the drill to attain a row spacing of 20 to 24 inches. This will give grazing livestock a path to walk between the rows. Without that path they can tromp a lot of plants and this can hurt regrowth.”

Choosing when to turn the cattle in to graze can also affect yields and performance, he said.

“It’s a good idea to let hybrid pearl millet get 18 to 20 inches tall, and sorghum-sudans about 24 inches tall, before you turn the cattle in for early grazing,” Trostle said. “You’ll want to wait a bit longer if you’re using photoperiod sensitive forages.

“You also need to leave adequate stubble for regrowth whether you are cutting it for hay or ensilage, or letting cattle do the harvest. For good regrowth, we recommend leaving 6-inch-high stubble with sorghum-sudans and 8-inch-high stubble with hybrid pearl millet.”

When to harvest should also be part of a production plan for summer annual forages.

“Forage quality and energy level declines with maturity,” Trostle said. “Use it when it’s young. If you want quality forage for grazing or hay, don’t let the forage head out even though it will cost you some tonnage.

“The decline in quality is rapid once a forage matures past the boot stage. On the other hand, optimum tonnage (yield) and quality for most forages grown for silage occurs in the soft dough stage. If you want quality, particularly for grazing or baling, you should harvest these forages prior to heading.”

Producers can access several Extension publications on summer annual forages - including variety trials, recommended production practices, and quality standards - online at: . Other publications keyed to forage production on are online at:

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