Arkansas farmers will likely plant more grain sorghum in 2001. In the mid-1980's, Arkansas cultivated over 750,000 acres of grain sorghum. In the 1990's, grain sorghum acres declined to the present day level of 140,000.
Arkansas producers will not revert to the planting of the 80s, but production meeting requests and attendance indicate more interest in sorghum. For example, 12 grain sorghum production programs were delivered this winter. In the past 4 years, we would conduct 1 to 2 clinics per year.
Several reasons are cited for increased interest. Primarily, grain sorghum is considered a drought-tolerant crop. The past three years in the Mid-South have not been good years for non-irrigated soybeans, especially the full-season production system. Grain sorghum can tolerate dry conditions for short periods of time.
Typically, grain sorghum will have adequate soil moisture until early July. Arkansas is usually blessed with that July 4th mud rain. With adequate June and early July moisture, farmers will harvest sorghum yields of 5,000 to 7,000 pounds per acre.
Another reason for increased sorghum acres is nematode problems in cotton and soybean. Grain sorghum will significantly reduce nematode populations by being a non-host crop. Under irrigation, these productive cotton soils will produce sorghum yields ranging from 8,000 to 10,000 pounds per acre.
Weed control concerns have resulted in more interest in grain sorghum. Fields that contain sicklepod, pigweeds, morningglories, hemp sesbania, red rice and other troublesome weeds are easily controlled by atrazine. By utilizing the different mode of action, the Roundup Ready production system will be here longer. Waterhemp in Missouri and marestail in Maryland have been documented to be resistant to Roundup.
Other advantages of grain sorghum include spreading harvest periods and returning substantial crop residue to the soil to add organic matter.
Hybrid selection is a very important management decision. Farmers are encouraged to obtain the latest performance trial information representing their farm location and soil type. Asgrow A570, FFR 322, Pioneer 83G66, Southern States 800, Terral TV 1050 and Triumph TR82G hybrids have performed well in Arkansas.
Seed size varies greatly across hybrids. The number of seeds per pound will range from 12,000 to 18,000 seed per pound. Producers are encouraged to plant sorghum according to desired population instead of pounds per acre. We recommend 50,000 plants per acre on non-irrigated, low water holding capacity soils. For river and creek bottom soils with good water holding capacity, the recommended plant population would be 60,000 plants per acre. With available irrigation, final plant populations of 75,000 per acre are recommended.
On average, 75 percent of the planted sorghum seed survive and develop into a plant The above listed population should be multiplied by 1.25 to determine the number of seed per acre to plant. For example, a desired stand of 60,000 sorghum plants per acre would require the planting of 75,000 seed per acre.
Jeremy Ross, Corn and Grain Sorghum Verification Coordinator, has developed a seeding rate guide for both corn and grain sorghum according to row spacing and desired plant population. These tables are available at the U of A Cooperative Extension offices or can be obtained from: [email protected]
Row spacing of 30 inches is the most popular. Vacuum planters provide the best seed metering. Some producers utilize grain drills. Grain drills are very challenging to meter at 7.5 inch spacing and many producers duct tape every other cup resulting in 15 inch row spacing.
Gaucho-treated seed provide control of aphids, especially greenbugs. Where fire ants occur, Gaucho is essential in protecting the seed from these harmful insects.
Grain sorghum planting should be based on soil temperature. Sorghum seed are small and will rot easily if not planted under the proper conditions. Soil temperature of 65 degrees F by 9 a.m. at 2 inches of depth is needed for seed germination and emergence. The seed should be planted from 1 to 1 _ inches deep. Proper root development will not occur under shallow planted conditions.
Seed should be purchased that are Concep or Screen-treated to allow the use of grass herbicides. Most fields contain enough broadleaf signal grass that Dual, Frontier or Lasso should be applied pre-emerge. Many package mixes of these herbicides containing atrazine are more economical. Atrazine applied at a rate of 1 to 1.25 quarts/acre of 4 pounds material prior to 12 inches grain sorghum provides season long control of weeds. Refer to the University of Arkansas Weed Control Guide (MP44) for additional details.
Note: Fields containing heavy Johnsongrass pressure should not be planted to grain sorghum since herbicides are not available. Accent, Beacon and Basis Gold will kill grain sorghum Grain sorghum requires good fertility management for high yields. Soil pH should range from 5.7 to 7.0. Soil tests are essential for supplying proper phosphorus and potassium levels.
Potassium is one of the most important elements since K is responsible for regulating plant/water relationships. Optimum potassium levels allow the plant proper water levels in leaf tissue. Without adequate K, the plant will become moisture-stressed leading to charcoal rot. Charcoal rot is one of the most mostly costly diseases in grain sorghum. The pathogen infects the stalk just above the ground level causing weak stalks, thus more lodging potential. Few hybrids are resistant to charcoal rot.
Nitrogen is the other big player when it comes to grain sorghum production. Estimate yield levels when calculating nitrogen recommendations. We recommend applying one-third of the total nitrogen at planting. A rule of thumb on nitrogen requirements for grain sorghum is two pounds of N for each 100 pounds of grain.
Example: A 5,000-pound per acre yield would require 100 total pounds of nitrogen; 33 pounds of N applied preplant and 67 pounds of N when the sorghum is knee-high. Irrigated grain sorghum with yield potential of 8,000 pounds per acre would require 60 pounds per acre N preplant and 100 pounds of N side-dressed at the knee-high stage.
In general, apply the side-dressed application three weeks after stand establishment. Typically, grain sorghum yield will be set by the time the plant is 35 days old, thus proper N timing is essential in setting high yields.
Grain sorghum responds well to irrigation. The crop requires 20 inches of water for maximum yield. From emergence to boot, the crop requires 10 inches of water. From booting to grain formation, the plant will need an additional 10 inches of water. The University of Arkansas has developed a computer-based irrigation scheduling program for grain sorghum. Please contact a local county agent for additional details.
You should check with grain elevators concerning delivery of grain sorghum. Grain sorghum is one of the most difficult grains to separate in a combine. Proper separation adjustments and fine-tuning are essential to avoid harvest loss. Producers are encouraged to contract county Extension agents, consultants and ag dealers about production questions. We hope our educational programs this winter will help farmers who decide to grow an alternative crop that is profitable and good for the rotation.
William Johnson Jr. is an Extension agronomist — wheat and feed grains with the University of Arkansas. e-mail: [email protected]