Snow and moisture is welcome news for sorghum producers.
Agronomists said having a game plan with quality seed and good stewardship practices makes a difference.
Brian Arnall, state Extension specialist with Oklahoma State University, said producers should start with good soil fertility and that begins with a soil sample.
“Don’t assume you need or don’t need nutrients, both assumptions, if wrong, can lead to economic issues,” Arnall said.
Ideally soil pH is between 6.0 and 7.2 and while it maybe late to fix soil acidity and a producer cannot economically correct high pH, he can manage both, Arnall said. If his pH is below 6.0, adding at least 15 pounds of P205 an in-furrow phosphorus, DAP (18-46-0) or APP (10-34-0) preferably, are options. If he does not have in-furrow capability then 30 pounds of broadcast phosphorous can be applied.
For calcareous soils, phosphorus is crucial, but in extremely high pH levels (7.6 and above) iron deficiency can be troublesome and the best method for iron application is at planting time, Arnall said.
While nitrogen is critical for maximum yield production, work at Oklahoma State shows preplant nitrogen for sorghum does not provide the best results, Arnall said.
“Years of research is showing that putting nitrogen on 30 to 45 days after planting is resulting in significantly better yields than preplant,” Arnall said.
Waiting a couple of weeks after planting allows a producer to make sure he has a good stand and gives him more time to see how the season’s rainfall is panning out.
“If you have the option or capability of applying nitrogen in-season, give the crop a week or two before putting out the nitrogen,” Arnall said.
Seeding rate
“Seeding rates in western Kansas can vary a lot with a precipitation zone from 30,000 to 65,000 (seeds per acre) within those areas,” said Logan Simon, assistant professor and Southwest area agronomist at Kansas State University’s Extension Center in Garden City. “We can go much higher with irrigation depending on (water) well capacity.
Sorghum is a plant that tillers (multiple stems from the same plant) though with a strong ability to hit higher yields even with lower seeding rates, if the growing season is right, he said.
“Higher seeding rates may reduce tillering, but might reduce lodging risks too,” Simon said.
A narrower row spacing (15 inches instead of 30 inches) may help to close the canopy sooner and potentially capture greater yields in yield environments of 70 bushels per acre or more, Simon said.
Planting date, seeding rate and hybrid selection are tied together, he said. Sorghum will tiller more readily in cool temperatures and less under warm conditions. As a result, later plantings in warmer weather should be on the high side of the recommended range of seeding rates for each environment since there will be less tillering.
“Make sure that your planting date aligns with your hybrid maturity to ensure enough heat units will be available to get that hybrid to maturity before frost,” the agronomist said.
However, the selection of sorghum hybrids should be based not only on maturity, Simon said, but also on other traits such as resistance to pests, stalk strength, head exertion, seeding vigor, and overall performance.
While winter has provided some good moisture in some areas, Simon said producers who have been difficult drought situation will need to take note in their planning.
Under more difficult drought scenarios, producers should be most mindful of soil moisture in the seed zone at planting, he said. Optimum seed placement for sorghum is about 1 to 2 inches deep.
Shallower or deeper planting depths can affect the time between planting and emergence, affecting early-season plant uniformity, Simon added. Seeding depth should be considered to ensure that seeds are placed into adequate moisture for germination.
“Care should be taken to avoid placement of seed at the interface of wet and dry soil where seeds may have enough moisture to begin germination, but not complete it, resulting in short and non-uniform stands,” Simon said.
Drought stress
Often after extended droughts soil nitrogen levels are elevated and less fertilizer is needed, Arnall said.
“It is tough to determine in-season what is happening with the nitrogen cycle, which is why I recommend that N-Rich strips or zero N blocks,” he said. “These reference strips let the crop tell you how much nitrogen is naturally providing.
He suggested growers visit https://osunpk.com/2023/01/12/jan-2023-edition-of-wheat-n-management/.
Challenges
Kansas sorghum producers should always be mindful of stalk rot, Simon said. Stalk rot is a stress-related disease. Any stress on a crop can increase both the incidence and severity of the disease.
“No hybrid has complete immunity to the stalk rotting pathogens,” Simon said. “When choosing a hybrid, a grower should select a hybrid that is not only a high yielder, but one that has good standability and ‘stay-green’ characteristics. This will help assure that if stalk rot does occur, losses due to lodging will be minimal.”
Arnall’s expertise is in soils, but he noted that insects are a growing concern and management of them tends to be reactive and less preventative.
“The biggest suggestion is regular scouting,” Arnall said. “Looking beyond the leaf surface, looking at the whole plant around the stem at the soil (ground level). Early mornings and evenings are better for finding insects like chinch bugs.”
Weed pressure
Agronomists want producers to start clean with grain sorghum because there is not an in-season option for problematic weeds like Palmer amaranth, Simon said.
“An effective burndown prior to planting is essential if any weeds have emerged,” Simon said.
Postemergence options for grass control in sorghum are limited, Simon said. Inzen and igrowth sorghum hybrids are two herbicide-resistance traits that allow the use of specific ALS-inhibiting (Group 2) herbicides in grain sorghum, he said. Inzen hybrids allow postemergence application of Zest (nicosulfuron), which is effective on some key grass species, and igrowth hybrids allow the either pre-emergence or postemergence application of IMIFLEX (imazamox), which will control some key grass and broadleaf weeds, Simon said.
DoubleTeam grain sorghum hybrids allow postemergence application of the herbicide FirstAct (quizalofop, Group 1), the Southwest Kansas agronomist said. FirstAct will control many grass species, but, similar to Zest and IMIFLEX, FirstAct is not labeled for control of johnsongrass or shattercane.
There are new varieties that provide over-the-top herbicide options, Arnall said, and use them with known weed problems.
“Make sure you have a plan for herbicide availability and timely application,” Arnall said.
Dave Bergmeier can be reached at 620-227-1822 or dbergmeier@hpj.com.
