That grain sorghum is a great cropping option in water-short areas is a given. But there are strategies to maximize grain sorghum yield without breaking the bank, according to speakers at Sorghum U.
Scott Staggenborg, director of technical services for Chromatin, Inc.; Brian Arnall, precision nutrient management specialist at Oklahoma State University; Kent Martin, a northwest Oklahoma farmer who operates Martin Agronomic and Environmental Consulting; and Jason Warren, OSU soil and water conservation specialist, addressed producers.
Staggenborg recalled the words of retired Kansas State University agronomy professor Stan Ehler, who said, “Ninety percent of what you do for a crop is done when you park the planter.”
“When you just finish planting a crop and pull out of a field, you’ve already made a lot of decisions to set the crop up,” Staggenborg said. Prior to planting, most farmers have decided when and how fertilizer will be applied. “And for the most part your herbicide decisions have been made, especially if you are applying a pre-emerge product,” he added.
Planting rates and seed treatment choices are other issues, with decisions in fungicide, seed safener, insecticide or naked (in the case of organic seed) to be made. While everyone has an ideal planting date, Staggenborg said Mother Nature usually has the final say.
“We all have ideals we want to use, but then there is what we end up doing,” Staggenborg said. “Between weather, breakdowns and everything else that happens on the farm.”
Seed number per acre drives yields but watch for having a planting rate that allow optimum head size without compromising standability.
“Big heads look nice, but I worry about standability. So I’ll tell you to plant more than you typically think about,” Staggenborg said. “Higher yields also come from longer maturing hybrids.”
Soil fertility is a process
It’s easy to get caught up in fancy products and technology, but Arnall said to not forget about the simple things like pH and phosphorus levels.
“All of the technologies in the world as far as fertility goes—crop models, climate, variable rate, gird soil sampling won’t matter if you have a pH of 4.7 that you don’t lime,” Arnall said.
Arnall uses a concept he calls “stepladder of progression” which describes his thought processes of fertility problems farmers face large to small.
All agronomy is based upon pH, he added. Crop growth, herbicide efficiency, nutrient efficiency and atrazine falls apart in acidic pH but will go crazy at high pH. So monitor it closely, and manage accordingly.
“Low pH is killing you on phosphorus. High pH you have to start thinking about your micronutrients to put in zinc, manganese, iron and things like that in with your starter, so need to really deal with that,” Warren said.
The second rung of the ladder, phosphorous and potassium can maximize yield, when managed properly.
And nitrogen and sulfur—the third and fourth rungs—are more challenging due to their mobility.
Sulfur and nitrogen are a lot alike because for “every X pounds of nitrogen, you need so many pounds of sulfur.”
“Fifteen pounds of nitrogen, 1 pound of sulfur, somewhere in that range for sorghum is a pretty good number,” Arnall said.
Secondary and micronutrients in sorghum production are not a big key until soil pH is squared away
“That stuff you can worry about once your pH is good,” he said.
Warren noted that grain sorghum is simply a more efficient user of water than corn. In 10 years of research in the Oklahoma Panhandle, the highest yielding corn hybrids neared 240 bushels, with average across all hybrids reaching about 200. Sorghum, on the other hand ranged from 160 to 140 bushels per acre. But those high-yielding corn crops take on average 21 inches of water to achieve. Sorghum is 8 inches on average.
Warren said the reasons for switching from corn to grain sorghum in Oklahoma have to be economic, as water laws in that state are fairly flexible. But declining groundwater and well capacities have producers taking note. Warren has found by watering corn, capacities have gone down from 6.5 gallons per acre to 1 gallon per acre.
“When we look at profitability per inch of water, sorghum wins every time,” he said. To maximize profitability, Warren suggested variable irrigation and management strategies for drip irrigation, which will improve evapotranspiration effiency. The decision to limit irrigate sorghum to maximize its efficiency is the general practice, especially since sorghum is a low input crop.
“In doing so, often in irrigation we want to limit water early, early then pour it on at 30 days after emergence and keep it moist into grain fill,” Warren said. “But we limit our yield potential by doing that in that early part.”
In order to bump yields of sorghum past 160 or even near the 200-bushel mark, producers will have to bump seed population and carefully manage both nutrients and water application.
“As we try to push toward the 200-bushel mark, sorghum is less flexible on water usage,” Warren said. “That’s the beauty. Growing 140-bushel sorghum to me is very easy, but 200-bushel sorghum is like growing 300-bushel corn. That isn’t easy.”