Balancing yield and protein content in a wheat crop

Thursday, October 12, 2017

With Oklahoma wheat producers heading into another growing season, the bottom line will be top of mind, as always, and for many, that means focusing squarely on yield, yield, yield.

However, doing what it takes to boost the bushels also can lead to other important things, like increasing the protein content of a crop.

In fact, the protein content of the Oklahoma wheat crop is garnering increased attention these days after two straight years of registering less than ideal levels.

“Low protein wheat can create pricing and marketing challenges for everyone in the supply chain,” said Brian Arnall, Oklahoma State University Cooperative Extension precision nutrient management specialist. “Perhaps even more concerning is that low protein is an indicator that nitrogen was limiting during grain fill and therefore, a field’s maximum yield potential wasn’t achieved.”

The happy news for proactive producers is this is a fixable concern.

Variety selection, growing environment and fertility all play major roles in driving up the protein content in a wheat crop.

While some varieties, on average, offer higher protein, the differences among varieties can be overshadowed by the environmental conditions at different locations, said David Marburger, OSU Cooperative Extension small grains specialist.

Ideally, during grain fill, optimal conditions would include cooler temperatures and ample available moisture, which could positively affect yield but negatively impact protein levels in the crop.

“We’ve seen that over the past couple years. We fertilized with our normal nitrogen rate to achieve our yield goal, and this usually provides an adequate protein content as well. But we’ve had better yields partly due to the better growing conditions, and therefore lower protein content,” Marburger said. “We can get the opposite, as well, especially with drought or other stresses, where there are less kernels and/or the kernels become small and shriveled. Now you have that same amount of nitrogen, but over less grain to put it in. So, you might actually have a higher protein content.”

That leaves fertility, or more specifically nitrogen, as the X factor.

Protein is a function of nitrogen concentration, Arnall said, and if the nitrogen concentration in grain is low, so is protein.

“If the nitrogen well is running dry at the end of the season, protein will be low,” he said. “We typically see low values if nitrogen rates were below crop need. Or, perhaps the nitrogen applied was lost through leaching or other mechanism, which is more likely to happen when all of the nitrogen is applied pre-plant.”

Bottom line? Managing nitrogen and maximizing yield come down to ensuring nitrogen is available to the plant at important growth periods.

“It’s always best to apply nitrogen when the plant needs it, which is right after tillering for grain-only. In dual purpose, we have a high need in the fall and again at tillering,” Arnall said.

Producers do not need to guess about the nitrogen levels in their fields either.

N-Rich strips, used in conjunction with GreenSeeker ^TM hand-held sensor technology, and a sensor-based nitrogen rate calculator, are key tools producers can use to guide them on nitrogen application.

Ultimately, the goal is to enhance the overall quality of the Oklahoma wheat crop, Marburger said.

“If we all work on improving protein and quality, in general, we’re going to raise the overall quality of the Oklahoma wheat crop and we’re going to have end-users who want to buy this grain first before any other,” he said.

For more information on nutrient management, download free of charge OSU Current Report CR-2277, “Applying Nitrogen Rich Strips,” and OSU Fact Sheet PSS-2258, “Evolution of Reference Strips in Oklahoma” at factsheets.okstate.edu.

Producers also can visit npk.okstate.edu, the Down and Dirty with NPK blog at www.osunpk.com and contact the nearest county Extension office.