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Breaking Through the Wheat Yield Barrier


One of the latest trends in row-crop production appears to be that of breaking yield barriers – 100-bushel soybeans, 500-bushel corn, 8,000-pound peanuts, and the list goes on. So where does wheat fit into all of this?

The world record wheat yield was 229 bushels per acre, recorded in New Zealand, says Wade Thomason, Extension grains specialist with Virginia Tech University.

“We’ve had some 200-bushel wheat yields recorded in North America, in British Columbia,” said Thomason at the Alabama Corn and Wheat Short Course held in Auburn. “It was one of the first examples of a systems management approach for wheat and small grains in the Northern Hemisphere. They had four nitrogen timings and three different fungicide applications, and they used growth regulators. It was the initiation of this modern intensive management program for wheat and obviously was very effective in this particular environment.”

One-hundred-fifty or even 100-bushel wheat would present a challenge for most, says Thomason, but he challenges growers to concentrate on outcomes rather than management strategies in their wheat production.

Fairly simple?
The concept of intensive wheat management is fairly simple, he says, including the number of heads per acre multiplied by weight per head multiplied by kernels per head equals yields.

“Conceptually, this is simple to solve, but the problem is in the details. When you push one up, something else tends to go down and vice versa.”

Practical constraints to yield, says Thomason, include site selection, seedbed/tillage prep, fertility and liming, variety selection, plant stand and pest management.

“We’re looking at 55 to 60 percent or so of the potential of a wheat crop being set when the drill hits the field. We’ve done our preplant fertility, we’ve chosen the genetics – we’ve already put in place several things to help establish that potential. Once we put all of that in place, we can’t then lose it to weeds, insects or diseases. Also, we have a particular challenge in wheat with lodging. You can put just about as much nitrogen as you want on corn, with very few detrimental effects to the plants themselves, but small grains are different,” he says.

When someone talks about the theoretical implications of the impact on yield, they’re assuming that water and nutrients will not be limited, says Thomason.

“But that’s not the world most of us live in with modern agricultural production. We are dealing with questions of field-specific parameters, so we need to move away from the theoretical and more towards the practical.”

Thomason says he spends a lot of his time on variety testing and evaluation, and there’s a good reason for it.

“My growers in Virginia tell me it’s one of the most valuable things I can do to help them be profitable wheat growers. If you’re not spending a significant amount of time on your own, looking at these variety test results and interpreting them for your farm, then you’re missing out on a lot of opportunities. A lot of site-specific variety management can be accomplished with just a little digging into this testing information.”

Paying attention to the details
Many seed treatments are being offered, says Thomason, and he typically sees a 2 ½ to 3 bushel advantage when using the “run-of-the-mill first-cut” seed treatments.

“It’s almost always at least a break-even proposition, and in some of these instances, we had 6 to 7-bushel yield responses where we had some early season plant diseases and other things that limited stands. Most of these treatments at the very basic level are almost always break-even and need to be part of a management program, even with saved seed.”

Planting date is especially important for Virginia growers, says Thomason, as everyone waits for the Hessian fly to leave fields.

“But the later we go, the longer it takes to accumulate the heat necessary to get that crop out of the ground. Nine days in September is equivalent to 12 days in October and 19 days in November to accumulate the same total number of heat units.”

Good stand
The tillers that develop in the fall tend to have more kernels per head and larger numbers of heads than tillers that develop in the spring, he says, and they are more mature and more likely to be competitive at the end of the year.

Part of the wheat yield-building plan is getting a good stand and shooting for the right plant population, notes Thomason.

“At the end of the year, we know in Virginia that we need at least 60 or 70 heads per square foot to reach our optimal yield level. We know that we need more than one tiller per plant, so we can back-calculate and see that we need 22 to 25 vigorous seedlings per square foot when the drill leaves the field in order to achieve 60 to 70 heads. It’s a little more complicated than with corn but not much.”

Knowing that germination and emergence is not 100 percent, growers will want to plant about 30 to 35 seeds per square foot, he says. We bump that up 10 percent if we’re two weeks late. But at a month or more late, adding a few seed is not going to build yield potential in a field.

As for as fertilization, there’s a significant advantage to some nitrogen in the fall almost without fail, says Thomason.

“About 70 percent of our wheat is following corn, and 60 percent is strictly no-till. We almost always see a nice benefit of 20 to 40 pounds of nitrogen prior to planting. We do some nitrate soil sampling from the top 12 inches.”

No-till revolution
“We do see a slightly lower yield on average with no-till wheat, but producers say they more than make up for that with their time, labor, equipment and fuel savings. But there are a number of instances where our no-till yields are as good if not better than our conventional yields, usually when we have dry springs.”

A challenge of no-till is that soil temperatures are lower in the fall and tillering is not as good, says Thomason. Sunlight radiation is reflected by the residue on the surface and it doesn’t stay as warm at night, he adds.

“We’re doing the one thing we know will make plants grow a little more during that time of year, and that’s to give it a little more nitrogen. For Virginia growers, it works out to be a deer-season or Thanksgiving application.”

University of Kentucky research looked at fall weed management strategies over 11 years and found an advantage to using a burn-down herbicide even if they didn’t see that many weeds, says Thomason.

“Wheat is made much more competitive by taking out the early season weeds and eliminating those holes for the opportunistic spring weeds to take hold.”

Virginia’s wheat nitrogen plan is based on two spring applications, one shot at GS 25 followed by another in about a month.

“We need about 60 to 70 heads at the end of the season, so our management at this time dictates how much nitrogen we apply based on tiller density. If we’ve got more than 100 tillers per square feet, just back off, but that’s rare.”

At 50 to 100 tillers per square foot, growers apply 30 to 40 pounds of nitrogen in January/February, he says. At less than 50 tillers per square foot, 40 to 50 pounds of nitrogen needs to be applied as soon as possible. January, says Thomason, is too early to apply more than 50 to 60 pounds of nitrogen on most soils.

“If we go for 100-bushel wheat, at 1.15 pounds of nitrogen per bushel, we need 120 to 150 pounds of N from soil and fertilizer. If we go to 150-bushel wheat, we’re at 175 to 200 pounds of nitrogen, and it’s a real chore trying to figure out how to do this. We can’t put two shots of 90 pounds of nitrogen on wheat. So we’ll have to be inventive on how to feed this crop is we’re going to push yield levels.”

Source: Paul Hollis, Southeast Farm Press

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