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Can wheat compete?
Wheat and other small grains, once a staple in the crop rotations on upper Midwest farms, are losing their spot due to market forces and biotechnologies that favor other crops.
“Oat acreage is at the lowest in recorded history, and wheat is not far behind,” says Jochum Wiersma, a small grains specialist with the University of Minnesota. “If we're going to maintain any wheat acreage, we will need to maximize grain yield and push the limits.”
Wheat does have good value as a rotation crop and for spreading out planting and harvest seasons. And, says Wiersma, wheat breeders and farmers have made great strides at improving wheat yields.
“Since 1995, yields in northwest Minnesota have gone up an average of 1.6 bushels per acre per year. On a percentage basis, that's as good or better than corn!” he exclaims.
To make wheat competitive, Wiersma says you have to select varieties with high yield potential, plant them as early as possible, and manage for maximum grain yield. You also need to produce 14% protein in the grain.
Following are his ideas for achieving those goals.
This practice of applying nitrogen late in the growing season originated in Europe about 40 years ago. It's used on bread-grade wheat to boost the protein level into premium ranges.
“Pre-plant nitrogen is the best way to maximize grain yield. But late-season nitrogen is how you can improve grain protein content,” says Wiersma.
The most common way to do this is by applying 10 gallons of liquid urea ammonium nitrate (UAN) with an equal amount of water as a foliar application just after anthesis, says Wiersma. Dry sources of fertilizer like urea or ammonium nitrate, commonly used in Europe, haven't been effective in the U.S. The shorter grain-fill period and lower rate of precipitation don't give the crop opportunity to take up the additional nitrogen through the soil.
“We get anywhere from a .5% to 1% higher protein in the grain at harvest this way,” says Wiersma. “Do not expect all fields to respond equally well. Research has not been able to identify which varieties respond best to the foliar nitrogen. Differences can be attributed to the conditions during and immediately following application, but they don't explain all the variation we observe.
“We do know that the best time to apply is in the evening hours; the worst time is in the heat of the day with the sun glaring and the winds blowing,” he says.
Unfortunately, there are no in-season predictors to tell you when it makes economic sense to use UAN to boost protein.
“Increasing grain protein from 11% to 12% often still means substantial discounts at market. Bringing protein from 13% up to around 14% allows you to avoid discounts as high as $1 per bushel,” he says.
Leaf rust is one of the most significant fungal diseases of wheat, and it's common in upper Midwest fields. Even a 5% severity at anthesis on the flag leaf and penultimate leaf will produce economic yield losses,. More serious infestations will reduce yields by 50%. The reddish-brown spores the fungus produces in large quantities can mean that “you have a red combine, even if you bought a green one,” quips Wiersma.
Leaf rust is most significant where dew is frequent during wheat jointing and temperatures are mild. That's usually June. Spores are deposited into fields by wind and rain from the winter wheat in the Great Plains. “What plant pathologists describe as the Puccinia pathway, most of us know as Tornado Alley,” says Wiersma. “The southern winds that bring springtime thunderstorms also bring the leaf rust spores. If conditions are right, it develops into an epidemic quickly.”
Spring wheat breeders have been successful at providing growers with varieties that are genetically resistant to leaf rust. Unfortunately, one of the resistance genes (called Lr21) that is shared among a number of very popular varieties broke resistance, first in 2010. “In 2011, we saw a reoccurrence of this and ended up with damaging levels of leaf rust pressure on these varieties, in particular Faller and Prosper,” says Wiersma. “This complicates our fungicide management tactics.”
Research has shown that the optimal time to suppress the other great wheat nemesis (Fusarium head blight) is at the beginning of anthesis. Unfortunately, leaf rust cannot be left uncontrolled that late into the growing season. Consequently, you should scout varieties like Faller for leaf rust when the flag leaf appears. Determine if you need to intervene with a fungicide when the flag leaf is fully extended.
The other disease that is gaining ground in wheat country is bacterial leaf streak. It produces translucence in the leaf. If you hold it against your finger, you can see right through it. “It can invade a field when there is physical injury to plants, something like wind damage or tire tracks,” says Wiersma.
Although the bacteria can be seed-borne, preliminary research suggests that sanitation will not help control the disease in the field. Fungicides will not control the disease either, leaving variety selection as the best solution. Research is in the process of identifying those varieties, he says.
This practice has come about as growers attempt to get higher wheat yields along with higher protein in the grain. About 20% of the wheat planted in the winter wheat belt of Kansas is blended, where it's done also in an attempt to improve winter survival.
“We've done tests where we blended varieties noted for high yields with those noted for high protein,” says Wiersma. “Our results say the performance of blends is equal to the ratio of the blended components. And we didn't overcome the inverse relation of yield to protein; namely, as yield goes up, protein goes down.
“Our bottom line is that there is little advantage to blending wheat seed this way in our area,” he continues. “Why not just split the field by variety and then manage and market each of them to their best advantage.”
University of Minnesota Northwest Research and Outreach Center www.nwroc.umn.edu