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Winter kill is probably not a problem yet for the current winter wheat crop, but Blake Vander Vorst, regional agronomist at Ducks Unlimited, suggests producers keep an eye on it. “Right now, it's still okay because of the snow cover and the residue,” said Vander Vorst at the N.D. Wheat Commission's first Best of the Best Wheat Show in Dickinson.

Without stands and residue, there can be significant winter injury. In addition, winter hardy varieties are important in the Upper Plains.

There is “quite a buffer” in the upper portion of the soil that helps protect the plant from injury, he said.

“We will see the most losses in the more open fields,” he said. “It's the temperature in the last two weeks of March and the first two weeks of April that will matter.”

Vander Vorst is working on a hard red (and some white) winter wheat variety characteristics list for producers that will include varieties from private companies.

An incomplete initial list he distributed puts the following varieties in the good to excellent winter hardy category: Jerry, Radiant, and Ransom. CDC Buteo was rated excellent. The following varieties were rated good: CDC Falcon, Darrell, Expedition, Harding, Overland, Wesley and Yellowstone.

In the white wheat, winter hardiness for Wendy is rated good.

Joel Ransom, NDSU agronomist, said varieties for the best combination of winter hardiness and yield are Ransom, CDC Buteo, CDC Falcon and Jerry.

NDSU compiled yields for winter wheat varieties in 2007 and three-year average yields from 2005 to 2007.

Top yielding variety in 2007 at Mandan in central North Dakota was Millenni-um, with 84.2 bushels per acre, with a three-year average of 53.7 bushels per acre. Other varieties that did at least 70 bushels to the acre were CDC Buteo, Darrell, and Wesley.

In Prosper, located in the eastern part of North Dakota, the top yielder was Millennium with 76.3 bushels to the acre in 2007 and 86.9 bushels per acre for the three-year average.

In Dickinson, located in southwestern North Dakota, the top yielding winter wheat for 2007 was Millennium at 86.7 bushels to the acre with the three-year average at 78.3. Other top yielders with at least 80 bushels/acre were Jerry, Paul, CDC Buteo and NuDakota.

Several varieties have different disease resistant packages. Mace, a new winter wheat developed by the ARS, is the only variety that is listed as resistant to wheat streak mosaic, often a problem in areas where both winter and spring wheats are planted. Winter wheat has several benefits as a rotational crop, Vander Vorst said. Those include disease, insect and weed control, yields, soil nitrogen, soil moisture and soil structure. A rotation study done at Fargo from 1977 to 1984 evaluated the effect of previous crops on wheat yields.

When the previous crop was soybean, the effect was 45 bushels/acre; sunflower, 40 bushels/acres; sugarbeet, 42 bushels/acre, while wheat on wheat produced 31 bushels/acre.

“The goal is to get four years out from wheat to get the most benefits,” Vander Vorst said. “That will give the highest yields.”

A study conducted at Dickinson in southwestern North Dakota by Pat Carr, NDSU agronomist, and Roger Ashley, NDSU Extension agronomist, looked at wheat yield effects after both wheat on wheat and wheat-pea rotations from 2000 to 2005. Planting methods used in the study were either clean, reduced or no tillage.

The study found a “pronounced” tillage effect with no-ill producing the highest yields. A 20 to 67 percent increase (10 to 12 bushels per acre) was demonstrated under no-till compared to the clean and reduced-till acres.

The same study showed more soil moisture was available when no-till was used.

“Moisture was a big factor,” Vander Vorst said.

In addition, in three out of the five years of the study, no-till had higher plant stands, he added.

Wheat yields were highest in the wheat-pea rotation. A nine to 11 bushel/acre effect was found in four out of the six years - a 17 to 38 percent increase, Vander Vorst said.

Carr's data suggested a nitrogen credit of 20 to 30 pounds per acre in those years. However, Vander Vorst said he was “caught off guard” by Carr's finding that the rotation effect from planting peas was not due to just the availability of N (ammonium and nitrate) in the soil.

“If we look at the soil N, it was the same in the (wheat on) wheat as it was in the wheat-pea,” Vander Vorst said.

Conclusions from the study showed eliminating tillage increased wheat yield from 20 to 70 percent, and rotating wheat with pea increased wheat yield from 0 to 40 percent.

Another study from Randy Anderson, ARS, demonstrated yields increase when crops are varied in sequence.

Dakota Lakes research captured winter wheat yields when used in three different crop rotations.

In a winter wheat, corn, flax or chickpea rotation, winter wheat yields averaged 66 bushels/acre.

In a HRSW, winter wheat, corn, soybean or sunflower rotation, winter wheat yields averaged 66 bushels to the acre. In the winter wheat, sunflower or soybean, corn, lentil or field pea rotation, winter wheat yield averaged 62 bushels/acre.

Vander Vorst said there should have been a higher yield in the last rotation but the winter wheat had winter injury.

In addition, some crops give other crops synergy (when combined, they have a mutual advantageous effect). Corn is one of those crops that give wheat synergy, and that helps with yield increase, he added.

Dakota Lakes research also shows that profits were highest for winter wheat than for the other crops in a HRSW/

HRWW/corn/warm season broadleaf rotation. The data was collected from 1993 to 2001, so would not include recent prices and recent inputs.

A study by Joel Ransom looked at several crops to determine the best prior crop for winter wheat survival and the best prior crop for the highest winter wheat yields. He found survival was highest when HRSW was planted prior to winter wheat, followed in order by best to poorest, oats, barley, flax or canola, peas and soybean.

Yield was highest when peas were planted prior to winter wheat, followed in best to poorest order by soybeans, flax or canola, oats, barley and HRSW. That holds true only if there's no winter injury, Vander Vorst said.

A 2007 research study at Ellendale, N.D., demonstrated the winter wheat yield response when planted after flax, HRSW, pea and soybean.

Yields were highest when planted into the soybean residue, 66 bushels to the acre, followed by HRSW, 59 bushels to the acre, peas, 53 bushels to the acre, and flax, 51 bushels to the acre.

“I think moisture was the issue here,” Vander Vorst said.

Weeds are an issue to consider when winter wheat is added to the crop rotation, Vander Vorst said.

Weed density can also be reduced by balancing winter and summer crops, he added.