May 22, 2003

 

Should I Switch Wheat Varieties if the Season is Delayed?

Generally wheat grain yield will be reduced by at least half a bushel per acre for each day past the optimum planting date, according to Terry Gregoire, North Dakota State University Extension cropping system specialist in Devil’s Lake. "Many counties in northeastern North Dakota and counties north of U.S. Highway 2 still have a lot of acres to plant. Some of the intended wheat acres may be switched to another crop. However, many producers will continue to plant wheat until prevented planting crop insurance becomes a consideration."

In the northern part of the state, the optimum planting date is before May 20. Usually wheat will take 50 to 55 days to head when planted in late May. This means grain fill will occur during the warmest part of the growing season. For a cool season plant like wheat, the result is smaller kernels and reduced yield potential.

Growers do have some options with varieties that are more tolerant to heat stress according to Gregoire. "Varieties like Ingot, Russ, and Alsen seem to handle heat stress during grain fill better than Gunner, Marshall, and AC Barrie. Research at NDSU’s Langdon Research Extension Center shows that planting Gunner and AC Barrie late will result in a larger decrease in grain yield relative to varieties like Ingot and Russ."

Leaf rust damage potential also increases with late planting. In sensitive varieties like Ingot and Russ, a fungicide to protect against leaf rust should be considered or plant a leaf rust tolerant variety. Gregoire urges growers to review local data for other varieties that have the characteristics desired and perform well when planted late.

The NDSU Langdon Research Extension Center had a late planting trial in 2000 and 2001. The two-year average yield for AC Barrie was 26.6 bushels per acre while Gunner averaged 30.9 bushels per acre. All other varieties in the trial had average yields of 40 bushels per acre or above. The varieties Alsen, Russ, and Parshall had average yields of 43 bushels per acre. In a similar trial planted the first week of May, Gunner and AC Barrie had yields similar to the other varieties.

When should producers consider switching varieties? "While each year is different, general producer experience and research data suggest that Gunner and AC Barrie and perhaps varieties with similar genetics should not be planted after May 20 in northern North Dakota and Minnesota and perhaps earlier in southern portions of North Dakota," Gregoire says. "If planting is delayed into June, consider planting an early maturing variety if one is available. A week earlier heading can make a difference of two weeks in harvest maturity or more when the variety is maturing in September. The risk of frost and sprout damage also increases as maturity occurs in September."

Some growers are considering an adjustment in seeding rate to reduce losses to late planting. Bryan Hanson, agronomist at the Langdon Research Extension Center conducted two, three-year planting date and seed rate studies in the mid 1980's with a semi-dwarf durum and Cando and Robust barley. Seeding rates of 500,000, 1 million, 1.5 million, and 2 million seeds were used on three dates in late April, mid May and early June. There were no significant differences among seeding rates for planting dates for any measured trait. Results show that it did not help to increase the seeding rate as the planting date changed. However those trials and trials with Grandin wheat in the early 1990's did show that seeding enough seed to establish a minimum of 17, 27, and 26 plants per square foot of barley, durum and spring wheat, respectfully, maximized yields. Establishing these minimums for any seeding date should be a producer’s goal.

###

Source: Terry Gregoire, (701) 662-1364, terry.gregoire@ndsu.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu