Delayed planting of wheat to avoid the kind of devastation dealt by a record April 11 freeze in 2007 to upper Southeast growers may come back to bite in the form of lower yields.
“The April 11 freeze taught us several lessons about wheat production in North Carolina, but delaying fall planting is not one of them,” says North Carolina State University Wheat Specialist Randy Weisz.
Unfortunately drought prevented many growers from planting wheat on time. Others delayed planting to avoid spring freeze damage. The total affect is to have a lot of early, mid- and late-season wheat varieties all planted later than is recommended.
“In North Carolina, we are seeing a lot of wheat planted late, and in some cases replanted, that is far behind fields planted on time. Though we can do some things to manage this slow growth in the spring, the late-planted wheat will never catch up and never reach the yield level of the wheat planted on time,” according to Weisz.
“In 2007 we saw some wheat with 50-60 percent of the tillers destroyed by the April 11 freeze. In adjacent fields we saw other wheat varieties virtually undamaged. The difference is maturity date or heading date,” Weisz says.
Early heading varieties typically come out around April 4-6. Late season varieties typically come out later in April. In general, the late-maturing varieties escaped damage from the April 11 freeze. Of the 10 top-yielding varieties in 2007, only Southern States 8308, USG 3910 and Vigoro Dominion were mid-to early-maturing varieties.
The most popular and most consistent high-yield varieties in the upper Southeast have been early to mid-maturing. However in 2006-2007, these were among the lowest yielding varieties — because of the high level of freeze damage on April 11.
Among the varieties hardest hit by the freeze were Southern States 520, Panola and USG 3209, which are among the most heavily used varieties in North Carolina and Virginia.
By comparison in the 2006/2007 season, the highest yielding wheat varieties were in the late-maturing group. These include Coker 9436, NC Neuse, Pioneer 26R-12 and Southern States 8302.
“I've talked to a number of growers who say, ‘what if we don't have a freeze — I know I can make good yields with these early to mid-maturing varieties’. That's a big risk that farmers don't have to take. A better approach is to plant at least three varieties, with at least one of these being in the late-maturing category,” Weisz says. “Don't plant more than 30 percent of your crop to early-heading varieties,” he adds.
The North Carolina State specialist says it's a good idea to plant the early-maturing varieties late or last. Early-maturing varieties are the most susceptible to planting date. By planting these varieties early, that variety is set up for more freeze damage. Late-maturing varieties, by comparison, need to be planted early to take advantage of warm fall weather to make maximum tillers, he explains.
Drought and fear of freeze damage has left many thin wheat stands in the upper Southeast, which results in reduced tillering. Growers with thin stands will need to apply nitrogen — in most cases 50-70 pounds per acre as early in 2008 as possible to help develop enough tillers to reach a decent yield.
The high cost of fertilizer is another good reason to plant wheat on time. By comparison, wheat planted on time will not need nitrogen until Growth Stage 30, and in most cases less nitrogen will be needed than in later planted wheat.
Weisz warns wheat growers to know the difference between thick and thin-tillering and to apply nitrogen accordingly. Applying nitrogen in January and February when it's not needed can increase lodging and freeze damage risks, disease problems and reduced yields.
Though some of the freeze risks for late-planted wheat can be overcome by adjusting fertilizer application rates and time, a much better way is to plant varieties with different maturity, or heading dates and to plant these based on time of maturity.