Ongoing wheat research at Kansas State University reinforces the idea that even when planting wheat later than the optimal date for any given area, yields can be recovered somewhat, but not completely, by bumping up seeding rates and ensuring the crop receives adequate moisture.
“We initiated this study because as farmers move to more intensive cropping rotations, they are harvesting crops and then planting wheat on that same field late—sometimes two to three weeks later than what we would consider the optimum planting time for a given area,” said K-State Research and Extension agronomist Brian Olson. He and K-State agronomy colleague, Rob Aiken, wanted to determine if it is possible to receive all or most of the highest potential yields on late-planted wheat by altering seeding rates.
Wheat seeding rate is increased because wheat planted later in the year will have a shorter period to develop tillers before winter dormancy. Therefore, the increased seeding rate possibly could compensate for the reduction in tiller number from an individual wheat plant.
Prime wheat planting time in northwest Kansas is the end of September to the first part of October, said Olson, who is based at K-State’s northwest area office in Colby, where the fourth year of the study is about to begin with the fall planting.
All wheat used in the study, which was funded by the Kansas Wheat Commission, is TAM 111, a hard red winter variety, planted no-till. Beginning in 2008, plots were planted Sept. 26, Oct. 10, Oct. 24 and Nov. 7. On each planting date each year, plots were planted at 60, 90, 120, and 150 pounds of seed per acre.
Eighty pounds of nitrogen and 30 pounds of phosphorus per acre were applied to the study area prior to planting.
In the first two years (2008-09 and 2009-10), moisture was adequate and emergence, development and yields were consistent, Olson said. But just like for producers in western Kansas, dry conditions during fall 2010 impeded the researchers’ efforts.
“I put that wheat into very dry ground in 2010,” Olson said, noting that with so little soil moisture, emergence was delayed.
Once the scientists irrigated the study at the end of October, however, wheat in all of the plots began to emerge at about the same time, regardless of planting date.
“We finally watered and the wheat emerged. That just reinforces what (K-State agronomist) Jim Shroyer says: ‘it’s not when you plant it, it’s when you get moisture,’” Olson said. “The potential yield is not when it’s planted but when it comes up.”
The study indicated that although yield potential is reduced by planting wheat after the optimum window for a given area, some of the potential yield can be recovered by increasing the seeding rate. In the fall of 2008 and 2009 when wheat was planted on Sept. 26 and Oct. 10, wheat yields were similar across the planting rates of 60, 90, 120, and 150 pounds per acre. However, when wheat was planted on Oct. 24 or Nov. 7, the lowest yield for that date was observed with the 60 pounds per acre seeding rate and a stair-step increase was observed with the 90, 120, and 150 pounds per acre seeding rates on these dates.
“But it is important to note, that although the 150 pounds per acre seeding rate on Oct. 24 and Nov. 7 had the highest yield for that date, that yield was not as much as wheat planted during the more optimum planting period for the area of Sept. 26 to Oct. 10,” Olson said. “We’re planning to plant again for this next year,” he added. “Hopefully, we’ll have good moisture.”