The first step in producing a good wheat crop is to get a good stand. Where emergence is uneven or poor, producers will have to make the difficult decision of whether to replant, says Jim Shroyer, crop production agronomist with Kansas State University Research and Extension.
"The decision is not always clear-cut. This year, for instance, the shortage of seed in some areas of central and eastern Kansas may prevent replanting, even if it's necessary," says Shroyer, who offers some helpful guidelines.
"First, it's useful to know how many plants per acre you could reasonably expect, based just on the seeding rate and a normal emergence rate. If you planted 90 pounds per acre in 7 ½-inch rows, for example, you could expect to have about 11 to 13 plants per foot of row, depending on seed size. If you planted 60 pounds per acre in 12-inch rows, you could expect an emergence of about 14 seedlings per foot of row," he said.
In general, when the actual average number of plants is about 50 percent or more of the calculated "reasonably expected seedlings per foot of row," Shroyer recommends keeping the stand. For fields with less than 40 percent of expected, his recommendation is to replant. With a stand that is between 40 and 50 percent of expected, however, the decision is more difficult.
Growers have two major concerns other than yield potential to consider when deciding whether to replant, he explained. One is the susceptibility of the ground to wind erosion. The other is the potential for weed and grass infestations.
"Where stands are less than 40 percent of expected, these would become major concerns, even if yield potential weren't an issue," Shroyer says. "When the soil is blowing or weeds and grass infestations become severe, the stand probably should have been replanted and thickened."
Another complicating factor can be pattern of emergence.
"Stands may not be uniformly good or uniformly thin. There may be areas of both, in which case, there's no hard-and-fast rule about re-seeding," the agronomist says. "If most of the field has a good stand and a few large areas are thin or bare, producers can go in and just thicken up the areas. But, if the entire field is a patchwork of thin and adequate stands, the best approach may be to re-seed the entire field."
Using a double-disc opener drill might be advisable when cross-drilling into an existing stand, he says. With a hoe drill, the seeding rate must be slightly higher than what was originally planted, because the hoe drill will also destroy much of the original stand.
If possible, producers should replant at a 45-degree angle to the original stand, as well, to help minimize damage to the existing stand.
The most common emergence problems for wheat are soil crusting, dry soils, poor quality seed and seedling rot diseases, Shroyer says.
"Where crusting has occurred, producers should determine whether the seeds or seedlings are still viable or the coleoptiles have become bent or crinkled, due to the crusting," he says. "Sometimes a light rain will soften the crust, so viable seedlings can emerge.
"Otherwise, a rotary hoe will break up the crust in a conventional-tillage system, allowing the seedlings to emerge. In reduced-till or no-till systems, however, rotary hoes will not perform satisfactorily."
If dry soils are the problem, replanting makes no sense when the seed is still hard and viable, Shroyer says. But, if the seed has partially germinated and stalled out before emerging, it may no longer be strong enough to emerge, thus making replanting the better option.
In fields with adequate moisture and no crusting, the base cause of little to no emergence can be poor quality seed or seedling rot diseases. In either case, producers will need to replant with good-quality, treated seed, the agronomist says.