By David Marburger, Extension Small Grains Specialist
Some producers throughout Oklahoma have been delayed in getting their wheat crop established due to fall armyworm and/or the rainfall we have had throughout October. While we are now outside of the optimum planting window for grain-only wheat production, the good news is that late-planted wheat can still yield well if environmental conditions cooperate and if producers make a couple management adjustments.
Seeding rates: The main problem with late-planted wheat is reduced tillering and slowed canopy closure when compared to earlier-planted wheat. On average, wheat plants sown in early- to mid-October will produce 2-3 tillers/plant. At a seeding rate of 60 lbs/acre (20-25 seeds/ft2 depending on seed size), the 2-3 tillers/plant can help us achieve the 60-70 heads/ft2 needed to maximize grain yield.
Wheat planted in early- to mid-November may only produce 1-2 tillers/plant. Therefore, seeding rates right now should be increased by as much as 50% and increased by as much as 100% if planting gets delayed past mid-November. So, if a producer uses a 60 lbs/acre seeding rate during the optimum planting time, the seeding rate should be increased to around 90 lbs/acre for right now and then increased to 120 lbs/acre past mid-November.
There may be questions too on replanting decisions during this time of year. This can be a challenging decision, but the first step is to count the number of plants in different parts of the field to assess the stand. A thin but uniform stand will have more yield potential than one that is thick in some areas but nonexistent in others.
During the optimum planting time, a thin but uniform stand (50% of the target stand for example) would likely be enough to keep, given adequate fertility and favorable weather conditions that would allow for tillering to help compensate. However, a similar scenario for a wheat field emerging at this time will need help. After assessing the stand, areas with thin or nonexistent stands should be filled in to reach your desired stand target. If replanting into an existing stand, it should be done at an angle (up to 45 degrees) to minimize damage to the existing stand.
Fertility: Late-planted wheat will need all the help it can get when it comes to fertility. The root system for late-planted wheat will likely not be extensive enough to intercept a significant amount of soil phosphorus until the spring. An in-furrow application a P fertilizer (50 lbs/acre of DAP for example) can be of great benefit. With this, the fertilizer is closer to the young seeding, and the plant can get to it sooner. Nitrogen fertilizer can also be used to encourage tillering.
However, rather than increasing fall N rates, late-planted fields should be put at the top of the list for topdressing in January or February. There is most likely enough N available between residual soil N and any starter fertilizer N for growth this fall since wheat in grain-only production does not need much N (up to 20-25 lbs/acre) in the fall to get good establishment. Using N-rich strips can aid in determining when to apply topdress N, and a more accurate amount to apply can be determined using sensor-based methods.
Variety selection: It is most likely too late to make any switches in variety selection. If there is an opportunity to change varieties though, using a variety with good tillering ability and earlier maturity may be of benefit. A good tillering variety can help compensate for the less available time this fall for tiller development; whereas, a low-tillering variety may not be able to produce any tillers this fall.
Late-planted wheat may also result in delayed development in the spring and force the grain fill period to be shorter by occurring later when environmental conditions are likely warmer and drier. An earlier maturing variety could be used to offset this chance that grain fill occurs during suboptimal conditions.
Pests: Finally, it is important not to short-change a late-planted wheat crop in terms of pest management. Remember that a late-planted crop has less competitive ability than an early-planted crop. Control insect pests as soon as thresholds are reached, and make herbicide applications while weeds are still small and have not yet removed large amounts of nutrients and soil moisture.