Nitrogen Management- Wheat Tillers and N Application

       By: Blake Patton, MS Sales Agronomist, Top Ag Cooperative

        In order to count on increasing wheat yield, we will have to start counting wheat tillers.  Thin spring wheat stands don’t have to equate to lower yields, and inversely, thick stands will not necessarily produce the highest yields.  Both scenarios need to be managed accordingly to ensure optimum yield. January through early March is a critical time to manipulate the total amount of wheat heads that will be harvested. Counting wheat tillers will be the way we do so.
        So what are the numbers we are looking for? Phil Needham, a global crop consultant with Needham Ag claims that 600 wheat heads per square yard has shown to be the maximum wheat yielding statistic. This equates to around 250 plants per square yard (ending population of 1.21 million seeds/ac) when factoring in an average of 3 tillers per plant, minus some loss due to germination issues/environmental factors. Other Wheat professionals would like to see an increased population due to the value of the true plant bringing more potential yield than that of the tillers from the primary wheat plants.  
        Nitrogen can be applied in one or more applications depending on the total amount of tillers present at Feeks Growth Stage 3 (Refer to Figure 1), early in green up. These application timings are recommended at green up, Feeks Growth Stage 3, and Feeks Growth Stage 5/6 during stem extension. If low tiller counts (300 - 500) exist at Feeks GS 3, then 2 applications are recommended. Feeks 3 application will allow for an increase of tillers to maximize total wheat heads at harvest.  Second application at Feeks 5/6 is focused on plant nitrogen needs for increased yield. High tiller counts, generally 700 or more per square yard, will not need an early application of nitrogen due to the density of potential wheat heads that already exist. A nitrogen application with 700 + tillers at green up will result in lodging and higher disease pressure which will lower yield potential.
With these factors being considered, nitrogen rates should be tailored to the correct amount of tillers for total amounts of nitrogen at the correct timing to optimize yield for a more effective nitrogen utilization. Figure 2 can be followed for a quick reference to help better understand specific scenarios.  
        Next, we will want to factor in total amount of nitrogen needed to achieve your desired yield.  Ohio State University provides a simple equation to help determine the total amount needed.  N rate = 40 [1.75 x (yield potential – 50)].  100 bushel yield expectation will then require 127.5 lbs of total nitrogen for the crop.  If 30 lbs are applied in the fall, the remainder will be split accordingly depending on the tillers at Feeks 3.
        At Top AG Cooperative, we are developing a nitrogen program based on the farmers’ current and future needs and expectations.  Each wheat variety planted may act different depending on plant date and environmental factors. With field conditions becoming ready for the first application of nitrogen, please let us know if you want to prepare a detailed nitrogen plan to optimize your wheat productivity!