Southern Spotlight: Topdressing

Amanda Fairley

Amanda Fairley

Winter wheat plants crave Nitrogen.  For each bushel of wheat produced, growers should plan on applying two pounds of N.  This is a significant amount, of course, and a split application will help your plants maximize their use of N.

The first application of N should either be broadcast before planting or included as a starter.  The second application of N is your topdress, and is the difference between your total N requirements (which is based on your yield goal) and the amount of N already included in your broadcast or starter application.  If your wheat will be grazed, adding 30-40 pounds of N for every 100 pounds of beef weight gain removed from the field is additionally necessary to balance out the nutrients that your cattle have removed from your fields.

Your topdress application can be applied in the winter or early spring depending on your management and soil type.  Medium to fine soils (which comprise the majority of our acres in North Central Kansas) allow for topdress in either season.  If your soil is sandy, poorly drained, or a shallow clay pan type however, a spring topdress will be most beneficial.  These soils can promote denitrification and leaching, which lessen the amount of N that survives from winter topdress into the spring for use by your plants.

Regardless of the season in which you choose to topdress, ensure that N is applied early enough to allow moisture to work the fertilizer down into the root zone so that it is accessible to plants before jointing.  Timing your topdress for December or late February allows for this crucial movement of N into the soil.

In addition to timing, the source of N that you plan on using in your topdress application and your application method are important factors to consider.  Application methods include broadcasting, streamer nozzles, and streamer bars.  Which method is best depends on the N source you choose: UAN and Gradual N are liquids that can be applied with any of the three methods; Dry Urea, as the name suggests, is dry and needs to be broadcast.

If you choose a liquid source, there are many optional additives to your topdress.  You can mix UAN and Gradual N to provide your wheat plants with both an immediate and lasting source of the nutrient.  You might also consider adding sulfur to your topdress to ameliorate leaf burn and chloride if levels in your soil are low.  Herbicides and fungicides are other possible additions that contribute many benefits to your acres, increasing their value and the efficiency of your operation.

Whichever season, source, and application method you choose for your topdress, your application is of the utmost importance and can add tremendous value to your acres and your wheat crop.  The value of N to your plants can’t be overstated and careful consideration and planning of your topdress will ensure that your plants enjoy the maximum benefit of this vital nutrient.