Nitrogen and Texas Wheat Grain Production—Topdress N Timing is Critical: 

Twelve Common Grower Questions about N for Texas Wheat Grain

Calvin Trostle, Ph.D., Professor & Extension Agronomist, TAMU Dept. of Soil & Crop Sciences, Lubbock, (806) 746-6101, ctrostle@ag.tamu.edu

Jake Mowrer, Ph.D., Associate Professor & Extension Soil Nutrient & Water Resource Management Specialist, TAMU Dept. of Soil & Crop Sciences, College Station, (979) 845- 5366, jake.mowrer@tamu.edu

March 6, 2023

Much of Texas wheat has entered jointing and reproductive growth.  This includes regions into the northern Rolling Plains and in the lower southeast South Plains near Snyder.  Growing point differentiation is the defining point between vegetative and reproductive growth.  This is when the growing point switches from producing another leaf to now initiating the head.  This is an important component of yield potential.

Growing point differentiation (GPD) can be determine by visual observation or feel.

• By vision: 1) prostrate wheat transitions to erect vertical growth (a few days later than initial GPD), or 2) cutting the stem with a fine blade to find the growing point, which if present will be a small head, even just 1/8” long.  In comparison, Oklahoma State University often relies on finding the very first ’hollow stem’ to understand that the rest of the field is likely now in GPD/jointing.
• By feel: a small bump in the lower stem when stroked between the thumb and forefinger.

Much of the remaining topdress N decision for the Texas High Plains depends on whether you will get rain in the next ~14 days to wash surface-applied nitrogen on dryland wheat into the soil.  As High Plains wheat growers know, rainfed conditions in late winter/early spring are not reliable.  Fertilizing in advance of likely rain or snow, even if a month before you would otherwise target topdress N, can be a wise decision.

The current ‘Twelve Questions’ wheat nitrogen topdressing guide is updated.  It is available at http://lubbock.tamu.edu/wheat

The twelve questions for discussion are:

• What is the general N requirement for wheat grain production?

• What are the common rules of thumb for gauging the amount of N to apply for wheat grain?

• When is the best time to top-dress N for grain yield?

• If I make a ground application of N fertilizer vs. applying through an irrigation center pivot, should I change my application timing?

• Is there any benefit for N applied after jointing? What if I am late applying my N, should I still do it?

• Should I split N applications between fall and late winter for rainfed/dryland wheat?

• There is a good chance of rain or snow in the forecast. Should I go ahead and apply my topdress N?

• My wheat stand is thin but uniform. Can N management help me overcome this thin stand?

• Is there a preferred N form to use for wheat topdressing?

• Is there a limit on how much liquid N can be applied with a ground rig without burning the leaves?

• My irrigation water has nitrate-nitrogen (nitrate-N, or NO₃-N) in it—should I apply this toward my wheat crop N requirement?

• I had a major freeze that may have hurt my yield potential. Will late N applications drive compensatory tiller growth to recapture yield potential?

For further questions, please contact the authors or your county agricultural extension agent or regional Extension agronomist.