Northeast Ohio Agronomic Crop Progress Report

The rain continues to fall and field work in many areas has yet to begin. This week I want to highlight an articles from the corn newsletterby Dr.Robert Mullen OSU State Soil Fertility Specialist.There was more than a few acres of wheat planted in Northeast Ohio last fall and the majority of that wheat has not been topdressed due to wet weather conditions.This has many farmers concerned that they will experience yield loss if this the wheat is not topdressed soon. We are late topdressing by the calendar but it is the stage of wheat growth that we need to be paying attention to. Just like everything else wheat growth is behind schedule due to the wet cold season. Here is what Robert has to say about what is happening to wheat that was topped dressed and the rest that has seen no nitrogen this season:

Nitrogen Loss from Topdressed Wheat Fields, Am I Losing Any N? What if I Have Not Supplied N Yet?

Robert Mullen, Ed Lentz

In this same newsletter, we have discussed concerns regarding N loss from anhydrous ammonia for corn this summer. In case you did not read that article, the jest was that we are not overly concerned about N loss from those applications. So is the same true for topdressed wheat? Not necessarily.

Our concern about N loss this spring from wheat is somewhat form specific. Topdress applications of N from urea are unlikely to have experienced much in the way of loss. The greatest concern would have been volatilization losses of N after application, but with our rainfall pattern this spring that should have been minimal. Additionally, the cool soil temps have also limited biological activity meaning very little of the N has been converted to nitrate. As you know, nitrate-N is the form we are concerned about losing. The question that typically is asked is – should I have included an inhibitor (either urease or nitrification)? The research that we have been doing over the last ten years, reveals that typically you do not need a urease or nitrification inhibitor. This is due to cooler soil temperatures in the spring when these applications are taking place.

The story is a little different for urea-ammonium nitrate (UAN). When you apply UAN, a quarter of what you apply is in the nitrate-N form the day it hits the ground. This fraction of N is subject to loss, and there is really very little you can do to protect it. Inhibitors will in no way shape or form protect the nitrate-N you supply. So with all the wet weather some of that nitrate-N fraction may be lost via leaching. The good news is that the greatest loss potential is for coarse textured soils, so those who farm clay soils have a lower loss potential. Since soil temperatures have been so cool, denitification of nitrate-N has likely not occurred to any great extent (our greatest concern for heavy soils).

What about those fields that have yet to receive their topdress N? Are you too late? The one thing we want to point is calendar day late and crop growth stage late are two different things. Just because your topdress N application is falling a little later than normal does not necessarily mean that your crop is missing an opportunity. The fact is most of our wheat is a little behind schedule -- thanks to cool, wet conditions. So much of the wheat is still at a period where timely applications of N can still be made. For those who have wheat passed stem elongation (Feekes 7) and N has not yet been applied, you should still get out and apply N. You might have lost some yield potential if the crop has been N stressed, but the crop will still respond to N applications. In fact, most research shows that applications as late as Feekes 8 can see beneficial yield responses. Let’s hope we do not have to wait that long. For the later N applications, if the weather forecast is for an extended drying period with windy and warm temperatures (>75°) and no rain for several days, you may want to consider a urease inhibitor with urea applications. However, these weather conditions appear to be unlikely the next several weeks.