“Some of these small-stature winter weeds are not on the upper part of our radar screens in terms of competition with wheat because they don’t look very significant. But they will hold back tiller development in the spring.”

Herbicide application can have an influence in wheat yields, as shown in trials conducted in Mississippi, he says.

In his state, says Larson, a lot of the wheat crop is grown in the northwest or Delta region, with flat soils and poor surface drainage. This results in problems with water management and soil saturation.

“That makes it very difficult in terms of nitrogen management for wheat production. Our wet winters can cause de-nitrification and leaching. So we apply nitrogen only in the fall when we’re planting wheat late or have very thin stands, or where we’re planting into a pasture or where we need to break down the residues that are tying up nitrogen in the production system.”

Mississippi growers don’t apply much nitrogen in the fall because they know they’re going to lose it over the winter, says Larson. This makes application timing during the spring very important.

“If we go out too late with that first application of nitrogen, we’re not going to supply the nutrition needed to support as many tillers as that wheat plant has the potential to produce, so we lose wheat potential right off the bat.

“If we do put out nitrogen during that time of the year — which could be during the first couple of weeks of February — the crop won’t enter rapid nitrogen uptake until at least six or seven weeks after that time period. It won’t hit those rapid growth stages until mid to late March. We don’t want all of our nitrogen applied in early February, where it could be subject to tremendous nitrogen losses for five to seven weeks.”

This is why, says Larson, split nitrogen applications are recommended on wheat in Mississippi. “There are years when we have a dry spring, and we probably won’t get responses to split applications in those years.”

Nitrogen, he says, should be delivered according to crop demands, and that means the first application in the spring after dormancy should probably be no more than one-third of the total spring-time nitrogen.

“Then, come back with the remainder of the nitrogen just prior to stem elongation. Some growers who have aerial application capabilities are not making that last application until a little bit later on in the vegetative stages. Then, it just needs to be put out prior to the boot stage.”

phollis@farmpress.com