Wheat nitrogen management

By Matt Reese

As wheat fields around the state are greening up, last year’s wet fall, late harvest and marginal prices have left many questions about wheat this spring.

In the case of John Hoffman, in Pickaway County, the wheat crop is looking good so far. Hoffman got his soybeans off early last fall and got the wheat planted in good time. He was able to apply his first 28% on March 5, which is normal, and hopes for a second application around April 15. Weeds were sprayed last fall prior to planting and control seems to be holding so far in most fields.

“Wheat looks good in the area if it was planted early,” he said. “You can tell the fields that were planted a little late and wet. With this weather, we could have a dramatic improvement in wheat quality if these conditions continue.”

It is also time to make some decisions about nitrogen on wheat.

“Spring nitrogen should be applied between greenup (now) and beginning stem elongation (Feekes 6). Ohio State University research has shown that yields are not affected by delayed nitrogen until after early stem elongation (generally the end of April),” wrote Ed Lentz, with OSU Extension, in a recent CORN Newsletter. “Studies over the last five years have shown that yields were the same or slightly better when a single application occurred at Feekes 6 (first node visible of early stem elongation) compared to initial greenup. Yields dropped 10-15% when a single application was delayed to early boot stage. At this time, we would recommend producers to apply N as soon as field conditions allow application equipment.”

In addition, Lentz suggests that stands be carefully evaluated for estimated yields compared to other years.

“Many fields in Northwest Ohio were planted late and will most likely result in a yield reduction. Also, many fields have drowned out areas. Increased N rates will not correct these problems,” Lentz wrote. “A realistic yield potential is needed to determine the optimum nitrogen rate. As a producer, you can greatly increase or reduce your N rate by changing the value for yield potential.”

Tri-State recommendations use the following equation for mineral soils, which have both 1% to 5% organic matter and adequate drainage: N rate = 40 + [1.75 x (yield potential – 50)].

“We do not give any credit for the previous soybean crop, since we do not know if that organic N source will be released soon enough for the wheat crop,” Lentz wrote. “Generally, we would recommend that you subtract from the total (spring N) any fall applied N up to 20 pounds per acre. Based on the equation above and deducting 20 pounds from a fall application, we would recommend a spring application of 110 pounds N per acre for a yield potential of 100 bushels, 90 for 90-bushel potential, 70 for a 80-bushel potential and 40 pounds of N per acre for a 60-bushel potential.”

Lentz also points out that there may be more N available to wheat due to the mild winter conditions and, for split applications, the first application should be the smaller amount. And, of the common N sources available, ammonium sulfate would have the least potential for loss, followed by urea, and 28% solution the most potential for loss.

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