Wheat growers can arm themselves with more accurate nitrogen recommendations.
A new nitrogen calculator takes into account both soil testing and previous crop credits, as does the more basic decades-old formula, then goes a few steps further, calculating in values for soil productivity, types of tillage, soil organic matter and a cost-return value for based on the cost of nitrogen and value of wheat.
“I think this is such a huge step forward. I’m really excited about it,” says Dave Franzen, North Dakota State University soils specialist.
Added to the calculator is a feature that Franzen considers unique to this type of decision-making tool.
“There were long-term no-tillers that were coming up to me and saying, ‘We really need to do something about these nitrogen recommendations because I started backing off my nitrogen rate several years ago and never looked back,’” he says.
Long-term no-tillers, those who have employed the process for more than 5 years, have learned that they can get by with significantly less nitrogen.
“When we did that, you know, those long-term no-tillers were right. In order to hit a specific yield, it took at least 50 pounds less nitrogen in no-till than it did in conventional till,” Franzen says.
To hit a certain protein target, no-tillers apply 50-plus pounds less nitrogen than conventional tillers. But the 5-year benchmark is critical.
“If you’re a beginning no-tiller, from 1 to 5 years or something like that, it actually takes a little bit more nitrogen because the residue ties it up for a period of time and it doesn’t get used right away,” he says. “So if you’re a short-term no-tiller or you just no-till part time, there’s a 20-pound tack-on of nitrogen. But if you’re a long-term no-tiller, 6 years or more, there’s a 50-pound credit.”
The calculator handles all this, allowing selection of long-term no-till, short-term no-till and conventional till.
In areas that have significant amounts of organic matter in the soil, the nitrogen recommendation can be further refined.
“You really don’t worry about that unless you have 6% organic matter or more,” Franzen says.
About 2% of the soils in the state are such soils, often as small portions of crop fields.
“It’s not a lot of acreage, but if you’re a farmer who has 10 or 15 acres in the middle of a field someplace, it’s something that you need to pay attention to,” he says.
Once the data is entered, the final nitrogen recommendation is displayed as a pounds-per-acre value in a blue box near the bottom of the screen. A note is included next to it, advising the grower to consider a rate within 30 pounds of the number.
“Whether they go higher or lower, that number is kind of up to them,” Franzen says. “They’re supposed to use their common sense. So if you have a low-protein variety, then you probably need to beef it up a little bit. If you’re using a less-than-optimum nitrogen application method, like putting urea over the top and not working it in, or a shallow application of ammonia, you need to beef it up a little bit.”
Also, the amount of straw left on the field can affect nitrogen needs. The standard amount of wheat straw left on an acre is about 2,000 pounds.
“This year, we probably have twice that much in some fields,” he says. “So if you have 2,000 pounds more residue than what you plan on — like if you grew 80 or 90 bushels of small grain instead of 40 or 50 — then you need to add about 30 pounds of nitrogen to take care of what that straw is going to tie up this next year.”
The North Dakota Wheat Nitrogen Calculator is free to use online.