Nitrogen concerns in the mix?

This week I sat through three meetings on nutrients of concern in Ohio. Tuesday, Wednesday and Friday — oh and while I was at one on the meetings I got a text with a picture of an Ohio legislator giving testimony on potential new phosphorus legislation.

On Tuesday, I was an invited speaker to the OSU soil fertility class along with a couple of others; the environmentalist of the group said that nitrogen was a great concern environmentally. I knew this but was surprised to hear her say it, because all I hear is about phosphorus and Lake Erie.

I sat through a meeting and discussion Wednesday on managing nitrogen in Ohio using precision application tools. Although the meeting was supposed to be about managing nitrogen, it seems to me it was more about selling goodies to hopefully manage nitrogen. And then on Friday I attended the rollout of the 4R retailer certification program statewide. Several of the speakers mentioned nitrogen, and with the move to a statewide program nitrogen is now part of certification program.

So lets talk about nitrogen management. It leaks, like everywhere. Up and down — up as a gas when the soils are saturated and moves down and out with water movement. Even though 80% of the atmosphere is N we have to supply it for our grass crops. And we add more than we need, because we don’t want to be short — that’s an economic concern.

 

So what can we do about managing nitrogen?

The current tool to make nitrogen recommendations for corn in Ohio is the CNRC; that stands for Corn Nitrogen Rate Calculator. The tool is housed at Iowa State University and includes our Ohio data in the model: http://cnrc.agron.iastate.edu. This includes Indiana and Michigan data and recommendations too — a total of seven states are involved in the tool.

How do you determine your N rate for your crop? The old rule of thumb was 1.2 — 1.2 pounds of N for every bushel of your yield goal. So in the old days for 200 bushel per acre corn, apply 240 units of N. But genetics, economics and environmental concerns have changed that. And we have learned that yield goal is not a factor in setting your N rate.

Nitrogen calculators have been around since about 2005, they are used to calculate the economic optimum rate of nitrogen. With high nitrogen prices and low corn prices, we were looking for the minimum rate to maximize economic yield. Then we went through the high grain prices of 2008 to 2014 — and no one worried as much about the economic concerns. Today’s different.

I made a run on the CNRC with my numbers for next spring — corn at $3.50, N priced at $0.40 per unit N; in Ohio, in a corn/soybean rotation. Our most profitable recommended rate of N would be 168 pounds N; with a profitable range from 153 to 184. The “profitable range” is within $1 per acre of the recommended rate.

So try out the Corn Nitrogen Rate Calculator on you own, with your prices: http://cnrc.agron.iastate.edu. And perhaps think about how to most efficiently use that rate of nitrogen.

 

What practices can you use to keep N where you put, and keep it for crop needs?

  • Right source — NH3 vs. 28% or urea, manure? N is basically the same, generally it goes into the crop as a nitrate. Do make use of the N in manure. And depending on placement and timing, a stabilizer may be necessary for some sources.
  • Right rate — use an N rate calculator? Use the CNRC. Or there are some other models out there, still a lot to learn with these but their goal is to take in-season information into account when selecting the right rate.
  • Right time — as close to the time for crop needs as possible? Corn needs little nitrogen early in the season, but by V8, V10 or so there is rapid uptake. Perhaps apply 40 to 60 N at plant then delay the remainder until V8? Or apply 100 N with anhydrous ammonia pre-plant then use a crop sensor at V8 to determine the needs for the rest of the season.
  • Right place — next to the row, incorporated? Definitely get N into the soil. If we are dry and the nitrogen is on the surface, then it may not get to the crop as needed. Does N need to be next to the row? Not really, we have enough rain and soil moisture in Ohio that we can put it between the rows and the roots will get the N.
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