Let’s talk nitrogen. 50 lbs. of N


I always like to make the joke that no matter how much money you make, you will be in the same debt as everyone else depending on your house and your car. It is not always true but many times, it is.

We want to maximize things and if we have the capability, we strive to do so.

Let’s talk forages. Ideally, we want high biomass and great quality.

Typically, a recommended rate for nitrogen (N) to stockpile cool-season forages would be 50 pounds/acre as a balance to maximize production compared with costs.

This could be in various forms: just over a hundred pounds of urea (~46% N) or even around 250 lbs./acre of ammonium sulfate (~21% N).

After all that, I should probably get a good 1,500 extra pounds of high-quality forage.

Well, the eastern Ohio OSU Extension educators got together, and while trying to answer one question; inadvertently answered another one as well.

The first question was about nitrogen stabilizers and how well and economically viable they are, but that is for another day.

The question that drew me in was: “What does 50 lbs./acre of N do for forages consistently?”

The way 50 pounds of N came about was in examining these nitrogen stabilizer products. One specifically was a urease inhibitor that would act solely on urea products and should not have much of an effect on something like ammonium sulfate.

We had both, so this way, there would be various controls in the experimental design. The experiment was also intended to simulate forage stockpiling.

Forage stockpiling is allowing the forage to grow late in the season to be grazed as higher quality winter-feed. The experiment was conducted on three grazing, cow-calf operations located in eastern Ohio: Monroe, Noble, and Morgan counties. There were four replicates in each site for accuracy. This experiment was conducted in 2016-2018 for a total of three years.

Let’s look at 2017. Nitrogen applications were made late in July and the plots were measured in mid-November.

Without any additional in-puts (nitrogen), the site in Monroe County produced 1,781 pounds of dry matter per acre; Noble, 2,068; and Morgan, 4,084. Those are drastic differences in site variation alone.

In that year, Morgan produced 56 percent more biomass than Monroe did in similar pasture situations. Remember that it is not all about quantity, but quality is also very important from a producer’s standpoint.

Here is how that looked: Monroe was 12% crude protein (CP), Noble was 13% and Morgan was 10%. A high quality forage will typically be at least 12%; average quality will be over 9%, and low quality below 9% CP.

In that same year, 50 pounds of actual N was put on the cool season grass pastures as both urea and ammonium sulfate (AMS) forms. The forms of N were done in separate areas of the field.

From what we were taught, there should not be too much variation in response to the N unless environmental conditions were prone to volatilize the urea, the less stable form in this case.

Here are the additional biomass gained in pounds/acre:

  Monroe: additional forage with urea was +1,463 and AMS was +1098.

  Noble: additional forage with urea was +499 and AMS was +272.

  Morgan: additional forage with urea was +72 and AMS was +529.

One site almost seemed to have the “expected” response of nearly 1,500 lbs./acre increase in forage (Monroe). Most of the sites were coming up shorter than expected.

As for quality, when examining CP as an indicator, there was not a significant increase due to nitrogen. Variations in quality were consistently correlated with location more so than with the addition of nitrogen.

To me, this brings up questions of soil health and forage type being a driver for quality.

Take home

The point of running through these numbers is to highlight that your field and your neighbor’s field might be similar or they might be very different. There is no doubt that variations in your own fields are there even when you treat them the same.

Not everything works the same and some places will just perform better than others will.

What’s working

Take time to understand what gives you good results and what is not working. Get information by soil testing and keeping records of how much yield you obtain and cost of amendments on your land.

Everyone seems to have the silver bullet, but that bullet could be from a completely different gun. The point is your neighbor does not have your answers, which is something that you have to figure out for yourself.

Advice is never a bad thing, but it might not be the correct answer for a specific situation.

Back to nitrogen

Also, do not be discouraged if you expect a larger response from nitrogen. Sometimes we should focus on areas that do respond to our treatments better than areas that do not.

Current studies have highlighted high corn growth responses to nitrogen at much lower rates than previously done.

Soil health, environment, and novel varieties have such a complex interaction. Finding a financially sound program that works most of the time, not necessarily all of the time, is a grand goal to achieve in a very chemically complex and living environment like your pasture and hay fields.

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