Nitrate Nitrogen or Nitrate — What's the Difference?

Nitrate Nitrogen or Nitrate — What's the Difference? October 26, 2016

I just got the nitrate test results back from the lab and the level was 3,000.  Am I in trouble?

Every year I get questions similar to this one from individuals who have just had their forage tested for potential use as a livestock feed.  Unfortunately, with just this information I can’t give a useful answer. I need to know whether the number they're looking at was reported as nitrates or as nitrate nitrogen.

Why is it important to know the difference between nitrate nitrogen and nitrates?  Using the previous example, if the score was 3,000 parts per million of nitrate nitrogen, the forage has a nitrate concentration that is almost 50% higher than what we often consider to be potentially toxic.  It would be risky for cattle to eat this forage without taking some precautions.

However, 3,000 parts per million of nitrate should not be a problem since this is less than one-third the danger level for nitrates.  Thus, the same number can reference something quite dangerous or something perfectly safe.

These big differences are due to how individual labs test for and report results for nitrates.  Labs that report nitrate concentration are referring specifically to the nitrate ion, designated chemically as NO3-.  Most labs and advisors consider 9,000 to 10,000 parts per million of the nitrate ion to be the level where toxicity concerns begin.

Some labs, though, report the amount of nitrogen in the nitrate ion as nitrate nitrogen and report it chemically as NO3-N.  Thus, a much smaller amount of nitrate nitrogen is needed to produce the same effect as the entire nitrate ion.  As a result, the danger level for nitrate nitrogen begins between 2,000 and 2,300 parts per million.

Next time you test your hay, corn stalks or cover crop for nitrates, look closely to see how your lab reports your results.  Then, when you talk with someone about the safety or feeding options for your forage, you can be sure both of you are talking the same language.