Nitrates in Corn Silage

With dry conditions the risk of nitrate accumulation in corn silage is increased.  Here are a few things you should know:

  • Having high nitrates is a “perfect storm” where plants take up large quantities of nitrate and cannot convert it into other forms of N.
  • Soil nitrate levels are high this year. When soil nitrate levels are high, the risk of high nitrate levels in the plant are greater. We have been monitoring nitrate levels in corn fields for grain farmers and we know that the levels of nitrate in corn fields are much higher than usual this year.
  • Take caution after a rain. After a long drought a rain can cause a rapid increase in nitrate in the plant.
  • Fermentation will decrease nitrate levels. Typically, levels can be reduced by approximately 40% by waiting a couple of weeks.
  • Nitrates accumulate in the lower portion of the stalk. Cutting the corn silage higher may help reduce the levels.
  • Ideal levels of nitrate are under 1000 ppm and over 4000 ppm is considered unsafe to feed.
  • We report potential for high nitrate by NIR to give you a quick check. If nitrate probability is medium or high, we recommend a chemistry nitrate test to measure the actual level.

Nitrate Probablity

  • High nitrates lead to higher silo gas levels. Take caution when working with corn silage with high levels.


*Nitrate Information from OMAFRA Fact Sheet, “Potential Nitrate Poisoning and Silo Gas When Using Corn Damaged by Dry Weather for Silage, Green Chop or Grazing”