SDSU Forage Tests Show High Nitrates in Some Samples

BROOKINGS, S.D. -- More than 1,000 forage samples tested as of July 30 show high nitrate levels are frequent in South Dakota corn, oats, barley, and sorghum/cane, but are not as common in wheat.

About one-half of the corn samples, one-third of the oat samples and one-fourth of the barley samples have been potentially toxic to livestock.

That's according to Nancy Thiex of Olson Biochemistry Laboratories at South Dakota State University, where the testing has been done.

Thiex said the laboratory is receiving about 40 forage samples daily as drought-stricken producers test crops for toxic nitrate levels. Farmers and ranchers are haying, grazing or ensiling small grains and corn to feed livestock.

Thiex said SDSU research shows that 0.15 percent of nitrate nitrogen on a dry matter basis is safe for livestock.

She added that there's always a risk with using crops as forage, and that a test is only as good as the sample -- if it's not representative of the field, or not representative of what will be harvested or fed, it may not accurately reflect nitrate levels in the crop or in the forage that will be fed. Consult local Extension agronomy educators for tips on sampling.

Here's a look at what test results so far indicate from South Dakota:

Corn: Of the 154 samples tested so far, more than half -- 53 percent -- were potentially toxic. Ten percent of the total were so high in nitrate that SDSU doesn't recommend feeding it even if diluted, which means producers would likely have to ensile the corn or let it grow longer in order to reduce the nitrate levels. Proper fermentation during the process of making silage reduces nitrate levels.

Oats: SDSU has tested more than 270 oat samples so far. Oats is the small grain most likely to show high levels of nitrate. "On oats about 66 percent of the samples are safe and 34 percent are potentially toxic," Thiex said.

Barley: SDSU has tested 23 samples. "About one-fourth of the barley samples, or 25 percent, are potentially toxic. About three-fourths are safe to feed," Thiex said.

Wheat: SDSU has tested about 490 samples. "On wheat, 96 percent of samples were safe to feed," Thiex said.

Of the samples that were potentially toxic for all three small grains, Thiex said most could be fed by limiting the forage to no more than one-half of the total dry matter in the ration, or in some cases to no more than one-fourth the total dry matter, depending on the nitrate level.

Only a very small portion of the small grain samples -- 3 percent of the oats, and less than 1 percent of the wheat -- were so high in nitrate that SDSU doesn't recommend feeding it at all, even if diluted by other feed. None of the barley samples showed levels so high that the forage couldn't be used by diluting it with other grain.

"The bottom line is that most of these small grain fields are manageable," Thiex said. "Producers should test to find out what level of nitrates they are dealing with so they can assess the risk. The risk can be reduced by properly managing the feeds they have available and diluting their forage with other feed sources if necessary."

Ensiling forages is also an option for reducing nitrate levels.

Sorghum/cane/sudan: SDSU has received so few samples that it's hard to draw firm conclusions, Thiex said, adding that producers don't always use the same names for those crops. But of the 15 samples labeled "sorghum," 10 have been potentially toxic, two of them too toxic to dilute.

Of the five samples labeled "cane," four have been potentially toxic -- all of them too toxic to dilute.

Of the six samples labeled "sudan," only one has been potentially toxic.

Weeds: A few producers also are testing weed samples as they search for alternate feeds for livestock. Thiex said that's potentially dangerous because many weeds -- among them wild sunflower, pigeon grass, pigweed, kochia, thistle -- are known to accumulate high levels of nitrate. Of the three kochia samples tested by SDSU, all are potentially toxic above the level recommended for feeding to livestock. Three samples labeled "weeds" were potentially toxic.

Sunflower: Of the four samples received, three are potentially toxic, two at high levels.

Contact: Nancy Thiex, (605) 688-5466
** For links to other sites showcasing SDSU's work in teaching, research, and Extension, visit http://sdces.sdstate.edu.

Lance Nixon, Editor
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-4653
Lance_Nixon@sdstate.edu