Last week, we received an interesting phone call regarding nitrates in hay and the process for having the hay tested. So, I thought we would share the highlights of the discussion.

High nitrate concentrations are often found in oats, barley, wheat, sorghum, sudangrass, millet and corn, and many weeds like kochia, Russian thistle, and pigweed. On rare occasions, even alfalfa can have high nitrate levels.
Nitrate itself is not toxic to animals, but at high levels, it can cause nitrite poisoning.

Nitrogen from the soil is taken up by plant roots in the form of nitrate. Plants convert nitrate to nitrite which in turn is converted to ammonia and then to amino acids, the building blocks of protein. Plant tissue collects nitrate during the night when there is no photosynthesis. During the day, nitrate is quickly converted to protein when adequate sunlight energy is available.

Under normal growing conditions, there is little nitrate buildup in plants. However, drought, frost, extended cool temperatures, hail, herbicide damage or other stressful conditions can put a stop to plant growth. The roots accumulate nitrate faster than the plant can convert nitrate to protein.
At normal levels, forage nitrate is broken down by rumen microbes to nitrite (NO2), and then further to ammonia (NH3). This ammonia is then converted to protein by the rumen microbes for use by both the animal and its rumen microbes.

When higher than normal amounts of nitrate are eaten, an accumulation of nitrite may occur in the rumen. Nitrite will then be absorbed into the bloodstream and will render hemoglobin unable to transport oxygen. Thus, when an animal dies from nitrate poisoning, it is from asphyxiation.

Nitrates are nonvolatile and remain in plants after cutting, curing and baling. Nitrates are soluble in plant tissues and will leach from the plant during sustained rainfall. However, since weathering greatly reduces the nutritional value of hay, it is not a good way to manage nitrates.

Fortunately, the Texas A&M AgriLife Extension Service Soil, Water and Forage Testing Laboratory offers testing which indicates the level of nitrates in forages.

For sampling hay bales, the Forage Testing Laboratory recommends using a hay probe to take one core for each 5 large round bales (or 1 core for each 100 small square bales). All subsamples should then be combined and mixed thoroughly. Hay should be cut into stem lengths of 3 inches or less, being careful to prevent leaf loss. Afterwards, place the samples in a paper sack or envelope (avoid using plastic bags, fertilizer bags, or feed sacks, as these containers may produce inaccurate results).

For greater details, contact the Sutton County Extension Office at 387-3101.