Nitrate Poisoning in Drought-Stricken Corn and Sorghum Fields

There will be some years in Texas when, even following the recommended management practices, the rainfall is not sufficient to support profitable grain yields. When grain crops have been established satisfactorily, and rainfall is insufficient to support grain yields for economic harvesting, alternative uses of the crop should be considered very cautiously. This is especially true with respect to fields which have been fully fertilized with nitrogen for normal yields. Crops which appear to be sufficiently drought-stressed that grain yields will be too low for harvest, and the alternative of harvesting the crop for its forage value is considered, the producer should collect stover samples and have them analyzed for excessive nitrates. Plants that are stressed by drought may accumulate nitrate to lethal levels. Therefore it is very important to have the nitrate test run on the plant tissue before it is either grazed or mechanically harvested for livestock consumption.

Stover samples should be collected which includes the whole plant as will be harvested. The equivalent of five corn or sorghum plants should be submitted for nitrate analysis. It should be remembered that nitrates in the lower stalks will likely be higher than that in the leaf tissue. Also, nitrates will not decrease in harvested crop plants. Therefore, before harvesting drought-stressed crop plants as forage, the nitrate content of a representative sample of these plants should be determined. Nitrate analyses of crop plant samples may be obtained from the Texas Agricultural Extension Service, Soil, Plant, & Water Testing Laboratory in College Station. More information can be obtained from your local county Extension agent's office. The local veterinarian should be consulted if drought-stressed forage is to be fed. [See Extension Publication L-5149 "Preventing Nitrate Problems in Drought-Damaged Corn".]

Limited rainfall and resulting short forage supplies have forced livestock producers to consider utilizing corn and sorghum fields for forage. Corn and sorghum stubble, or corn and sorghum fields which are too dry to make a crop, can be utilized by livestock through haying, silage or grazing.

Corn, sorghum or weed plants that contain more than 1 percent nitrates (on a dry matter basis), may result in livestock death when fed or grazed. Even if the animals survive this level of nitrates, other economic losses may occur, such as: abortion, weak or poor viability of recently born young, infertility and difficulty in conception, lameness, and decreased milk production.