Using On-Farm Nitrate Test Kits as a Forage Management Tool.

Nitrate accumulation can be a serious problem in certain forage species. Livestock consumption of high nitrate forage causes reduction in livestock growth and production, and can be fatal. Nitrate accumulation is worse in droughty years and with nitrogen fertilization. The Nitrate Elimination Company, Inc. (NECi) has developed an enzyme based on-farm test kit as a tool for assessment of forage safety. The kits allow producers to accurately assess risk from nitrate poisoning within minutes. Ensiling and blending with low nitrate forage are methods of reducing forage nitrate concentration. Pearl millet (Pennisetum glaucum) a nitrate accumulating species, redroot pigweed (Amaranthus retroflexus) nitrate accumulating, common lambsquarters (Chenopodium album) nitrate accumulating, and giant foxtail (Sefaria faberi) non-nitrate accumulating, were ensiled to determine nitrate reduction after ensiling and assess test kit accuracy. The four species were ensiled individually as well as 50% blends of weed species with pearl millet. The reduction in nitrates after ensiling ranged from 1250–38 parts per million of nitrate nitrogen (ppm NO3-N) with an average nitrate reduction of 84%. The recommended threshold of nitrate nitrogen in safe forage is under 350ppm. Fresh redroot pigweed and common lambsquarters had dangerous nitrate levels, but were reduced to safe levels with ensiling. Overall forage digestibility also improved with ensiling. Crude protein levels from blended silage for 50% giant foxtail, 50% common lambsquarters, and 50% redroot pigweed were as follows; 9.10%, 12.81%, and 11.06%, respectively. The colorimetric test kits were an accurate and efficient way of measuring forage nitrate concentration. One disadvantage to the test kits is the difficulty of obtaining sap for the test from very dry samples. Overall, these test kits are a good tool for farmers because of the simplicity and accuracy of on farm testing.