Forage nitrate analysis: laboratory performance study.

Four forage samples were analyzed by 16 laboratories for KNO3 content. Individual reported KNO3 values varied widely for each sample; coefficients of variation for the 4 samples were 36.0, 51.0, 12.8, and 55.0%. Recovery of KNO3 from the spiked sample averaged 105%. The analytical results, as a group, were unacceptable both statistically and for use in feeding recommendations. Three values reported could have resulted in feeding potentially toxic forage to livestock.