Nitrogen Use Efficiency, Nitrogen Fertilizers, NUE, Nitrogen and the EnvironmentCritical Tissue N Levels , AGE of Water
World Nitrogen Use Efficiency for Cereal Production is 33%,
Agronomy Journal 91:357
Forage Critical Levels for Cattle Consumption  
5000 ppm NO3 (pregnant cows)

10000 ppm NO3 (calves and steers)

Seasonal and long-term changes in nitrate-nitrogen content of well water in Oklahoma.  1997.  J. Environmental Quality, 26:1632-1637.
Water Age:  Pre WWII, post WWII
Hiroshima, August 6, 1945 (Japan surrendered, August 15)
Industrial Age: production of commercial fertilizer (inorganic), 1946
Was NO3 in ground water from inorganic fertilizer or mineralized soil organic matter?
Nitrate Toxicity in Livestock (OSU Fact Sheet 2903)

Trimble Pocket Sensor, Greenseeker, NDVI, nitrogen