ABSTRACT
Inorganic N in soils is predominantly in the form of nitrate (NO3) and ammonium (NH4).
Nitrite is seldom present in detectable amounts, and its determination is normally unwar-
ranted except in neutral to alkaline soils receiving NH4 and NH4-producing fertilizers
(Keeney and Nelson 1982). Soil testing laboratories usually determine NO3 to estimate
available N in agricultural soils, while laboratories analyzing tree nursery and forest soils
often determine both NO3 and NH4.
