FATE OF ADDED NITROGEN IN SOILS

Abstract

The transformation of added N in some Manitoba soils was studied in the laboratory. Addition of urea-N to acid soils led to accumulation of nitrite ions and some of this nitrogen was chemically dent-rifled. The initial rate of molecular N production was 3.2% of added N02 per day in acid Well wood soil and 1.4% for acid Pine Ridge soil. Nitrite ions also accumulated in the calcareous Almasippi soil (pH 7.7) for a short period, but was denitrified. Oxidation of ammonium ions was very slow in the acid soil.

Soil fixation of added N was greater at low than at high soil pH, and soil organic matter fixed approximately 5 to 10 times as much N per unit weight as did clay. Liming the acid soils considerably reduced the amount of added N fixed.