Native Clay-Fixed Ammonium Content, and the Fixation of Added Ammonium of Some Soils of Eastern Canada

A study was made of the native clay-fixed NH 4 + of some typical soils of Eastern Canada. Usually the amount of fixed NH 4 + was related to the clay contents and increased down the profile but there were frequent exceptions to both of these generalizations. The amounts found ranged from 12 to 450 μg fixed NH 4 + –N/g soil. In general, with some cultivated soils, the cropped areas had lower native fixed NH 4 + contents than areas that were in sod. The capacity to fix added NH 4 + was usually low in the sandy soils and in general the B and C horizons fixed more NH 4 + than the A horizons. For the soils that did fix NH 4 + , a larger amount but lower percentage was fixed as the amount of added NH 4 + was increased. The amount of water in which the NH 4 + was added had a slight effect on the percentage fixed, being a little lower as the amount of water was increased. The cultivated New Brunswick surface soils had low NH 4 + fixing capacities. Analysis of the clay mineralogy of some soils showed a fairly close relationship between vermiculitic clay content and NH 4 + fixation.