Abstract
The NH4-fixing properties of twelve West Indian soil clays representing six diverse soil types from Trinidad and Barbados were studied. The data indicate that the clays have high native NH4 contents-due most likely to prolonged use of nitrogenous fertilizers and some mineralization. All clays fixed NH4 in amounts ranging from 1·06 to 9·54 mequiv./1OOg. NH4 fixation was associated with reductions in surface area and mineralogical changes were evident in one of the samples.
