AMMONIUM FIXATION AND AVAILABILITY IN VERMICULITE

Abstract

Natural vermiculites absorb 40-85 m. eq. of ammonium per 100 g. that is not released by extraction with [image] KC1. The quantity so absorbed is about 70-90% as high when kept moist as when heated at 100[degree]C. This ammonium is slowly extracted with either [image] NaCl or [image] CaCl2 and is readily removed by boiling with 0.2 [image] NaOH, but not with 0.2 N KOH. Minerals that have been exfoliated by heating absorb less ammonium. In natural vermiculites the fixed ammonium was about as available to nitrifying bacteria as that in ammonium sulfate in 2 samples but largely unavailable in 3d sample. The cation exchange capacity was not an important factor in N release to bacteria.