Studies on non-symbiotic nitrogen fixation in New Zealand tussock-grassland soils

Abstract

Soil samples from a number of tussock-grassland soils have been examined for the presence of non-symbiotic nitrogen-fixing micro-organisms and estimates made of the contribution by these organisms to the nitrogen status of tussock-grassland soils.

Blue–green algae belonging to three genera (Anabaena, Nostoc, and Tolypothrix) and bacteria belonging to seven genera (and Rhodopseudomonas) were isolated, although of these only Clostridium species was found to be ubiquitous. Estimated numbers of these organisms in the soil were generally low.

Acetylene-reduction assay of unamended soil samples indicated annual rates of nitrogen fixation equivalent to 0-3 kg N/ha.

Additional information

Notes on contributors

M. A. Line

M.A.L. is a Miss E. L. Hellaby Indigenous Grasslands Research Fellow.