الفهرس 
contentsOnly 14 pages are availabe for public view
 |  | from | 147 |  |  |
| | | from | 147 | | |
Abstract
ological N,-fixation
N2-fixation is the conversion of atmospheric nitrogen into ammonie utilizable by plants and transformed there into Accurate estimates of annual various nitrogen compounds. turnever of nitrogen in the biosphere very from 100 to 200 million metric tons (Deluiche, 1970; Burns & Hardy, 1975). of which 2/3 come from biological sources. Estimates of the contribution of non-symbiotic nitrogen fixers to soil as given by Henzell nitrogen are usually 10-15 T/ha/annum 8 Norris (1962).
2.1.1. Symbiotic 2-fixation
Procaryotes capable of N-fixation have representatives in many genera. The well known examples and most thorou- ghly studied of the biological -fixation processes are the root nodule associations of Rhizobium with legumes (Norris, 1956: Vincent, 1974). The genus of the N-fixing endosymbiotic organisms residing in root nodules of non- leguminous angiosperms such as Casuarina, Alnus. Myrica, Purehis, and Ceanothus was designated as Frankie (an Callahan et al (1978) actinomycete) by Becking (1970). and Burggraaf et al (1961) reported on the isolation and grouth of Frankia on a yeast extract medium. Certain actinomycetes were reparted to nodulate Comptonia and.