Effect of ammonium or nitrate on nitrogen fixation by a terrestrial blue green alga
Plant and Soil 64(2): 263-266
The effects of ammonium or nitrate-N on biological N fixation by an algal [Nostoc muscorum] crust were compared. Nitrate-N up to 3.0 .mu.mol N g-1 sand/algal crust at 60% water holding capacity did not affect fixation, whereas an ammonium-N concentration of 0.2 .mu.mol N g-1 crust markedly depressed fixation. Consequences of these differential effects are considered.