Evaluation and significance of associative dinitrogen fixation for arid soil rehabilitation

Abstract There are indications that in soils of arid lands associative dinitrogen fixation may be an important factor in providing plants with nitrogen. The actual values of fixation rates and amounts of nitrogen accessible to vegetation are difficult to determine due to inherent difficulties with the commonly used acetylene reduction methodology. It appears, however, that the arid zone plant species forming rhizo‐sheaths are best suited for rehabilitation purposes. The rhizosheath‐forming plant species show more consistent and higher dinitrogen fixation rates than those without the rhizosheaths. In general, the phenomenon of dinitrogen fixation by root‐associated, nonnodule‐forming organisms is poorly understood. There is a dire need for experimental work with 15N2 in the field to ascertain the actual amounts of fixed dinitrogen delivered to vegetation in various environmental situations.