What factors influence levels of nitrogen fixation in legumes?
The two biggest factors influencing nitrogen fixation in legumes are the cultivar and species of legume host, and the strain of bacteria used as inoculant. Part of the research in the Rhizobium Research Laboratory is on identifying cultivars of bean and soybean that are better able to fix nitrogen, and to better understand the basis for such differences. • Nitrogen fixation is also an energy requiring process, so that anything which influences plant photosynthesis will also affect nitrogen fixation. Such influences can include shading from other plants, enhanced levels of carbon dioxide, or even adequate supplies of phosphate fertilizer, since phosphate fertilizer is used to make adenosine triphosphate (ATP), an energy-rich substance. • Plants that are fixing nitrogen in symbiosis will also differ from N-fertilized plants in terms of their nutrient requirements. Thus in addition to phosphorus, iron is needed for the hemoglobin associated with nitrogen fixation and as a component of the
