ates produced by the plant. In return for the carbohydrates expended by the plant, the plant receives nitrogen, which is fixed by the Rhizobium.
             The available nitrogen in the soil can affect the process of nitrogen fixation. Nitrogen influence can be stimulating or depressing depending on the amount of nitrogen supplied. The highest rates of nitrogen fixation are obtained when nitrogen is available in amounts sufficient for vigorous plant growth in the first few weeks of legume establishment. If levels increase, nodule weight and nitrogen fixation rate decline drastically, high concentrations can even inhibit root infection with Rhizobium.
             Legumes also have feed feed back control mechanisms; the
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