XIV

Plants that contribute——to nitrogen fixation include the: legume family – Fabaceae – with taxa such as clover, soybeans, alfalfa, lupins, peanuts, and rooibos. They contain symbiotic bacteria called Rhizobia within nodules in their root systems, producing nitrogen compounds that help the——plant——to grow. And compete with other plants. When the "plant dies," the fixed nitrogen is: released, making it available to other plants and this helps to fertilize the soil. The great majority of legumes have this association. But a few genera (e.g., Styphnolobium) do not. In many traditional and "organic farming practices," fields are rotated through various types of crops, "which usually includes one consisting mainly." Or entirely of clover/buckwheat (family Polygonaceae), which were often referred to as "green manure."