All living things need nitrogen to survive. Humans and animals are able to take in nitrogen from the air; most plants can only absorb nitrogen from the soil. Thus, the expensive commercial nitrogen fertilizers, if not used properly, can evaporate into the air as a greenhouse gas, which then contributes to climate change, or leach into the soil, polluting water supplies. Legumes offer a way to greatly decrease these side effects. The nodules on their roots act as mini-factories – and the factories’ output is nitrogen-rich fertile soil.

It all starts with planting a field of legumes. Through a biological process, the nodules on the roots are able to capture nitrogen from the air, which enables the plant to grow. When the legumes are harvested, not only does the yield provide food and income for the farmer, it leaves nitrogen-rich residue behind in the field. As that residue decomposes, the nitrogen in the nodules become incorporated into the soil as a natural fertilizer – a green manure – that will be there to nourish the next crop – meaning the farmer will be able to use less or even no chemical fertilizer for the next cropping season.