Guest Columnist
Most are aware that legumes make excellent cover crops in gardens while helping to build up nitrogen in the soil. We use a mixture of crimson, Dutch white and red clovers in our three gardens at home. The clovers protect the soil in multiple seasons by providing cover. Knowing they provide nitrogen is one thing, but how they do it, however, is another!
Nitrogen is it exists in the atmosphere (N2) cannot be used by plants. It has to be converted to an NH3 form before it can be used to manufacture needed nutrients such as nucleic and amino acids, proteins, etc. needed by plants to survive, grow and prosper.
With legumes, we’re talking about plants such as soybeans, peas, beans, vetches, alfalfa, clovers, and peanuts. These plants have tiny nodules on their roots that are invaded by “good” soil bacteria (not fungi) called rhizobia and establish a symbiotic relationship with the legume.
The root nodules provide rhizobia with a place to live, while the rhizobia pull nitrogen out of the soil air, convert it to ammonium-nitrogen (NH3) and use it to feed the legume. This is important, because as already indicated; the legumes are unable to do this conversion themselves.
The result is that the legumes can generate their own nitrogen fertilizer. This conversion process can provide anywhere from 25-75 pounds of nitrogen per acre per year, considerably reducing nitrogen fertilizer requirements for the cash crop.
On the other side of the fence, legumes work with soil fungi (mycorrhiza) to obtain other needed nutrients needed for growth. The result is a nutrient rich legume that can feed carbohydrates to the mycorrhiza, and as portions of the roots die (a daily occurrence) or the entire plant dies, the nodules provide nitrogen to your cash crops, thus reducing overall fertilizer requirements.
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