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Garden with Insight v1.0 Help: legume

A legume is a plant belonging to the plant family Leguminosae, which includes peas, beans, alfalfa, vetch, and clover. Legumes have a unique symbiotic relationship with bacteria that form nodules on the plant's roots: the bacteria use carbohydrates from the plant and fix atmospheric nitrogen (N2), making it available to plants as nitrate (NO3-). Because of this symbiosis legumes usually take up little nitrogen from the soil, and sometimes increase the net amount of nitrogen in the soil. This is why legumes are often called "green manures." Rotating a crop that needs a lot of nitrogen with green manures can reduce the amount of fertilizer needed. It is also important to maintain a healthy soil ecology so that these symbiotic bacteria can thrive to carry out N fixation.

In this simulation nitrogen fixation is calculated for leguminous plants every day. Nitrogen fixation is a fraction of the nitrogen demanded by the plant that depends on the heat unit index of the plant (because it takes time for the symbiosis to develop), the amount of nitrate already in the soil, and the soil water content. We assume here that the bacteria to form the N fixing symbiosis exist in adequate numbers, either in the soil or as an inoculant on seeds.

How it works:
nitrogen fixation
heat unit index

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Updated: March 10, 1999. Questions/comments on site to
Copyright © 1998, 1999 Paul D. Fernhout & Cynthia F. Kurtz.