January 10, 2025, 4:19 pm | Read time: 3 minutes
Nodule bacteria are the secret stars of the soil. They form a symbiotic relationship with legumes and provide the plants with a valuable nutrient – nitrogen. Read here to find out how this works and how the bacteria benefit from it.
Most vegetable gardeners will have heard the term “nodule bacteria” before. But many people don’t know exactly what these bacteria are all about. On myHOMEBOOK, you can learn more about these special soil organisms.
What Are Nodule Bacteria?
Nodule bacteria, also known as rhizobia, are secret supporters in the garden. They bind nitrogen from the air and make it available to legumes such as beans, peas, soybeans, chickpeas, peanuts, and lentils. Other legumes such as clover, lupins, and alfalfa also benefit from cooperation with the bacteria.
What Do the Bacteria Have to Do with Nodules?
The name “nodule bacteria” comes from the small thickenings that form on the roots of the host plants. The process of nodule formation begins with chemical signals from the plant that attract the bacteria. As soon as the bacteria have arrived, they penetrate the root cortex and trigger specific cell divisions. This creates the nodules in which the bacteria colonize. The inside of the nodules is usually pink-red in color. This color comes from an iron-containing protein that ensures an optimal oxygen content.
How Does Nitrogen Fixation Work?
Nitrogen is a vital nutrient for plants. Although it is abundant in the air, it cannot be absorbed by plants in its elemental form. The nodule bacteria use an enzyme called nitrogenase to convert atmospheric nitrogen into a form that is available to plants. This process takes place in the nodules. In return for their performance as a nitrogen supplier, the bacteria receive sugar and nutrients from the plant’s photosynthesis.
Advantages of Nodule Bacteria in the Garden
Nodule bacteria increase soil fertility and promote plant growth. They reduce the need for artificial fertilizers and improve the soil structure in the long term by building up organic material that loosens the soil and increases its ability to store water. This benefits not only the legumes themselves but also the subsequent crops. Enriching the soil with nitrogen also supports plants that do not use nodule bacteria themselves.
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How Can Gardeners Use Nodule Bacteria?
- Targeted plant selection and crop rotation: The cultivation of legumes such as beans, peas, or lupins helps to increase the nitrogen content of the soil. Alternating crop rotation with plants that have a high nitrogen requirement, such as cabbage or pumpkin, makes optimum use of the benefits of this enrichment.
- Green manure: Plants such as incarnate clover or the winter white pea can be tilled under to store nitrogen in the soil and improve the soil structure. At the same time, green manure protects against erosion and supports soil organisms that contribute to humus formation.
- Bacterial inoculants: Soy requires very special nodule bacteria of the genus Bradyrhizobium japonicum for successful growth. However, as soy is not a plant native to our latitudes, these bacteria do not occur naturally in our soils. It is, therefore, advisable to inoculate the beans with these bacteria before sowing. The inoculant is usually available where you buy seeds.
- Targeted soil improvement: Nodule bacteria can be used specifically on nutrient-poor soils. Together with the use of compost, this improves soil fertility in the long term.