Lucerne trees’ nitrogen-fixing nodules

Here are the nitrogen-fixing nodules on the roots of our young saplings.  These rhizobia nodules develop on young lucerne trees’ roots once they are potted into the soil or planted in your lands. 

“Rhizobia is the group of soil bacteria found in the soil that infect the roots of legumes to form root nodules where they fix nitrogen gas (N₂) from the atmosphere turning it into a more readily useful form of nitrogen. Rhizobia live in a symbiotic relationship with legumes.  From here, the nitrogen is exported from the nodules and used for growth in the legume.” Wikipedia

This glorious tree, as well as all other legumes such as clover, alfalfa, beans, peas, and soybeans, develop rhizobia nodules on their roots which feed themselves, your soils and their neighboring plants with nitrogen! This means that your lucerne tree provides its own fertilizer and shares this with nearby plants, making it an incredible, full-time, fertilizer-producing companion plant to your fruit trees and vegetable gardens – a permaculture wonder plant!

Many poor farmers do not have access to fertilizers, so the sustainability of rhizobial inoculum is an important aspect in saving money. Other crops planted after a legume are healthier and higher yielding, so planting food forests, vegetables and fruits near or under lucerne trees will automatically receive this wonderful “free” fertilizer.

Because our seeds and saplings come from soils that already have this bacteria, our trees do not require an inoculant. However, if you prefer to inoculate your seeds we recommend the Groundnut & Cowpea Group Inoculant which contains Bradyrhyzobium sp. (Vigna) bacteria, a bacterial legume inoculant. We do not supply inoculant, but you can order a packet from your local agricultural supplier. Once your trees establish rhizobia, they will automatically ‘infect’ your soils with this bacteria and your trees and their seeds will not require any additional inoculant.

Do NOT add any nitrogen-rich fertilizer or manure when you plant out your young trees. This added nitrogen will prevent your saplings’ roots from developing and forming their rhizobia nodules and nitrogen can actually burn their sensitive feeder roots at this stage.

We do add about 50g of rock phosphorous in each hole when we plant out our young trees.  Phosphorus is an essential nutrient for plants in the nitrogen cycle. Higher nitrogen levels will help to make more phosphorus (and other minerals) available for the plants, but by making sure there is available phosphorus at the beginning it will speed up the whole process. With time and larger sized plants, and with mycorrhiza fungi inoculation and efficient nitrogen fixation, your lucerne trees will be able to make phosphorus that’s already in the soil available. You can read more here – permaculturenews.org.  We always add a generous amount of compost into our holes when we plant out our trees.

Happy farming!