Green fertilizers: why and how to use them to enrich your soil naturally

Planting green manure is an extremely virtuous technique that benefits the health of the soil and the crops that thrive there, but which still remains largely unknown to the majority of gardeners.

At Floramama, we have been sowing green manure every season for several years now and we would like to convince you of all the benefits that come from it!

What is green manure?

A green manure is a crop that can be plowed into the soil or left as a cover crop to protect the soil, improve its structure, and enrich it. Our fertilization plan is complemented by growing cereals and legumes (pea mix, oats in our case) that we use as green manures. Cereals act as a vertical support for the growth of certain legumes, in addition to providing carbon, while legumes provide nitrogen. Many varieties of legumes also have the exceptional power to capture nitrogen from the air and return it to soil level.

Called "nitrogen fixation," this process is made possible by rhizobia-type bacteria. These form nodules on the roots of legumes through which the exchange takes place. It is possible to check whether nitrogen fixation is taking place by digging up the roots of a legume plant to confirm the presence of nodules. The bacteria necessary for the process may not be naturally present in soil that has not supported legumes for a long time. In this case, it is possible to inoculate the seeds with the right bacteria at the time of sowing.

Green fertilizers are also used to add organic matter to the soil (burial), protect it (plant cover) or prevent the proliferation of weeds (plant cover).

If we choose to use a green manure to improve the organic matter of the soil , it must be mown just before flowering, when it is most nitrogen-rich but still tender enough to decompose easily. We accomplish this task using a flail mower, which not only cuts the greenery, but also shreds it as it passes, making the residue smaller and accessible to decomposers in the soil. We then bury it just a few centimeters below the soil surface using a rotary harrow or by transporting the soil from the paths on top of the bed using a rotary plow. Finally, we cover everything with a screening fabric to create an inviting environment (dark and humid) for microbial life, which takes care of decomposing everything.

If you want to use a green manure to protect the soil from erosion and leaching in winter , i.e. as a cover crop, you must sow it at least six weeks before the hard frosts to ensure that its root system is sufficiently developed to allow its growth. And a late cover crop of one inch in height is better than soil left bare during the cold season.

Green manures can also be sown as a cover crop during the season to prevent weed growth in a bed that will be left unplanted for a long time. For example, buckwheat, known for its rapid growth, can be sown, which will quickly form a cover crop that prevents weeds from proliferating, in addition to promoting soil life and attracting a large number of pollinators.

In summary, why is it virtuous to plant green manure:

• Limit weeding

• Prevent soil erosion, leaching and drying out

• Improve soil quality and structure

• Increase organic matter

• Produce reserves of potassium, phosphorus or nitrogen

• Avoid the proliferation of phytosanitary attacks

• Can be used as mulch when left on the surface

There are many gentle and natural methods to support crops in a virtuous way, and the more we put them into practice, the more virtuous our relationship with nature can become. This is the system we try to promote at Floramama, and we hope to inspire you to put it into practice on your side :)