Common or spring vetch - Green manure

The common or cultivated vetch, in Latin Vicia sativa, is a leguminous annual plant cultivated on a large scale as a forage plant, but also used as a green manure between two vegetable crops. It has the ability to fix atmospheric nitrogen in its roots, helps to loosen the soil, limits weed growth, and prevents soil compaction caused by rain. It is sown from March to June or from July to September in an empty plot in the vegetable garden or raised bed. It should be buried after destruction, from May to August or from October to February depending on the sowing date. Particularly suitable for poor and heavy soils, it is recommended to avoid using this green manure before planting beans, peas, onions, garlic, and shallots.

The vetch has flexible stems with pinnate leaves consisting of several leaflets and ending in a tendril. This tendril allows it to easily cling to supports since the vetch has a climbing habit. The vetch is often sown in association with a cereal crop (such as rye), which serves as a support. Its flowers have an irregular corolla with 5 petals and are violet in color. It produces elongated pods with protein-rich seeds. Thanks to its vigorous growth and extensive coverage, it effectively suppresses the development of weeds. Vetch is suitable for clay soils but is not very frost-resistant.

Widely used in organically cultivated gardens, green manures like vetch have many advantages. They nourish and improve the soil by providing various nutrients and stimulating soil microbial life. Their roots loosen, break up, and aerate the soil. Furthermore, the presence of a vegetative cover protects the soil from leaching (nutrient loss in sandy soil), rain compaction (formation of a crust in loamy soil), and erosion (caused by runoff on sloping terrain during heavy rains). This vegetative cover also helps to limit weed growth by preventing the growth of unwanted plants. Finally, green manures are often attractive to pollinators as they provide nectar and pollen.

Green manures are sown on uncultivated plots or intercalary plots between rows of vegetables. They can be naturally destroyed by frost or by mowing before seed formation. Once destroyed, they can be left in place as mulch, or shredded and incorporated into the top layers of the soil, or collected and added to compost.