What do legumes like alfalfa contribute to the soil?

Legumes, such as alfalfa, play an essential role in enriching soil quality primarily through nitrogen fixation. They have a symbiotic relationship with specific bacteria, primarily those in the genus Rhizobium, which live in their root nodules. These bacteria convert atmospheric nitrogen into a form that plants can use, which is crucial for plant growth and development. When legumes decompose after being cut or when they die, the nitrogen that was stored in their biomass becomes available to the soil, contributing to its fertility.

This nitrogen contribution is particularly significant in crop rotations and sustainable agricultural practices, as it can enhance the nutrient profile of the soil without the need for synthetic fertilizers. Although legumes do impact other nutrients in the soil to some degree, their most notable contribution is the substantial amount of nitrogen they add, making them a vital component of many agricultural and ecological systems.