How does nitrogen fixed by legumes become available to other plants?

Legumes in the order Fabales form a mutualistic symbiosis with Rhizobium bacteria within their root nodules. These bacteria convert atmospheric nitrogen into ammonia, which the host plant uses for its own growth and development.12

The nitrogen fixed by these legumes becomes available to other plants primarily through the process of decomposition. When the host plant dies or sheds its parts, the nitrogen-rich compounds stored in its tissues—including its roots—are released into the soil as the organic matter decays. Once in the soil, these nitrogen products undergo further microbial transformations, such as ammonification and nitrification, which convert them into forms like nitrates that other plants can readily absorb and incorporate into their own tissues. Additionally, farmers often utilize this process by plowing legumes under as green manure to enrich the soil for subsequent crops.23