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How do nitrogen-fixing cover crops add nutrients to soil?

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A green cotton combine harvests a field of mature cotton plants, with white cotton bolls visible across the landscape. — Agricultural technology Cotton combine harvesting a cotton field.

Nitrogen-fixing cover crops, primarily members of the Fabaceae (legume) family, enhance soil fertility through a symbiotic relationship with nitrogen-fixing bacteria, such as Rhizobium.

These bacteria colonize the plant's root nodules, where they convert atmospheric nitrogen—which is otherwise inaccessible to plants—into ammonia compounds that the host plant can utilize for growth.12

The nitrogen becomes available to the soil and subsequent crops through two primary methods:
* Decomposition: When the cover crop dies or its roots decay, the nitrogen compounds stored within the plant tissues are released into the soil.1
* Green Manure: Farmers may plow the living cover crop directly into the soil, a practice known as using green manure, which incorporates the nitrogen-rich organic matter back into the earth to nourish future plantings.13

Beyond nitrogen enrichment, these cover crops serve as essential tools in agricultural technology by preventing soil erosion and improving overall soil health.13