How do legumes improve soil fertility?

Legumes contribute to improving soil fertility primarily through their ability to fix atmospheric nitrogen via a symbiotic relationship with nitrogen-fixing bacteria found in their root nodules. This process allows legumes to convert freely available nitrogen gas from the atmosphere into ammonia, which can then be used by plants. As legumes grow and eventually die or are tilled into the soil, they release this nitrogen back into the soil, enhancing its fertility and providing essential nutrients for subsequent crops.

This nitrogen fixation is particularly valuable in agricultural systems, as it reduces the need for synthetic fertilizers, thus promoting more sustainable farming practices. Furthermore, the incorporation of legumes into crop rotations can enhance overall soil health and biodiversity, as well as improve soil structure.

In contrast, the other choices do not align with the fundamental role of legumes in soil fertility. While legumes do not absorb all nutrients and store them or decrease soil nutrient content, their efficiency in utilizing water compared to other crops does not directly pertain to their role in enhancing soil fertility.