Well, yes, but no. A well nodulated clover plant is manufacturing N for it's own use. But, the same nitrogen is available ONLY for its internal use. The release of nitrogen into the soil and available for other plants occurs as parts or all of the clover plant dies.
https://www.agprofessional.com/article/how-do-clovers-add-nitrogen-pastures
The bacteria in these nodules take nitrogen from the atmosphere and put it into a form that the legume can use to make protein and grow. This process is known as nitrogen fixation.
How does the nitrogen get over into the grass? The legume is able to use this nitrogen to grow, but the grass surrounding the clover plant does not have access to that nitrogen. The grass can get that nitrogen through an indirect process. As the legume grows, producing new leaves and roots, there is the constant death and replacement of roots, root hairs, and leaves. As these plant parts break down in the soil, the nitrogen in these parts is released into the soil, then becoming available to the grass for uptake and use in growth. The nitrogen transfer is due to legume plants dying and the nitrogen being recycled.
