Volcanic Soil that can be used in farming as extra-fertile Farmland

In the real world, volcanic soil is very rich in plant nutrients and produces high crop yields. My proposal is that a sparse volcanic dirt block be added to the Basalt Delta biome that rarely grows a light colored green moss that can be flattened to form a dark path, or be hoed to produce super fertile farmland that decreases grow times by maybe half. I believe this would provide an additional incentive to travel to that biome, and would enrich the experience.