a deceptively simple experiment: plant seeds in lunar soil, add water, nutrients and light Seeing that they added nutrients, what was the purpose of the regoli

a deceptively simple experiment: plant seeds in lunar soil, add water, nutrients and light Seeing that they added nutrients, what was the purpose of the regolith? Was it merely to provide anchorage for the plant? Was there a control experiment that duplicated the setup except for replacing the regolith with inert sand? Would the water and nutrient perform the same if the plants were produced hydroponically without either sand or regolith? I am not convinced by this experiment that regolith is useful.