"Tis a method to make poor soil more fertile," he explained. "To grow, plants must draw certain nutrients from the soil; if those nutrients have been used up by previous plantings- or if they were never present at all- anything planted in the soil would struggle, if it didn't fail entirely. Planting a fish near a seed however, can remedy this, as the fish returns those nutrients to the soil as it breaks down. Spreading animal dung on the soil's surface can have a similar effect."