![Down To Earth Rock Phosphate - [hydropros]](http://hydropros.com/cdn/shop/files/723749-01-170055_500x500.jpg?v=1717701744)
Soft rock phosphate, or colloidal phosphate, is a natural, untreated source of long-lasting phosphate and soil-building calcium. Phosphate will remain available across a wide pH range. For best availability, soft rock phosphate should be mixed into soil or compost prior to planting. A superb nutrient resource for all types of plants.