Soil Sunrise Oyster Flour Soil Amendment (Choose Size); Soil Conditioner for Plants Our oyster flour is a 100% natural fertilizer with no added ingredients. Oyster Shell Flour is a high quality potting soil conditioner which consists of 96% calcium carbonate and many micronutrients, Oyster Shell Flour provides a long-lasting, steady release of nutrients to help regulate pH levels, improve fertilizer uptake, promote healthy cellular structure and enhance soil tilth. Oyster flour can also be used for several other purposes such as: chicken feed, bocce ball court material, or used in a walkway or driveway. Watch your plants thrive when you choose Soil Sunrise for all your gardening needs! Tips To enrich calcium in your soil mix, use 0.5 to 1 cup per gallon. To adjust pH, use half a cup per gallon. Ingredients Horticultural grade oyster flour (also safe as a poultry supplement)