Gaia Green Oyster Shell Flour is a natural soil conditioner derived from oyster shell which is an organic source of high quality calcium carbonate. Easily dissolved and absorbed, variable particle size provides both immediate and long term fertilization. Oyster Shell Flour balance pH levels in acid soils, promotes healthy root growth and helps create well aerated, loamy soil. Repeated applications may be needed to balance Ca. and pH levels. Oyster Shell Flour can also be used in compost piles and worm bins to encourage a higher rate of microbial activity in the soil.