Down To Earth s All Natural Fertilizer Rock Phosphate Down To Earth Rock Phosphate is essential for building soil phosphate levels for long-term plant productivity and for preventing calcium deficient soils. It should be applied to soils prior to planting and can be mixed with compost or manures for additional soil building benefits. This premium powder grade is an excellent nutrient resource for all types of flowering plants including bulbs fruits shrubs trees and vegetables.Containers For new plantings add ? cup per gallon of soil and mix thoroughly OR add 5-10 lbs per cubic yard. For established plants lightly mix 1 tbsp per gallon into the soil surface every other month during the growing season.Containers For new plantings add ? cup per gallon of soil and mix thoroughly OR add 5-10 lbs per cubic yard. For established plants lightly mix 1 tbsp per gallon into the soil surface every other month during the growing season.Trees & Shrubs Spread 1 lb per 1? of trunk diameter around the base outward