Calphos Soft Rock Phosphate (5 lb bag)

This 5 lb bag of Calphos Soft Rock Phosphate is sized for raised beds, individual planting areas, and gardeners who need a manageable amount of a slow-release phosphorus and calcium amendment. Its fine texture makes it easy to mix into soil or compost before planting.

When to use it

Use Calphos when a soil test shows that phosphorus is needed, particularly when preparing beds for root development, flowering, or fruiting crops. The material averages about 20% P₂O₅, including 3% available phosphate, plus approximately 18% calcium. Because phosphorus moves slowly through soil, incorporate it into the root zone rather than leaving it only on the surface.

Application

• For phosphorus-deficient soil, the general published rate is 5 lb per 100 sq ft; reduce the rate for more fertile soil.
• For trees and perennials, published guidance ranges from 1–10 lb per planting hole depending on plant size.
• Confirm the appropriate rate with a current soil test and local recommendations.

Organic status: This repackaged 5 lb size is not represented as organic or as listed or approved for certified organic production. The 50 lb original package carries its own organic-use listing; that status does not transfer to this repackaged size.

Learn more in our guide to using soft rock phosphate.

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