Calphos Soft Rock Phosphate (25 lb bag)

Calphos Soft Rock Phosphate is a natural, slow-release source of phosphorus and calcium that boosts soil fertility and supports strong root development. This finely ground mineral powder averages 20% P2O5 (about 3% immediately available) and 18% calcium, feeding plants gradually for up to 5 years after application. This is the 25 pound bag.

At a glance

• Type: Natural soft rock phosphate amendment
• Form: Finely ground mineral powder
• Analysis: About 20% P2O5 (3% immediately available), 18% calcium
• Size: 25 lb bag
• Broadcast rate: 5 lb per 100 square feet, or 1 ton per acre on deficient soils
• Planting hole rate: 1 to 10 lb per hole by plant size
• Longevity: Supplies phosphorus and calcium up to 5 years

Best for

• Phosphate-deficient garden and orchard soils
• Root vegetables, fruiting plants, and flowering ornamentals
• Trees and perennials at planting time
• Natural and organic-style soil building
• Long-term, slow-release fertility

How to use

Apply at about 5 pounds per 100 square feet before planting, or work 1 to 10 pounds into each planting hole depending on plant size. It can also be used as a top dressing through the growing season. Because it releases slowly, a single application supports phosphorus and calcium needs for several years on most crops.

About Grow Organic

Grow Organic supplies non-GMO seeds and natural soil amendments for growers who build fertility the sustainable way.