Calphos Soft Rock Phosphate - Regular Powder (50 lb)

Calphos Soft Rock Phosphate is a natural phosphate fertilizer made from finely ground soft rock. It is OMRI-listed for organic use and is especially effective in acid soil and slightly acidic environments. This product is a reliable source of calcium phosphate and trace minerals that gradually release into the soil. The slow release of nutrients supports healthy plant growth, improves soil fertility, and provides benefits that last for the long term.

Why Use Calphos Soft Rock Phosphate?

Unlike many synthetic phosphate fertilizers, Calphos is a natural phosphate source that feeds plants steadily over time. Because it gradually releases phosphorus, it does not wash away easily with rain. Instead, it stays in the root zone, helping plants build strong root systems and maintain healthy soil structure. This makes it an excellent choice for growers focused on enhancing soil naturally while reducing the need for frequent reapplication.

Calphos contains about 20% P₂O₅, with 3% immediately releasing phosphorus for quick results and the rest breaking down slowly for long term benefits. It also provides around 18% calcium, which helps maintain proper soil pH and supports optimal growth.

Key Benefits of Calphos Soft Rock Phosphate

• Balanced Nutrition: Supplies phosphorus and calcium phosphate in a form that plants can use steadily.
• Slow Release Performance: A true slow release fertilizer that feeds plants for up to 5 years.
• Supports Healthy Soil Ecology: Works well when mixed with organic matter, encouraging microbial activity and improving soil structure.
• Minimizes Nutrient Loss: Reduces leaching and keeps nutrients available in the root zone.
• Versatile Applications: Useful for row crops, orchards, trees, and general soil-building programs.

Application Guidelines

For best results, always start with a soil test to understand the nutrient needs and recommended application rates for your soil type and crops.

• Field Use: Spread about 1 ton per acre on phosphorus-deficient or acid soil.
• Tree & Orchard Use: Apply 1–10 lbs of Calphos in each planting hole, mixing it well with the surrounding soil.
• Pre-Planting or Blending: Incorporate into the soil before planting or blend with compost and organic matter for a balanced amendment.

Because Calphos gradually releases nutrients, it provides both immediate and lasting results, reducing the need for repeated fertilizer use.

A Sustainable Choice for Plant Growth

Calphos Soft Rock Phosphate is derived from ancient marine deposits, giving it a natural balance of phosphorus, calcium, and trace minerals. By combining these nutrients, it helps create fertile soils that support healthy root systems, vigorous crops, and healthy plant growth.

Its natural composition makes it one of the most reliable phosphate fertilizers for gardeners and farmers who want to focus on enhancing soil rather than relying on quick fixes.

Why Gardeners and Farmers Choose Calphos

• OMRI-listed for organic production.
• Reliable, natural source of phosphorus and calcium phosphate.
• Excellent for slightly acidic soils and acid soil.
• Improves fertility while supporting healthy microbial life.
• Provides both quick and long term nutrient availability.
• Ideal for row crops, fruit trees, and soil-enrichment programs.

Available Sizes

This 50 lb bag is perfect for larger gardens, farms, and orchards. For smaller applications, Calphos Soft Rock Phosphate is also available in a convenient 5 lb bag.

For smaller applications, Calphos Soft Rock Phosphate is also available in a 5 lb bag.

Explore more options in our High Phosphorus Fertilizer Collection or shop the full range in Fertilizer & Growing Supplies.