Calphos Soft Rock Phosphate - Regular Powder (50 lb)

Calphos soft rock phosphate powder supplies phosphorus and calcium for gardens, orchards, and farms. This finely ground soil amendment suits fertility plans where testing shows a need for phosphorus. The original package holds enough material for larger planting areas.

Product Features

• Calphos fertilizer carries a 0-3-0 analysis, with 3% available phosphate expressed as P₂O₅.
• This rock phosphate powder comes from mined soft phosphatic clay, also called colloidal phosphate.
• The powder grade blends into soil as directed.
• The manufacturer lists the standard product with OMRI for organic production. Guaranteed Analysis

Phosphorus is an essential nutrient that supports root development, flowering, and seed formation. Using rock phosphate for plants makes sense when both nutrient needs and soil conditions suit the material.

How Nutrient Release Works

Soft rock phosphate fertilizer releases nutrients slowly. It is not readily water soluble, so it should not be treated as a quick fix for a severe shortage.

Soil pH affects how rock phosphate fertilizer performs. Release is generally better in acidic soils and may be too slow in alkaline ground. Results vary depending on moisture, soil chemistry, and the crop. extension.psu.edu

As a calcium phosphate fertilizer, this material supplies mineral nutrients rather than organic matter. Compare calcium phosphate powder products by their label analysis, since their composition and intended uses can differ.

Plan Your Application

Use a current soil test to set the application rate before you apply rock phosphate. Account for nutrients already supplied by compost, manure, bone meal, and other inputs.

• Measure the treatment area and follow package directions.
• Incorporate phosphate powder only as directed.
• Avoid repeated applications when soil already has high levels of phosphorus.
• Keep records to guide future crop production.

For organic farms, confirm the exact package and current listing with your certifier.

Choose a Suitable Phosphorus Source

Chemical fertilizers made through acid processing differ from untreated mineral sources. Phosphoric acid is used in manufacturing some phosphate fertilizer products; it is not an instruction for home mixing.

Request current laboratory data for heavy metal questions. Compare phosphorus fertilizers to select a source that matches your soil and planting goals.

Application guidance: Phosphorus moves slowly in many soils and can accumulate when overapplied. Use soil-test results, place or incorporate only as directed, and account for phosphorus already supplied by compost and other fertilizers. Follow label rates for the specific crop and growth stage.