Soft Rock Phosphate

Heavy Metals (PPM)

Arsenic       19.8

Cadmium     <0.99

Mercury        0.13

Lead         6.93

Nickel         42.9


Source:   Data From Oregon Department of             Ag Organic Certification Database

Soft rock phosphate is a slow-releasing mineral phosphorus source used as a pre-plant amendment. While the total phosphorus is often 20%, only 2-3% is immediately available. The remaining mineralizes over multiple years.

It's more effective in low pH soils due to the faster release of phosphorus. Smaller particle size also increases the rate of phosphorus availability.

We suggest applying large quantities of soft rock phosphate to build phosphorus supplies in your soil for multi-year production. It's easiest to justify the investment if you own the land.

As a naturally-occuring mineral, soft rock phosphate also contains significant levels of arsenic. We suggest using bone meal instead of soft rock phosphate if arsenic is at all a concern.