Soft Rock Phosphate



Soft Rock Phosphate, also known as Calphos, is a great natural source of slow release phosphorous and calcium.


It can also provide low levels of trace minerals and valuable trace elements such as: iron, sodium, magnesium, boron, and iodine.

  • Calphos is a great source of slow-release phosphorus and calcium. A small percentage of the nutrients are available immediately and the majority are released slowly over a period of a few years.
  • When using calphos as a soil amendment, keep in mind that, for the roots to absorb the phosphorus and calcium, the soil must be acidic or have a high level of microbial activity. To accelerate the absorption process, you can mix the calphos with compost when applying.  The continual application of compost over time will allow the plant roots to continually take up the nutrients from calphos.
  • Typical N-P-K analysis is 0-3-0*


If you are looking to order larger quantities, come visit us at our store in Magnolia (Seattle) or contact us at

*We do our best to provide you with useful, accurate information. That being said, we can make no guarantees. Much of what we have posted we believe to be common knowledge in the agricultural and horticultural worlds. In addition, we want to give credit where credit is due. Our resources page lists resources we commonly use and encourage you to use too.

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Weight N/A

2lbs, 4 lbs, 10 lbs, 20 lbs


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2209 West Elmore Street
Seattle, WA 98199




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