Organic Soil Amenders, Inc provides our products to the Pacific Northwest, including Washington, Oregon, Idaho, Montana and Canada.

Gypsum/Calcium Sulfate

gypsum in hand

Agricultural Gypsum is one of those rare materials that performs in all three categories-as an amendment, a conditioner, and a fertilizer.

Other Products

High Calcium Limestone

Calcium performs many required functions in the growth of plants and the production of fruit, seeds, pollen and more. It’s a key nutrient for soil quality, plant health and resistance to disease and pests…continue reading.


Known as “The Calcium Helper”, boron is absolutely essential for plants to metabolize calcium.…continue reading.

Compost & Manures

Long employed by home gardeners, humus, in the form of compost and manure, has shown its worth building soil health and benefiting plants…continue reading.


Humates are large complex molecules made up mostly of stable carbon.…continue reading.

Soft Rock Phosphate

Phosphorus supplies the energy for plants. It’s critical in the photosynthesis process where light is converted to chemical energy inside the plant.…continue reading.

Ready to Get Started?

OSA has very competitive pricing on our products and services. We do our best to make natural amendments your logical choice for improving soil and plant health, as well as your bottom line.​