(48% CaO and 52% SiO2). Cal Carb Equivalent 76.0%. Soluble-grade and at least 95% pure (may contain trace amounts of iron, manganese and magnesium). Silicon is not traditionally considered a limiting cofactor for plant growth, but researchers are finding that despite ample amounts of silicon in most soils, plants supplemented with silicon often yield better (even in prime growing conditions). Silicon strengthens cell walls, which reduces lodging and improves resistance to insects and disease; stimulates immune response pathways (possibly increasing production of resins and terpenes); and reduces transpiration (improving drought resistance).

Especially beneficial in sandy or muck soils, which are both naturally lower in silicon than clays and loams. May be applied as a foliar spray to build resistance to powdery mildew; for yield benefits, incorporate into the soil.

Particularly recommended for cannabis, orchard crops, cucurbits, sweet corn, grains and forage crops. Customer Norman B. of West Baldwin, ME, credits wollastonite for his exceptional potato crop in 2019: ”I bought a 50 lb bag of wollastonite and sprinkled it into the rows as I went along and the Green Mountains, which have a reputation for low yield, did commendably. Out of that small bag of seed, I filled a five-gallon pail, over 35 lbs, and that was after discarding some that I had damaged during hilling. My uncle stated that he had never seen so many large Green Mountains as well. I used a lot of composted horse manure, but I do every year. The only thing different was the wollastonite.”

Most soil tests do not offer recommended application rates for silicon; one approach is to use wollastonite to correct your soil pH. For this purpose, wollastonite has a liming equivalent of 86% (relative to Calcitic Lime). Dusty! Wear a mask when handling. MOFGA

8207 Wollastonite
Item Discounted
A: 5.0 lb $10.50
   MOFGA Approved
B: 50.0 lb $44.00
   OMRI Certificate
currently on backorder
C: pallet 40 bags $1440.00
   OMRI Certificate
currently on backorder

Additional Information

Understanding Calcium

See Understanding Calcium and pH for more information about calcium and soil health.

Soil Amendments and Fertilizers

Thriving sustainable agriculture is built on the ground of a healthy soil. In fact, organic certification requires a soil management plan. Do a soil test to determine your soil’s needs before embarking on a program of soil improvement. Check with your local Cooperative Extension for testing in your area, or consider our soil testing and recommendation service.

Soil amendments used with a program of crop rotation, composting and cover cropping can enhance fertility, improve soil tilth, promote disease resistance, support beneficial soil microorganisms, and even help restore balance to the garden and the world around it. Application rates vary depending on soil type and results of soil tests.

Fertilizers provide nitrogen and other nutrients in a form that is readily available to plants. Organic fertilizers can provide both an immediate boost and additional long-term fertility, feeding both the plants and the organisms that maintain soil health. We also offer soil amendments that have limited available plant nutrients but help to remineralize the soil, improve soil structure, or provide a long-term slow-release source of plant nutrients. Foliar sprays get nutrients directly to the leaves and can increase resistance to disease and to insect infestation.

Analyses provided here are those provided by the manufacturers, or, if none are available, from a Maine state lab test performed on our most recent lot: there is some variability in the nutritional analysis of natural fertilizers, so view these numbers as guides, not gospel. Fertilizers should be used as a supplement to, not a replacement for, the nutrients provided by healthy soil. Sustainability requires developing a long-term plan of cover-cropping, green manuring and composting.

Organic Certification

Inoculants, soil amendments, fertilizers, livestock supplies and pesticides are labeled as:
OMRI: Organic Materials Review Institute. Most state certifying agencies, including MOFGA, accept OMRI approval.
MOFGA: Reviewed and approved by the Maine Organic Farmers & Gardeners Association Certification Services. Allowed for use on MOFGA-certified farms. Check with your certifier.
WSDA: Listed by the Washington State Department of Agriculture’s Organic Certification division for use in organic agriculture in Washington State. MOFGA has indicated that they will accept products on this list for their certification program. Check with your certifier.
Nat’l List: One-ingredient products on the NOP* List of Allowed Substances (subpart G of the Organic Foods Production Act, sections 205.601-606). Check with your certifier.
AYC: Ask your certifier. Has not been reviewed by a certifier, but the active ingredient is allowed. Ask your certifier.
Not Allowed: A few of the products we list are not allowed for organic production but we think they have a place in sensible agriculture and can be used when certification is not an issue.