(48% CaO and 52% SiO2) 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) and have better resistance to insect and disease pressure. Silicon strengthens cell walls and stimulates immune activity.

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; best applied via fertigation (see fertigation chart) or as a soil amendment. Particularly recommended for orchard crops, cucurbits, sweet corn, grains and forage crops.

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 Hi-Cal Lime). MOFGA

8207 Wollastonite
Item Discounted
A: (5#) $6.00
B: (50#) $30.00
C: pallet 40 bags (2000#) $1000.00 ($850.00)
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Additional Information


Pounds of limestone (calcitic or dolomitic) needed to raise the pH of 1000 sq ft to 6.5.

Current pHSandy SoilLoam SoilClay Soil

Source: L.B. McCarty, Best Golf Course Management Practices, 2001
1 acre = 43,560 sq ft

Click here for more info about calcium and pH.

Rock Powders and Soil Amendments

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.

Rock powders and soil amendments used with a program of crop rotation, composting and cover cropping will 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. Used with organic fertilizers, rock powders and soil amendments will help address immediate fertility needs as well as long-term requirements of sustainable growth. Rock powders can be applied directly to soil but their nutrients will be more readily available to plants if incorporated into compost.

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: Maine Organic Farmers & Gardeners Association. Reviewed by MOFGA and allowed for use on MOFGA-certified farms. Check with your certifier.
WSDA: The Washington State Department of Agriculture’s Organic Certifying division has approved these products 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: Products whose active ingredient is on the list of allowed substances, but which are not on the OMRI or WSDA list. 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.

Click here for our list of soil amendments, fertilizers, and disease and insect controls along with their certification status and manufacturers.