Soil Amendment Calculator

Know what your soil needs and how much to add. Enter your soil test results, select your crops, and get a custom amendment plan with quantities.

Vancouver Island Soil Types

Most of the island has naturally acidic soil from centuries of conifer forest. Know what you are starting with.

Forest Soil (Most Common)

pH: 4.5 - 5.5

Character: Acidic, high organic matter, low calcium, often compacted under duff layer

Needs: Lime to raise pH, calcium, sometimes phosphorus

Valley Clay

pH: 5.5 - 6.5

Character: Heavy, holds water, slow drainage, nutrient-rich but locked up

Needs: Gypsum for structure, compost for drainage, minimal lime

Coastal Sandy

pH: 6.0 - 7.0

Character: Fast-draining, low nutrients, warms quickly in spring

Needs: Compost for water retention, kelp meal, regular feeding

Amendment Calculator

Enter your garden details and soil test results. If you have not had a soil test done, use the estimated values for your soil type above.

pH Adjustment

Amendment Shopping List

    Amendment Reference Guide

    Common organic amendments available on Vancouver Island. NPK values and application rates per 100 sq ft.

    AmendmentN-P-KRate / 100 ft²What It DoesWhen to Apply
    Dolomite Lime0-0-0 (Ca + Mg)2-5 lbRaises pH. Adds calcium and magnesium.Fall (needs 2-3 months to react)
    Calcitic Lime0-0-0 (Ca)2-5 lbRaises pH. Use if magnesium is already adequate.Fall
    Wood Ash0-1-3 (Ca, K)1-2 lbRaises pH fast. Adds potassium. Use sparingly.Fall or early spring
    Elemental Sulfur0-0-00.5-1 lbLowers pH for blueberries and acid-lovers.Fall (slow-acting)
    Compost1-1-1 (approx)30-40 lb (1-2")Improves structure, water retention, biology.Spring or fall
    Aged Manure1-0.5-120-30 lbAdds nitrogen and organic matter. Must be aged 6+ months.Fall (fresh) or spring (aged)
    Blood Meal12-0-01-2 lbFast nitrogen boost. Good for leafy greens.Spring, side-dress in summer
    Bone Meal3-15-02-3 lbSlow-release phosphorus. Root development and flowering.Spring, work into soil
    Kelp Meal1-0-21-2 lbMicronutrients, growth hormones, soil biology. Locally available on VI beaches.Spring or fall
    Fish Fertilizer5-2-2dilute per labelQuick-release balanced feed. Good foliar spray.Growing season, every 2-4 weeks
    Rock Phosphate0-3-03-5 lbVery slow-release phosphorus. Works best in acidic soil.Fall
    Greensand0-0-35-10 lbSlow-release potassium and iron. Improves clay soil structure.Fall or spring
    Glacial Rock Dusttrace minerals5-10 lbBroad-spectrum trace minerals. Remineralizes depleted soil.Any time
    Gypsum0-0-0 (Ca + S)2-4 lbBreaks up clay without changing pH. Adds calcium and sulfur.Fall or spring
    Biocharvaries2-5 lbPermanent carbon structure. Holds water and nutrients. Charge before use.Any time -- use the biochar calculator
    Worm Castings1-0-05-10 lbPremium soil biology. Gentle, balanced, impossible to over-apply.Any time

    Soil Building Strategies for Vancouver Island

    Sheet Mulching

    Layer cardboard, compost, and mulch to convert lawn or forest floor to garden beds without tilling. Takes 3-6 months. Best started in fall for spring planting.

    Cover Crop Green Manure

    Grow crimson clover or fall rye over winter. Turn under 2-3 weeks before planting. Adds nitrogen, organic matter, and feeds soil biology.

    Chop and Drop

    Cut comfrey, clover, or other dynamic accumulators and lay them as mulch around your plants. Free fertility from deep-rooted nutrient miners.

    Biochar + Compost

    Mix biochar with compost at 10-20% ratio and let it charge for 2+ weeks before adding to soil. Permanent soil structure improvement. Calculate your biochar needs →

    No-Till / Minimal Till

    Top-dress with compost instead of turning soil. Preserves fungal networks and soil structure. Works well on VI's heavy clay soils.

    Hugelkultur Beds

    Bury logs and branches under mounded soil. Acts as a sponge during dry summers. Takes 1-2 years to fully activate as wood decomposes. Calculate your earthworks →

    Keep Building Your Garden

    Good soil is the foundation. Plan your crops, rotations, and water next.