Coastal Oyster Shell Flour – High-Calcium Natural Soil Amendment

Coastal Oyster Shell Flour is an all-natural, micronized source of coarse-to-fine calcium carbonate (CaCO₃) specifically processed for living soil, commercial crop production, and organic farm management. Sourced from high-purity, ocean-derived oyster shells, this premium soil builder delivers a sustained, multi-season release of plant-available calcium while gently raising and buffering soil pH over time.

Unlike standard agricultural lime, Oyster Shell Flour breaks down slowly through biological activity, making it an ideal choice for long-term soil building, no-till beds, potting mixes, and high-demand crops like tomatoes, peppers, and brassicas. Available in individual bags up to full commercial bulk quantities.

Key Benefits

• Sustained Calcium Release: Provides a steady, long-lasting supply of calcium (Ca) to strengthen plant cell walls, enhance root development, and prevent deficiency disorders like blossom end rot and tip burn.

• Natural pH Buffer: Gently corrects acidic soils without the harsh, rapid pH spikes associated with synthetic hydrated lime or quicklime.

• Microbial Support: Biologically active soil microbes consume and process the ground chitin and calcium carbonate, fostering strong soil microbiology and improving overall soil structure.

• Ideal for Living Soil & Bulk Blending: A foundational ingredient for custom soil mixing, Super Soil recipes, raised bed construction, and market garden prep.

• 100% Natural: Ocean-sourced, chemical-free input suitable for sustainable, natural, and regenerative agriculture systems.

Technical Specifications

• Product Format: Fine Ground / Flour (~20–100 mesh blend)

• Primary Nutrient: Calcium (Ca) – Approx. 33% to 37%

• Chemical Composition: Calcium Carbonate (CaCO₃)

• Source Material: Natural Ocean Oyster Shells

• Application Type: Soil Amendment / Top-Dress / Soil Mix Additive

Recommended Application Rates

1. Custom Soil Mixes & Potting Substrates

• Rate: Mix 1 to 2 cups per cubic foot of soil, or 5 to 10 lbs. per cubic yard of bulk substrate.

• Best Practice: Blend thoroughly with peat moss, coconut coir, compost, and aeration components prior to planting.

2. Raised Beds & Garden Plots

• Rate: Broadcast 3 to 6 lbs per 100 sq ft of bed area.

• Best Practice: Lightly incorporate into the top 2–4 inches of soil in early spring or late fall.

3. Broad-Acre & Commercial Field Crops

• Rate: Apply 250 to 500 lbs per acre, depending on soil test recommendations and baseline soil pH.

• Best Practice: Apply ahead of high-calcium demand crops or cover crops to allow microbial breakdown.

4. Top-Dressing & Living Soil Maintenance

• Rate: Apply 1 tablespoon per gallon of container size, or ½ cup per plant canopy footprint every 4–6 weeks during active growth.

Q: What is the difference between Oyster Shell Flour and Oyster Shell Meal?

A: Oyster Shell Flour is ground into a fine mesh particle size compared to coarse shell meal. The finer flour consistency offers a significantly larger surface area, allowing soil microbes to process and unlock calcium more quickly and uniformly throughout the root zone.

Q: Will Coastal Oyster Shell Flour burn my plants?

A: No. Because it is a natural form of calcium carbonate with a low solubility rate, it releases slowly through biological activity and will not burn root systems or cause sudden alkaline spikes when applied at recommended rates.

Q: How does Oyster Shell Flour compare to agricultural limestone (calcite) or dolomite lime?

A: Oyster Shell Flour contains trace ocean minerals and breaks down at a rate that matches active biological soil systems. Unlike dolomite lime, which contains high levels of magnesium (Mg), Oyster Shell Flour supplies calcium without overloading soils that already have elevated magnesium levels.

Q: Can I use this product in hydroponic systems or sprayers?

A: No. Oyster Shell Flour is insoluble in water and intended strictly for soil, compost, and growing media amendments. It will settle in tanks and clog drip lines or spray nozzles.