Crushed Bluff Oyster Shells (calcium carbonate + chitin)
Crushed Bluff Oyster Shells are a slow acting calcium carbonate grit made from Bluff oyster shell. Growers use oyster shell flour as a slower alternative to ag lime that holds pH up over a long time in beds and living soil mixes.
At a glance
- Type: amendment (liming material, shell grit)
- Analysis: calcium (Ca) 36.50%, about 95% calcium carbonate
- Use for: slow, long lasting calcium and pH hold in beds, pots and reused living soil
- Rate: by soil test and pH meter; no fixed rate is printed for this product
- Pack: bulk 500 kg and 1000 kg by quote
What it is
Crushed shell from Bluff oysters. The composition is around 95% calcium carbonate, with small amounts of magnesium, sodium, iron and trace elements, as the batch analysis below shows. The shell's organic matrix is where the chitin in the name comes from.
Bulk is available in 500 kg and 1000 kg quantities. Email store@seaclifforganics.nz for a quote.
What it does
- Shell is the same carbonate as lime, so it neutralises soil acid and raises pH. As a grit rather than a fine powder it dissolves slowly, which is why growers use it where they want a long, gentle pH hold rather than a quick lift.
- Supplies calcium for cell walls and root tips as it dissolves.
- Used in place of ag lime by growers who want the slower release and the trace elements that come with shell.
Analysis
Batch analysis (supplier laboratory test, November 2021)
- Nitrogen (N) 0.00%
- Phosphorus (P) 0.00%
- Potassium (K) 0.00%
- Sulphur (S) 0.00%
- Calcium (Ca) 36.50%
- Magnesium (Mg) 0.30%
- Sodium (Na) 0.30%
- Iron (Fe) 0.06%
- Copper (Cu) 2.8 ppm
- Manganese (Mn) 14 ppm
- Zinc (Zn) 7.7 ppm
- Boron (B) 20 ppm
- Cobalt (Co) under 1 ppm
- Molybdenum (Mo) 4 ppm
- Selenium (Se) under 10 ppm
How to use
- Oyster shells will increase pH. Use a pH meter to keep your soil between 6.2 and 7.2.
- Mix into beds or living soil mixes, or top dress, at the rate your soil test calls for.
Watch out
- Slow means slow: a coarse grit keeps releasing for seasons, so do not add more because nothing happened in the first month.
- pH is not a calcium test. Check the calcium line on the report before adding any carbonate.
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Handling and storage
- Wear a mask to avoid inhaling particles and open the bag in a well ventilated area.
- Wear gloves and eye protection, and wash hands after use.
- Once opened, keep sealed and dry.
- If swallowed, or if the product gets into the eyes or irritates the skin, rinse the area well and call the National Poisons Centre on 0800 POISON (0800 764 766).
Shipping and returns
We ship nationwide across New Zealand. Orders are usually dispatched within 1 to 2 business days and rural delivery can take longer. Unopened products can be returned within 30 days.
