nutrients from the ocean
Crab and lobster shells are an excellent dry organic source
of nutrients, including calcium (approximately 12-23 per cent)
and magnesium (up to one per cent). Of course, they have
varying analysis, depending on where it was caught and what
kind they are. They also give the roots something to grab onto
and wrap around for a food source, creating a deeper root
system. The shells also retain moisture in the soil and build
the organic matter. Since crab and lobster shells are high in
chitin, they promote the growth of chitin-eating bacteria in
the soil. This will help eliminate ants, grubs, fungus, and root
nematodes because they are all chitin-based in structure. Put
around plants, crab and lobster shells will keep slugs and
snails off. They also help choke out weeds and keep moles,
voles, mice, etc. from digging things up.
Early experiments showed that a single application of a liter
of seawater per square foot of garden would last five years.
Later, studies demonstrated astounding increases in bacterial
populations when sufficient minerals were provided.
Shellfish Waste
The edible shellfish include soft-bodied mollusks, such as
clams, scallops, and oysters with hard calcareous shells, and
crustaceans, a class of arthropod that includes crabs, shrimp,
and lobsters. Crustaceans have jointed legs and a carapace or
external skeleton largely made of chitin.
Oyster shells act faster than limestone to raise soil pH
and come with lots of trace elements. Crushed oyster shell
has the following gross analysis: 56 per cent carbonate;
37.7 per cent calcium; 1.2 per cent magnesium; 0.73 per cent
sulfur; 0.57 per cent sodium; and 0.21 per cent phosphorus.
These amounts can vary.
Overuse of seashells can cause problems, which is why
rumor has it pretty shells should not sit in potted plants. The
sulfur in shells adds acidity, and high calcium may block
uptake of magnesium and important trace minerals. We can
do harm with indiscriminant use of any fertilizer or amend-
ment, as most gardeners have learned. Get a soil test, so you
know where you’re starting.
Seaweed
The most common seaweed fertilizer is made from
Ascophyllum nodosum, commonly known as rock weed. It’s a
fast-growing brown alga that’s oxygen rich and exceedingly
dense in important elements such as iron, zinc, copper,
manganese, and boron, plus 60 to 80 other trace minerals.
Products include kelp meal, soluble seaweed powder, or
liquid extract, all containing organic compounds that feed
soil bacteria. It’s also a rich source of growth regulators,
“
Though many do neutralize
the salt in their product, research
on adding seawater to plant media without
salt removal showed no problems due to sodium.
”
52
feature