I get curious about the strangest things sometimes. Last summer, during a contemplative moment lying on my lawn, I rolled onto my stomach and parted the grass to sneak a peek at the soil surface. What I saw was a literal junkyard of refuse including seeds, grass clippings, shredded leaf parts, worm castings and, most interestingly, lots of insect exoskeleton pieces. I thought to myself, “All those bits of chitin-rich exoskeleton must be a valuable commodity to the Soil Food Web.”
For years, I’ve told gardeners that chitin serves as a rich food source for soil microbes, which, in turn, provide the soil ecosystem and plants with essential building blocks for healthy growth. The soil depends on a food pyramid similar to our own with carbohydrates, protein, fats and fiber. In fact, the most common food sources in nature are cellulose, starch and chitin.
Chitin’s molecular formula is (C8H13NO5):
The chitin molecule is essentially a series of modified sugar molecules hitched together. As a food source, it packs a lot caloric energy. That’s why lobster, crab and shrimp shells compost really well. Crustacean shells are composed of a matrix of this chitin and calcium and magnesium bearing molecules. The claws have much higher concentrations of the hard stuff whereas flexible body parts are higher in softer chitin.
We know chitin plays a critical nutritional role to the Soil Food Web and that a healthy soil system recycles the bodies of chitin-rich insects. Clearly, poisoning all the insect life in your lawn and garden disrupts Nature’s beautiful design! A lawn or garden with no insects is missing a key food source.
I believe a healthy natural Soil Food Web keeps predators, prey, parasites and diseases in balance. My 40 year old natural lawn, with all those expired insect bodies, does not get grub damage, insect infestations or fungus diseases. Anecdotally, I have used lobster compost on several grub infested lawns and found it deters grubs. A little research unearthed the hypothesis that adding chitin to the soil surface promotes the proliferation of chitin eating bacteria….. There are specific bacteria for eating everything! And, behold, grubs’ jaws are made of chitin! It is possible that the bacteria leach into the soil and irritate the grubs so they leave or stop eating. I don’t know the mechanism exactly, but have seen it work.
In conclusion, shellfish compost is a great choice when you want to boost the vigor of the Soil Food Web in your lawn or garden. The calcium and magnesium are critical plant nutrients and we are still learning about all the miraculous benefits of chitin.
Pete Bottomley, AOLCP
Coast of Maine Organic Products