Organic Growing: Feeding the Worms

Recommendations for trouble free wormy diet

Plant-sourced material only. Wastes from fruit, vegetables, berries, tea bags, paper/cardboard/tissues. Not only do these contain a lot of nutrients like P and K, but it seems to me that worm castings made with this kind of feed make for sweet vivid taste and high trichome content!

Know your limits! Experiment with ‘new’ foods.

Do earthworms need a complete diet, or can they survive on a single unbalanced source of food, very high in N, P, or K?

I think that composting earthworms can survive on a single food source, BUT that food source must contain at least minute amounts of the minerals they need.

For example, only paper or only cardboard would support a worm population very well. But they do need a bunch of minerals just as we do to survive. I’m guessing nitrogen, calcium, phosphorus and magnesium would be the most important ones just as they are for us.

Earthworms do not actually eat the food materials themselves, but the BACTERIA that are feeding on the materials. These bacteria do the work of extracting the minerals and making more complex organic compounds for the wormies, like amino acids and vitamins and what not.

What foods need to be avoided?

Salt. Salt kills worms. Do not add any foods with high salt content into the bins. Often breads and processed foods contain high salt.

Cat and dog manure. Humanure. These can act as a vectors for human diseases, such as toxoplasma, the brain cell parasite, and thus may not contribute positively to your health in the long term. Manure from livestock should be safe to use (ie. horse/cow/sheep/poultry manure).

Generally it is thought that worms can process ANY organic material, given enough time to adjust. From pH 2 vineyard waste to actively ‘hot’ decomposing horse manure – but they will need time to adjust to the conditions, and the worm farmer will need to create suitable conditions. Experiment carefully.

Does the material have to be partially decomposed already?

Not at all. While in commercial operations the waste material is often ‘pre-decomposed’ or ‘pre-composted’, it is perfectly ok to add undecomposed organic waste such as fresh vegetable peels in a worm bin. One just has to watch out not to create a thermophilic compost that heats up and cooks the worms.

While the earthworms can only ‘eat’ material that has already started decomposing, usually adding fresh veggie waste, for instance, poses no problems whatsoever, especially if buried in the bedding.

My question is should I run my kitchen waste through a blender before adding it to the bin, or can I just chop it finely with a knife.

If you run the kitchen waste through a blender it will be consumed much faster – but chopping with knife would work quite well. I think blending the waste might halve the time required for decomposing.

I don’t process my veggie waste, just throw them in there. I have 3 main bins with 8 month cycles, 6+ months of feeding and 2 months or less of settling. Once the cycle is through, the worm caste is dark brown muddy pudding that sticks to everything.

What about adding sand? My kitchen waste contains no sand!

Sand – and grit – important, but also not a absolute must in my humble opinion. It helps the worms digestion, and it helps breaking down the organic matter.

For sand one can, in my opinion, substitute eggshells, perlite or dolomite lime. Sand is basically broken down inert, hard, rock-like material, so I suppose anything inert and hard would work. Do not use metals or plastics.

One doesn’t need that much grit, and note that sand will concentrate on the bottom of the bin due to weight, so the top layer wouldn’t have that much sand. I would say that sand content of one percent would be just fine.

There are all kinds of critters in there!? Can I harvest or should I wait?

A worm bin or a worm farm may support many kinds of creatures, mostly useful ones. But the fact that you can see that other decomposers are present usually means that the feed/waste has not yet decomposed very well, and needs some more time to become worm castings (unless worm compost is what you are after).

Usually critters like mites, springtails or tiny white Enchytraeid ‘potworms’ are feeding directly on the foods present. Unlike composting worms, they cannot survive by eating the bacteria present in the worm castings, and thus they will die off as soon as the foods have been decomposed.

Could I possibly add my soil fertilizers like kelp, alfalfa, and guano to the worm bin to up it’s NPK. That way, my worm shit would be the only thing I needed to use for fertilizing, make a tea for every watering.

Yes, very much so. But with some ingredients its best to only use them for the final soil-mix because of their cost or composition. Kelp and guanos are both very very costly to be used as worm food.

As to using worm bins to process different food-wastes into different nutriens like veg or bloom nutrients, it works quite well, but often nitrogen and magnesium supplementation seems to be a requirement.

Worms like alfalfa meal, but one must not use too much at once as the high nitrogen content might cause heat-composting or even fermentation.

I think perlite that has spent some months in a worm bin would have lively bacterial cultures on its surface – yet another benefit..