I make compost tea in a brewer that I bought in Eugene. I use worm castings, and I wonder what aeration does to the tea. The brewer activator's ingredients include “trace metals." Why might those be in the activator? Also, does the vermicomposting process increase plant nutrients?
Aeration of compost tea increases the dissolved oxygen in the brew and shifts the microbial community to bacteria and fungi that can tolerate oxygen. In an environment like soil, or a compost bin, or a compost tea brewer, the microbes become active or dormant according to their tolerance for dissolved gases, temperature, pH and nutrients. Those that are disfavored by the current conditions will go into stasis until conditions change to something more favorable to them.
As for trace metals, they are important in enzyme-driven interactions. Sometimes enzymes include a metallic atom in their structure. And sometimes the metal acts as a catalyst to speed the reaction along. Zinc, manganese, iron, copper and molybdenum are the plant micronutrients that are metals. Chlorine and boron aren’t metals but they are also plant micronutrients. Micronutrients are essential for robust plant growth. The differences between too much and tool little are fairly narrow. This is especially true for boron, which has the narrowest window of all.
Finally, vermicompost is a manure product. All manures, generated by all eaters, are the by-products remaining after the eater has absorbed what they require for their metabolic processes. So, whatever you’re feeding the worms will predict what could be in the castings. But if a plant nutrient, such as a micronutrient, isn’t in the diet of the worms, it won’t be in their castings. Digestion will concentrate the nutrients not absorbed by the eater, but it won’t create nutrients that weren’t there in the first place.
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