Hey johnmark that is a great question. I dont have direct experience with using saps, but it makes sense that they would feed some microbe groups.
Here is some discussion i found.
The selection for the preferred microbial community, given a compost of say equal bacterial to fungal biomass, can be made by adding components to the tea solution before the tea brewing process begins.
Additives that help bacteria most are simple sugars, syrups such as molasses, cane syrup, sugar beet syrup, spoiled carrot juice, apple juice from applesauce production, and yeasts (vitamin addition).
Materials that help fungi more than bacteria are things like fruit pulp (the cellulose in the pulp generally helps fungi more than bacteria but bacteria will grow on the sugar portion of the pulp), soluble kelp (protein and micronutrients), humic acids, or other high cellulose containing pulp material. Plant extracts, such as comfrey, nettle or dandelion “soups” can also be added to enhance the micronutrient content of a tea. Anecdotal information from growers suggests that comfrey is high in Ca, N and K, and thus alleviates nutrient stress if plants are lacking these nutrients. Comfrey has been chopped and added to the compost before it is composted, or after composting is finished (dangerous if there is any disease on the comfrey that could spread through the compost), to the compost basket during the tea brewing operation, or as a brewed soup (stuff a bucket full of comfrey leaves, add water, churn the leaves in the bucket for a day or so, then add the liquid to the water at the start of the brew process). In each instance, significant benefit to plant production was observed, most likely explained by improved Ca uptake by the plant. However, these were not replicated studies, and to fully accept this type of work, controlled scientific studies are required.
I might do some of my own tests on that to see about replacing molasses.
link to tea document The above quote came from. It has a lot of detailed info about tea in general.
1
