1. Commercial products. Working with product companies, the following products have been shown to result in significant increases in bacterial biomass in the following conditions:
- Estecol and Hydra Hume Plus (Helena Chemical Company). Shown to increase bacteria
in clay, silt and sand soils, in both lab greenhouse tests and fields
trials in California. When bacterial biomass are below 5 µg per gram dry
soil, apply 1 gallon per acre. If bacteria are greater than 5 µg but less
than 100 µg per gram, apply 1 quart per acre. Repeat applications if
bacterial biomass does not increase to desired level. It may be beneficial
to apply a soil conditioner such as Ece-X to drive salt out of the soil,
and add calcium products or rock dust or Eco-Min to replace lost or leached
micronutrients.
- Blend (Advanced Agri-Tech, Pasco, WA). Testing has been done on particular soils in Washington and Idaho and shown to improve both bacteria and fungi.
2. Simple sugars such as table sugar, syrups or molasses. The question
always becomes how much sugar in what volume of liquid over what amount of
land area. Dosages need to be worked out, but generally, try an increasing
gradient of concentration. Start with 1 gram of sugar in 100 ml (1% sugar)
and apply to a 1 meter square area. Apply a solution of 10 grams in 100 ml
(10%) to another area, and a solution of 20 g in 100 ml (20%) to another
area. Wait a week, perhaps two, and test to see if this was effective in
increasing bacterial biomass. Be aware that too high a concentration of
sugar will cause a bacterial bloom, and will cause symptoms of N-deficiency
in the plants. Avoid concentrations that result in plant yellowing.
3. Molasses - There are a few humic materials in molasses, giving molasses
the dark color. Blackstrap molasses contains more of these humic materials
than less thick and dark molasses suspensions. Test as above for rate.
4. Plant extracts usually contain the sap of the plant material, which are
combinations of simple sugars, protein, carbohydrates.
- Yucca extract is a product that appears to enhance "stickiness," selecting for bacteria that produce extracellular slime. About 1 pint per acre.
- Nettle extract contains an unknown compound with antibiotic-like
qualities. Typically made in the same fashion as a compost tea, but using
mown nettles instead of compost. Highly variable potency. Testing from
batch to batch is required.
5. Fulvic acids appear to be food resources for bacteria. Apply at about 1
quart per acre. The molecular weight of these "humics" is less than that
of humic acid, and at least in some cases, supply food for bacteria more
than fungi. More work is needed to understand the difference in microbial
communities selected by fulvic versus humic acids.
6. Yeast provides vitamins for bacterial growth. The kind of yeast is
important, as Baker's yeast provides quite different sets of vitamins than
Brewer's yeast, or champagne yeast, as examples. This material has not
been well-tested for it's dose-response, so testing on your own land will
be required.