How to Interpret Soil Foodweb Assays

Table 3

(1) Based on 25 year’s of data, Grass:0.5-1.5; Berries, Shrubs, grape: 2-5; Deciduous Trees: 5-10; Conifer: 10-100.

(2) Warm spring, early summer: 0.25 to 0.95; Early spring, late winter & mid-summer: 0.10 to 0.15; Fall rain: 0.15 to 0.20; Drought/frozen soil/heavy metal/many pesticides: 0.05 or lower. Values greater mean the organisms are recovering from a negative impact. Values lower mean organisms are not recovering and help is needed, typically addition of their food resource is required.

(3) Generally 1:1 results in good soil aggregate structure in crop soil; 2 to 5 for deciduous trees; 5 for conifers.

(4) Based on release of N from protozoan and nematode consumption of bacteria and fungi (see Ingham et al 1985, and recent papers in Ecology supporting this work).

(5) Identification to genus.

Total Fungal to Total Bacterial Biomass: Control and Bio1 both on the bacterial-dominated side, while HH is fungal-dominated. Need to add more fungal foods and possibly need fungal inoculum in control and Bio1 samples. Control and Bio1 samples reveal food webs appropriate for vegetables, annual plants. The HH sample has a ratio appropriate for bentgrass and other productive pasture or lawn grasses.

Active to Total Fungal Biomass: Only HH has decent levels of active fungi. Neither the control nor the Bio1 sample has enough active fungi to protect the plant against disease-causing organisms. An inoculum of beneficial fungi would be wise, but certainly fungal foods are needed.

Active to Total Bacterial Biomass: Both the control and HH have adequate active bacteria relative to total bacteria, but the Bio1 treatment has reduced the active bacterial component severely. This amendment is detrimental to both active and dormant bacteria.

Active Fungi to Active Bacteria: Which microbial group is winning? Bacteria are in the control, so the soil will become even more bacterial over the next few weeks. In the HH treatment, the beneficial fungi were enhanced and the ratio shows that the soul will become more and more fungal with time. In the Bio1 treatment, the bacteria were killed, so this ratio is very fungal. Because active bacteria were harmed more than the fungi, the ratio is quite skewed. Fungi will grow in this soil more than bacteria, until conditions change, but it may well be un-desirable fungi because the bacteria are not performing their jobs.

Plant Available N: Low in all three soils. Need a protozoan inoculum.

Nematodes: No root-feeders detected, but no beneficial nematodes found either. Need a beneficial nematode inoculum. Nematodes are the most difficult group to get re-established.

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