How to Interpret Soil Foodweb Assays

Table 1 - (click to open in a separate window)

Dry Weight: All three composts have moisture in good range. If the soil is too wet, aeration will be a problem and roots will be killed. Too dry and organisms cannot grow.

Active bacterial biomass: Control is in good range. HH is in good range, not significantly different from the control. In Biol, bacterial activity is low, resulting in poor decomposition, poor nutrient retention, a lack of soil structure building and limited disease suppression. Need to add bacterial inoculum, or bacterial foods to wake up the bacteria that are present (see total bacterial biomass).

Total Bacterial Biomass: Control has adequate total bacterial biomass but both treatments have low total bacterial biomass, for different reasons. Fungal growth is probably out-competing bacterial growth in Plus HH, while something in Bio1 is detrimental to bacteria. In all samples, sleeping, dormant organisms are present (active subtracted from total). Some unknown percentage of these dormant, sleeping organisms would grow on plate counts.

Active Fungal Biomass: Active fungi low in the control and in the Bio1 sample. Plus HH has in desired range activity. Disease suppression, nutrient retention, and soil building will be present in HH, not in the control or in the Bio1 samples. Need to add a fungal inoculum and fungal foods to these two samples.

Total Fungal Biomass: Both control and Bio1 too low, and therefore fungal diversity is lacking. Need to add fungal foods to get fungal decomposition going. Fungal foods are, for example, humic acids, many fulvic acids, dry, brown leaf materials, wood chips, sawdust, paper, cardboard. May need to add a fungal inoculum as well. The HH treatment has adequate fungal biomass, showing that just by adding humic acid that fungal biomass can be resuscitated.

Hyphal Diameter: As indicated by the footnote on the table, the diameter of the hyphae observed in these samples indicates typical soil fungi, a mix of beneficials and not-so-beneficial are present in the control and in the Bio1 treatment. In the HH treatment, this amendment has provided food for the beneficial fungi and they grew in preference to the less beneficial fungi. This is a very good result for any soil.

< Example - Table 2 >