Different methods measure different fungal and bacterial populations. The chart below, adapted from Wang et al review of 192 different F:B ratios, illustrates how three different methods came up with three different F:B ratios for Forest, Farmland and Grassland. Note that microBIOMETER® correlates well with the gold standard, microscopy. By plate culture, forest F:B is about 1/3 that of farmland, whereas PLFA forest F:B is slightly higher, and microscopy and microBIOMETER® forest F:B are 10 times higher than farmland.
We receive this question often and the answer is no.
How do we know this? microBIOMETER® shows that soil removed from the earth and plants lose microbial biomass every day which we have confirmed with microscopic studies. The literature also confirms this.
Why is there confusion? Most of the microbes in soil are in the “dormant” state, they only wake up when stimulated by the plant or some other stimulus. For a long time people thought dormant microbes were dead. Now we know they have lost as much water as possible and encased themselves in a tough cocoon that can allow them to survive for up to thousands of years. microBIOMETER® measures these earth-colored dormant microbes.
What microbes are dormant? All soil microbes have the ability to go dormant. This allows them to survive drought, freezing, starvation, etc. Bacteria and fungi build tough spore walls to protect themselves. microBIOMETER® measures those spores.
In the winter when it is below freezing in New York, if we microscopically examine the microbes that are separated from soil using microBIOMETER® we see very few fungi but plenty of spores. In spring the arbuscular mycorrhizal fungi spores will germinate and find a plant to colonize. In the Fall when roots are dying and decaying organic matter is present in the soil, we see a profusion of the saprophytic fungi that break down the tough vegetable matter. Bacteria can sporulate but even the bacteria that do not sporulate manage to wrap themselves in a tough outer coat by collecting clay and minerals in their gluey outer biofilm.
For more information on fungal spores, please visit mycorrhizas.info.
Arbuscular Mycorrhizal Fungi (AMF) colonize 80% of crops. Their effect on plant growth can be positive, neutral or negative. It depends on many factors including the crop species and genotype, the species of AMF, and the characteristics of the soil. A low pH favors colonization of the plant by AMF while application of chemical fertilizers, especially phosphate, inhibits colonization by AMF. In the absence of chemical fertilizers and in the presence of low levels of pH, AMF provides the plant with phosphorous. AMF can extract P from rocks so it can get P from soil that tests low for P.
AMF can dramatically increase plant yield and resistance to pathogens and drought, as well as decrease irrigation needs and sensitivity to salinity. Thus, AMF can be of great assistance in transitioning from conventional to sustainable/regenerative agricultural. There are now many suppliers of AMF but there is no guarantee that any one product will be optimal for your crop and your soil.
The new microBIOMETER® test, which estimates fungal to bacterial ratios in soil, can help you decide which AMF works best with your plant and soil because it can detect colonization of rhizosphere soil for fungi within a month of AMF application.
Leifheit, E. F., Veresoglou, S. D., Lehmann, A., Morris, E. K., & Rillig, M. C. (2014). Multiple factors influence the role of arbuscular mycorrhizal fungi in soil aggregation—a meta-analysis. Plant and Soil, 374(1-2), 523-537.
Types of fungal spores. The sizes vary from microscopic to visable..
Arbuscular Mycorrhizal Fungal (AMF) are dependent on the plant for their food, therefore, they die when the plant dies. Lucky for us before they die they form spores that can live a long time in the soil.
When we have looked at the soil from vineyards in winter it is filled with fungal spores. Pictured here of some of the types of AMF spores. The size of these spores can vary from microscopic to visible.
The spore starts growing when it receives a chemical message from a nearby plant. It has a day or two to reach the plant, enter the root and build a little space called an arbuscule where it can get food from the plant. If it fails at this, the fungi dies. This is why we like to plant seeds with AMF. The plant feeds the fungi because the fungi send out long hair like structures called hyphae that bring minerals and water back to the plant. In fact, scientists have recently shown that the fungi and the plant actually barter with one another, i.e. when phosphorus is low, the fungi gets more food for delivery of phosphorus.
microBIOMETER® measures both fungi and fungal spores as well as bacteria. The lab methods of PLFA and Carbon Fumigation do not adequately measure spores. Standard microscopy also does not adequately measure fungi.
