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.
Leeston Pastoral is a 5th generation, family owned farm in New South Wales, Australia. Historically, they have had a fine wool Merino & Hereford cattle breeding operation. Over the last 20 years they have moved to focus on cattle.
The 2019 drought forced them to reevaluate what operation they wanted to continue in. They decided to adopt a more regenerative approach and move from a cattle breeding operation to a cattle trading operation. They now have one large mob grazing holistically using short grazes and long pasture rest periods.
microBIOMETER® has allowed them to quickly, easily and inexpensively record existing benchmark measurements of their soil microbiology and now reassess the effects of stock movements and plant/soil amendments. They are excited to see the new F:B ratio measurement, as they want to make sure the soils stay fungally dominated so they can more effectively create stored soil organic matter.
They were happy to see their microBIOMETER® results showed an almost 30% increase in microbial biomass and fungal to bacterial ratio one month after holistic grazing. Studies have shown that a 1.5x increase in your soil’s F:B ratio can lead to a 3x increase in carbon sequestration. Thank you Adam for sharing your experience with us!
The Sítio Escola Portão Grande is a Brazilian NGO, nonprofit organization which was founded in October 2012.
Sítio Escola Portão Grande hosted students from the Mentoring and Language Acquisition Program (MLAB) for a full day immersion at the farm in Brazil which featured soil testing with microBIOMETER®. MLAB is a mentoring and language acquisition program for Harvard students and Brazilian high school students, with low income and high performance. In addition to mentoring, the program brings foreign students to an immersion in Brazil, exploring themes that motivate them.
The students were delighted to observe the use of microBIOMETER® to assess fertility based on the measurement of soil microbial biomass. It was explained to the students that microBIOMETER® is used monthly to assess the evolution of fertility due to the different inputs applied to the soil, the crops and harvests carried out, as well as throughout the seasons. Therefore, providing a database of great importance to make future decisions. In addition, due to its ease of use, microBIOMETER® also proved to be an good tool to assess the quality of the inputs we produce on the farm, such as bokashi and compost tea, allowing the tuning of the culture media we use for them.
A big thank you to Antonio Feres Neto for sharing this story with us! We love hearing how our customers are using microBIOMETER®.
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.
Source: Food Web and Soil Health
The graph pictured here from the USDA website depicts the ratio of fungi to bacteria as a characteristic of the type of system it is in. An excerpt from the article:
“Grasslands and agricultural soils usually have bacterial-dominated food webs – that is, most biomass is in the form of bacteria. Highly productive agricultural soils tend to have ratios of fungal to bacterial biomass near 1:1 or somewhat less. Forests tend to have fungal-dominated food webs. The ratio of fungal to bacterial biomass may be 5:1 to 10:1 in a deciduous forest and 100:1 to 1000:1 in a coniferous forest.”
If you are measuring soil attached to the roots colonized by mycorrhizal fungi, your ratios should be much higher than is shown for agricultural soil. Also the saprophytic fungi population increases when there is a lot of litter for digestion, so you would expect to see different ratios at different times of the year and under different conditions.
The graph pictured below based on USDA website information shows the expected fungal to bacterial ratio for various plants.
Please visit our Using the Fungal to Bacterial Ratio with microBIOMETER® on YouTube for more information on fungal to bacterial analysis.
