Getting a good Microscope for on farm monitoring of soil development
Life in the soil is what drives fertility. As primary producers our responsibility is to feed, nourish and grow soil. At a training for farmers on the King & Queens home island in Stockholm we looked at several effective ways for farmers & land managers to engage in the monitoring of the impacts of their activities & decision making on soil health. Certain tools are really worth having. A good soil microscopy unit means we can monitor population changes of soil foodweb organisms, monitor compost processes and create compost teas that are simply teaming with beneficial support organisms to restore healthy populations back into the soil. Building healthy soil is our primary responsibility and the core solution to many agricultural problems.
The role of key soil organisms in healthy living soil
The image above gives a simplified schematic of the soil foodweb trophic orders. So what are the roles of these key organisms?
Bacteria are tiny, one-celled organisms – generally (1 µm) wide and somewhat longer in length. What bacteria lack in size, they make up in numbers. A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria. 2.5 tons of microscopic bacteria may be active in each ha of soil!
Nematodes are non-segmented worms typically (50 µm) in diameter and (1 mm) in length. Those few species responsible for plant diseases have received a lot of attention, but far less is known about the majority of the nematode community that plays beneficial roles in soil. An incredible variety of nematodes function at several trophic levels of the soil food web. Some feed on the plants and algae (first trophic level); others are grazers that feed on bacteria and fungi (second trophic level); and some feed on other nematodes (higher trophic levels)
Protozoa are single-celled animals that feed primarily on bacteria, but also eat other protozoa, soluble organic matter, and sometimes fungi. They are several times larger than bacteria – ranging from (5 to 500 µm)micro metre in diameter. As they eat bacteria, protozoa release excess nitrogen that can then be used by plants and other members of the food web. Ciliates are the largest of the protozoa and the least numerous. They consume up to ten thousand bacteria per day, and release plant available nitrogen. Ciliates use the fine cilia along their bodies like oars to move rapidly through soil. Another group of protozoa, the flagellates are like big drunken blobs, dizzily crashing around bumping into things! It's their movement characteristics that allow us to identify some organisms.
Many bugs, known as arthropods, make their home in the soil. They get their name from their jointed (arthros) legs (podos). Arthropods are invertebrates, that is, they have no backbone, and rely instead on an external covering called an exoskeleton. Arthropods range in size from microscopic to several inches in length. They include insects, such as springtails, beetles, and ants; crustaceans such as sowbugs; arachnids such as spiders and mites; myriapods, such as centipedes and millipedes; and scorpions. Nearly every soil is home to many different arthropod species. Certain row-crop soils contain several dozen species of arthropods in a square mile. Several thousand different species may live in a square km of forest soil.
Earthworms occur in most temperate soils and many tropical soils. They are divided into 23 families, more than 700 genera, and more than 7,000 species. They range from an inch to two yards in length and are found seasonally at all depths in the soil. In terms of biomass and overall activity, earthworms dominate the world of soil invertebrates, including arthropods. They are major decomposers of dead and decomposing organic matter, and derive their nutrition from the bacteria and fungi that grow upon these materials. They fragment organic matter and make major contributions to recycling the nutrients it contains.
Fungi perform important services related to water dynamics, nutrient cycling, and disease suppression. Along with bacteria, fungi are important as decomposers in the soil food web. They convert hard-to- digest organic material into forms that other organisms can use. Fungal hyphae physically bind soil particles together, creating stable aggregates that help increase water infiltration and soil water holding capacity.
Selecting a good microscope for soil analysis
There are many options for microscopes but some key points are vital if you want to be studying soil samples regularly and effectively. I bought my scope set from the US as I liked the choice, price and camera set ups. (I opted for a trinocular unit for teaching/ monitoring files) There are much better quality scopes, and much worse. I have no complaints about this one, it does everything you could wish for, was a good price and is well packaged in a good quality flight case. You want binocular eyepieces so you don't strain your eyes. Monocular microscopes will strain your eyes if you are doing much work with the unit.
10x wide field eye pieces are best. Stronger eye pieces will not give you better resolution, which is needed for observing/ counting organisms. You will also need at least 10x, 20x and 40 x objectives. That means with the 10x eye pieces you can magnify samples to 400x, plenty for good soil foodweb analysis. You use the 10x or lower to scan around the slide and focus the condenser and image then carefully switch around to the 40x objective for analysis and counting. You should always look carefully at what you're doing as the 40x objective will only just fit, and you don't want to crush your most expensive lens by being clumsy. Some fine focusing will be necessary, as within your slide you will find multiple layers of activity. Adjusting the condenser will reveal untold wonders! Be sure your eye pieces are focused exactly the same- you will quickly get headaches otherwise.
A good condenser is necessary to focus the light properly on your sample (like the aperature of a camera). Mine has an abbe 1.25 condenser, which is ideal. You also need a halogen/ led lamp to adequately light the sample. You need to study how to set up soil samples properly, as an incorrectly set up microscope can prevent you seeing anything at all.
I opted for a trinocular microscope which allows me to hook up a 9MP camera for film/ photography which is useful both in education and monitoring reports. If we are making regular compost tea applications we monitor the results by taking randomized soil samples and then taking randomized views of various slides and counting organisms present. This gets quicker as one gets accustomed to the visual field and can make proportional estimates (counting 5000 bacteria in a single field of vision would be challenging!) Observe & record and monitor over time.
This is one of a range of tools & techniques we use to monitor the impacts of our holistic decision making at the farm. We will be doing a lot of research at ridgedale with recording & documenting changes within our ecosystem. We will be publishing results of all aspects of our work in mixed media with the help of our dedicated crew. If you want to stay in touch with whats happening at the farm you can customize our newsletter to fit your needs, or follow us on Facebook.
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