Question Prompt:
How has your soil changed during the growing season?
Figure 1. Soil collected from the garden
(Photo Credit: Holly A. Stuart)
Whether you choose to address the question prompt above or create your own questions, you and your students can take a deep dive into the microscopic world of soil with a classroom set of Foldscopes.
Even though it may not look like it at first glance, the garden soil has undergone many changes during the past few months. Macroscopic and microscopic animals have moved in, soil particles have been broken down into smaller pieces, and plant material has been added. Now is the perfect time to compare the current state of your soil to where it began in the late winter when the garden was brand new.
Figure 2. Nematode in the soil viewed under a Foldscope 2.0 at 140X magnification plus 5X digital zoom on phone
(Photo Credit: Holly A. Stuart)
Background:
Soil is a living, constantly changing thing. There are physical changes that happen in the soil due to rain, wind, and temperature changes. The soil particles experience weathering from plant roots, worms, bugs, insects, microbes, and bacteria. Decomposers are actively breaking down organic material to build up even more nutrients for the entire soil community. While many of these changes are happening on a microscopic scale, that doesn’t mean that these changes are minor and don’t have large scale implications. The health of the soil, and the plants that grow in it, is vital to the health of every living thing on the planet!
Figure 3. A pill bug (Armadillidium vulgare) viewed under a Foldscope 2.0 at 140X magnification (top) 140X magnification plus 5X digital zoom on phone (bottom)
(Photo Credit: Holly A. Stuart)
This month you will study the microscopic changes taking place within the soil. This blog includes sample ideas, slide techniques, and student research ideas to guide you and your class’s longitudinal study in the garden!
Materials:
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Dissecting Kit or Set of Tweezers
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Small Trowels or Scoops
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Petri Dishes (these are in the Foldscope 2.0 Accessory Pouches)
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Ring Stickers (a variety of thicknesses)
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Garden Soil
Figure 4. Soil in a petri dish
(Photo Credit: Holly A. Stuart)
Soil Particle Size
Throughout the growing season, the larger soil particles get broken down, creating an ideal mixture of loam which contains sand, silt, and clay. The smaller soil particles of clay and silt are important for garden health for many reasons. Smaller particles can retain more water than large particles, and the increased surface area of smaller soil particles makes mineral absorption by plant roots greater.
Soil particles are three dimensional, so it is helpful to use the ring stickers to mount the sample on the slide. This creates a well to hold both soil and water. (NOTE: Adding water is a great way to break up any clumps of soil on the slide allowing better viewing of individual particles.)
Figure 5. Smaller soil particles after being broken down during the growing season viewed under a Foldscope 2.0 at 50X magnification plus 5X digital zoom on phone (left) and 140X magnification plus 5X digital zoom on phone (right)
(Photo Credit: Holly A. Stuart)
When your students look at the soil under their Foldscopes they may notice that some areas of the garden have different soil particle sizes than others. Perhaps they can do an investigation to compare and contrast the plants, insects, and microbial life in the different areas. Can they think of a correlation between soil particle size and the soil microbiome?
Soil Microbiome
The soil microbiome is a hot topic in the world of agriculture today! Scientists are only just beginning to develop an understanding of what is happening under the soil that impacts what we see above ground. From microbial communities, to bacteria/fungal/plant relationships, to nutrient recycling by decomposers, there is a rapidly growing field of research just waiting for your students’ scientific contributions!
Figure 6. A sparkling field of bacteria and microbes viewed under a Foldscope 2.0 at 140X magnification plus 5X digital zoom on phone with darkfield lighting
(Photo Credit: Holly A. Stuart)
To prepare your samples, add water to your soil, stir it around, and place a drop (take care not to put too much sediment on the slide or you won’t be able to see anything swimming around!) on a slide with a ring sticker. Cover the ring sticker and place the slide in your Foldscope 2.0. You should see lots of microbial life swimming, crawling, and spinning around in that single drop!
Figure 7. A rotifer (with its corona actively extended) viewed under a Foldscope 2.0 at 140X magnification plus 3X digital zoom on phone
(Photo Credit: Holly A. Stuart)
Your students might also find pieces of insects or plant debris mixed in the soil. To view these specimens they can place the objects directly on the slide and cover them with a clear sticker or cover slip. This is the technique used to get the following images of various insect parts.
Figure 8. Montage of insect wings, legs, and exoskeletons viewed under a Foldscope 2.0 at 50X magnification (wing, top left), 50X magnification plus 5X digital zoom on phone (wing, top right and legs, bottom), and 340X magnification plus 5X digital zoom on phone (exoskeleton, center)
(Photo Credit: Holly A. Stuart)
To view the microbial activity around plant roots, use the ring sticker to mount the root and then add a drop of water before covering the sticker. This allows you to see the root hairs and cells while also providing space for the microbes and bacteria to continue moving around the root.
Figure 9. Root hairs viewed under a Foldscope 2.0 at 140X magnification plus 5X digital zoom on phone (left) and 340X magnification plus 5X digital zoom on phone (right)
(Photo Credit: Holly A. Stuart)
If you would like to see the microbes I found in my garden in motion, take a look at this microcosmos post with the videos attached. Seeing their movements might generate additional questions from your students and inspire them to keep investigating the soil microbiome on their own!
Microcosmos Post: Soil Microbiome
Connect:
Remember, these are only suggestions to guide you along your garden study. What questions do your students want to answer? Which microbes did you see in your soil microbiome? Let us know! Share your observations, discoveries, and pictures with the Foldscope community on the Microcosmos. Your contributions will build up a strong scientific database that can help support new and innovative scientific research. Tag us on social media, too. We love to see how Foldscopers around the world are using their Foldscopes in new and innovative ways!
As fall begins next month, we will turn to the world of decomposition. Until then, happy gardening and Foldscoping!
Figure 10. Mushrooms sprouting up in the garden
(Photo Credit: Holly A. Stuart)
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Sources:
https://www.sciencedirect.com/science/article/pii/S2589004223001050
