Agriculture is science. If you’re growing something – whether flowers in a pot on the windowsill or vast fields of vegetables – you’ve got a ready-built classroom.
There are some obvious lessons: What does a seed require to sprout? How do plants “eat and drink” from the soil? Which animals are harmful/helpful to plants? Etc. But there are other things that can be learned in the garden as well. A good gardener has a grasp on chemistry, physics and math.
Each Friday for the rest of the month of April I’m going to be sharing ideas for very simple, low-cost ways to use your garden to explore science and math.
1) Acid or Base?
Soil can become acidic or alkaline over time. To find out which way your dirt is leaning you can take a handful of earth and mix it with water until it’s liquid mud. Separate it into 2 cups. Add vinagar (acid) to one cup and baking soda (base) to the other. Watch for a reaction. If the mud is acidic the baking soda will create a foamy reaction. If it is alkaline the vinegar will do the same. If it is neutral (or close to it) neither substance will react.
Why does the reaction happen? Because the acid will dissolve the bonds holding the molecules together in the base. That creates energy which is released into the liquid. When the energy is burned up, the reaction calms and the bubbling effect will slow and, eventually, come to a stop. For a much more thorough (but still quite kid-friendly) explanation check out this website.
Different plants grow well in different types of soil. Tomatoes love very damp earth. Pumpkins will sprout on a hot compost pile. Lavender loves dry, gravelly sand. The reason for the variation (at least in part) is that each of these plants have a different requirement for the amount of water needed to grow and each type of soil has a different rate of absorbency.
Go around the yard and see if you can find some different types of soil. You may find that you have several kinds, naturally. In my yard I have one streak of red clay, a sandy stretch and a lot of black loam. Get creative. Do you have playground sand? Potting soil? Mulch? Gravel?
Put a sample of each type in a cup or bowl. Using a measuring cup start adding water to each sample to see which types of soil are the most absorbent.
Wikianswers has a great explanation of why the different types of soil hold water differently.
Take a plate full of earth and have your child blow, as hard as they can on the dirt and see if they can make it blow away. Can they make it into shapes, like sand dunes? Discuss in what ways the wind shapes the dirt.
If you hold the dirt at a slight angle and run a small amount of water over it what happens? Can they cut a valley? Does it wash away entirely?
Now try the same thing with dirt that has something growing in it (like a piece of sod). Can you still move the earth? How do the plants help “anchor” the dirt to the ground?
These experiments can offer a great opening into discussions about all sort of things. Why do farmers plant cover crops? Why are there stands of trees between fields in the midwest? Why do architects need to know about how erosion works when building bridges over rivers, houses on hillsides or planning cities in valleys?
Come back next Friday! We’ll cover trajectory, simple machines, measuring area and more!
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