Have I mentioned that I post on Instagram (and Facebook) as Sandra Mack the Science Hack? It’s a funny name my nephew Julian gave me one summer at the lake cabin, as we tried to solve the science mystery of the disappearance of frogs on the property since my childhood. Well, this post feels like a Sandra Mack the Science Hack adventure. Hope you enjoy the ride!
The purpose of this blog and the project it describes is to demonstrate that urbanites and suburbanites can sequester carbon in the soil and plants of our yards. But as they say in science, if you can’t observe it and you can’t measure it, it ain’t science! So to really start our project, a baseline soil test must be completed here at the Mothership Garden right away. The amount of total organic carbon in the soil needs to be established, and then by testing the soil yearly we can see if the soil carbon content is increasing. If it’s not, all of my recommended garden practices will be proved meritless vis a vis the purpose of the project. Remember though, it’s okay to have your hypothesis disproved, (and thus fail in your purpose) as long as it was a wonderful experience. I mean, if you’re a professional scientist, you’re getting paid so I guess it doesn’t always have to be wonderful, but for us science hacks, it’s essential. Ah, science!
At first I thought this soil testing business was going to be easy; after all, I’m a gardener and Earth science teacher — piece of cake, I thought. I didn’t think it would be as easy as ordering something from Amazon, but I sure didn’t expect that it would prove to require extended study and multiple discussions with experts; but so it has proved.
Whoa, my first shock was how little I knew about many areas of soil science! Soil science is not some minor, tidy science (if such a science exists) – it’s an absolute universe of dynamic, active research. My relative ignorance was quickly revealed. Yet in order to decide which lab tests to order and how to sample my soil, I had to start with some research of my own. Studying, people! Sheesh, I said to myself, I sure am doing a lot of studying these days for this blog.
If you get inspired to get a complete soil analysis of your place as well, I hope that by sharing my experience you can sail through it. However, I have to warn you: if you go as far as to get a complete soil analysis you are going to have to commit yourself to the study of soil science over time to get the most out of it.
Collecting the first annual Mothership soil sample
Our adventure begins with the way I took my soil samples. I decided to treat my entire yard as one site, since I believe that the soil is much the same everywhere I have seen it. Our site is also flat, so there are no hugely different areas. As is standard practice on a small field or yard, I took random samples all over the property – in my case nine in all. The soil was sampled for the first eight inches. Each of these decisions took some time to make, and I can explain my reasoning for any of them if anyone is interested. And finally, I want to note that I got totally stuck in all my research, and only after I called my friend Cheryl Kent, a former soil scientist, extension agent and current science teacher and mom, was I able to feel sure enough to settle on these decisions.
For tools I used a shovel, trowel, bucket and ruler, as well as my Dewit broadfork. I washed everything off with the hose first to avoid contamination. I removed the layer of mulch on top of the soil.
Next, I added my own hack to the standard process: because our soil is so dry and cold, it was hard to dig so I first loosened it with the broadfork. You may not have such a tool, and you may not need such a hack (I should add that I consider this elegant little one-piece forged broadfork one of the most indispensable tools I have ever acquired for the garden).
Once I could insert my shovel at least eight inches deep, I lifted out a shovel-full. Using the ruler I measured the soil and cut away any deeper than eight inches with the trowel. I also cut away the soil on each side of the shovel, so that I wouldn’t get such a huge sample from each spot.
I repeated this process at eight other sampling sites, and I took pictures of the sites so that I can sample near them next year. In the bucket, I mixed the soil samples, removing any chunks of organic matter or roots, and then left the soil in the shade to dry even more. This week, I will put about two cups of soil in each of two labeled ziplocks, and send them off to two different labs – Colorado State University, and Ward’s or a similar commercial lab. One lab is sufficient and Colorado State University is a great choice. I just want to see if I get the same results at another lab.
In part two of this blog I will talk about what else, in addition to Total Organic Carbon, that the tests will measure and how my project will benefit from that information. I will share a bit more information about Total Organic Carbon and a related measurement, Total Soil Carbon.
If you are considering a complete test of your own soil, think about the time of year you would like to do it – retesting should be done around the same time of year.
After finishing the soil testing posts, I will be delving into garden planning using Google Earth, my Hugelkultur experiment in the high desert, and preparing beds for planting.
Finally, here is a video of my soil sample process in case it helps!
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