The Right Auger For Water Content Sensor Installation
Traveling around the world, I’ve seen many ways to install soil moisture sensors. Digging a trench to the required depth and inserting the sensors into the sidewall is certainly the most common technique. But using a shovel takes a lot of effort, especially in rocky soil. To solve this problem, I like to use an auguring tool because of its ability to dig through soil to deeper depths without taking a lot of time. Also, the footprint of an augured hole is also only a few inches, which makes for a much cleaner installation. Still, borrowing an auger from the lab next door and heading to the field may not be the best option. This is what we did on the Cook Farm project a few years back.
The Cook Agricultural Farm is a 37 Ha managed research site near Pullman, Washington where a combined team of Decagon and WSU scientists installed 150 water content sensors over 30 sites a few years ago. At each site, we used the techniques outlined in METER’s installation video, which can be found here. However, the hardest thing about this installation was that we used some borrowed, standard bucket augers to bore the holes. These had a cutting surface along the bottom and an enclosed cylinder to hold the soil. Once we filled that bucket, we had a difficult time getting the soil out which really slowed the installation.
Recently while traveling to Germany, I learned about the Edelman Auger. The company that makes these (Eijkelkamp), says that most people in America use bucket augers to bore into fine soils which is needlessly time consuming. Edelman Augers, originally designed by the Army to dig latrines, will save time and labor.
At first, I was skeptical. It only had two cutting blades that ran up the auger in kind of loop; how would the soil lift out of the hole? However, when I tried one later in the day, the auger cut through the soil, making a 10 cm hole with very little effort, and as I removed it, the soil came out easily. It wasn’t hard to get the soil out from between the blades because there was no enclosed cylinder for the bucket. I wish I’d known about this auger when I was trying to install sensors at the Cook Farm.
So, here are a few tips about augers to help you pick the best one for your work:
- The Eijkelkamp Edelman augers are best for silty soils to clay soils so pick this one if you’re working in sites with these types of soils. It’s also great for digging a quick latrine.
- Bucket augers are best for sandy soils because of the enclosed cylinder will help lift the loose sand out of the borehole.
- If you’re trying to install your soil moisture sensors in very rocky soils, try a stony soil auger. It has big blades to help move small rocks and lift them out of the hole.
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