Deep soil moisture and temperature sensor installation
Most of the data scientists collect is about surface soil layers (<30 cm). We wanted to collect data at a depth of 50cm without damaging experimental plots. Here are a few snapshots and pointers from that experience.
Some tools you will need- a small pvc pipe with a light and a tamping rod. The tripod used to bore into the ground at a 45 degree angle. The soil bucket auger is a common tool in many labs, but the tripod was custom fabricated for applications like this one. The white tray is used to collect soil from the auger as the hole deepens. A side view of the auger and stand installing a deep sensor at the plots. Once the hole is deep enough, I threaded the communications cable through the PVC pipe and inserted the sensor into the new hole. The light is incredibly helpful for keeping good sensor orientation and observing what is going on in the hole during installation. A silly photo showing how the PVC can help as a sensor installation stick.
Threading sensor cable into protective housing
Rodent-chewed sensor cable in the Chihuahuan desert
In the dryland systems where I currently work, destruction of sensor cables is quite common. Large herbivores and rodents are the worst culprits, ripping out cable and chewing through multiple protective layers and disabling sensors.
To overcome this, we have been using irrigation tubing to protect sensor cables, both above and below soil surface level. Here I share a few photos of the process I’ve used to protect the cables.
Step 1- roll out the irrigation tubing to the length that you need. I typically uses paces as a relative measure and give myself just a little extra so I don’t come up sort. Importantly, make sure the tubing lays flat and is not twisted from being in a coil. Step 2- roll out sensor cable to length alongside tubing. Because I did this work by myself, I used a full water jug to “hold” the end of the tubing. You can see the sensor cable on the ground by the tubing. Step 4- Roll out your fish tape starting at the end your cable and tubing, and go the distance you are threading beyond the end of the cable/tubing. Insert the fish tape end into the tubing, and gently walk the tubing along so that the fish tape threads through the tubing as you go. Through trial and error (is there any other way?) I found this was much faster than manually feeding the fish tape into the tubing off of the reel. Here is the fish tape I used, it was really helpful to have a high-quality one that was pretty long (~100 meters). Here the fish tape is fully threaded through the tubing.Final step- Attach the sensor cable to the end of the fish tape. I used electrical tape to ensure it did not separate inside the tubing. Once it is attached, the most gratifying step is walking the tubing along and watching the sensor cable zip into the tubing. If the tubing is rolled out well and you are working on flat ground, there should be very little force involved and the sensor cable should thread easily into the tubing.
Here you can see how the sensor cable emerges from the tubing at a junction box. Also note the amount of wind-blown sediment in the box from just being open for a few hours!Once the junction box is completed, I wrap all joints with metal tape and then spray paint it white to deter any rodent chewing and help keep temperatures a little lower. Good luck!
Science by Sam Jordan 