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Soil Sampling in the Sacramento Valley

In mid-April, the soil in the Northern Sacramento Valley was already bone dry. It hadn’t rained for weeks and had been very windy and gradually getting warmer. We hoped for rain to make soil sampling easier, but unfortunately, they had to get taken as soon as possible. The McConnell Foundation was starting a soil amendment study on one of their fields and we had to make sure to get all the initial soil samples before the amendments were applied. The only problem was that taking soil samples here was going to be very difficult. We have clay soil around here and when the soil dries out, it almost turns into concrete. You can no longer just press a soil probe into the ground and pull it back out, like you could if it had rained recently.




We quickly discovered that there weren’t any soil sampling tools made for hard soil. All of the different kind of probes were designed to be twisted or pushed into the ground by hand, but that was simply impossible. The only way to get something into the ground was if you pounded it into the ground with a mallet. Soil probes and soil sampling tubes aren’t made to be hit by a mallet. After getting hit a few times, the metal starts to bend and weaken. We had to take 150 soil samples and broke 4 soil probes by the time we hit the 25th sample. Using a soil auger worked but it took a much larger sample than we needed and took quite a bit of time to get into the ground as well. We eventually settled on using a soil sampling tube, pictured here. While it definitely wasn’t made to be hit into the ground with a mallet, it was the tool that lasted the longest before breaking. As long as we were careful about how we hit it and how we pulled it out of the ground, the tubes lasted about 20-30 samples before breaking. They broke either when we hit a rock or when it was stuck in the ground and we had to twist and pull it in a way that bent the metal too much. Once we figured out the right technique, it took us a few days to finish all 150 samples and we only broke 3 more soil tubes.



During this time, we figured out all the weak points in this soil tube. We really liked this tool and just wished it was more durable for the type of soil we were working with. It was so difficult to get in and out of the soil, that we had to be really careful with the soil tube so it would last longer. While soil sampling, I came up with a list of ways to make this soil tube more durable by reinforcing it in the weakest areas. The top bar had to be hit directly in the middle by the mallet, or it would start to bend and the top piece would become loose. Welding the top piece to the bottom tube, rather than securing it with two small pins, prevents the top piece from becoming loose, making it easier to pull out of the soil without bending it. It would have to be welded all the way around the circle of the tube to prevent the top piece from being pulled away from the tube. The top and bottom of the tube are closed, but not completely, they’ve just been bent to look like they come together, but they are not actually connected. Welding another piece of metal to connect these two sides together would also reinforce these parts from bending and separating or overlapping, as that was one of our main problems. Once the bottom of the tube got bent out of its perfect circular shape, the soil tube didn’t go into the ground well. With just a few simple additions, this tool could have lasted us a lot longer. It was frustrating to keep breaking tools and not finding one that fit our needs well. If you are ever in need of several small soil samples but are dealing with hard soil, these easy modifications may help you to get what you need.


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