In my previous blog I left off at the beginning of the meeting with Mr. Christensen, so now I will continue that story. After formally introducing ourselves, he showed me the Soil Moisture Probe, called the Aquaterr M-200 Moisture Probe. He continued to tell me that the device hasn’t been used for a while now due to the fact that the piece of equipment is outdated, it certainly works well but just simply outdated. The M-200 Moisture Probe hit the market in 1986! It was made by ‘Aquaterr Instruments & Automation.’
This model is considered as a portable capacitance probe. This is how it works, “The electrodes are encapsulated in the tip of a rigid metal stem attached to the meter. Readings can be interpreted depending on the soil type using the chart shown on the meter. The readings are sensitive to the soil temperature” (The South Dakota Section of The American Society of Agricultural Engineers).
After learning this information from Mr. Christensen, we went outside to the nearest grass field and tested out the probe. The reading we received in that specific spot in the field was 75, which means the soil is more towards the wet spectrum than the dry. It is fascinated to me how this probe was able to get a reading like that. There was just a ceramic tip at the end of the probe, who would’ve thought that it could do something so incredible. Mr. Christensen told me that to use this piece of machinery would be quite easy since it has already been calibrated for me and all I had to do was “plant” it into a proper spot of my choice and press down the ‘Test’ button and write down the number and analysis what the number meant.
After my meeting with Mr. Christensen, I was ready to take sample readings all by myself and that is exactly what happened. In that exact same field I kept moving from place to place and tested the soil. Each spot was completely different. One spot about 10 feet away from where I received the “75” reading, I received “34.” There are many reasons to why this could be. One is, one spot could directly next to irrigation or sprinkler as oppose to another spot that never receives water from the sprinklers. But one variable that I could control was the ceramic tip not carrying soil from one spot to another, which would rig the reading. So, what I did was bring a wet paper towel and dry one, after each soil testing I would clean the ceramic tip. Believe or not but it is really fun sticking this piece of equipment into the ground and seeing the reading. It is something that will never get boring because the sample surprises you every time you take one.
Evaluation of soil moisture sensors in potato fields