The Search for a Soil Moisture Probe

 My Final Project assignment was the “Soil Moisture Probe.” At first I had no clue to what a Soil Moisture probe actually is. I just figured that it had something to do with the moisture of soil. I wasn’t given much instruction on the assignment or of how to move forward, it was more like “here is your topic and start researching pronto.” Here I was, just a young man and a project topic.

Here is the web search for a "Soil Moisture Probe." You can see many of these probes for sale as well as information on it

Here is the web search for a “Soil Moisture Probe.” You can see many of these probes for sale as well as information on it

I started researching like anyone else would, starting with ‘Google.’ I then found myself upon the Wikipedia article, Soil Moisture sensor. It said that “Soil moisture sensors measure the water content in soil” as well as “A soil moisture probe is made up of multiple soil moisture sensors.”  Just clarify, if you come across something called a “Tensiometer” then that is something that is similar to soil moisture probe but not the same thing. I found out that the purpose of Soil Moisture probes is to measure the moisture volume of soil.
“A tensiometer consists of a tube containing water, connected to the soil through a membrane permeable to water and solutes, but not to the soil matrix.  Thanks to the second law of thermodynamics, water moves from the reservoir to the soil until its energy is equal on both sides of the membrane.  That creates a vacuum in the tube.  The tensiometer uses a vacuum gauge to measures the strength of that vacuum and describes water potential in terms of the negative pressure.  Solutes move freely through the membrane, so only the matric potential is measured” ( Tensiometers measure the tension of the soil by using a pump and a vacuum gauge and is the only instrument that makes a soil suction.

The more I researched the more bombarded I was from all of the results. I learned that there are so many different types of Soil Moisture sensors such as: “lysimeters, tensiometers, neutron probes, resistance meter, capacitance meters, heat dissipation methods, time domain reflectometry, and infrared probes.” Each type of soil sensor gave the same kind of result but just had a different way of getting the answer. I knew that I needed to purchase a soil moisture sensor quickly because I needed to be able to use it so that I could have hands on experience in this project but the search was overwhelming. Like I said earlier, there are so many different types of moisture sensors and because of that it makes the design of which type of sensor to purchase difficult.  

In the left column you can see the different main types of Soil Moisture Sensors. In the right column it shows the pros and cons to each type of sensor.

In the left column you can see the different main types of Soil Moisture Sensors. In the right column it shows the pros and cons to each type of sensor.

 Along with many informational websites, I looked at the table off to the left for guidance when figuring out what kind of sensor to buy.  Before I got too serious about purchasing one, my teacher, Mrs. Beamish, told me that there is a New Mexican farmer, Mr. Morgan, who she is very close to. Mrs. beamish highly encouraged me to contact him and schedule an appointment with him at his farm and learn how soil moisture sensors work. That plan was going great until I contacted him. He told me that he would love to help me but sadly he was going out of town for the next week. That was an enormous problem because I needed a Soil moisture sensor right away. Time was running out and Mrs. Beamish had another personal friend that could help me on the subject. That close friend of hers is John Christensen, the Direct of Physical Plant, at my school.  With that helpful piece of information I quickly emailed Mr. Christensen and told him who I was, why I was emailing him, and asked if he had a soil moisture sensor that I could use for my project. He responded fairly quickly and told me that, “I believe we have one you can use. Let me check with grounds” (John Christensen). After a couple of days of no response I began to become worried about whether I needed to buy a sensor for sure or just wait patiently. I decided to meet with his secretary and schedule an appointment with him.

 Read my next blog, “Aquaterr M-200 Moisture Meter, the soil moisture extrodanare” to learn about what happens next…














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