It's now been 18 days since I started the soil moisture measurement experiment. This was a test I began 18 days ago, when I saturated the soil that had a soil moisture probe submerged into it, for measuring conductivity. To be able to accurately determine how moist the soil is, measurements at both total saturation and total dryness must be known. In this case, voltage is the measured value, and this will be converted to a percentage scale. The raw data is below.

It appears that temperature and soil conductivity are correlated, so I've included the temperature data to explain the bumps in the soil probe voltage.

The volume of this pot is roughly 1 liter. The soil is very degraded (dense) with a lot of clay (fine particles), which could explain the high conductivity for the majority of the test. The plant that's in the pot is also a slow-growing succulent (cactus), and does not require a great amount of water. These things combined make it difficult to determine the voltage at which it would be most appropriate to water. Other plants and soil makeups will invariably need the system to be calibrated again.

I have been meaning to purchase a grow light and tent to conduct actual grow studies, but due to my motorcycle being stolen recently, and having to deal with insurance and transportation issues, I've had to put that off until I am more financially stable.

In the mean time, I can theorize about optimal soil moisture and methods for improving this system. One improvement that may be beneficial would be to remove a small core sample of the dense clay soil and fill that with more loosely-packed soil, which the soil moisture probe could be placed. This allows the plant to retain the soil surrounding its roots, but enable the moisture probe to potentially react more quickly to moisture changes. The loosely-packed soil surrounding the probe would still be affected by the surrounding soil's moisture ,yet because of the lower conductivity, could react quicker and yield a more discernible voltage difference earlier in the test.

Having two soil moisture probes to measure at the same time would be ideal for this type of test, however with the assumption this data curve is reproducible throughout this soil, one probe will suffice.

I hope to bring more tests, Mycodo features, and a working automated plant monitoring and grow setup in the near future.