using capsense to measure soil moisture?

[raggedyanne]

In Australia we have a government agency called the CSIRO that produces scientific publications on such things as exponential plant growth of species.
Plants grow all the time , they grow under particular conditions related to nutrient, sun, heat etc.
So the first step would be knowing your expected growth rate/biomass.
Biomass over a period of time, time being a constant.
The second thing that is important is the rate in which moisture evaporates from soil in a volume.
There is a median temperature particular to the region based on the season.

Indicative to biomass over time / evaporation over time

You could estimate when the calibration will be & what the offset will be.

Remembering that a little water is better than no water.

[raggedyanne]

This however an article somewhere on the internet that discusses making a probe with plaster of paris.

[WhiteHare]

Not sure how well, or even if, this approach to measuring soil moisture would work, but it does have the virtue of being simple (provided that your temp-rh mote is small enough to fit inside the waterproof shell):

https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=2114.10010108.1000013.6.PVGRb3&traffic_analysisId=recommend_2088_3_81019_new2&scm=1007.13339.81019.0&pvid=b9edd7ff-9069-4c39-be95-b2d3ca8bdf17&tpp=1

https://www.aliexpress.com/item/2pcs-YS1560J-Temperature-and-humidity-sensor-shell-Waterproof-temperature-sensor-protective-cover-SHT10-SHT15-SHT20/32725840346.html?spm=2114.10010108.1000013.25.PVGRb3&traffic_analysisId=recommend_2088_13_81019_new2&scm=1007.13339.81019.0&pvid=b9edd7ff-9069-4c39-be95-b2d3ca8bdf17&tpp=1

https://www.aliexpress.com/item/TM16-115-temperature-and-humidity-sensor-protective-cover-waterproof-SHT10-SHT11-SHT20-SHT21-SHT15-SHT75-sensor/32578099865.html?spm=2114.10010108.1000013.10.gZI6yC&traffic_analysisId=recommend_2088_5_82199_new&scm=1007.13339.82199.0&pvid=3cc09c58-99e7-4a67-834a-3313c87ab573&tpp=1

On the face of it, it seems plausible.  Not sure what the failure modes are, or how they might be avoided if there are any.  Plainly, you don't want to use components which might rust or otherwise corrode from humidity.   Probably my biggest worry would be the possibility of condensate forming on the humidity sensor and skewing results until it evaporated.  However, a sensor heater, such as some sensors (e.g. si7021) already have, might remedy that if it were to occur. 

Has anyone either tried one of the shells above or anything similar?  For instance, perhaps wrapping a mote in Tyvek and sealing the seam  with Dupont housewrap tape would work just as well.

[WhiteHare]

Upon closer inspection, apparently the shells are only large enough to contain a sensor, not a moteino.  It doesn't completely kill the idea, but it would mean additional work.