The ideia is an open source low cost high precison soil sensor for all.
The good ones in market go from $100 - $200 ... So open sorce wins , but needs time and cooperation.
Developing is a challenge, so why not to do it?
I'm developing a precison soil sensor but I'm lazy so I want simple and efficient stuff.
Return loss bridge method is probably the best. LTC6905 (17MHz to 170MhZ Oscillator) 2euros plus AD8307 (logaritmic instrumentational amplifier)
20cents . plus 5 external components R C
PCB soil probe four layer 4euros (cooper strips inside PCB to avoid corrosion, long time potted) , oscillator/detector/analog out ,two layer pcb 1,5euro.
For now about aprox 8euros to have performance of a $100 or $200.
I'm doing some calculations on return loss bridge. Matching impedance to soil probe.
Analog out direct to arduino raspberry esp8266 or any other microcontroller with ADC.
All knowledge is welcome.