Software apps and online services
In this video, I'd like to present you cheap Chinese capacitive humidity sensor for Arduino or ESP.
See quick setup with Arduino IDE together with Wemos D1 Lite. It has 3-pin interface and analog output. You can use it as alternative to more expensive Chirp! combo sensor board (see Chirp! here: https://youtu.be/WLyolOGSAXI).
Where to buy:Capacitive soil moisture sensor v1.2Wemos D1 mini Lite.