Today I added the Eagle files for Vinduino-H and Vinduino-R to Github. See Vinduino-R schematic below.

The circuit supports up to 3 soil sensors. there are 6 2N7000 FETs used to isolate the sensors from each other.
Without these FETs there is considerable measurement error because of soil resistance between the sensors.

The Arduino Pro Mini is most of the time in deep sleep state to conserve power. The RTC alarm fires an interrupt that wakes up the system, takes measurements and sends the data, then goes back to sleep again. This allows tiny solar panels to keep the system alive.
To further conserve power, pin 13 enables a load switch that controls the WiFi module via a 3.3V regulator.

For connectivity, use ether APCxxx or ESP8266, both together does not work. Remove the programming cable (FTDI) for operation.

Errata:
R9 shown as 3k3, needs to be 10k.
ESP8266 pin 7 and 5 must be wired to 3.3V supply
RTC module supply strap need stop be connected to either back battery or Vbat