However, I used the official Arduino Starter Kit ($100), which includes everything I needed, minus the nuts, bolts, wires, and ring terminals for making the soil probes. Wiring the Hardware ...

Are you looking for another compact temperature and humidity sensor? ... by wiring a single sensor to the I 2 C line. Here is a crude schematic of the AHT10 module (borrowed from web). Arduino & AHT10 ...

It runs on an Arduino MEGA 2560 PRO (or similar microcontroller) and supports a wide array of additional hardware including pressure transducer, water level sensor, flow meter, OLED display, and more.