WiFi is great for communication between your Arduino and a computer host.
Other peer-to-peer wireless connections are better for communicating with sensors.
However the sensors as you describe appear to need an Arduino (or other microprocessor) to read them out: measure the soil resistance, count bucket clicks. I don't think you plan on adding 50 Arduinos in the mix. So that's likely going to be wired to your main Arduino (or, with the number of sensors, maybe a few that in turn communicate over WiFi).
As you want WiFi, check out the ESP8266 based systems like NodeMCU and WeMOS D1. Considerably less ports than Arduino, though, especially ADC is lacking and you probably want that for your soil moisture sensors (unless you have sensors that communicate over I2C or so).