several moisture sensors

How to connect to arduino several soil moisture sensors and measure soli moisture ? I want to measure soil moisture in several places in greenhouse.

You could run wires + power to all the sensor point from a single Arduino.
You could run power + wireless (or wireless + battery) from several of these to a central Arduino.
How many point are you talking about?

15-20 point + lcd 20x4 . I bought Arduino mega for this.