Andy Warburton has blogged this great project with the Raspberry Pi Pico. He has used a SparkFun Soil Moisture sensor to detect moisture levels inside a plant pot. This is then wired up to the Pico, using one of the analog inputs to take the readings. The readings are then briefly analysed and a colour indicator on a Neopixel circle is then activated. It’s a great proof-of-concept for using the analog capabilities of the Pico and Andy’s blog post is well worth a read and it includes the code for you to get going.