Perhaps we should build some of [MakersFunDuck]’s Moisture Duck boards. As you can see in the video below, the simple PCB with an ATtiny13A ... divider with the soil, and dry soil has higher ...

Although there are ways to get around this, a 2022 paper by Maja Škiljo and colleagues in Sensors covers ... printed (PCB) antenna was optimal for soil moisture sensing purposes.