moisture sensor multiplexing

I’m short on ADC inputs, so I would like to put multiple sensors on the same input as follows:

  • each sensor power input can be cut out using a transistor.
  • all sensor’s outputs are connected to the same GPIO/ADC

When I want to read one sensor, I will first power it up (and all the others are off), and read the ADC, then cut the power again.

Is it safe for the sensors? Do I need to add some diodes for each sensor outputs?

Thank you