Q.Can Cardboard Be Used With Root Crops?
First time using cardboard in garden. Just doing it for above ground crops. Not sure if we can use it for any root crop. Thank you for your help.

Certified GKH Gardening Expert
I would not opt for that method. Since it, already, carries an elevated risk to soil infections, any of those to the root zone could ruin the crop. With that being said, if you can really watch your watering and moisture levels then you may be able to get crops like carrots to grow. Because of the way that you would treat potatoes, this cardboard method would not work.
With all said and done, it couldn't hurt to try for an experiment. Just be sure that you have some in the regular fashion, also, just in case. A moisture meter will be a good idea to keep handy to measure the moisture in the soil under the cardboard.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm