The drying part?

[Washing Machine]

So I used to just leave the gate open for this entire time (only the exit gate in case of rain), but after noticing the status screen at last found out my rice is Dehydrated after this.

The scrolls say Dehydrated status comes if you let the soil go dry. So should I leave some % of water in there, or leave both gates open, or is the duration you let it dry really short and then back to 20%? Ended up having Overgrown status going high at the end anyway, so I guess I did the drying part wrong in every way possible, lul.

[F A T B $ $ $ R T D]

open the exit gate for 1 day, it's usually all it needs. then fill with water again

[phenir]

By drying part, you mean when you hang the rice on the racks to dry after harvesting? Rice doesn't get dehydrated at this part. It gets dehydrated when you leave it without water when it's still planted (during summer/third offshoots). Dehydrated is a good status though but you want to re-add water once the bar is full which takes about a day.
Overgrown status is caused by too much fertilizer I believe. Herbicide can remove it.