Both tasks are material quantity dependent already, but they are quite fast procedures.
For setting stalks to to dry it's about 50 stalks per minute, plus the few minutes starting time.
For setting them to soak it's about same plus a little longer initial preparation time.
So the changes between 15 or 600 stalks isn't that dramatic. Without testing it by ourselves these are estimations, so they are debatable.
For soaking you would actually have to set the stalks under slender tree trunks submerged with the help of stones. This isn't required in the game, but if we add it some point then the soaking preparations time may increase.
For drying the bundles were simply set leaning against slender trunk, each others, etc. It doesn't take much time.
Drying stalks, like many other tasks, is allowed also indoors although the results would in real life be better outdoors.