I know that since the game is already out it is probably too late for this. But my thoughts would be since the field is irrigated that they would not perform the Watering action at all. Instead, I would prefer them to do something like Weeding the Crops.
Also, it would be nice if working the cropland would give a benefit in addition to increasing skill. For example, after a certain number of succesful actions on the field, the crop timer decreases a set time. (Sample: weed the field successfully 3 times by a master farmer, time to next harvest decreases by 1 minute.)