A row unit for a cotton harvester. The cotton harvester is adapted for forward movement through a field to harvest cotton planted in rows in the field. The row unit includes a unit housing defining a row receiving area and a cotton exiting area. A moistener column door is pivotally coupled to the unit housing. An adjustable compression structure is coupled to the unit housing and configured to exert an adjustable pre-load on the moistener column door, placing the moistener column door in a closed position. The adjustable compression structure is configured to yield to a cotton plug pressure that exceeds the adjustable pre-load, which pivots the moistener column door to an open position. When the adjustable pre-load exceeds the cotton plug pressure, the adjustable compression structure is configured to return the moistener column door to the closed position.