I might add that there is a reason farmers have excess mucus and have the need to blow their noses often. Farming, whether plowing, swathing(cutting the hay), baling (bundling the hay into manageable squares), or stacking (stacking the squares in large piles called haystacks) creates a large amount of dust. If a farmer were to use his or her ever present bandana or handkerchief each time he had a need to clear his nasal passages, several cloths a day would be required. Thus, the practical answer is to simply blow the offending nasal clutter onto the ground.
I can also tell you from experience, having grown up on a cattle ranch and done my share of the above chores, that the farmer blow is not an easy skill to master. It requires judgement of the appropriate amount of blockage to create sufficient pressure, good lung capacity, and lots of practice. Failure in any of these areas results in an incomplete clearance of the blockage and usually must be attended to by a sleeve or bandana. Farmers who havent mastered the farmer blow may be identified by the tell tale signs of their failed attempts on their clothing. | 
