The traditional sickle bar mowers are difficult to find in some areas, because they are being replaced by rotary mowers -- also called disk or drum mowers. Sales of more expensive, heavy-duty rotary mowers exceeded those of sickle mowers beginning in 1997. In general, rotary mowers perform better for land maintenance, but they are more expensive.
Rotary mowers cut alfalfa, weeds or scrub with sharp disks mounted on a bar. Some rotary mowers are mounted in sets of two or three, one on each side and one on the front of a tractor so they can cut up to 20-foot swaths. Rear-mounted units are called scrub cutters in some countries.
Sickle mowers were originally drawn by horses. A 6- to 7 ½-foot-long bar with stationary finger plates has a skid at the end. The skid supports the bar as it rides along the ground. Triangular blades are mounted on a reciprocating sickle that moves in a channel on the bar. As the blades move back and forth on the moving sickle, alfalfa, forage, weeds or scrub are cut between the sickle blades and the finger plates. A board at the end of the bar separates the cut from the uncut hay, providing a path for the mower skid on the next pass.
Rotary mowers are good when forage is thick, rough, wet or lodged, meaning that it is flat or toppled over from the wind or because it has grown too tall. This makes rotary mowers better for tough land maintenance chores. Rotary mowers cut at higher speeds, so they are better than sickle mowers for large acreage. It is also easier to adjust the height of rotary mowers, and they do not plug or become stuck.
Conventional sickle mowers don't require as much power as rotary mowers, so they can be operated by smaller tractors. They give a cleaner cut, whereas a rotary mower leaves a more ragged look. Sickle mowers are good for small acreage and cutting alfalfa.
Rotary mowers cost more than sickle mowers. A rotary mower that is pulled behind a tractor can cost 20 percent to 30 percent more than a sickle mower. A self-propelled rotary mower can cost up to 50 percent more. Early models of rotary mowers were difficult to maintain and repair; those problems have been corrected in more recent models.
While sickle mowers are cheaper, they do not perform as well for rough chores and heavy growth. They can become plugged or stuck, and the cutting blades can break. Since sickle mowers are no longer sold by many dealers, buying parts can often be more difficult.
When sickle bars become jammed, they sometimes have to be cleared by hand. When a jammed sickle bar is being cleared, it can suddenly shift, threatening any fingers that might be in the way. A sickle bar also may shift when it is being stored, posing the same danger.