Brush shredders are similar to pasture or crop shredders but are more heavy duty. Shredders use rotating, horizontal blades attached to a vertical shaft that can be driven by the tractor’s power-take-off (PTO) or hydraulic system. The blades are enclosed in a metal frame and shroud for safety and to increase the mulching effect. Width can be 5 to 20 feet. The wide models, 15 feet or more, use three sections that flex to conform to the terrain. Some manufacturers classify their shredders according to the diameter of trees or shrubs they can cut: up to 1 inch, light duty (pasture); 2 inches, medium duty; 3 inches, heavy duty; and 4 to 6 inches, extra-heavy duty. A few models that can cut from 6- to 12-inch diameter trees are built for excavators or loaders. Flail shredders use blades attached to a long, rotating horizontal shaft.
Flail shredders used for tree masticating are called rotobeaters. Blades can be flails, swing stirrup cutters, or hammers. Tree size capabilities are similar to those for horizontal-blade shredders. All of these shredder-types can be pulled by a tractor drawbar or three-point hitch mounted on the side or front of the tractor, or they can be mounted on a boom that can reach up to trim trees or down into ditches. Tractor horsepower required to power the shredders varies from 35 to 150 or more. Self-propelled units are available with either the horizontal-blade-type or the rotobeater-type shredders and tree size can be 6 or more inches in diameter (check manufacturers’ ratings).
Brush shredders are effective in removing weeds and small trees of non-sprouting species in pastures, rangeland, and utility or road rights-of-way. Shredding results in a manicured appearance with vegetation a few inches above the ground. Repeated mowing is necessary to remove top growth of sprouting species and re-occurring weeds. Brush shredding is prone to mechanical failures when cutting too large a tree or too many trees too fast and should not be attempted on rocky ground. Protection of the operator, tractor, and tires is usually required (see Tractors). Self-propelled units can shred dense stands of brush and trees and can traverse rough terrain. Care must be taken to match the shredder to tractor size and size of the trees/brush to be cut as some manufacturers have over a hundred models. A recent innovation is spraying herbicide on the blade for a stem application at time of cut. See Diamond Mowers, Inc. website below for additional information).
References / Additional Information
Wiedemann, H.T. 2007. Sculpting brush mechanically: Current state of the art. Rangelands. 29(5): 10-17.