Clemson Extension Forestry and Wildlife

Tractors and Implements for Forest Landowners – Part 4 Vegetative Management

Our series’ first, second, and third articles covered tractor selection, ground contact implements, and property maintenance (see links at the bottom of the article). The fourth part will cover two primary vegetative management implements that the forest landowner should consider adding to their arsenal.

The first implement for consideration is a rotary cutter, commonly referred to as a bush hog. Granted, there has been much emphasis recently on putting away the lowly bush hog and more favor given to other management practices such as fallow field disc’ing and/or prescribed fire for land managers. However, there are still times and places for a rotary cutter to help manage vegetation. Examples of such would be mowing instead of plowing due to soil erosion issues, mowing where vegetation is too high to disc over because it will just wrap around a harrow’s axles if the discs can even cut past the vegetation in the first place. Mowing such material and letting it lay for days/weeks allows it to begin decomposing, and then discing afterward is a more productive venture.

Image of a rotary cutter. Photo credit: Stephen Pohlman, Clemson University.
Image of a rotary cutter. Photo credit: Stephen Pohlman, Clemson University.

When selecting a rotary cutter/bush hog, one must first decide which width to purchase. When choosing the width, keep the following in mind: A. you want one wide enough to cover your tire tracks at least, and B. make sure you have a large enough horsepower (HP) tractor to spin the size you hook to the tractor. When selecting the width, remember the obstacles you may have to mow around on your property: tree spacing, end of fields turning around, roadside widths, etc. Lastly, when considering size/width, decide if you plan to attach this rotary cutter via a 3-point hitch or pull type. Remember to consider your 3-point hitch’s ‘Category hitch size’ too. If you are utilizing a quick hitch on your 3-point hitch, remember to look into what might be needed to make everything mesh together. Some quick hitches require bushings on the implement, and some do not.

Once we have selected a width, we need to look at the intended task of your rotary cutter. If you plan on mowing nothing but herbaceous-type vegetation, then a standard-duty rotary cutter will do fine. However, if you plan to mow bigger stuff, such as hardwood sprouts, small-diameter trees, etc., you may want to consider a medium-duty or heavy-duty rotary cutter. Typically, the components are more substantial for each bump up in ‘duty’. For example, a gearbox may jump from a 40hp gearbox on a standard-duty to a 90hp gearbox on a medium-duty, even though the cutter is expected to be used on a 40-60hp tractor. Also, the metal used for the cutter’s deck will typically be thicker at each jump up in ‘duty.’ Also, manufacturers will beef up a cutter’s deck through additional top deck bracing/bracketry and/or added bends in the deck metal itself instead of it being just a flat piece of metal.

One feature to consider on your rotary cutter is how the PTO shaft attaches to the gearbox. Smaller and lighter-duty rotary cutters typically have what’s known as a shear pin. This shear pin design is to shear should you hit something you should not have. Thus shear pins are made of a softer metal, and operators should never replace them with hardened bolts. The other option to this is what’s known as a slip clutch. The slip clutch has a series of stacked discs with spring pressure applying just enough force not to let them slip under normal operation. Still, as soon as you hit something you should not have, it allows the discs to slip and then go back to grabbing after you resume normal operation. As great as a slip clutch is, the operator needs to maintain their slip clutch on an annual basis (or more frequently if environmental conditions dictate, please refer to any owners/service manuals for details). Maintaining a slip clutch is very simply accomplished with basic wrenches. However, it does take a little time to perform correctly. Not maintaining a slip clutch allows the discs to rust together to the point that they do not slip properly, thus causing a safety hazard.

Safety is always a concern when using a rotary cutter. The three primary sources of injury typically come from PTO entanglement, direct contact from moving blades, and thrown objects while in operation. To help prevent thrown objects, ensure that your rotary cutter has the proper safety chains hanging over the intake and discharge shoots as a bare minimum. Woody debris, rocks, and other large items fly out at extremely dangerous speeds when utilizing this attachment.   Sadly, the internet is full of gory details of dismemberment and even death due to this. Thus I’ll not labor you with the details. Just know that everybody says it will never happen to them or a loved one standing nearby until it happens. Objects can come flying out from underneath in any direction. Again, use extreme caution when operating a rotary cutter.

Herbicide sprayers (‘spray rig’) are another vegetation management tool that can be mounted to tractors and utilized by forest landowners. For the sake of time and space, I’m only going to refer to the most commonly used tractor 3-point hitch-mounted spray rigs, as this is what most forest landowners use. Another type of spray rig that a large landowner might use, especially dove, duck, or quail field managers, is a pull-behind sprayer mounted on a cart/wagon-type system, often referred to as a pull-type sprayer.

There are a few features that the landowner needs to identify as needs when selecting the exact configuration for their spray rig. First, tractor size and how it relates to safely carrying the weight of herbicide mixture to determine tank size. Secondly, will the pressure pump utilize a PTO-mounted pump for optimum volume and pressure, or will it be an electric pump typically found on smaller spray rigs. Due to the larger tasks at hand, most tractor-mounted spray rigs will use the PTO-mounted pump system.

Nozzle selection will depend on the primary intended usage. Do know that good quality spray equipment is not inexpensive as it is not cheaply made. High-quality nozzles throw a predictable pattern consistently. They will also last a lifetime if an operator properly takes care of his equipment immediately after usage. For those that want a nozzle primarily for spray work known as forestry release spraying (such as eliminating sweetgums in pine plantations), nozzles known as Boomless nozzles are popular. These nozzles are designed to be a single point that sprays out in an arching manner. This then allows a spray rig to be compact, so the operator doesn’t have to worry about physically hitting limbs, small trees, etc., with his equipment. A traditional boom-style sprayer with spring-actuated breakaway booms is popular for those primarily spraying fields and/or large food plots. Some of these sprayers may have foam markers added to the tip of the boom to aid in seeing where you have sprayed in your last pass. Manufacturers make short-armed booms for those who prefer to spray smaller fields/food plots versus spraying with a boomless setup. Many spray rigs will still have a single wand or spray gun rigged into the plumbing. A hand-operated spray gun/wand provides operators with the ability to spot-spray individual plants/trees as well as around objects. Usually, a shutoff valve is put into place to divert your tank mixture to either the wand or your boom/boomless setup.

Another critical component of your spray rig is your pressure valve and pressure gauge. Remember, applying herbicides is about putting ‘X’ amount of product spread over ‘X’ size area. Consistency of speed, sprayed width, and amount sprayed is imperative to achieving properly applied amounts. We will assume that you can hold a constant speed with your tractor (cruise control, gear selection at constant RPM, etc.), and we will assume you are using high-quality spray nozzles to get a constant width. Still, if the pressure valve/pressure gauge is not consistently maintaining the same pressure, it will cause you to either over-apply or under-apply. Under-applying can mean plants are not controlled in a timely manner or not at all. Over-applying can have environmental impacts depending on the product used, mortality in plants that should not show symptoms, and not to mention wasted money on the amount of product sprayed that should not have. Most good spray rigs utilize quality components like this.

In case you missed them, here are the prior articles in this series:
Tractors and Implements for Forest Landowners- Part 1: Tractors-

Tractors and Implements for Forest Landowners – Part 2: Ground Contact Implements-

Tractors and Implements for Forest Landowners – Part 3: Implements and Attachments for Property Maintenance-


Stephen Pohlman, Cooperative Extension, Forestry and Wildlife Agent

This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. 

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