TURNING DIRT Part Three: Discs and Tillers for Food-Plot Tractors

By Mark Trudeau

In this series of articles, The Whitetail Institute’s agricultural expert, Mark Trudeau, passes along his decades of real-world experience in farming and related matters to our Field Testers.
In the first segment of “Turning Dirt,” Mark provided his insight to help first-time tractor buyers shop for the right tractors to fit their needs. In our last issue, Mark discussed plows, when they should and should not be used, and gave his insight into how to choose a plow to perform a particular job. If you missed the earlier segments or if you would like to review them, they are available online at www.whitetailinstitute.com under the “Whitetail News” link. In this segment, Mark discusses two types of ground-turning implements which can be used for initial ground breaking in some cases and for final soil intermediate seedbed preparation after plowing. In later segments, Mark will discuss other tractor implements for doing food-plot work. It his segment of “Turning Dirt!”, we will cover two implements that can be used to do initial groundbreaking in some cases and that will further prepare the surface of the soil after plowing. These are disc implements (or just “discs” as I’ll refer to them here to save space) and tillers.


First, let me repeat a warning I mentioned in our last segment, which dealt with plows. Ground tillage, whether with plows, discs, tillers or any other ground working tools, is not appropriate in all circumstances. Always be aware of what any tillage operation will do to the soil. If you are in an area with a very thin layer of top soil over a deep layer of sand, for instance, do not disc or otherwise work the soil. If you do, you will likely mix the top soil with the sand, destroying the top soil. Instead, consider planting Imperial No Plow or Secret Spot, two high-quality annual forage blends specifically designed by the Institute for no-till planting.


If you are planting in soil that is appropriate for tillage, disking and tilling are great alternative options for smoothing plowed ground and, in some cases, even doing initial ground breaking. Whether you plow first or not, you’ll still need a disc or tiller to perform intermediate soil preparation before final smoothing with a cultipacker or drag and prior to seeding. There are several reasons.

Disking or Tilling After Plowing: Discs and tillers generally have two functions in preparing a seedbed in ground that has been plowed. Those are intermediate smoothing of the seedbed prior to planting, and incorporating lime into the soil to raise soil pH. Plows tend to leave the seedbed in rough condition, with big chunks of soil and deep cracks on the surface. Imperial perennials grow optimally if planted in a smooth seedbed. As we will discuss, the seedbed should be finally smoothed prior to planting with a cultipacker or drag. Discs and tillers can remove the largest chunks and cracks left by plowing, thereby preparing the seedbed for final smoothing prior to seeding. Optimum soil pH for growing Imperial Clover is 6.5 or higher. Fallow ground will almost always have lower soil pH (be more acidic) than 6.5. To raise your soil pH to optimum levels, you will need to incorporate lime into the soil by disking or tilling. That’s because lime works in particle-to-particle contact with the soil, meaning that a piece of lime has to physically touch a piece of dirt to neutralize its pH. Discs and tillers are optimum implements for thoroughly incorporating lime. You may ask, “If I have a plow, why can’t I just use it to incorporate lime instead of using a disc or tiller?” There are several reasons. First, the lime must be mixed into the top few inches where the plant’s main root systems are. Some plows, for instance moldboard plows, invert soil as a column and so won’t mix the lime and soil thoroughly to provide optimum particle-to-particle contact. Second, plows can also incorporate lime deeper than you need it, thereby costing you money you didn’t need to spend. Consider that the soil in the top few inches of an acre weighs something like 2,000,000 pounds. That’s why lime recommendations are often expressed in tons per acre — it takes a LOT of lime to touch so many dirt particles. If you try to mix lime in with your plow, you’ll likely dig deeper than you need to. That means more dirt particles and therefore more lime you’ll need to add to get the same effect. Third, remember that the more deeply you turn the soil, the more dormant weed and grass seeds you will bring to the surface, where they will receive the moisture, air and sunlight they need to germinate and grow. That means more grass and weeds you’ll have to control. So, again, till only as deeply as you need to, and incorporate lime with a disc or tiller, not a plow. Initial Groundbreaking with a Disc or Tiller: In some cases, you can dispense with plowing and do both your initial and intermediate ground tillage with a disc or tiller. For example, most disc and tiller blades will easily reach into the soil deeply enough to prepare an optimum seedbed for Imperial Whitetail Clover.


Ground tillage, whether with plows, discs, tillers or any other ground working tools, is not appropriate in all circumstances. Always There are basically three types of discs. These are offset discs, agricultural discs and finishing discs. The best option for food plot work is a finishing disc, but let’s look at each one so you’ll know what they are when you see them.

Offset Discs: Offset discs, also referred to as “bush-and-bog discs,” are not suitable for food plot work with smaller tractors because they’re way too heavy. They also leave the ground in too rough condition. Offset discs have very heavy frames, and their blades are deeply concave, set wide apart and of large diameter to aid in cutting heavy fescue and the tough, woody plants and heavier debris found in setaside fields. These mount to the tractor’s drawbar. More appropriate to commercial operations, offset discs are usually controlled with the tractor’s hydraulics and their own hydraulics, and they are supported by tandem wheels because of their weight. Although their blades are usually adjustable for angle, the adjustment is not one easily made in the field.

Agricultural Discs: Also sometimes called “heavy discs,” agricultural discs have smaller blades (usually about 28”), closer blade spacing (about 9- 12”) and can have with either serrated (notched) or smooth blades. However, agricultural discs, like offset discs, aren’t suitable for most food plot work because they generally require tractors with 100 Hp or more to pull, which is well beyond the range of most tractors in the food-plot-tractor category. Finishing Discs: Finishing discs are much better suited to food-plot work with smaller tractors. Their blades are usually spaced about seven inches apart, and changing blade angle on finishing discs is vastly easier in the field than when changing blade angle on an offset or agricultural disc. This is very important for reasons I’ll discuss below. Also, models are available with either drawbar or three-point-hitch attachment.

Tillers: Tillers are becoming a very popular seedbed-preparation tool. They can be a great option as a one-step tool for turning fallow fields that are covered with light vegetation such as grass (e.g. not woody briars or debris). In such cases, a tiller can do as good a job as can be done with a plow followed by a disc, but there are potential drawbacks. On the positive side, tillers require less horsepower to effectively operate — a 30-40 horsepower tractor will easily handle a four-foot tiller. Also, all tillers are three-point-hitch mounted and PTO driven. However, there are a couple of potential disadvantages to tillers. First, they can cause the seedbed to be overly fluffy or loose. Seedbeds which are overly fluffy must be cultipacked to optimally firm the soil prior to seeding Imperial perennials. Second, tillers can actually compact the soil below the reach of the tiller’s tines, making it more difficult for deeper-rooted forages such as Imperial Chicory Plus, Alfa-Rack Plus, “Chic” Magnet or Extreme to penetrate the soil with their roots. Speed is a crucial factor when tilling—if you are going into an undisturbed field, you should not till faster than 1-1.5 miles per hour. Attempting to operate the tiller faster will keep it from cutting properly and cause it to start tossing out chunks instead of blending the soil.


Discs are commonly described in three ways: by gangs, inches and feet.

Gangs: To understand what disc gangs are, you’ll need to know the basics of how finishing discs are constructed. It all starts with the disc blades which are the concave, disk-shaped tools that dig into the soil. Multiple blades are mounted in fixed positions evenly spaced along a shaft. Each shaft with its blades attached is referred to as a “gang”. On finishing discs, two gangs are mounted end-toend to make one row of blades all the way across the implement. Some discs have two rows — a second set of two gangs set end-to-end behind the first. Even so, each individual shaft with discs is referred to as a “gang.” For example, if you had to have a mechanic replace a bearing in your disc and you told him to “replace the outside bearing on the left rear gang,” he’d know that you have a disc with two rows of blades (four gangs total), and that he will need to remove the left gang of the back row to replace the bearing.

Inches: The distance between each blade mounted on a shaft is described in inches. For example, the blades on a “9-inch disc” are set at nine-inch intervals. The size of this interval directly affects how smooth the implement is capable of leaving the ground after it passes— the closer the blades are to each other, the smoother the soil can be finished with the implement.

Feet: The overall width of the implement as measured from the outermost blade on one side to the outermost blade on the other is expressed in feet. For example, a “7-foot disc” measures seven feet between the outermost blades on a gang. This is how the overall size of disc implements is described in conversation, which is important in getting a general feeling for how much horsepower it will take to pull it.


To get the most out of your finishing disc, you need to understand how to adjust two things: the angle of its blades and the height of its front end.

Blade Angle: “Blade angle” refers to how far away from the direction of the tractor’s travel the edges of the blades point. When the blades are set with “no angle,” the edges of the blades point directly ahead, in the same direction as the tractor’s direction of travel. When blade angle is “added,” the edges of the blades will point either left or right of the tractor’s direction of travel. Let’s look at how the adjustment is made. First, recall what we said earlier — that finishing discs have one or two rows of blades all the way across the implement, and that each row consists of two gangs. One end of each gang is connected to a fixed bearing in the implement’s frame. The other end is connected to an adjustable mechanism in the frame. Depending on how the disc is designed, this adjustment may be an arm in the center of the disc, or a bracket, and the adjustment can automatically change the angle on the whole row of discs at once, or change them only for one gang at a time. When the pin is pulled out and the arm or bracket is slid forward or backward, it takes one end of the gang with it. When the desired angle is achieved, you just drop the pin back through the arm or bracket and through the appropriate adjustment hole in the frame. Blade angle determines how aggressively the blades mix the soil. When the blades are set straight ahead so that their edges point directly in line with the direction of the tractor’s movement, they will cut deeply but not mix the soil as much. The more angle you add to the blades, the more aggressively the blades will cut and blend the soil.

Setting Front Implement Height: Leveling or lowering the front height of a disc is accomplished in one of two ways, depending on the system the implement uses to attach to the tractor. Three-pointhitch discs attach to a tractor in three places — on each of the tractor’s two lift arms and by a top link. To adjust front implement height on a three-pointhitch disc, the top link, which resembles a turnbuckle, is moved in or out. Discs that attach to a tractor’s drawbar usually have a simple hand crank to adjust the front height of the implement.

HOW DO I USE MY DISC FOR SPECIFIC FUNCTIONS? It would take a book, and actually probably several of them, to describe all the ins-and-outs of how to use a disc properly. Accordingly, I won’t even try to cover all the bases here, but I did want to pass along a few tips on how to get the most out of your new disc. First, I want to mention something that you do NOT want to do with a disc — turn the tractor with the disc still in the ground. Doing so puts tremendous strain on your equipment and can quickly break disc blades or worse. Instead of turning with the disc in the ground, lift the disc when you reach the end of a pass, turn around, and lower the disc back into the ground when you start your next pass. And no, this won’t keep you from working the corners of an oval plot; at worst it will just require you to back up to “cut the corners” of the plot. Now, let’s talk about how to use your disc for initial groundbreaking (to break ground that hasn’t been plowed first). You’ll want your disc to cut as aggressively as possible for initial groundbreaking, so you’ll need to adjust both blade angle and implement angle. A wide blade angle disturbs the soil the most, so add as much blade angle as you can. Front implement height affects how deeply the implement will cut the soil. The lower the front of the implement relative to the back, the more “down pressure” you add to the discs (or to the front discs on a two-row implement). During your first two passes, you should find that the disc is really tearing up the ground, but not very deeply. Once you have made a few passes and the surface, including grass roots and other vegetable matter, are pretty well chewed up, you can start to reduce blade angle and to level front implement height back out. The reduced blade angle will allow the discs to cut deeper and mix what you chewed up in your initial passes with lower layers of soil. Now let’s turn to intermediate disking operations— those that come after initial groundbreaking with a plow or disc and before final smoothing with a drag or cultipacker before seeding. In most cases, you should start with a moderate blade angle and implement level. Disc only to the depth needed and no more for the reasons I mentioned earlier. Instead of disking too deeply, it’s usually a better idea to disc more often. Every time you turn the soil, you’ll probably bring up dormant weed and grass seeds. Disking every two weeks to a month during the spring and summer before you plant can substantially reduce the infestation by bringing most of these seeds to the surface where they will germinate and then be killed when you disc again. The more often you disc, the earlier you’ll probably notice a reduction in surface infestation. And what’s more, spacing your diskings out like that can even help minimize loss of soil moisture. Again, be sure to disc to the same depth each time. Repeatedly disking your seedbed can create high points, or “crowns” and low points, or “divots” in the seedbed if you don’t do it correctly. There are a number of ways to avoid these problems. One way to avoid creating crowns or divots and leave your seedbed as smooth as the implement can make it, is to change directions or set the blades at a different angle for each pass. Another way is by “offset disking” or “double cutting.” To offset disc, add angle to the blades and make a shallow first pass. The blades on the right half of the implement should be angled off to the right and the left blades to the left at the greatest angle possible. Then, move the tractor over only one-half the implement’s width for the next pass. That way, the soil you just cut with the blades angled one way will be cut again with the blades angled the other way. The resulting surface will be optimum for final smoothing with a drag or cultipacker before seeding, If you end up with crowns or divots anyway, there are a couple of ways to remove them. One way with a drawbar-mounted disc is by “floating the disc.” Set the blades at a slight angle, and raise the implement so that it just disturbs the surface of the soil deeply enough to remove the tractor’s tire tracks. If you are just deep enough to remove the tire tracks, you are deep enough to remove crowns and divots from the surface. Another way to remove crown and divots is by “feathering” the seedbed by raising the front of the implement higher than the rear.


Scrapers are an optional item for finishing discs, and let me tell you, they are worth their weight in gold. If you have ever turned ground that is sticky, for instance, with high clay content, you’ll know that discs can clog up very quickly. Scrapers knock the soil off the blades as the implement works. [PHOTOS] Another great option is outriggers, or “furrow fillers” as they are sometimes called. Discs sometimes cut a deep furrow on the outside edges as they are pulled. This can be greatly reduced by outriggers, which essentially are devices with smaller disc blades on them that clamp to the outside of the rear disc gangs. If you add outriggers to a disc implement you already have, remember to add them to the outside of the rear gangs, not the front.


As we discussed in our last segment concerning plows, the biggest variable that will control how large an implement your tractor should try to pull is the tractor’s “engine horsepower”. In our first segment, we mentioned that tractors in the 40-50 engine-horsepower range are usually optimum for food plot work, in that they can provide the 18-20 horsepower it takes to pull each plowing assembly on a two-bottom plow. A tractor delivering this much horsepower should be easily able to pull a six-foot disc, but check the owner’s manual or confirm that with the tractor’s manufacturer first if you aren’t sure. Let me also repeat a caution I gave in an earlier segment: avoid the temptation to get an implement so large that your tractor has to continually operate at peak output to pull it, because such constant, repetitive strain will prematurely age your tractor.


One tip that can help your tractor’s (and other) hydraulic systems last as long as possible is to take the load off them when you are finished working. Just before you turn your tractor off, lower the implement to the ground or other hard surface so that your hydraulics won’t have to continue to bear the load of supporting it. Do this with any hydraulically-operated attachment. The last item I want to mention is the most important of all, and I can sum it up with one word: GREASE! Grease, grease and MORE grease! Your disc implement will have grease fittings. Use them, and use them often. In fact, that’s true of any equipment, but it’s especially true with disc implements. You should grease the implement before AND AFTER every single use. Greasing before ensures that its parts will move freely. Greasing afterwards removes any moisture or dirt that may have collected in the bearings while the implement was being used. Replacing bearings and shafts is extremely expensive. The good news is that it can be avoided just by greasing the implement before and after each use. This is especially true with a disc.


A 4- to 7-foot disc implement is suitable for most food-plot applications. If possible, try to get an implement that has two gangs in each row of discs so that you can adjust blade angle for the broadest range of applications. Most tractors in the food-plot family provide the 30-40 engine horsepower necessary to pull at 4-to 7-foot disc implement. Before buying a disc or tiller, though, be sure to consult the owner’s manual that came with your tractor or get confirmation from the manufacturer that your tractor will easily handle the implement you are considering buying.