Soil compaction is the top problem we help our customers solve at NTS Tire Supply. In fact, having the right tires (or tracks) on all your equipment is one tool in the fight against this perennial problem. Why? Wheel traffic is the leading cause of deep soil compaction in your fields. Think soil compaction isn’t an issue in agriculture today? You’ll want to keep reading, because compaction is stealing a lot of dollars from operations just like yours.
A $587 Million Problem?
In January 2022, University of Minnesota Extension, North Dakota State University, and Manitoba Agriculture and Resource Development sponsored a conference to discuss compaction and proven strategies to alleviate it. We’re going to cover one of the takeaways here: A 2020 study that projected the economic costs of compaction across North Dakota and Minnesota.
The study found that farmers in North Dakota and Minnesota may lose $587 million over two years for every 10% of land that is affected by compaction(1). Before we review how the study arrived at this estimate, we’re going to review a few soil compaction basics.
Com + Pact = Damage to Your Fields
The very word compaction—com (together) pact (fasten)—tells us what it does to the soil. Excessive weight presses the soil tightly together, which drastically reduces the amount of pore space in the soil. Soil can tolerate a certain amount of weight stress (depending on soil type, condition, etc.), but when you exceed a particular soil’s limits, the soil will “fail.”(2)
The Many Ways Compaction Squeezes Your Bottom Line
Heavily compacted soil becomes more dense, which results in several problems that impact your bottom line:
Destruction of Healthy Soil Structure
- Reduced drainage: Lacking well-distributed pore space, compacted soil is slow to drain water. This means more days when you’re unable to work in the field. Healthy soil functions like a sponge: it can both accommodate and shed water easily. Compacted soil is more like a brick—it’s hard for water to penetrate it(3).
- Less microbes. As draining slows, the soil remains cooler and wetter. The cooler temperatures are less friendly to microbial and plant growth. At cooler soil temps, crop residue is also slower to break down, which further cools the soil.
- Loss of fertile topsoil from erosion & runoff: Compacted soil lacks the variety of soil particle sizes found in healthy soil—some larger pea-sized chunks, some smaller, etc. As the soil is tightly pressed together into one thick sheet, it’s easier for wind and water to carry its top layers away. If you lose topsoil to erosion and runoff, you’re losing the fertility vital to the health of your crop.
- Increased risk of drought: As the soil is pressed tightly together, the elimination of pore spaces also diminishes the soil’s water-holding capacity. Sure, it will take water longer to drain through compacted soil, but very little water remains in the soil once it does. Ideally, soil should be made up of 50% solid particles, 25% water, and 25% air(3).
- Stunted roots: Roots have a hard time pushing through dense soil, which results in smaller root systems. And smaller roots result in less water and nutrient uptake in your crops. At harvest time, this adds up to a direct yield hit(4).
- Late emergence: Because of the factors we’ve already listed above, plants in compacted areas of your fields tend to emerge later. In very wet years, compacted areas may see no emergence or severe effects on stand due to water ponding in tire tracks(4).
- Reduced nutrient absorption: Compacted soils increase the amount of nitrogen that’s lost into the air, which means less nitrogen is available where it counts—for your crop. Compacted soil also makes it more difficult for other nutrients, such as potassium, to reach your plants.
- Oxygen starvation: Healthy soil is made up of around 25% air. Throw this ratio off, and your plants will turn yellow—nature’s cautionary color that signals a yield loss in your future.
Higher Operating Costs
- Increased fuel consumption: Tilling compacted soil requires more fuel, but this is only the beginning of compaction’s hit to your farm’s efficiency. Poorly-drained fields require more fuel to work thanks to the mud, and any time your tractor and/or implements are sinking into the ground, your fuel bill is climbing too.
- More inputs needed: If you lose nitrogen and other inputs thanks to waterlogged soil, your input costs will climb(4).
- Maintenance needs increase: Harder pulling means more wear and tear on equipment—everything from consumable parts, such as ripper shanks, to your tractor’s drivetrain.
Compaction Steals Profits Again and Again
Equipment traffic is the biggest cause of compaction in your fields. This chart shows how compaction’s effects from heavy axle loads tend to stick around.
Notice the 30% yield hit in year one. By year 4, the corn yield had completely recovered and actually surpassed the yield at the beginning of the study. But notice how in years 7, 9, and 12 you see yield hits once again? These were wet years (1988, 1990, 1993) at the testing location.
Yes—compaction is more likely to rear its ugly head during challenging conditions. Tillage fixes compaction in the upper levels of the soil, but the deep, subsoil compaction remains and will cause problems as soon as conditions turn south.
And Deep Wheel-Traffic Compaction Isn’t Fixed By Tillage
The blue line on this chart represents the maximum depth at which tillage is effective at combating compaction.
As axle loads have increased with larger and larger equipment, compaction has pushed deeper into the soil. Much of this damage is outside the range of tillage implements. When you attempt deep zone tillage, with a straight or parabolic shank chisel plow, you run the risk of hitting tile lines (if your land has eroded) and digging up a crop of rocks you don’t want. Plus, tillage will further compromise soil structure, especially if the ground is wet and you wind up with trenches of “smeared” soil. Not to mention, the cost in fuel to perform this operation is enormous(5).
A Potential $500+ Million Problem in MN & ND Alone
Now that we’ve covered some compaction basics, it’s time to loop back around to this article’s original question: What is compaction’s potential cost to farmers?
This 2020 report makes an attempt to project the economic costs of compaction based on a review of 12 compaction studies from way back in 1962 through 2011. A few key takeaways are:
- The largest yield losses from compaction occur in the first 2 years following wheel-traffic compaction.
- Across the studies reviewed, yield losses ranged from 9%–55%.
- Compaction’s longer-term residual effects tend to show up during challenging weather years.
- A review of the 12 studies found a median 21% yield reduction for 2 years following wheel traffic compaction(1).
How the Study Calculated the $587 Million Cost
The researchers then used the median 21% 2-year yield reduction to calculate the economic costs of deep soil compaction. Since the study authors are from the Upper Midwest, they focused their cost projections on North Dakota and Minnesota using regional prices for corn and soybeans, the amount of acres planted each year, and the cost per acre to level ruts with tillage(1). (See Table 2 in the study for the full details on how they arrived at the $587 million figure.)
Is 10% of Farmland Compacted, or More?
This study was designed to calculate the economic cost of compaction over two years for every 10% of land affected by compaction. As we’ve discussed in our Practical Traction Knowledge articles in the past, compaction from wheel (or track) traffic can affect large portions of your field. When you add up all the different passes you make in a year, 60 to 80 percent of your farm is likely driven on. So, the assumption that an average of 10% of land is affected by compaction across the Upper Midwest may be very conservative(1). There is no reporting or monitoring system in place to figure out how much ground compaction actually affects.
Compaction’s Cost is Likely Higher
The study only looked at a few factors when calculating the $587 million cost per 10% of land compacted. The study’s authors argue that this is the minimum economic cost using the study’s crop prices(1). The study didn’t take into account costs that add up from the many other ways compaction squeezes your bottom line. If you’ll remember from above, these costs can range from the loss of crop inputs to extra fuel and maintenance bills.
The Final Cost Tally
Let’s say 30% of North Dakota & Minnesota corn and soybean fields are affected by compaction. The cost estimate, as calculated by this study, would then balloon to $1.76 trillion over 2 years(1). Or, it’s possible that the area affected by compaction could be lower than 10%. Remember: there’s no reporting system in place to actually monitor how much ground is affected by compaction in any given year, nor is such a system likely in the future. So, per the study, the actual 2-year cost of compaction could range significantly. We encourage you to scan the actual study for a complete explanation of how the researchers arrived at their cost conclusions.
How to Reduce Compaction’s Costs in Your Fields
There are several strategies you can use to reduce compaction’s impact on your soil, including cover crops and traffic control. But for now, we’re going to focus on optimizing your equipment with the right tires. Basically, you want tires on your equipment that will allow you to run at lower air pressures in the field. Under 15 psi is ideal, and the lower, the better.
In fact, NTS Tire Supply recently partnered with AgRevival Research to explore the connection between yield and different tire pressures at planting.
New NTS Tire PSI study: First-year data suggest lower tire psi at planting can bring yield increases.
The first year of our study showed a yield increase each time we reduced tire pressure on both corn and soybeans. (See the complete charts in the linked article above.) With soybeans, we saw a yield bump at our first tire pressure drop to 28 psi; with corn, we had to drop the pressure to 20 psi before we saw any yield benefit. Overall, the most interesting result of the study is that we saw a yield increase with every incremental decrease in tire pressure.
There are a couple strategies you can use to lower your air pressure in the field, including IF & VF radials, which can handle the load of a standard radial at up to 20% or 40% lower inflation pressures, respectively.
Learn More: Roll your way to bigger yields with IF/VF tires.
Central tire inflation systems are another option that allow you to drop your air pressures to the safe minimum for field work and inflate your tires to their maximum pressures for low rolling resistance and longer tire life on the road.
Which Tire Solution is Right for Your Farm?
Will a central tire inflation system or a new set of VF radials help you limit compaction’s negative effects on your farm? To a certain extent, yes. Axle load always determines the depth of soil compaction, but you can take steps to help alleviate its negative effects on your yields even if you run mega equipment. Which tires and other strategies will help you lighten the load on your soil? Talk to one of our tire experts today. NTS Tire Supply is here to help you drive your farm forward.