Two Years of Research Confirm that High Tire Pressure Can Squash Yields

In December of 2020 NTS Tire Supply asked Nate Firle, chief agronomist with AgRevival and regional agronomy manager with Beck’s Hybrids, to design a study to test the effects of different tire pressures during planting on yield at harvest time. Firle designed a three-year study to explore this question by testing five different tire pressures: 35 psi, 28 psi, 20 psi, 12 psi, and 6 psi.  Firle chose a wide pressure range to reflect the growers who run their tractor tires at roading pressures in the field (the 35 psi group) all the way down to more ideal and super-low pressures. (The tractor fronts, tractor rears, and planter tires were all set to the same pressure for a particular plot during the study.)

Read More: Review our study’s design and year-one results. 

The first year of the study showed a yield increase each time the researchers reduced tire pressure on both corn and soybeans. But, as Firle told us in 2020, “I don’t like making drastic decisions off year one data. It’s a needle pointer. It shows that this is a direction we can focus on for the next year of the study.” 

So what did year two of the AgRevival Tire PSI Compaction Study find? Very similar results to the year-one data. In fact, in some instances, we saw a bigger ROI in year two—even larger yield increases as they decreased tire pressure from 35 psi down to 6 psi.

Read More: Download the 2022 AgRevival Research Book and review more than 20 studies conducted across 440 acres.

Wet Ground Shows Largest Improvements in Yield with Lower Tire Pressures 

We had a chance to sit down and quiz Firle about his personal observations during year two of our tire pressure study. Here are two key takeaways that reinforce the value of lower tire pressures in the field:

1. In wet areas of the test field, the researchers saw a much more drastic difference between the highest psi and lowest psi. In the perennial wet spots, with poorer soil conditions, there was a significant yield increase when lowering tire pressure to just 28 psi from 35 psi. According to Firle, “The historical problem spots of the farm is where we saw a higher benefit of adjusting tire pressure.”
2. “The reason we saw bigger overall numbers this year,” according to Firle, “is because of the year-over-year residual effects of the higher tire pressures.” With this study, Firle is planting the exact same GPS lines with the same tire pressures year after year. So, in effect, Firle is creating more compaction damage on the 35-psi lines compared to the 28-psi lines, and so on.

For year three of the study, Firle is going to ramp up in-field observations during the growing season to search for other compaction consequences, such as delayed water infiltration. 

AgRevival Study also Shows How Lower Tire Pressure Puts More Power to the Ground and Saves Fuel  

Firle used his John Deere 7280R planting tractor to pull a 9-shank ripper for fall tillage on his farm. He set the ripper’s depth at 10 inches and pulled it at 5.5–6 miles per hour. He made 14 passes with his tractor’s tires set at 28 psi and another 14 passes with the tires set at 12 psi, for about 7.2 acres of tillage with each setup. Here’s what he found:

• At 28 psi, his tractor used 1.6 gallons of fuel per acre. Wheel slip was 6% at 75–80% engine load.
• At 12 psi, his tractor used 1.3 gallons of fuel per acre. Wheel slip was 3% at 85–90% engine load.

For year three of his tire pressure study, Firle is going to expand his observations around wheel slip and fuel use on both his spring and fall tillage passes. As he said, “Farmers are asking me, why does this matter? What the number tells us is . . . taking more of that fuel and putting it into power and getting much better performance.” Using the performance improvement in Firle’s example, you’d see 30 gallons of fuel saved per 100 acres worked.  What seems like an insignificant number (.3 gallons per acre) becomes a much larger change when you consider the size of today’s farms.

Beck’s PFR Study Shows that Low Tire Pressure is Important on Every Tire,  Implements Included

Beck’s Hybrids began a similar study in 2022 as part of its Practical Farm Research (PFR) program. The study’s design closely resembles AgRevival’s study, with tire pressures that ranged from 35 psi down to 10 or 6 psi, depending on a particular tire’s minimum safe pressure. 

Here’s what’s interesting about the results: The Beck’s study only showed a 2.2 bushel-per-acre increase on corn from 35 to 6 psi. Remember that the AgRevival study logged a whopping 10 bushel-per-acre increase from highest to lowest psi. Does this shoot a hole in our theory that tire pressure matters? 

"It’s not the single wheel, it’s the whole system. You have three tires in one pass touching that soil."

Firle, who is also a regional agronomy manager for Beck’s Hybrids, noted one important difference between the AgRevival and Beck’s tire pressure studies: The Beck's researchers were unable to fluctuate their planters’ tire pressures as Firle did with the AgRevival study. Some of Beck’s planter tires were running as high as 60 psi, with many over 35 psi. “That 60 psi donut tire on that planter just erased any benefit that lowering the PSI of the tractor would have done . . . and it shows in their data,” says Firle.

In addition, Firle adds that AgRevival’s tractor is equipped with VF-rated duals and properly weighted to allow the tires to deflect and create longer, more stable footprints at low pressures. Some of the Beck’s tractors were very small or equipped with standard radials or single rear and front tires, which may have caused the inconsistency in yield response across the multiple test sites. 

So the Beck’s data actually reinforces the importance of having the pressure of every tire in a setup as low as possible in the field. As Firle remarked:

“The less [ideal] pressure is going to be what limits yield. It definitely has to be this combination of inflating or deflating all the tires in a particular pass."

Read More: Download the 2022 Beck’s PFR Book.

A Hefty Yield Increase at Hefty Brothers from One Simple Variable: Tire Pressure

In the spring of 2022, NTS Tire Supply outfitted the Hefty Brothers’ 8R 370 and DB60 planting setup with a PTG central tire inflation system (CTIS). Hefty’s Ag PhD program provides farmers with the latest agronomic information to help take their operations from good to great. Using the central tire inflation system, they were able to test what would happen once they dropped the machines’ tire pressures down to their lowest safe field pressures (versus running them at the higher pressures required to handle roading). 

Using CTIS, the researchers were able to run the tractor’s rear VF radial tires at 9 psi in the field—down from the 26 psi needed to carry the weight of the planter down the road. For the planter, the researchers were able to drop the tire pressure down to 25 psi—down from the 70 psi required for road travel. What did they find? 

A 3.4% increase in yield using the optimized pressures made possible by the central tire inflation system.

Read More: Why You Need a Central Tire Inflation System for Your Planter

USE VF Radial Tire Technology and CTIS to Safely Drop Tire Pressures

Results from these studies echo what we’ve long told farmers who are seeking to improve equipment performance in the field: You need the right tires set to the optimum tire pressure for the task at hand. How do you get there? You may need a larger tire setup on a particular machine. You may need to upgrade to VF-rated radials, which can run at 40% lower air pressure than standard radials for the same load. And, if you do a lot of roading with your equipment or operate a front-fold planter, you may need to invest in a central tire inflation system (CTIS). Want to decrease compaction in your fields, burn less fuel, and enjoy a better ride and machine handling? The right tires and air pressure will make all the difference. Call and talk to one of our tire experts to Drive Your Farm Forward in 2023 and beyond.