What’s Next In The Strategy To Reduce Soil Compaction?


If we are going to put big equipment into farm fields, soil compaction will continue to be a threat. Farm equipment, especially that which carries heavy loads (spreaders, sprayers, planters, grain wagons) needs to be configured to support that maximum load under road conditions. This often requires significantly higher tire pressures than what should be used in the field. The combination of big loads and high tire pressures increases compaction risk significantly.

This often results in farmers making compromises. Most compromises are losing propositions! For example, a new set of 900/60R32 tires for a manure spreader would require a road pressure setting of 40 psi whereas the field setting could be as low as 10 psi. If the “compromise” was to split the difference (which shouldn’t be done) and set the tires at 25psi, the compromise is a failure. This compromise results in reduced road safety, greater chance of tire failure, reduced tire life, higher fuel consumption, and increased soil compaction compared to optimizing the pressure for changing situations.

Unfortunately, no new piece of equipment comes from the dealer optimized for all its uses. Even with the best tires, ballast and accessories installed the requirements for road and field travel, along with different uses in the case of a tractor, it’s essentially impossible to optimize equipment for all situations. Even if your equipment is configured for a single purpose such as a self-propelled sprayer, if it has to move down the road it won’t be optimized for both the road and field. In this case the closest you can get to optimized is having 2-3 sets of tire configurations that you switch out, but this still it is not optimized and is time consuming and expensive.

The exception is the rare circumstance where all the fields farmed are in close proximity and the farmer consciously chooses to road travel at much slower than normal transport speed allowing tires to be set at a much lower pressure.

One solution is to have a compressor on hand and manually adjust tire pressures when transitioning between road, field, and back to road. As if that is going to happen! With the tire size, the number of tires on some implements, and the frequency of field to road transitions, it’s just impractical.

Enter, CTIS!

Central Tire Inflation Systems (CTIS)

CTIS works by manipulating the contact patch of the tire on the ground by changing the pressure (Figure 1). The larger the tire volume the more opportunity there is to change the pressure while still carrying the load and ensuring tire integrity and safety. Reducing tire pressure allows the tire side walls to flex, leading to a longer contact patch. This reduces the weight per square inch on the soil, reducing the stress exerted on the soil. In Figure 1 the contact patch/footprint of the same size tire changes length significantly as the psi changes. These squatting tires look to be getting wider but in fact create a longer footprint.

Figure 1. The changing footprint of ag tire contact patch as a result of changing inflation pressure. (Would you run 100 psi teaching 0510)

These systems allow the operator to optimize tire pressures automatically from the cab. That optimization can be manually or autonomously controlled to manage tire pressure according to the transport and field conditions. CTIS can be used to adjust tire pressure differentially as the implement weight changes with loading or unloading as it travels across the field. But using CTIS still requires the right tires for the intended applications.

Even with CTIS, optimization is still somewhat of a compromise depending on the situation. Returning to the self-propelled sprayer example, producers often change over from early/late season wider tires to narrower ones for in-crop spraying. However, these narrower tires have lower tire volume which prevents them from taking full advantage of CTIS. Higher volume wider tires can handle lower pressures based on the same load and are thus able to create a larger contact patch on the ground to spread out the load on the soil compared to narrower tires. Thankfully, but not always, the soil conditions during in-crop spraying are usually dryer than in spring/fall.

There are now two viable options for CTIS available in Ontario (AgriBrink & TreadRight ) (Figure 2). Any farmers who have installed CTIS on their self-propelled sprayer (or any implement for that matter) are convinced it pays regardless of tire size. Every farmer should be examining CTIS systems for what they offer in savings to yield loss, fuel efficiency, less tire failure and tire life. Don’t let the initial sticker shock scare you away from thoroughly understanding what these systems offer and what the pay back is. If you are spending big dollars on new equipment or upgrading implement tires but not adding CTIS to optimize that equipment’s setup, you are significantly impacting your ROI on that investment.

Figure 2. Example setup of CTIS installed on an implement.

Another consideration is that CTIS systems added to equipment can be transferred to newer equipment as replacement occurs. Mounting brackets for compressors and controllers make this a minor cost ($1500-3000) relative to the savings achieved by their use.

Watch for our follow-up article in the next edition of Crop Talk for some striking examples from soil compaction demo days that show the value of CTIS.