As a farmer myself, I see crop stubble becoming more and more of an issue for tires. In the past, it was common to get complaints from growers about driving over corn or cotton stalks resulting in tire punctures. As crop genetics improve and growers focus on agronomics, additional crops like soybeans and cereal grains are now leading to tire damage. Growing up, Grandpa and Dad would drill soybeans at a population rate of 200k to 220k, and the stalks would have a maximum stalk diameter of 3/16”. Today, agronomists are suggesting rolling back those seeding rates to allow the soybeans to bush out. When I measured the stalk diameter of a soybean field planted at 140K population rate, the diameter ranged from ¼” to ½”. (See picture 1, which shows the stalk diameter of 7/16” from a 2018 soybean plant.) The larger diameter stalk means a better stand at harvest, but it also causes more damage to tires.
When customers have stubble issues, the common assumption is that the tire’s tread rubber is softer or under-cured. To get into the science of tires, tire manufacturers measure tread rubber hardness with a tool called a durometer (See picture 2). The typical agricultural tire rubber hardness ranges from 66 to 74 units. This level of hardness is required to allow the rubber to flex over different terrains and with different inflation pressures. Firestone has measured crop stubble in the field and it can range between 80 to 110 units. The hardness of the soybean plant we measured, which had a stalk diameter of 7/16” was 90 units. When a softer material makes contact with a harder material, the softer material is damaged. Tire manufacturers are working on a solution, but at this point in time there is no solution. Yes, a harder tread compound could be used to help reduce stubble damage, but the harder tread rubber could cause decreased tire performance because the harder rubber would have less flex. It is a balancing act for tire engineers, and until a solution is identified, tire companies encourage customers to find mechanical ways in their operations to manage the stubble.
Stubble can be managed in a variety of ways, from something as simple as not driving directly over the stubble, to installing a stubble-deflecting device. I encourage customers with stubble problems to install stubble prevention equipment on the corn head or platform to push the stubble down while harvesting. If the customer cannot install stubble deflectors on the heads, there are nice stubble deflection devices that attach to the front of a tractor. Customers do not have to spend a lot of money on stubble deflection devices, the device can be custom made. Firestone Ag does not recommend one system over another; the main point is to consider a deflector because it pushes the stalk over, helping to keep the stubble from coming into direct contact with the tire. If you are interested in looking at stubble protection solutions, we recommend talking to your local tire dealer or implement dealership.
If your tires do have stubble damage, they likely can remain in service unless the tire’s body ply or tread ply cords are exposed. The tires in pictures 3 and 4 have stubble damage, but it is just cosmetic. The interior construction is undamaged and the tire can remain in service.
If a customer is in the market for new tires and has concerns about stubble damage, they should ask the tire dealer about the tire’s stubble protection policy. Stubble damage is typically not considered a warrantable condition by most tire companies. However, Firestone Ag, along with other tire companies do have a stubble damage policy. This policy is different from the tire manufacturing warranty and the coverage is not as long. Your tire dealership should be able to explain different coverage options. I also encourage customers to avoid running brand new tires in heavy stubble conditions. If your operation is planning to install new tires on equipment, I suggest installing them after the planting or harvesting season. Giving the tires extra time to sit before use allows the processing waxes to migrate to the exterior of the tire. As these waxes move, a tire will slightly harden by 1 or 2 points.
Again, there is no perfect solution for preventing stubble damage on tires. Ag tires are going to operate in conditions that will expose them to the potential of stubble damage. Taking the correct measures in your operations to minimize the exposure to damage by using stubble deflection devices or not running directly on stubble will help your operation minimize stubble damage