Due to the seasonal nature of combines and grain carts, most farmers only think about them at harvest time—and often only think about the tires on this equipment when they fail. However, because of the growing size of harvest equipment, it’s more important than ever to pay attention to tires.

According to a study from Iowa State University Extension and Outreach, from 2006 to 2015, the average horsepower of combines rose from 230 to 342. Over that same time, the average capacity of grain carts grew from 689 bushels to 883 bushels. Because of the massive weight and power of these machines, they’re capable of creating deeper, longer-lasting compaction. Luckily, farmers can take a few measures to reduce the impact of their enormous equipment.

Check Soil Moisture

The simplest way to avoid compaction at harvest is to avoid operating equipment on fields that are too wet, as this not only causes compaction but can also lead to rutting. A good guideline for deciding whether or not to go into your field is the “ribbon test.” To perform a ribbon test, roll a ribbon of soil between your thumb and index finger. If the ribbon breaks within one or two inches, your risk for compaction is low. But, if the ribbon stretches out to four or five inches, your soil is too wet and would benefit from having an extra day or two to dry.

Another trick for checking the condition of your soil is to mold a ball of it in your hand and throw the ball in the air. If it breaks apart in the air, the ground is ready to support machinery. If not, there is too much moisture in the soil and you should wait a day or two before running machines on it.

Tire Size

Of course, conditions aren’t always optimal and sometimes you just have to get into the fields. It’s in this scenario that the benefits of today’s high-tech tires shine. Large tires running at low inflation pressures are a popular way to increase a tire’s footprint and minimize the pressure exerted on the ground by farm machinery.

In fact, over the course of a four-year continuous study, Iowa State University researchers found that soil farmed with equipment exerting a maximum of 6-psi surface pressure yielded 9 more bushels of corn per acre than soil farmed with more conventional equipment exerting 16-psi surface pressure. Even in a record-year like 2016’s 176 bushels per acre, an additional 9 bushels sounds good!

Radial tires can produce as much as a 25% larger footprint than a comparable bias-ply tire, making them increasingly common on combines and grain carts. IF/VF tires — further increase the advantage, as they’re capable of operating between 20% and 40% lower air pressures than conventional radials (or carrying 20% to 40% more load at the same inflation pressure), allowing them to produce a huge footprint that spreads the compaction force of gigantic machines over a much larger area than traditional tires.