Crops and equipment have opposing needs. Crops need porous soils to transport air, moisture and nutrients, and encourage root growth.

Controlled traffic farming (CTF) restricts soil compaction to narrow traffic lanes, allowing the remaining undamaged soil area improved soil structure and moisture storage for cropping.

A farmer standardizes his fleet’s operating width (sometimes working in multiples of that standard) to accommodate these field highways, which some call tramlines. Tires are slimmer, operate at higher inflation pressures, and may be “split duals” to accommodate heavy loads and row spacing.

“The consequential benefits to the soil structure and soil biodiversity are incredible,” wrote U.K. farmer and Nuffield Farming Scholarship winner Nick Ward, in his report after touring innovative farming systems on several continents. “The lack of compaction in these soils allows plants to produce deeper roots and access more of the available nutrients and water. Cultivation leads to reductions in soil organic matter by oxidation and losses to the atmosphere as carbon dioxide,” Ward wrote.

“As organic matter levels increase, so does the nutrient-holding capability of the soil and the amount of biological activity within it. The soils then become better at cycling nutrients and effectively feeding the crop,” Ward says.

"Hard, permanent traffic lanes reduce wet-weather delays, and also eliminate ruts in the crop zone,” according to Australian Engineer Jeff Tullberg says. “The improvement in timeliness is often critical to (Australian) double-cropping” (because the second crop can be seeded right behind a combine, even in very wet conditions).