Comparative Tests of Two Tire Models for Agricultural Tractors: Soil Compaction, Tractive Performance and Energy Requirements

Agricultural soil fertility is a key determinant of crop productivity and long-term sustainability. However, intensive farming practices often require repeated passes of heavy machinery, which can lead to soil compaction. This study examines the interplay between tractor traffic, tire inflation pressure, and their effects on soil physical properties and fertility indicators. Tire pressure management emerges as a crucial mitigation strategy: high inflation pressures concentrate the load and exacerbate subsoil compaction, whereas reduced pressures (within safe limits) enlarge the tire–soil contact area, distributing the vehicle’s weight more evenly. This in turn improves traction, lowers ground pressure, and reduces energy losses. As a result, both the depth and severity of soil compaction are reduced. Further advances may be achieved through innovative tires manufactured with eco-sustainable materials and tread patterns specifically designed to enhance traction and minimize slippage-related energy loss. In this context, CREA conducted comparative field tests on two tractor tire models from the same manufacturer: a conventional design and an evolved version featuring an innovative tread and larger footprint. The trials assessed the impact of each tire on soil compaction, traction performance, and energy efficiency. Tests were performed on a silty-clay agricultural soil naturally settled for a year, using a dynamometric vehicle to apply different controlled traction force levels, combined with two inflation pressure settings. To highlight performance differences between the two models, the tractor was rear-ballasted, and the study focused on the rear axle, which carried most of the traction stress. Results indicated that, under the specific test conditions, at high inflation pressure both tires performed similarly (with the innovative model slightly reducing fuel use and the conventional yielding marginally higher maximum tractive force), whereas at low pressure the innovative tire clearly outperformed the traditional model in traction efficiency and caused less soil compaction. The extent of the benefits associated with using the innovative tire model across various soil conditions, moisture levels, and in the absence of rear ballasting will be evaluated in further tests based on traction force control using the proposed testing system.