Effect of Increased Deflection Tire Technology on Soil Compaction

Highlights IF and VF agricultural radial tires are capable of carrying a greater load at the same inflation pressure than a standard radial tire. For this MFWD tractor and central-fill planter, the rear tractor tire is the main source of soil compaction during planting. The peak soil stress for the rear tractor tire was greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Potential soil compaction is expected to be greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Abstract. New agricultural tire standards, designated as Increased Flexion (IF) and Very High Flexion (VF), have been introduced for agricultural machines that offer larger contact areas compared to the standard radial tire carrying the same axle load. Limited studies have been conducted on how the newly adopted IF tires and precision tire inflation pressure management systems affect soil compaction, fuel economy, and crop yield responses. This study aimed to investigate the effects of field and transport (road) tire inflation pressure settings of row-crop agricultural tractor and planter tires on soil compaction. A completely randomized design experiment was conducted at the Iowa State University farm at Boone, Iowa, for two tire inflation pressure levels on the dual front (Firestone IF 420/85R34) and dual rear (Firestone IF 480/80R50) tires on a John Deere 8310R MFWD tractor, as well as transport tires (Super single 445/50R22.5) on a John Deere DB60 central-fill planter. Soil compaction was measured using Stress State Transducers (SSTs) buried at 150 mm and 300 mm depths beneath the untrafficked soil surface. The soil cone index depth profile was measured at the tire centerline before and after the tractor and planter tire passes. After the tractor and planter tire passes, rut depth was also measured at the tire centerline. Peak octahedral normal stress (soct) and the corresponding octahedral shear stress (toct) values in soil were calculated from the SST data. The peak soct for the rear tractor tire was significantly greater for the Standard Radial Tire Pressures treatment than for the IF Radial Tire Pressures treatment. The tire inflation pressure treatment did not significantly affect the peak soct for the front tractor tire and the planter transport tire. For this tractor and planter configuration, soil stress results identify the rear tractor tires as the main source of soil compaction during planting. The Standard Radial Tire Pressures treatment caused significantly higher soil cone index and soil rut depth compared with the IF Radial Tire Pressures (P < 0.05). As indicated by soil stresses, potential soil compaction from the tractor and planter transport tires is expected to be greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Keywords: Increased Flexion (IF) radial tire, Soil compaction, Soil cone index, Soil stress state, Tire inflation pressure.