Long-Term Effects of Different Passages of Vehicular Traffic on Soil Properties and Carbon Storage of a Crosby Silt Loam in USA

The passage of vehicles with heavy axle loads causes soil compaction, and this adversely affects soil properties and crop yield. The adverse effects can persist for several years due to significant changes in key soil properties. However, the mechanisms of the aforementioned effects are not well understood for conservation agriculture (CA) (e.g., no-till (NT)) wherein the use of heavy machinery is considerably common. Therefore, known compaction forces (0 Mg load for compaction (NT-0, control), two passages of 2.5 Mg water wagon axle load (NT-2), and four passages of 2.5 Mg water wagon axle load (NT-4)) were applied to all the plots annually for 20 consecutive years. The experiment was established in 1997 at the Waterman Agricultural and Natural Resources Laboratory (WANRL), Ohio State University, Columbus, Ohio. Each treatment was replicated thrice. Soil samples were obtained in November 2016 to determine the effects of variations in the axle load and vehicular passages on carbon (C) and nitrogen (N) storage and selected soil properties of a Crosby silt loam soil under NT-based corn-soybean rotation with residue retention in Central Ohio, USA. Three locations were also randomly selected in an adjoining natural woodlot (WL) soil plot and sampled (30 m away from the compaction field) to compare the effects of vehicular traffic on soil under NT with WL soil. Results revealed that soil bulk density (rho(b)) and total porosity at 0-10 and 10-20 cm depths were not affected by the passages of vehicular traffic for 20 years under the NT system. The penetration resistance (PR) (1.86 and 2.03 MPa at 0-10 and 10-20 cm soil depths, respectively) was significantly higher under NT-4 compared with that under other treatments. Saturated hydraulic conductivity at 0-10 and 10-20 cm soil depths ranged from 19.7 to 31.4 and 18.5 to 29.5 mm d(-1), respectively, across all the treatments. The proportion of macroaggregates (> 0.25 mm) and microaggregates (< 0.25 mm), mean weight diameter and geometric mean diameter of aggregates, pH, electrical conductivity, and C and N contents and storage did not differ significantly between the treatments at either of the sampling soil depths. The data indicated that 2 to 4 passages of vehicles with 2.5 Mg of axle load did not cause significant compaction of the Crosby silt loam under NT compared with that under natural WL. Therefore, the continuous cultivation of row crops with NT and residue retention is feasible with passages of vehicular traffic for well-drained soils in Central Ohio.