Subsurface Soil Compaction Effects On Soil Properties and Barley Root Growth.

Soil compaction can limit plant growth. This effect is frequently attributed to restricted nutrient acquisition and water stress. However, the underlying mechanisms and their relative contribution remain partly unknown. This study assessed the effects of subsurface compaction (i.e., similar to a tillage pan) on selected soil properties as well as on root morphology, aboveground biomass and yield of a barley (Hordeum vulgare L.) crop grown on a Templeton silt loam soil. The experiment was established using a Latin square design with 5 replicates. Following removal of the top 15 cm of soil, five treatments were established: untreated control, mechanically loosened (i.e., cultivation), and mechanically compacted using a 10 Mg roller to achieve three increasing compaction levels (i.e., one pass, eight passes, and eight passes with vibration). Subsequently, the top 15 cm of soil was repositioned on the corresponding plots and barley was planted. Measured soil properties encompassed pore size distribution, hydraulic conductivity (K) using in situ tension infiltrometry, penetration resistance (PR), and bulk density (BD). Quantified soil properties indicated that subsurface compaction can occur in these fine-textured soils (e.g., 1.5 times increased PR, ≥ 27% decreased macroporosity, 66% decline in saturated K, and 6% increased BD). Increased root diameter values also indicated the adverse effects of compaction on root development. However, these belowground effects did not translate into aboveground barley responses. These results could suggest that effects of impeding subsurface layers in fertile, fine-textured, irrigated soils depend on plant species and the ability of their root systems to penetrate compacted layers.