Root‐dependent recovery of pore system functionality of compacted subsoil: A field case study with bio‐subsoilers in Denmark

다국어 초록 (Multilingual Abstract)

Cover crop effects on soil properties are site specific, and their use as an alternative management strategy to create macropores for subsoil compaction mitigation has not been widely investigated. This study aims to evaluate the effects of bio‐subsoilers on gas and water transport of a compacted sandy loam subsoil. A field screening trial was conducted for 2 yr with spring barley (Hordeum vulgare L.) as the control treatment and lupin (Lupinus luteus L.), chicory (Cichorium intybus L.), lucerne (Medicago sativa L.), tall fescue (Festuca arundinacea Schreb.), festulolium [×Festulolium braunii (K. Richt.) A. Camus], and cocksfoot (Dactylis glomerata L.) as bio‐subsoiler treatments. Undisturbed samples of 100 cm3 were taken at 0.3‐ and 0.5‐m depth for measuring soil physical parameters. For chicory, lucerne, tall fescue, and spring barley, unsaturated hydraulic conductivity [K(h)] was measured at 0.3‐m depth and root pattern distribution was evaluated from 0‐ to 0.6‐m depth. Results showed a nonsignificant trend of larger air permeability (ka), gas diffusivity (Ds/Do), and ka/εa (where εa is air‐filled porosity) for lupin and lucerne, indicating enhanced pore continuity. Chicory and lucerne significantly increased the K(h) at −1‐cm matric potential at 0.3‐m depth in the second year of evaluation. Lucerne and tall fescue had a significantly larger root length and area than barley. We showed that under field conditions in a Danish sandy loam soil, lupin, chicory, and lucerne tended to increase gas and/or water transport on the compacted subsoil layer. The compaction mitigation potential of chicory and lucerne found in our previous soil column experiment with the same soil type was corroborated in our field screening trial.

Lupin and lucerne tended to enhance gas transport on compacted subsoil.
Chicory and lucerne increased the unsaturated hydraulic conductivity towards saturation.
Root distribution down to 0.6‐m depth corresponded with measured soil parameters.