Persistence of deep loosening of naturally compacted subsoils in Nova Scotia

Naturally compacted subsoils, as a result of geogenic and/or pedogenic processes, are a common phenomenon in soils formed on medium textured basal tills in the Maritimes. This study was conducted to determine whether soil loosening following tile drainage could improve the long-term physical condition of naturally compacted subsoils and consequently improve soil permeability and crop productivity. The effects of subsoiling at various soil depths (35 to 70 cm) perpendicular to tile lines on soil structural form, and crop biomass yield and root growth were investigated over a 4-yr period (1989-1993) on sandy loam to loam Luvisolic, Gleysolic, and Brunisolic soils, at three sites in Nova Scotia. For two of the sites, soil bulk density measured using gamma ray attenuation showed a significant decrease immediately after subsoiling, and soil hydraulic conductivity determined using a constant head well Guelph permeameter was increased, relative to the non-subsoiled control. At one of the sites, subsoil loosening increased crop winter survival and productivity. Subsoiling did not appear to significantly improve the long-term permeability or environment for root growth below the 45-cm soil depth. Evidence of subsoil reconsolidation was found at each site within the three year period.