Characterizing equilibrium physical condition near the surface of a fine sandy loam under conservation tillage in a humid climate

The adoption of conservation tillage may cause change in soil physical properties over time, especially at the soil surface. A study was initiated in the cool, humid region of Atlantic Canada to characterize soil physical quality, under quasi-equilibrium conditions, at the surface 0 to 10 cm depth of a fine sandy loam, Orthic Podzol (Haplorthod) subjected to long-term direct-drilling (DD; 5-cm soil disturbance) with a hoe-drill and moldboard ploughing (MP; at 20-cm soil depth) for cereals and protein crops. A range of methodology, including unsaturated infiltration, preferential flow, uniaxial compression, and non-limiting water range (NLWR), was used to assess changes in soil structural form and strength. Monitoring soil bulk density (D sub(b)) and organic carbon (OC) over a 12-year period indicated that the equilibrium D sub(b) established after 8 years under DD (D sub(b), 1.2 Mg m super(-3) at 22 g C kg super(-1)) and MP (D sub(b), 1.1 Mg m super(-3) at 20 g C kg super(-1)) was below the level associated with poor aeration (1.3 Mg m super(-3)) for this soil type. Unsaturated hydraulic conductivity was lower in the soil matrix under DD compared with MP; however, preferential water flow through soil pores (