Jeffrey S. Strock1, Stacey Burns1, Deborah Allan2, Jennifer King1, and Jay Bell1. (1) Univ of Minnesota, 23669 130th St, Lamberton, MN 56152-1036, (2) 1991 Upper Buford Circle, University of Minnesota, University of Minnesota, Soil, Water, Climate Department, St. Paul, MN 55108
Soil physical properties are important soil quality
indicators, as they have important agricultural and environmental implications
and are strongly affected by land management practices. The objective of this
study was to measure the effects of organic and conventional management
practices on soil physical properties including: bulk density, infiltrability, sorptivity, soil
water retention, and vertical saturated hydraulic conductivity (Ks).
Soil samples were collected during 2004 from the Elwell
Agroecology Farm (EAF) at the University
of Minnesota Southwest Research and Outreach Center
located near Lamberton, Minnesota. Soil types were a complex of Ves, Normania, and
Webster, clay loams (fine-loamy, mixed mesic
Calcic Hapludolls;
fine-loamy, mixed, mesic Aquic Hapludolls; and fine-loamy,
mixed, mesic Typic Endoquolls, respectively). These three soil types
represented well, moderately, and poorly drained soils on the upper, mid, and bottomslope landscape positions in this gently rolling
glacial till landscape. Bulk density in the A horizon was lower under organic management
practices than under conventional practices. Infiltrabiltiy
and saturated hydraulic conductivity were significantly higher in the A horizon
under organic management practices than under conventional management. Differences
in conductivity were greater for soils located at bottomslope
positions than soils at mid- or upper-slope positions. The b
value of Campbell's
moisture retention equation was significantly smaller for organic practices than
conventional management practices in the A, B, and C horizons. The Campbell equation air
entry value was significantly larger for organic practices than conventional practices
in the A horizon. Differences in bulk density, air entry, and Ks
between the organic and conventional management systems were attributed to
differences in crop rotations and tillage management between the two systems. These differences in physical and hydraulic
properties can be used by modelers to estimate the impacts of alternative
versus conventional agricultural practices on water movement and water quality.