Submitted to: International Soil Conservation Organization Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/27/2000
Publication Date: N/A
Technical Abstract: Land in South Dakota, USA was converted from grassland to cropland during the latter nineteenth century and early twentieth century. Intensive tillage systems result in a rapid loss in soil carbon, followed by a reduction in structural stability. Our objective was to compare the effects of no-till, conventional-till, and grassland on soil structure and hydraulic properties of Mollisols and Vertisols in central South Dakota. Nine Ustolls and three Usterts were considered in the study. Surface textures ranged from fine sandy loam to clay. At each site, no-till, conventional-till, and grasslands were chosen in close proximity and matched by soil series and topography. Measurements were made of aggregate size distribution, wet aggregate stability, aggregate slaking, bulk density, ponded infiltration, and infiltration at 30 and 60 mm of tension. Pedality (based on size, grade, and shape of aggregates) was quantified in relation to hydraulic properties. Wet aggregate stability and slaking test showed greater stability in the grass compared to the other treatments. Wet aggregate stability in no-till was higher than in till. Pedality was better developed in grass fields than in cultivated fields at all depths. Dry aggregate distribution measured at a depth of 0 -0.05 m reflected the difference in structure. Mean weight diameters were largest in till, intermediate in no-till, and smallest in grass. Infiltration measurements taken at 30 and 60 mm of tension were highest in the grass. Soil properties evaluated in this study suggest substantial improvement with no-till in wet aggregate stability and soil slaking. Increased crop diversity with introduction of perennial species and careful use of heavy equipment may further improve soil structure in no-till systems.