Soil Management Impacts Sampling of Soil Quality Indicators.

Soil management affects dynamic soil properties (e.g. bulk density) and resulting soil quality.  Soil quality characterization depends on adequate sampling. Ideally, adequate sampling uses existing knowledge of the soil property’s spatial structure. Geostatistical analysis of transect samples was used to determine the recommended sampling distance for properties indicative of soil quality in six fields under continuous no till and six fields under discontinuous no-till row-cropping.  Studied soil quality variates included bulk density, geometric mean diameter (GMD) of the drop shatter dry fragment size distribution, texture, infiltration, A horizon depth and organic matter. Selected fields had similar soils and terrain. One-way ANOVA found statistically significant differences, due to management, in bulk density, GMD, texture, A horizon depth, and organic matter.  Transect spatial analysis found, despite strong similarities in soils and landscape positions that tillage management resulted in differences in recommended sampling distances. Recommended sampling distance also depended on the measured property. Shorter sampling distances (20 to 70 m) would be recommended for organic matter, GMD, bulk density, and infiltration, while longer sampling distances (100 to 200 m) would be needed for texture.  In general, recommended sampling distances were smaller for continuous no-tillage than for discontinuous no-tillage. Different management systems changed the scale dependency of these soil properties. We conclude that management “should” be taken into consideration when establishing the sampling density for these indicators of soil quality.