Effects of Natural and Agricultural Land Management Practices on Physical Soil Quality Indicators.

Land use management has been found to affect certain physical soil properties. Such changes can be detrimental or restorative for soil quality. The objective of this research was to evaluate physical soil quality indicators under two natural and two agricultural ecosystems to measure the degradation or lack thereof in soil quality across those ecosystems. The physical indicators of water holding capacity, macroporosity, bulk density, soil compaction, soil organic matter, and aggregate stability were chosen as they are sensitive enough to indicate soil health. The study was conducted in silt loam soils in Lyons and Trigg Counties of Kentucky.  Natural ecosystems included undisturbed grasslands and undisturbed deciduous woodlands while agricultural ecosystems included conventionally tilled soils and no-till soils. Agricultural soils were cultivated in a corn, soy, wheat, tobacco rotation. Subsoil compaction was measured with a penetrometer. Undisturbed soil cores were sampled from topsoil at 0 - 7.5 cm and 15 – 21 cm deep to measure bulk density, macroporosity and WHC. The data was statistically measured using ANOVA single factor at α 5%. The top soil results indicated that the range of WHC was 36.8 to 40.8%, The range of macroporosity was 34.6% to 37.5%.  The range of bulk density was 1.26 to 1.74 g/cm³. Subsoil WHC was 24.3 to 26.3%. Macroporosity ranged from 21 to 24%. The range of subsoil BD was 1.47 to 1.56 g/cm³. Compaction measured by penetrometer was between 121 to 230 psi with the highest compaction detected in conventional tilled systems. Soil organic matter content and aggregate stability were measured as well. Overall, natural ecosystems showed higher variation across the fields compared to agricultural ecosystems. The findings revealed that bulk density and soil compaction are more sensitive indicators than water holding capacity and macro porosity; and that conventionally tilled soils suffer from significantly higher soil compaction.