Evaluation of Physical Soil Quality Indicators in Natural Vs Agricultural Ecosystems.

Soil quality indicators are generally used to evaluate sustainable land management in agroecosystems.   The objective of this research was to evaluate the physical soil quality indicators, including water holding capacity, macroporosity, bulk density, soil compaction, soil organic matter, and aggregate stability under two natural and two agricultural ecosystems.  The study was conducted in silt loam soils in Lyons and Trigg Counties of South Western KY.  Natural ecosystems included undisturbed grasslands and undisturbed deciduous woodlands while agricultural ecosystems included conventional tilled agriculture soils and no-till agriculture 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 highest WHC was found in woodlands and the lowest in grasslands. The trend of macroporosity followed WHC being the highest in woodlands.  The highest average measurement for bulk density was observed in grasslands and the lowest in no-till systems. The highest subsoil WHC was observed in conventional tillage and the lowest in woodlands. Macroporosity was the highest in conventional tillage and the lowest in grasslands. Subsoil bulk density was the highest in No-till and the lowest in woodlands. The highest compaction measured by penetrometer was detected in conventional tilled systems and the lowest in grassland.  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.