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 (WHC), macroporosity, bulk density and soil compaction 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 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, with the highest average measurement observed in grasslands and the lowest in no-till systems. Subsoil compaction was between 121 to 230 psi with the highest compaction detected in conventional tilled systems and the lowest in grassland. Overall, natural ecosystems showed significantly lower compaction and higher variation across the fields compared to agricultural ecosystems; and conventionally tilled soils suffer from significantly higher soil compaction. There was no significant difference in WHC. These findings reveal that bulk density and soil compaction are more sensitive indicators than water holding capacity and macro porosity. Keywords: Bulk density, compaction, macroporosity, silt loam, water holding capacity, soil ecosystems, soil quality, soil indicators, tillage, no-til