Tillage System and Cover Crop Effects on Soil Quality: I. Chemical, Mechanical, and Biological Properties

Optimal use of management systems including tillage and winter cover crops is recommended to improve soil quality and sustain agricultural production. The effects on soil properties of three tillage systems (as main plot) including direct drilling (D), harrowing to a depth of 8 to 10 cm (H), and moldboard plowing (MP) with and without a cover crop were evaluated in a long-term experiment on a sandy loam soil in Denmark. Chemical, physical, and biological soil properties were measured in the spring of 2012. The field measurements included mean weight diameter (MWD) after the drop-shatter test, penetration resistance, and visual evaluation of soil structure (VESS). In the laboratory, aggregate strength, water-stable aggregates (WSA), and clay dispersibility were measured. The analyzed chemical and biological properties included soil organic C (SOC), total N, microbial biomass C, labile P and K, and pH. Reduced tillage (D and H) resulted in a stratification of the chemical properties within the 0- to 20-cm topsoil layer but a uniform distribution for MP. There was an accumulation of SOC, total N, and labile P and K and reduced pH in the 0- to 10-cm layer. Reduced tillage increased soil strength in terms of greater MWD, VESS, WSA, aggregate tensile strength, and rupture energy. Five years of using a cover crop alleviated plow pan compaction at the 20- to 40-cm depth by reducing penetration resistance. A significant interaction between tillage and cover crop treatments indicated the potential benefit of using a combination of cover crops and direct drilling to produce a better soil friability. The usefulness of the VESS method for soil structural evaluation was supported by the high positive correlation of MWD with VESS scores.