Compressive behaviour of the soil in buffer zones under different management practices in Finland

Authors

• Mari Räty Department of Applied Chemistry and Microbiology, PO Box 27, Latokartanonkaari 11, FI-00014 University of Helsinki, Finland
• Rainer Horn Institute of Plant Nutrition and Soil Science, Christian-Albrechts-University zu Kiel,Olshausenstrasse 40, D-24118 Kiel, Germany
• Kimmo Rasa Department of Applied Chemistry and Microbiology, PO Box 27, Latokartanonkaari 11, FI-00014 University of Helsinki, Finland
• Markku Yli-Halla Department of Applied Chemistry and Microbiology, PO Box 27, Latokartanonkaari 11, FI-00014 University of Helsinki, Finland
• Liisa Pietola Research Centre Hanninghof/Yara Suomi Oy, Mechelininkatu 1 A, FI-00180 Helsinki, Finland

DOI: https://doi.org/10.2137/145960610791542370

Keywords:

buffer zone, air permeability, compressive behaviour,precompression stress, stress-displacement relationship, Vertic Cambisol, Haplic Regosol, Finland

Abstract

Soil structure that favours infiltration is essential for successful functioning of vegetated buffer zones. We measured bulk density, air permeability and precompression stress in a clay soil (Vertic Cambisol) and a sandy loam (Haplic Regosol) in Finland, to identify management-related changes in the physical and mechanical properties in the surface soil of buffer zones. In addition, the impact of texture on these properties was studied at depths down to 180?200 cm. Soil cores (240 cm3) were sampled from a cultivated field, from buffer zones harvested by grazing (only in a clay soil) or by cutting and removing the vegetation, and from buffer zones covered with natural grass vegetation. The samples were equilibrated at a matric potential of -6 kPa and compressed at a normal stress range of 20-400 kPa (7 h), followed by stress removal (1 h). Generally, the clay soil was more compressible than the sandy loam. Due to trampling by cattle, the young grazed buffer zone (0-3 cm) had the largest bulk density and the smallest total porosity. For the grazed sites, reduced air permeability (2.7-5.1 × 10-5 m s-1) was found, compared with that of the buffer zone under natural vegetation (15-22 × 10-5 m s-1), indicating decreased pore continuity. Although the old grazed site was easily compressed, compared with the younger site, it showed a greater resilience capacity due to the protective cover of organic residues accumulated on the soil surface.