Abstract

No-till is practiced for various environmental and economic reasons, but the absence of soil loosening by tillage affects soil structure and various soil properties and processes and therefore has significant implications for soil functions, including crop growth. The main objective of this study was to investigate the impact of two decades of no-till on soil gas transport properties in the Oberacker long-term field experiment in Switzerland. This trial was established in 1994 on a loam soil and compares two tillage systems, mouldboard ploughing (MP) and no-till (NT). We further sampled the permanent grass (PG) strips located between the experimental plots as references. Undisturbed soil cores were collected at 0.15 (topsoil) and 0.4 m depth (subsoil) from all three treatments. The soil cores were used for measurements of air-filled porosity (εa), air permeability (ka) and gas diffusivity (Dp/D0) at five matric potentials ranging from -30 to -500 hPa. Our results reveal that the soil pore system and gas transport properties of the NT soil were similar to those under PG for both topsoil and subsoil. In contrast, the soil under MP showed a clear stratification: εa, ka and Dp/D0 were higher than in NT and PG in the topsoil, but lower in the subsoil. The pore system showed a slightly higher specific diffusivity (Dp/D0 / εa) and much higher specific air permeability (ka/εa) in the topsoil of MP than in NT and PG, reflecting higher continuity, higher connectivity and lower tortuosity, but relations were reversed in the subsoil. The gas transport capability was lower in MP than in NT and PG, presumably due to fewer continuous biopores. The gas transport properties reached low values under moist conditions in the topsoil of NT and PG and in the subsoil of MP, which may restrict soil aeration. Thus is highly important to include the properties of the subsoil when evaluation tillage systems.