Schätzrahmen für die effektive Durchwurzelungstiefe mehrschichtiger Böden

Estimating the effective rooting depth of layered soils The values of the effective rooting depth given by the Soil Mapping Instruction are valid only for homogenous soils. In addition to these values a calculation is presented estimating the effective rooting depth of layered soils. This method is proposed as a reference method in databases of soil information systems.     

Wirkung mechanischer Belastung auf Gefüge und Ertragsleistung einer Löss‐Parabraunerde mit zwei Bearbeitungssystemen

Effect of mechanical stress on structure and productivity of a loess‐derived Luvisol with conventional and conservation tillage In Germany farmers are committed to caring for the land by a soil protection law. Yet vehicles with ever increasing axle load endanger productivity and environmental quality of arable soils. In spring of 1995 a field experiment was startet on a wet silty Luvisol to test the effect of single mechanical loading on soil and crop characteristics, when managed by mouldboard ploughing (PL) or conservation tillage (CT). CT soils are considered to be more resistant against compactive stresses and to recover from degeneration more rapidly than PL soils. Beside an unwheeled control the loading treatments were light (2 × 2.5 t; number of wheel passes times wheel load); medium (2 × 5 t) and high (6 × 5 t). In 1995 even light loading of the PL soil caused a significant yield decline by 50% in spring barley, but this happened on CT soil only with high loading. In subsequent years with winter wheat and winter barley yield decline was less distinct. Loading of PL soil reduced total root length (from 4 to 1 km m⁻²) and rooting depth (from 70—90 to 40—70 cm), but on CT soil only root length was diminished by high loading. A tillage‐traffic pan (30—35 cm) hindered subsoil rooting in PL, which was favored in CT by earthworm channels. High loading caused compaction to at least 50 cm depth. Within the pan of the PL soil, penetration resistance attained 5 MPa and bulk density 1.65 g cm⁻³. In the CT soil the zone of maximum compaction was closer to the surface (15—25 cm). In PL soil the saturated hydraulic conductivity and the O₂‐diffusion coefficient gradually decreased with loading, but in CT soil only with heavy loading. The compacted top soil was broken in subsequent years by ploughing (PL: 25 cm) or rotary implements (CT: 5—8 cm). With PL, structure in the pan layer and subsoil did not recover, and rooting depth was still limited. Some restoration, however, was indicated with CT. Here transmitting properties increased in time, which was attributed to the reconstruction of root and earthworm channels, as demonstrated by computer tomography. We conclude that in silty soils compacted layers below ploughing depth will hardly be regenerated by internal processes. CT soils are less susceptible to loading, but high stresses are harmful too. Therefore recommending CT as a measure for protecting soil from compaction would not be enough, considering the present development towards heavy field machinery.     

Schutzwürdige Böden in Nordrhein-Westfalen — Bodenkundliche Kriterien für eine flächendeckende Karte zum Bodenschutz

Valuable soils in Northrhine-Westphalia — soil scientific criteria for generating a complete map for soil protection At the Geological Survey of Northrhine-Westphalia a map was developed: Soils to be protected in Northrhine-Westphalia at a scale of 1:50.000. It is based on the Soil map of Northrhine-Westphalia at a scale of 1:50.000. This map indicates areas where such land uses should get high priority which need, save and develop the identified main soil functions. There are three groups of land use with main soil functions:

• natural habitat with high potential of biotope evolution
• agricultural production on soils with (regionally) high fertility
• regional specifica, including soils as archives of natural and cultural history.

Land uses disregarding or lowering these soil functions have to be placed otherwhere or have to be compensated by areas with comparable functions. The criteria generating this map are given and discussed. The evaluation of information coming from the digital soil map runs soil protection under the aim of securing the kind and state of soil substrate and characteristics, giving the functionality of soils in favor of other media of the environment.     

Die Anwendung der CP(Critical Point)-Trocknung bei der Präparation von Böden für licht- und elektronenmikroskopische Untersuchungen

The use of critical point (CP) drying for light and electron microscopy of soils The preparation of soils for light and electron microscopy usually requires the removal of water. Different dehydration techniques result in varying degrees of damage to the soil structure. The advantages and disadvantages of three dehydration techniques (CP drying, air drying and freeze drying) for soil clays are discussed in this paper. Observations with the scanning electron microscope (SEM) and shrinkage tests suggest that CP drying is particularly appropriate in soil samples > 5-6 mm.