Entwicklung eines räumlich-zeitlichen Bodeninformationsmodells zur Befahrbarkeitsanalyse von Ackerflächen

Räumliche Bodeninformationen sind notwendig, um befahrungsbedingte Beeinträchtigungen von Bodenfunktionen zu analysieren und zu vermeiden. Da der Boden jedoch ständigen dynamischen Prozessen durch Witterungseinflüsse und Bodenmanagement unterliegt, variieren auch die Bodeneigenschaften kontinuierlich. Dies wirkt sich wiederum auf die Befahrbarkeit des Bodens aus. Ziel dieser Studie ist es, ein Bodeninformationsmodell auf Feldskala zu entwickeln, welches die dynamischen räumlich-zeitlichen Eigenschaften des Bodens berücksichtigt. Mit diesem Modell können die Auswirkungen von Befahrungsintensitäten auf Bodenfunktionen evaluiert und eine Berechnung von optimalen Fahrwegen für eingesetzte Landmaschinen durchgeführt werden. Das Modell wurde zunächst für eine Fläche im südlichen Niedersachsen entwickelt. Auf dem 5 ha großen Feld (Parabraunerde, Ut3-Ut4) wurden flächenhaft Bodeneigenschaften wie Bodentextur und Kohlenstoffgehalte bis in 1 m Tiefe bestimmt. Diese eher statischen Größen wurden durch flächenhafte Messungen dynamischer Bodeneigenschaften wie Eindringwiderstand und Bodenfeuchte ergänzt. Die Bodenfeuchte wurde mit einem Sensornetzwerk bestehend aus 60 Sensoren (PlantCare-Sensoren) kontinuierlich ermittelt. Neben den flächenhaften Daten wurden an ausgewählten Standorten die Trockenrohdichte, Infiltration, gesättigte und ungesättigte Leitfähigkeit gemessen. Zusätzlich wurden alle Befahrungen auf dem Feld mittels RTK-GPS aufgezeichnet, um daraus Befahrungsintensitäten abzuleiten. Die Ergebnisse zeigen eine große räumliche Heterogenität der erfassten Bodeneigenschaften- und -funktionen. Die Heterogenität führt dazu, dass die Befahrbarkeit und die Auswirkungen der Befahrungen innerhalb des Feldes ebenfalls stark variieren. Teilbereiche des Feldes sind aufgrund hoher struktureller Stabilität und geringer Bodenfeuchte in der Lage, den durch Befahrung aufgebrachten Drücken zu widerstehen. Andere Teilbereiche sind jedoch aufgrund geringer Stabilität und hoher Bodenfeuchte einem erhöhten Verdichtungsrisiko ausgesetzt. Es zeigt sich, dass das Bodeninformationsmodell eine räumlich differenzierte Abschätzung der Auswirkungen von Befahrungen ermöglicht. Durch Berücksichtigung der dynamischen Veränderung beispielsweise des Wassergehaltes können kontinuierlich Bereiche hoher bzw. geringer Verdichtungsgefährdung ausgewiesen werden. In Kombination mit weiteren Modellen zur Fahrwegsberechnung könnten somit auch die Fahrwege der Maschinen auf dem Feld optimiert werden

Prozessorientierte Landschaftsanalyse mit einem geooekologischen Informationssystem Experimentelle Untersuchungen und Aufbau des Geooekologischen Informationssystems GOEKIS im Repraesentativgebiet Hagen (Nienburger Geest)

Available from TIB Hannover: RR2634(4)+a+b / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Integrating soil compaction impacts of tramlines into soil erosion modelling: A field-scale approach

Soil erosion by water is one of the main soil degradation processes worldwide, which leads to declines in natural soil fertility and productivity especially on arable land. Despite advances in soil erosion modelling, the effects of compacted tramlines are usually not considered. However, tramlines noticeably contribute to the amount of soil eroded inside a field. To quantify these effects we incorporated high-resolution spatial tramline data into modelling. For simulation, the process-based soil erosion model EROSION3D has been applied on different fields for a single rainfall event. To find a reasonable balance between computing time and prediction quality, different grid cell sizes (5, 1, and 0.5 m) were used and modelling results were compared against measured soil loss. We found that (i) grid-based models like E3D are able to integrate tramlines, (ii) the share of measured erosion between tramline and cultivated areas fits well with measurements for resolution ≤1 m, (iii) tramline erosion showed a high dependency to the slope angle and (iv) soil loss and runoff are generated quicker within tramlines during the event. The results indicate that the integration of tramlines in soil erosion modelling improves the spatial prediction accuracy, and therefore, can be important for soil conservation planning

Viscoelasticity and shear resistance at the aggregate scale of structured and organic carbon-free Chernozems

Soil rheology characterises the flow behaviour of soils at the particle-particle to aggregate scale. Amplitude sweep tests (ASTs) are often the method of choice for parameterizing soil flow properties, such as the shear strain values at the end of the linear viscoelastic range (i.e., the deformation is mainly elastic) and at the yield point (i.e., elastic equals plastic deformation). Samples from seven soil profiles and five soil depths of Chernozems, collected in the Maidanetske study area, close to Uman City of Ukraine, were analysed to evaluate the effect of soil organic carbon (SOC) on the parameters related to soil microstructural stability derived from ASTs. Soil organic carbon was removed with H2O2 to determine the soil texture-dependent values of soil rheological properties, which were compared to the values determined for samples with intact water-stable aggregates. The shear resistance-related parameters increased for aggregated soil samples compared to SOC-free soil samples, indicating an increase in soil stability due to SOC. In contrast, the values of the overall viscoelasticity and the shear strain were reduced for aggregated soil samples, indicating decreased soil stability. Pedotransfer functions were applied to predict the shear strain-dependent loss and storage moduli and shear stress values as a function of SOC depletion. Coarse particles (630-2 000 mu m) and volumetric water content improved the models. We conclude that increased SOC content, through the gluing and cementing effects of SOC and altered aggregate shapes compared to SOC-free soil materials, contributes to higher microstructural strength. However, the increased water content in the SOC-containing soil samples reversed soil strengthening effect. This was due to the fact that a more rapid increase in positive water pressure under shear stress weakened the samples and the spherical aggregates began to rotate more easily, thus loosing energy, when compared to platy particles of the SOC-free soil materials

Is soil loss due to crop harvesting the most disregarded soil erosion process? A review of harvest erosion

While water and wind erosion are part of intensive research activities all over the world, soil loss due to crop harvesting (SLCH) is rarely acknowledged. SLCH occurs in tuber and root crops, which were cultivated on at least 1.1 million km2 worldwide in 2019. Thus, 8.4% of arable soils were affected by this kind of soil loss which can reach erosion rates of 22 Mg ha−1 harvest−1. Although these erosion rates are as high as for water and wind erosion, there are only 27 scientific references available that focus on SLCH. Hence, the relationship between possible environmental degradation and perception in science appears to be ambivalent. The aim of this review is to raise awareness of SLCH and harvest erosion. To achieve this aim, firstly the current state of knowledge on SLCH is summarized based on peer reviewed and international references. A special focus is on the rates of SLCH, on available regression equations to calculate the soil losses by harvest and on the environmental effects. Secondly, important research gaps and necessary research activities are identified. It becomes apparent that (i) new data is required which considers developments in harvest techniques and soil management, (ii) data from North America, South America and Oceania is urgently needed as no references for these regions are available yet, (iii) models to predict SLCH are necessary and (iv) research is required on the fate of the adhering soil within the landscape and on its environmental effects

Sensitivity of mGROWA-simulated groundwater recharge to changes in soil and land use parameters in a Mediterranean environment and conclusions in view of ensemble-based climate impact simulations

This study examines the impact of changing climatic conditions on groundwater recharge in the Riu Mannu catchment in southern Sardinia. Based on an ensemble of four downscaled and bias corrected combinations of Global and Regional Climate Models (GCM–RCMs), the deterministic distributed water balance model mGROWA was used to simulate long-term mean annual groundwater recharge in the catchment for four 30-year periods between 1981 and 2100. The four employed GCM–RCM combinations project an adverse climatic development for the study area: by the period 2071–2100, annual rainfall will decrease considerably, while grass reference evapotranspiration will rise. Accordingly, ensemble results for our base scenario showed a climate-induced decrease in the median of annual groundwater recharge in areas covered by Macchia from 42–48 mm/a to 25–35 mm/a between the periods 1981–2010 and 2071–2100, corresponding to a reduction of 17–43%. To take into account the influence of additional plant available water storage in weathered bedrock on groundwater recharge generation, the model was extended by a regolith zone for regions covered by Mediterranean Macchia. In a set of model runs (“scenarios”), parameter values controlling the water storage capacity of this zone were increased step-wise and evaluated by comparison to the base scenario to analyze the sensitivity of the model outcome to these changes. The implementation of a regolith zone had a considerable impact on groundwater recharge and resulted in a decrease of the median in annual groundwater recharge: by 2071–2100, the 35% scenario (available water content in the regolith of 3.9 to 5.7 vol.%) showed a reduction of 67–82% as compared to the period 1981–2010 in the base scenario. In addition, we also examined the influence of changes in the crop coefficients (Kc) as well as different soil texture distributions on simulated groundwater recharge