Daily Based Morgan–Morgan–Finney (DMMF) Model : A Spatially Distributed Conceptual Soil Erosion Model to Simulate Complex Soil Surface Configurations

In this paper, we present the Daily based Morgan–Morgan–Finney model. The main processes in this model are based on the Morgan–Morgan–Finney soil erosion model, and it is suitable for estimating surface runoff and sediment redistribution patterns in seasonal climate regions with complex surface configurations. We achieved temporal flexibility by utilizing daily time steps, which is suitable for regions with concentrated seasonal rainfall. We introduce the proportion of impervious surface cover as a parameter to reflect its impacts on soil erosion through blocking water infiltration and protecting the soil from detachment. Also, several equations and sequences of sub-processes are modified from the previous model to better represent physical processes. From the sensitivity analysis using the Sobol’ method, the DMMF model shows the rational response to the input parameters which is consistent with the result from the previous versions. To evaluate the model performance, we applied the model to two potato fields in South Korea that had complex surface configurations using plastic covered ridges at various temporal periods during the monsoon season. Our new model shows acceptable performance for runoff and the sediment loss estimation ( NSE ≥ 0.63 , | PBIAS | ≤ 17.00 , and RSR ≤ 0.57 ). Our findings demonstrate that the DMMF model is able to predict the surface runoff and sediment redistribution patterns for cropland with complex surface configurations

Is Ridge Cultivation Sustainable? A Case Study from the Haean Catchment, South Korea

Non-sustainable agricultural practices can alter the quality of soil and water. A sustainable soil management requires detailed understanding of how tillage affects soil quality, erosion, and leaching processes. Agricultural soils in the Haean catchment (South Korea) are susceptible to erosion by water during the monsoon. For years, erosion-induced losses have been compensated by spreading allochthonous sandy material on the fields. These anthropogenically modified soils are used for vegetable production, and crops are cultivated in ridges using plastic mulches. To evaluate whether the current practice of ridge cultivation is sustainable with regard to soil quality and soil and water conservation, we (i) analysed soil properties of topsoils and (ii) carried out dye tracer experiments. Our results show that the sandy topsoils have a very low soil organic matter content and a poor structure and lack soil burrowers. The artificial layering induced by spreading sandy material supported lateral downhill water flow. Ridge tillage and plastic mulching strongly increased surface runoff and soil erosion. We conclude that for this region a comprehensive management plan, which aims at long-term sustainable agriculture by protecting topsoils, increasing soil organic matter, and minimizing runoff and soil erosion, is mandatory for the future

Pollution par les nitrates: quels remèdes?

Au cours des dix dernières années, la pollution des eaux souterraines par les nitrates n'a cessé d'augmenter. Principale accussée: l'agriculture, l'application de méthodes de techniques culturales devrait permettre une meilleure gestion des engrais azotés

Reconstructing Quaternary vegetation history in the Carpathian Basin, SE-Europe, using n-alkane biomarkers as molecular fossils

Seit einigen Jahren gibt es zunehmend Studien, die, basierend auf der Untersuchung von fossilen Holzkohlen und Schneckenschalen aus Löss-Paläoboden Sequenzen, die traditionelle Vorstellung von weitestgehend baumlosen Steppen im Karpaten-Becken während der letzten Kaltzeit in Frage stellen. Mit unseren Arbeiten versuchen wir anhand von Biomarkern einen Beitrag zu dieser Diskussion zu leisten und herauszufinden, welches Potenzial in der Untersuchung von Alkan Biomarkern für die Rekonstruktion der Vegetationsgeschichte während der letzten glazialen Zyklen steckt. Kürzlich veröffentlichte erste Ergebnisse weisen darauf hin, dass der Degradationsgrad der pflanzenbürtigen organischen Substanz einen starken Einfluss auf das Alkanmuster in Böden hat und dass der in der Literatur häufig verwendete Alkanquotient nC31/nC27 kein reiner Vegetations-Proxy ist, sondern auch maßgeblich die unterschiedliche Degradation widerspiegelt. In der vorliegenden Arbeit führen wir daher erstmals einen End Member Modellierungsansatz ein, bei dem der Degradationsgrad der organischen Bodensubstanz mit berücksichtig wird. Das Modell wird auf die Loess-Paläoboden Sequenz Crvenka auf dem Bačka Loess Plateau (Serbien) zwischen Donau und Theiss angewendet. Die so für den letzten Interglazial-Glazial-Zyklus rekonstruierte Vegetationsgeschichte bestätigt die Holzkohle- und Mollusken-Befunde und deutet auf Gras-Steppen während des letzten Interglazials und -stadials hin (Marine Isotopenstadien (MIS) 5 bzw. 3). Die Ergebnisse machen deutlich, dass Steppen während des gesamten letzten glazialen Zyklus vorgeherrscht haben. Für das letzte Interglazial und das Interstadial der Marinen Isotopen Stufe (MIS) 3 deuten die Biomarker Befunde auf reine Grassteppen hin. Dagegen prägten in den Glazialen vermutlich auch vereinzelte Bäume das Landschaftsbild einer ‚Taiga-Steppe’. Die so rekonstruierte Vegetationsgeschichte steht im Einklang mit den Holzkohle- und Schneckenfunden, wie auch mit Ergebnissen von Klima- und Biom-Modellierungen.researc

Distribution of Traditional Irrigation Canals and Their Discharge Dynamics at the Southern Slopes of Mount Kilimanjaro

On the southern slopes of Mt.Kilimanjaro like in many other regions in East Africa, agriculture strongly depends on irrigation. Water is supplied to farms by an extensive network of open unlined canals, most of them built centuries ago. However, information about the distribution of these irrigation canals and the dynamics of their discharge is rare thus hampering the implementation of sustainable solutions for agricultural water management. We suppose that several factors like topography, soil properties, shifts of cropping patterns, and weak institutions affect availability and management of agricultural water. Therefore, in this study we determined (i) the distribution of irrigation canals, (ii) their discharge patterns, and (iii) constraints to their sustainable management. Mixed–method approach consisting of both quantitative and qualitative methodologies was used. The discharge of canals was measured at 11 locations along an altitudinal gradient and selected canals were mapped to understanding their distribution, physical characteristics, and potential risks that limits their optimal discharge. Terrain attributes were derived from the Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Model (DEM) and soil physical and hydraulic conductivity were measured to understand permeability and stability of the soil. Additionally, we conducted focus group discussions with participants from 15 villages and 10 key informants interviews. We found that during the dry season the discharge of canals was higher than in the short rainy season. The discharge of canals increased with decreasing elevation. The median daily discharges equaled 12.6, 9.5, and 7.0 l/s in the lower, mid and upper areas, respectively. Landscape in the central part of the study area was the steepest (slope > 60%) and the roughest (Topographic Ruggedness Index > 80 m).We attribute this to terrain heterogeneity across the landscape, thus community decisions about distribution and maintenance of canals could differ across different villages. Furthermore, current shifts of cropping patterns increased irrigation water demands. Both formal and informal water institutions were constrained with several challenges that affected overall management of canals and their sources. Findings of this study could contribute to various efforts dedicated to improve management of water resources around Mt. Kilimanjaro

A stochastic model for 3-dimensional flow patterns in infiltration experiments

Modelling the 3-dimensional water flux at field scale is important for the design and the analysis of dye tracer experiments. Furthermore, it enables the estimation of the risk to groundwater by pollutants, and the visualisation and classification of flux patterns. A stochastic model is presented that allows for the modelling of a wide range of flow patterns in soils as they appear in dye tracer experiments. The leading idea is that infiltrating water runs along paths, not necessarily preferential ones, and water spreads into the soil uniformly from the paths into the matrix. The model is essentially based on a Poisson point process and three independent random fields. The point process defines the starting points of the paths at the surface. The values of two random fields determine the course of the paths. The third random field governs the depth of the infiltration front. As an extension of the model, we present two simulated examples for stratified soils