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Agricultural soils and environmental change: integrating Geomorphic and Agro-Ecosystem Modelling Across Spatial Scales

Final Report Summary - GAEMASS (Agricultural soils and environmental change: integrating Geomorphic and Agro-Ecosystem Modelling Across Spatial Scales)

The majority of Europe’s agricultural land is not situated on flat, stable landforms but on gently rolling topographies, where significant soil erosion/deposition has been observed and where soil properties are changing rapidly. Redistribution of soil by agricultural erosion has recently been identified as an important influence on the evolving spatial variability of soil properties and productivity, and as a consequence, as a key control on C sequestration, GHG emissions and leaching of nutrients. However, current experimental and modeling studies on soil functioning have either addressed dynamics at plot (profile) scales or at the regional (national or EU) scale, where is it assumed that regional estimates can be made by a simple summation of component dynamics from isolated and static soil profiles (e.g. Smith, 2004). Both these scales miss the interactions due to redistribution of sediment and nutrients induced by erosion processes and typical spatial variability of key environmental controls related to geomorphic processes at the crucial landscape scale.
The general research objective of this project was to improve our understanding of the role of the agricultural soil resource in environmental change with respect to greenhouse gas emissions, soil carbon sequestration and crop productivity. This was achieved through the development and validation of a coupled geomorphic/agro-ecosystem model that reduces uncertainties by moving from conceptual and simplified coupled approaches to more advanced process-level approaches. The GAEMASS project has linked geomorphic models describing erosion processes on agricultural land with exising agro-ecosystem models. The coupled model was successfully validated on 3 sites in Europe (NE Germany, Belgium and the UK).
We have compared crop production of spring crops generated by well-validated dynamic agroecosystem models using climatic projections. While both models showed that in Central Europe the costs of irrigated spring crop production increases, GAEMASS approach allows to estimate weights of water supply and erosion factors in details in various computer experiments. Secondly, soil redistribution significantly affected crop yields and N cycle in the simulations using coupled geomorphic-agroecosystem model. With inclusion of water effects, the model was able to capture the observed effects on crop yields and soil N. Continued erosion- driven soil redistribution in combination with intensive tillage has increased maximally spatial variability in crop yields, C storage and N losses at different soils and climates. This project showed that the inclusion of landscape features of agricultural fields is an important but challenging task in an agroecosystems analysis.