Nutrients cycling through farming systems in Europe

Circular resource use has been proposed to address environmental problems of agriculture, but uncertainties remain about how these principles can be implemented in practice. This PhD thesis explored measures to increase nutrient cycling and their effects on nutrient flows, agricultural productivity and the environment. First, a methodology was developed to quantify nutrient cycling at field, farm, and regional level. The resulting indicator Cycle Count was applied to Dutch arable farms and showed that on-farm nitrogen (N) cycling was higher with lower nitrogen inputs, crop residue retention and cover crops. An N flow model was then developed to assess alternative management options in four European regions. Regional N cycling increased most by reducing external feed and synthetic fertiliser inputs. Effects of alternative co-product use differed between European regions, mainly due to co-product availability. Supplementing the model results, farmer interviews showed that profitability was an important barrier to increasing local feed self-sufficiency, shaped by structural lock-ins in farm configuration and market infrastructure.