Efficiency improvement for a sustainable agriculture : the integration of agronomic and farm economics approaches

Keywords: Sustainable farming systems, Agronomic efficiency, Economic efficiency, Environmental efficiency, Sustainability index, Interdisciplinary analysis.

The objective of the research described in this thesis was to determine what role improved agronomic efficiency can play in the transition towards more sustainable production systems. Agronomic efficiency measures the technical performance. If it could be improved, environmental damage could be reduced while, at the same time, economic performance could be improved. The latter is an important condition for a successful transition to sustainable agriculture.

Because economists and agronomists use different concepts and assumptions, they disagree about the efficiency that should be feasible in practice. Therefore, first a conceptual model integrating agronomic and economic concepts was developed. The model presents a division into production levels and accompanying production restricting factors. The hypothesis that improved agronomic efficiency also improves sustainability was tested empirically for sugar beet growing. A positive correlation was indeed found between agronomic efficiency and sustainability. Next, the effect of some production restricting factors on the agronomic efficiency was assessed, using a model that simulated crop growth and water and nitrate processes in the soil to assess the effect of annual variation in weather on the efficiency. It was found that efficiency decreased by 13% due to variation in weather (including indirect weather effects). When the effect of differences in management was measured in an experiment using an interactive simulation model, socio-psychological factors were found to restrict the efficiency by 50-70%. Finally, using these results, the conceptual model was completed quantitatively. The refined conceptual model suggests that the differences between the theoretically-assessed efficiency levels are considerably smaller than the differences between 'average' and 'best practice'. The general conclusion is that normative economic models seem to be a valuable tool for the development of sustainable production systems, as they incorporate not only knowledge derived from practice but also new technological findings.