Keywords: Energy balancing, Energy intensity, Long-term field experiments, Management systems, Indicators, Sustainability.
A method for energy balancing in crop production is described. System boundaries, energy equivalents and algorithms are defined and the integration of the method into a complex computer-aided model is explained. The balancing approach has been tested both in experiments and at the farm level with the aim of analysing the effects of agronomic measures (fertilisation, crop rotation, tillage) and management systems (organic and integrated farming) on energy efficiency. In a long-term experiment with cereal/root crop rotations, maximised area-related net energy outputs (180-200 GJ/ha/yr) required higher mineral nitrogen rates (90-140 kg N/ha/yr) than minimised product-related energy inputs (60-100 kg N/ha/yr). A comparison of organic and integrated farm systems showed hardly any differences in energy intensity; in the organic system clearly less fossil energy was used per unit area, but the energy recovery was lower because of decreased yields.
Dr Kurt-JÃƒÂ¼rgen HÃƒÂ¼lsbergen, Institute of Agronomy and Crop Science, Martin Luther University, Halle-Wittenberg, Germany.
Dr Wolf-Dieter Kalk, Institute of Agricultural Engineering Bornim, Germany.
36 pages, 10 figures, 12 tables, 51 refs.