| Resumo: |
An understanding of agriculture's energy, material, and labor requirements is essential for achieving economic and ecological sustainability, and for assessing the effectiveness of relevant policy decisions (biofuel subsidies, regulations, labeling, etc.). Previous studies of energy, materials, and labor use in farming have been based on either unverified voluntary reporting or test plots, rather than on the high-resolution measurements of mass and energy flows. Here we present a recursive analysis of 1.25 million data points describing in unprecedented detail the resource transactions on a 60 ha farm functioning for over 6 years. This analysis highlights the importance of accounting for all types of materials, as well as capital equipment, non-field labor, and commuting. The superior energy efficiency of the farm's energy-saving methods, including green manure, crop rotation, composting, and short-duration grazing -- compared with conventional methods -- persists even when the higher labor requirements are taken into account. One of the farm's methods, however -- the use of horses for traction -- is shown to be highly inefficient compared with mechanical tractors.
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