ENERGY ANALYSIS OF TILLAGE AND HERBICIDE INPUTS IN ALTERNATIVE WEED MANAGEMENT-SYSTEMS

In view of the movement toward alternative weed management systems in crop production, the authors analyzed the energy efficiency of tillage practices and herbicide use in alternative systems featuring reductions in tillage and/or herbicide inputs. These systems were from an experimental trial near flora, Ontario and a farm survey in southern Ontario, Canada. Because weed management represented only 20-25% of the annual energy cost for systems using synthetic herbicides and fertilizers, modifications in fertilizer use are more important for energy conservation than weed management. However, energy was conserved in alternative weed management systems by elimination or reduction strategies for tillage and/or herbicide use. Eliminating tillage was more energy efficient than eliminating herbicide use, and resulted in the two lowest energy budgets for weed control among the 12 farms surveyed. Elimination of herbicide use could conserve energy and maintain acceptable yields, particularly in conjunction with farmer experience, and were associated with the use of organic fertilizer and a smaller proportion of energy-intensive crops such as corn. Low-input systems in which tillage and/or herbicides were reduced but not eliminated were more efficient in converting energy into yield than high-input systems, provided that other inputs substituted for reduced inputs (e.g. mechanical inputs instead of chemical inputs) were used in moderation. Thus, most alternative methods of weed control (e.g, reduced herbicide and tillage inputs) are more energy efficient than conventional weed control practices (e.g. broadcast application of herbicides at recommended rates).