Seedbed preparation for arable crops : environmental impact of alternative mechanical solutions

This study quantifies, using the Life Cycle Assessment (LCA) method, the environmental impact of sequences of operations for seedbed preparation for arable crops under different soil textures and soil refinement intensities. Comparing the environmental loads of alternative sequences of operations permitted to detect the most environmentally sustainable sequence in each working condition. To this purpose, 13 alternative sequences of field operations for seedbed preparation were analysed, considering primary and secondary soil tillage and minimum tillage. The study was carried out considering a cradle to farm gate perspective and selecting as functional unit “1 ha tilled with an appropriate soil refinement for sowing and seed germination”. Three 60-ha farms in Northern Italy were considered. Inventory data (e.g., farm and field information, machinery fleets, fuel, lubricant and materials consumptions and exhaust gases emissions) were calculated with the model ENVIAM (ENVironmental Inventory of Agricultural Machinery operations). The impact assessment was completed with the ReCiPe characterisation method. Results showed that seedbed preparation completed with two implements (one for primary and one for secondary soil tillage) instead of three (e.g., one for primary and two for secondary soil tillage) results in a better environmental performance on impact categories (e.g., eutrophication, ecotoxicity and metals depletion) affected by the manufacturing phases and by the consumption of materials along machinery life span. The impact categories affected by fuel consumption and exhaust gases emissions showed the best results with low energy-consumptive operations (e.g., slatted plough, no-Power Take Off harrow and minimum tillage). Coarse textured soils and soils lowly refined (i.e. unrefined soil particles adapt for crops characterized by seeds with a size close to that of winter crops or by high seed density) showed low burdens on all impact categories, whereas fine textured and highly refined soils (i.e. small soil particles adapt for crops with small seeds or by low seed density) were responsible for the highest impacts. This is primarily due to the larger number of harrowing repetitions and of energy and fossil fuel consumption. The results can be up-scaled to arable crop production systems with similar pedo-climatic and operative features, such as other Mediterranean countries. Farmers associations, stakeholders and politicians could promote policies and define incentives that encourage producers to adapt to more environmentally sustainable crop productions.