Trade-off analysis of conventional and organic crop rotations under current and future climate scenarios in Finland

Maintaining agricultural productivity while reducing soil organic carbon (SOC) loss, greenhouse gas emissions and groundwater contamination is a major challenge for European agriculture. Organic farming practices are expected to improve soil health and have increased their share of European cropland, but their effects on soil biogeochemical properties, biodiversity and nitrogen dynamics are mixed. This study uses the process-based ARMOSA crop model to assess the impact of conventional and organic farming practices on yield, SOC stock, nitrate (NO₃) leaching, and nitrous oxide (N₂O) emissions in both crop and livestock farms.

The research was carried out using simulations under current and projected future climate conditions in the South Savo region of Finland, which is characterised by a subarctic climate (Köppen-Geiger classification). The soil type was loamy sand (sand 76%, clay 4%, silt 20%) with a SOC content of 3.5%, a carbon-to-nitrogen ratio of 17, and a pH of 6.2 in the top 30 cm of the soil.

Five-year crop rotations that reflect prevalent practices in the area were designed for both crop and livestock production systems. Crop production rotations included cereals (with fodder peas in organic management), oilseed rape, and grass. Livestock farm rotations featured two years of cereals followed by a three-year fescue and timothy meadow (including clover in organic management). Nine scenarios were simulated to explore residue management and fertilisation strategies. Conventional systems used mineral fertilisers alone or combined with slurry. Organic systems used slurry, green manure, and a commercial organic fertiliser.

To evaluate the productivity and the environmental impact of these rotations, a fuzzy logic-based trade-off analysis was employed for each climate scenario. This analysis quantifies the trade-offs between crop yield, N₂O emissions, NO₃ leaching, and SOC stock changes. The result is a composite index known as the ∑ommit index. This index rates these trade-offs on a scale from 0 (poor) to 1 (excellent).  To accommodate diverse evaluation criteria, alternative versions of this trade-off analysis were implemented. Each version varies the weightings assigned to the trade-off components to mirror the perspectives and priorities of different representative stakeholder categories.

Using the ∑ommit index to evaluate a five-year rotation, rather than analysing individual cropping cycles, offers a significant advantage. This approach takes into account the interconnected effects of each cycle and its interactions with preceding and subsequent cycles. By considering these cumulative effects, the index provides a more comprehensive view of the trade-off dynamics during crop transitions. This holistic perspective is essential for making informed decisions about sustainable farming practices and long-term crop rotation strategies.