Grass leys promote soil carbon sequestration and improve nitrogen cycling and soil structure

Intensification and specialization of farming systems in Europe and elsewhere has resulted in poor crop rotations, with low plant and animal diversity. This has resulted in more uniform landscapes, soil carbon loss and low efficiency in nutrient cycling, particularly in regions dominated by annual crops. Inclusion of ley in crop rotations is expected to increase soil organic carbon (SOC) stocks, nitrogen availability and improve soil physical properties. The effect of ley-arable rotations versus continuous annual cropping on soil quality, soil organic carbon and soil biology was assessed by summarizing and discussing results from publications from long-term experiments in Norway and Sweden. These studies support the hypotheses that the inclusion of leys in crop rotations promotes soil fertility and carbon sequestration in Northern Europe, supplies nutrients to subsequent crops and improves soil physical properties. However, one or two years of ley in rotations may not be enough for maintaining SOC and good soil structure over time. For keeping the relatively high SOC concentrations occurring at many sites in Northern Europe, the proportion of ley in rotation should be at least 50%.