Seedbed structure of major field crops as affected by cropping systems and climate: Results of a 15-year field trial

•Seedbed structure of several major European field crops was characterized and classified.•Cropping systems differing in crop rotation and decision rules affect seedbed structure.•Cropping systems with higher occurrence of soil compaction resulted in coarser seedbeds.•Coarser seedbeds were more frequent for crops sown within a short time following late harvests.•High interannual variabilities of seedbed structure and no irreversible effect of cropping systems were observed. Seedbed structure directly or indirectly affects crop establishment by modifying seed-soil contact, acting as mechanical obstacles or modifying temperature, moisture and oxygen contents of seedbed as well as the dynamic of pests, pathogens and weeds. However, very few detailed descriptions of seedbed’s structure of major field crops exist to date, in terms of precise aggregate size distributions in relation to different factors including the cropping system (CS), soil and climatic conditions and their interactions. Here, we characterized seedbeds of major European field crops across three CSs over a 15-year period (1991–2005) of a long-term field experiment. CS I was the succession of spring pea/winter wheat/oilseed rape/winter wheat. Likewise, CSs II and III were the succession of sugar beet/winter wheat/maize/winter wheat with different sowing dates based on two different decision rules aimed at: minimizing the risk of soil compaction in the CS II or maximizing the duration of the crop in the CS III. We classified three types of seedbed structure, namely fine (with >20 mm soil aggregates 20 mm soil aggregates >15 < 25 %), and coarse (with>20 mm soil aggregates >25 %). We found a statistically significant effect of CSs (P < 0.05), crops (P < 0.001), previous crops (P < 0.01) and year (P < 0.001) while no significant effect of wheel traffic (P> 0.05) and tillage (P > 0.05) was observed on the soil aggregates > 20 mm. No irreversible effect of the CSs was observed over the study period on seedbed structure and the consequent risks of generating coarser seedbeds, which is unfavorable for crop establishment. This dataset offers a unique description of the seedbed structure variations for major European field crops. This information can be used for future simulation studies of crop emergence, using, for example, the SIMPLE model that has seedbed structure as one of the input variables.