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No-tillage permanent bed planting and controlled traffic in a maize-cotton irrigated system RESEARCH HIGHLIGHTS 12We studied permanent (PB) and conventional (CB) bed systems, and controlled traffic 13Crops in CB, PB and decompacted PB (DPB) behaved similarly above ground 14In PB and DPB, compaction by traffic reduced root density in the 0.6-m topsoil 15Root density below 0.6 m depth was higher in PB than in CB despite topsoil compaction 16After 6 years, SOC stock (top 0.5-m layer) was 5.7 Mg ha -1 higher in PB than in CB 17 ABSTRACT 19Under irrigated Mediterranean conditions, no-tillage permanent bed planting (PB) is a 20 promising agriculture system for improving soil protection and for soil carbon 21 sequestration. However, soil compaction may increase with time up to levels that reduce 22 crop yield. The aim of this study was to evaluate the mid-term effects of PB on soil 23 compaction, root growth, crop yield and carbon sequestration compared with 24 conventionally tilled bed planting (CB) and with a variant of PB that had partial subsoiling 25 (DPB) in a Typic Xerofluvents soil (Soil Survey Staff, 2010) in southern Spain. Traffic was 26 controlled during the whole study and beds, and furrows with (F+T) and without traffic (F-27 T), were spatially distinguished during measurements. Comparisons were made during a 28Preprint submitted to Elsevier 2 crop sequence of maize (Zea mays L.)-cotton (Gossypium hirsutum L.)-maize, 29 corresponding to years 4-6 since trial establishment. After six years, soil compaction was 30 higher in PB than in CB, particularly under the bed (44 and 27% higher in top 0.3-and 0.6-31 m soil layers, respectively). Around this time, maize root density at early grain filling was 32 17% lower in PB than in CB in the top 0.6-m layer. In DPB, the subsoiling operation was 33 not effective in increasing root density. Nevertheless, root density appeared to maintain 34 above-ground growth and yield in both PB and DPB compared to CB. Furthermore, at the 35 end of the study, more soil organic carbon was stocked in PB than in CB and the difference 36