Short- and mid-term tillage-induced soil CO2 efflux on irrigated permanent- and conventional-bed planting systems with controlled traffic in southern Spain

Use of permanent beds combined with controlled traffic (PB) has been proposed as an alternative planting system for reducing soil erosion and compaction while increasing soil organic carbon (SOC) in irrigated, annual-crop based systems in Mediterranean conditions. The objective of this study was to characterise, in space (beds and furrows with and without traffic) and time (hours, days, and weeks), soil CO2 efflux in PB compared with conventionally tilled bed planting (CB) and with a variant of PB in which subsoiling was performed in trafficked furrows (DPB). The three treatments were combined with controlled traffic. Tillage resulted in abrupt CO2 effluxes that lowered rapidly within hours. However, in CB, soil CO2 effluxes increased again significantly 12 days after tillage compared with PB or DPB. These differences were due to higher emissions from beds than from furrows where the soil had been compacted during the harrowing that formed the beds. In DPB, CO2 effluxes increased in furrows with traffic after subsoiling and the effect was maintained during the study despite subsequent traffic. Soil CO2 efflux increased with soil temperature (measured concomitantly) except after soil tillage. Tillage reduced SOC in both CB and DPB compared with PB.