Management Effects on Soil Carbon Dioxide Fluxes under Semiarid Mediterranean Conditions

Losses of soil organic carbon (SOC) have contributed to CO 2 emissions from soils to the atmosphere and to global climate change. We hypothesized that in semiarid agroecosystems of the Mediterranean region, a shift from the traditional management system (including conventional tillage [CT] and a cereal–fallow rotation) to a more conservative system, including no‐till (NT) and continuous cropping, could reduce CO 2 emissions during the cropping season. Thus, in this study, we studied the effects of tillage and cropping systems on C inputs and soil CO 2 fluxes during three cropping seasons at three different sites in the Ebro River valley (northeast Spain). Carbon inputs ranged from 650 to 6000 kg ha −1 and seasonal average CO 2 flux ranged from 0.10 to 1.76 g CO 2 m −2 h −1 Differences in rainfall led to marked differences in C inputs and soil fluxes among growing seasons. Although differences among tillage treatments were weak, CO 2 fluxes under NT were always lower. Intensification of cropping systems led to an increase in C input. A move from CT to NT together with cropping intensification is suitable to increase C inputs and to reduce soil CO 2 fluxes in semiarid Mediterranean agroecosystems.