Soil carbon and nitrogen changes after 28 years of no-tillage management under Mediterranean conditions

Mouldboard ploughing is known to accelerate soil organic matter (SOM) mineralization rate in Mediter-ranean regions. Long-term reduced tillage intensity potentially diminishes soil organic carbon (SOC) andtotal nitrogen (STN) depletions. Here, we compared long-term no-tillage (NT) and conventional tillage(CT) impact on SOC and STN sequestration rates at different depths ranging from 0 to 30 cm. The long-termexperiment started in 1986 on a Typic Xerofluvent soil in Central Italy using a randomized complete blockdesign with four replications. Ten years after the experiment began, SOC and STN concentrations in the0–30 cm soil layer were already higher under NT compared to CT. The shallow layer (0–10 cm) showed thehighest SOC and STN concentration increments. However, no differences between tillage systems wereobserved in the deeper layers. After 28 years, continuous NT increased SOC and STN content in the 30 cmsoil depth by 22% compared to initial values. In the same period, continuous CT decreased SOC and STNcontent by 3% and 5%, respectively. On average, the total SOC and STN gains under NT may be attributedto the shallow layer increments. In the 10–20 and 20–30 cm soil layers, SOC accumulation over time wasnegligible also under NT. In the whole profile (0–30 cm), the mean annual SOC variation was +0.40 Mgha−1yr−1and −0.06 Mg ha−1yr−1under NT and CT, respectively. Under NT, SOC content increased rapidlyin the first ten years (+0.75 Mg ha−1yr−1); later on, SOC increments were slower indicating the reachingof a new equilibrium. Data show that NT is a useful alternative management practice increasing carbonsequestration and soil health in Mediterranean conditions.