Potential carbon sequestration in a Mediterranean organic vegetable cropping system. A model approach for evaluating the effects of compost and Agro-ecological Service Crops (ASCs)

After two years from compost application, the SOC stock increased in all plots, by +1.8, +2.3 and +4.9 Mg C ha−1 for Cp0, Cp15 and Cp30 respectively, compared to the initial stock of 36.8 Mg ha−1. The effect of different ASCs termination and ASC × compost interaction was not statistically significant. The RothC10N model was used to predict the effect of ASCs (NoASCs, FB and GMB) and Cp doses in a 20 years period. Predictions of the calibrated and validated RothC10N model showed that SOC change in 20 years was negative in the scenario with no ASCs-no compost (NoASC Cp0), where the C inputs were not sufficient to offset C losses, whereas positive values were predicted for all the other scenarios. The average values of predicted C stock change in 20 years were 3.8, 13.3 and 19.8 Mg C ha−1 for NoASC, FB, and GMB respectively and 8.2. 12.2 and 16.5 Mg C ha−1. for Cp0, Cp15 and Cp30. Both field experiment and model showed that the green manure of ASC and compost application represent a valid option in terms of carbon sequestration increase. RothC10N model can be used successfully as a tool to compare the C sequestration potential of alternative agronomic practices.