Simulation of SOC dynamics under different fertilizing management practices using RothC carbon model

Soil can represent a suitable sink for carbon sequestration if properly managed. In recent years many researchers have strengthen the importance of soil carbon sequestration in agro-ecosystems under different management practices. Aim of this paper was to evaluate the efficiency of RothC model to simulate C losses observed over 10 years of fertilization practices on a silty-loam soil cropped with a rotation including maize, tomato and alfalfa. Mineral fertilizers were always applied each year, while organic inputs (FYM and vinasse) were not applied consecutively for 5 years in correspondence of alfalfa cropping. RothC model simulated accurately SOC decrease with a linear relationship between predicted (y) and observed (x) C stocks (equation: y = 0.527x + 31.882 ; R2 = 0.7028); moreover the model allowed to visualize the trend of C dynamics in presence of FYM (high increase of C), vinasse (low C losses), no organic matter added (sharp decrease and high C losses). Results point out that RothC model can provide useful information on soil carbon dynamics in cropping systems and point out the importance of organic fertilization, together with mineral dressing, in particular FYM, in order to maintain good levels of OC in the soil. When other organic materials (e.g. vinasse) or no organic material were added, the model simulates a smooth and sharp decline of SOC respectively; in this last two cases soil acted as a source and not as a sink of CO2, representing a real risk for the environment.