No abstract

Long-term experiments in Mu¨ncheberg, Braunschweig and Livada were used to understand the complex issue of carbon sequestration in soil. The investigations were focused on: effects of land use changes on the fate of soil organic carbon; options of agronomic practices to maintain or to increase soil organic carbon; relationships between organic fertilization and changes in soil organic carbon. The long-term observations showed that the amount of soil organic matter is primarily a function of the prevailing land use. Clearly marked differences were observed between long-term arable farming with lower and short-term with higher soil organic carbon content. Agricultural practices lead to a decrease of soil organic carbon with the result that arable soils are rather sources of carbon than sinks. The carbon sequestration potential is caused by the agronomic management to different extents. The combination of organic and mineral fertilization increased the soil organic carbon content compared to exclusive mineral fertilization. Optimum values of organic fertilizer application for maintaining soil organic carbon were calculated. Liming reduced the soil carbon pool when applied in large amounts. Long-term fertilization experiments are a useful tool for calculating the carbon sink or source potential of arable soils.