Organic Manure Increases Carbon Sequestration Far beyond the “4 per 1000 Initiative” Goal on a Sandy Soil in the Thyrow Long-Term Field Experiment DIV.2

Carbon sequestration has been proposed as a way to mitigate the impact of CO2 on the climate. At the COP21, the ‘4 per 1000 Soils for Food Security and Climate’ initiative was launched with the goal to increase global soil organic carbon (SOC) stocks by 4‰ per year. The Thyrow long-term field experiment DIV.2 was chosen to determine the feasibility of this 4 per 1000 goal under the dry and sandy conditions in Eastern Germany. The effects of different fertilizing regimes on SOC contents and winter rye yields were investigated. Winter rye is a representative crop for the region and grown as a monoculture in the experiment. The 4 per 1000 goal was achieved in all treatments including the unfertilized control, although ploughing takes place and straw is removed every year. The highest carbon sequestration of up to 0.5 t ha−1 a−1 was provided by a combination of mineral and manure fertilization. In three out of four years, no yield difference was observed between mineral-only fertilization (120 kg ha−1 N) and a combination of mineral and organic N (97.4 kg ha−1 plant available N) fertilization. Yields increased over the years in the treatment with pure organic N and decreased in all other treatments.