Carbon Stocks, Sequestration Rate and Efficiency over 50 Years of Increasing Mineral N Fertilization †.

Microbially mediated soil organic matter is an extremely sensitive pool that indicates subtle changes in the quality parameters. The calculation of different carbon pools (organic carbon—OC, labile carbon—PMC, light carbon—LFC and microbial carbon—MBC), their sequestration rate (Csr) and efficiency (Cse), as affected by 50 yrs. of mineral fertilization, was carried out. The C sequestration rates between the fertilized plots were not significantly different except for the control plot. The sensitivity index, which indicates the response of soil organic matter to changes in different carbon fractions, demonstrated a strong correlation with the amount of light-fraction organic matter (OM). The use of mineral N over 50 years resulted in increase of soil labile C, but did not result in greater C sequestration efficiency. The results give a deeper insight into the behavior of carbon pools and can serve as a reliable basis for further studies focused on neutral carbon emissions and effective C sequestration. [ABSTRACT FROM AUTHOR]