Characterization of humic carbon in soil aggrgates in a long-term experiment with manure and mineral fertilization.

Carbon stabilization in soil aggregates has been proposed as an important mechanism for carbon sequestration in agricultural soils. However, few studies have investigated how long-Term strategies for accumulating C in the soil (e.g., organic fertilizers) can affect humic substance composition in aggregate-size fractions. The aim of this work was to investigate the effects of long-Term application of farmyard manure (FYM) and mineral (MIN) fertilization on the humic carbon (HC) chemical structure extracted from macroaggregates (MA) (2000-250μm), microaggregates (MI) (53-250 μm) and silt-clay (SC) (<53 μm) fractions of two different soils (clay and peaty) by using d13C, solid-state 13C cross-polarization-magic angle spinning nuclear magnetic resonance (CP MAS 13C NMR) and diffuse refl ectance infrared Fourier transform (DRIFT) analyses. Results showed that FYM had improved the HC concentration compared with the unfertilized and MIN fertilization. In clay soil, MIN fertilization led to a ...