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Characterization of Humic Carbon in Soil Aggregates in a Long‐term Experiment with Manure and Mineral Fertilization
Author(s) -
Simonetti Gianluca,
Francioso Ornella,
Nardi Serenella,
Berti Antonio,
Brugnoli Enrico,
Francesco Morari Emanuele Lugato
Publication year - 2012
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2011.0243
Subject(s) - chemistry , humus , soil water , manure , environmental chemistry , soil carbon , magic angle spinning , humic acid , silt , fractionation , soil organic matter , fertilizer , soil science , agronomy , nuclear magnetic resonance spectroscopy , geology , organic chemistry , paleontology , biology
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 δ 13 C, solid‐state 13C cross‐polarization‐magic angle spinning nuclear magnetic resonance (CP MAS 13C NMR) and diffuse reflectance 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 significantly heavier isotope 13C enrichment in the SC than macro‐ and microaggregate fractions, suggesting that HC in this fraction was the oldest and most stabilized. This was not so evident in peaty soil, where the HC was probably in an early stage of the humification process. In addition, the HC structure changed in both soils as a consequence of the treatments. The FYM amendment caused a decrease in O, N‐alkyl‐C, and alkyl C from macroaggregate to SC fractions, suggesting an advanced state of humic component degradation. However, FYM led to a considerably positive effect on the aromatic C content in both soils. This effect was magnified in the microaggregates of clay soil. These results revealed that the structural changes of HC in different soil aggregates make it possible to understand the effects of mineral and organic fertilization on cultivated soils.