|XU, JISHENG - Chinese Academy Of Sciences|
|ZHAO, BINGZI - Chinese Academy Of Sciences|
|CHU, WENYING - Old Dominion University|
|MAO, JINGDONG - Old Dominion University|
|Olk, Daniel - Dan|
|ZHANG, JIABAO - Chinese Academy Of Sciences|
Submitted to: European Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2017
Publication Date: N/A
Interpretive Summary: Natural organic matter plays important roles in soil performance and water quality. Its effectiveness can be affected by both its quantity in soil and its chemical composition. Our knowledge is incomplete regarding whether fertilizer application affects the amount and type of natural organic matter in agricultural soils. We found that the variety of fertilizers applied to two rice fields on different soil types had different effects on the amounts of natural organic matter in soil and its composition. These results will improve management of fertilizers in crop production fields. They are of interest to farmers and other land managers, soil conservationists, and researchers of natural organic matter, fertilizers, and soil ecology.
Technical Abstract: Long-term fertilization strategies have been proven to significantly influence soil organic carbon (SOC) accumulation, while the underlying mechanism remains unclear. Using two long-term (>20 y) field experiments of a double-cropped maize-wheat rotation on a Calcaric Fluvisol and paddy rice on a Hydragric Anthrosol, the chemical natures of the SOC were characterized using multiple cross-polarization/magic angle spinning (multiCP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy. The treatments included: only organic fertilizer (OF), combined mineral NPK fertilizer with OF (NPKOF), mineral fertilizer pairings of NPK, NP, and NK, and an unamended control (Control). The continuous fertilizer treatments increased SOC to different extents on the Anthrosol, but shared similar chemical natures, suggesting a mere SOC accumulation. The chemical composition of Fluvisol SOC significantly differed from that of Anthrosol SOC as revealed by redundancy analysis (RDA) and was markedly influenced by fertilizer treatments, showing that the Fluvisol SOC was chemically divided into three subgroups, with the first subgroup consisting of NPK, NPKOF, and OF treatments, the second Control and NP treatments, and the third NK treatment. The SOC content followed in order first > second > third subgroup. The main structural changes from the first toward the third subgroups were a decrease in the abundance of aromatic C-O, aromatic C, anomeric C, O-alkyl C, and OCH3/NCH, and an increase of COO/N-C=O and alkyl C, which led to increasing alkyl-C/O-alkyl-C ratios and decreasing aromaticity values. These results suggest that balanced fertilization-propelled SOC accumulation in the Fluvisol can be attributed to less decomposition and more humification of the organic materials, while the lowest SOC from the unbalanced fertilization of NK treatment can be ascribed to the opposite reasons.