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Differences in chemical composition of soil organic carbon resulting from long-term fertilization strategies.

Li Z, Zhao B, Wang Q, Cao X, Zhang J - PLoS ONE (2015)

Bottom Line: We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure.There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009.The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China; Graduate School of the Chinese Academy of Science, Beijing, China.

ABSTRACT
Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1-3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4-6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3-52.6% and 9.4-64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.

No MeSH data available.


Solid-state CPMAS 13C NMR spectra of the soils collected in 1989, 1999 and 2009, separately.89 = soils collected in 1989, 99 = soils collected in 1999, 09 = soils collected in 2009.
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pone.0124359.g002: Solid-state CPMAS 13C NMR spectra of the soils collected in 1989, 1999 and 2009, separately.89 = soils collected in 1989, 99 = soils collected in 1999, 09 = soils collected in 2009.

Mentions: The 13C-NMR spectra of soils in 1989 and for seven different treatments during 1999–2009 are displayed in Fig 2. The major NMR bands and their chemical shifts seemed to be consistent among soils with different fertilization strategies or time, due to the general similarity of the constituent functional groups in soil organic matter. The alkyl C (0–45 ppm) region showed signals from CH2 groups in long-chain polymethylene structures (e.g. fatty acids, waxes and biopolyesters) and terminal methyl groups from both alkyl compounds and acetyl substituents in plant hemicellulose [23]. In the O-alkyl region (45–110 ppm), the peak at 56 ppm assigned to the methoxyl C/N-alkyl groups, are usually derived from guaiacyl and syringyl lignin derivatives, and/or C-N bonds in amino acids, respectively [24]. The signal at 74 ppm represented the overlapping resonances of C-2, C-3 and C-5 carbons in the pyranoside structure of cellulose and hemicelluloses of polysaccharides [24]. The peak at 104 ppm was associated with the anomeric C-1 carbon of cellulose and hemicelluloses present in fresh plant material [25]. The broad band around 130 ppm was attributed to the presence of lignin or partially degraded lignin structures, and condensed aromatic and olefinic C [26]. The small peak in the O-aryl C region (145–160 ppm) was more evident in spectra of some soil samples (OM-99, OM-09, 1/2OM-99 and 1/2OM-09) than others, further confirming the presence of lignin components [26]. Finally, the sharp signal at 172 ppm indicated that carboxyl groups (in aliphatic acids of plant and microbial origins) and/or amide groups (in amino acid moieties) were present in great abundance [20].


Differences in chemical composition of soil organic carbon resulting from long-term fertilization strategies.

Li Z, Zhao B, Wang Q, Cao X, Zhang J - PLoS ONE (2015)

Solid-state CPMAS 13C NMR spectra of the soils collected in 1989, 1999 and 2009, separately.89 = soils collected in 1989, 99 = soils collected in 1999, 09 = soils collected in 2009.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401563&req=5

pone.0124359.g002: Solid-state CPMAS 13C NMR spectra of the soils collected in 1989, 1999 and 2009, separately.89 = soils collected in 1989, 99 = soils collected in 1999, 09 = soils collected in 2009.
Mentions: The 13C-NMR spectra of soils in 1989 and for seven different treatments during 1999–2009 are displayed in Fig 2. The major NMR bands and their chemical shifts seemed to be consistent among soils with different fertilization strategies or time, due to the general similarity of the constituent functional groups in soil organic matter. The alkyl C (0–45 ppm) region showed signals from CH2 groups in long-chain polymethylene structures (e.g. fatty acids, waxes and biopolyesters) and terminal methyl groups from both alkyl compounds and acetyl substituents in plant hemicellulose [23]. In the O-alkyl region (45–110 ppm), the peak at 56 ppm assigned to the methoxyl C/N-alkyl groups, are usually derived from guaiacyl and syringyl lignin derivatives, and/or C-N bonds in amino acids, respectively [24]. The signal at 74 ppm represented the overlapping resonances of C-2, C-3 and C-5 carbons in the pyranoside structure of cellulose and hemicelluloses of polysaccharides [24]. The peak at 104 ppm was associated with the anomeric C-1 carbon of cellulose and hemicelluloses present in fresh plant material [25]. The broad band around 130 ppm was attributed to the presence of lignin or partially degraded lignin structures, and condensed aromatic and olefinic C [26]. The small peak in the O-aryl C region (145–160 ppm) was more evident in spectra of some soil samples (OM-99, OM-09, 1/2OM-99 and 1/2OM-09) than others, further confirming the presence of lignin components [26]. Finally, the sharp signal at 172 ppm indicated that carboxyl groups (in aliphatic acids of plant and microbial origins) and/or amide groups (in amino acid moieties) were present in great abundance [20].

Bottom Line: We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure.There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009.The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China; Graduate School of the Chinese Academy of Science, Beijing, China.

ABSTRACT
Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1-3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4-6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3-52.6% and 9.4-64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.

No MeSH data available.