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| Titel |
Composition of the amino acid and amino sugar for molecular weight fractions of hot-water extractable soil organic matters from soils with plant residue compost or mineral fertilization |
| VerfasserIn |
M. Moriizumi, T. Matsunaga, I. Uezono, N. Kato |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024770
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| Zusammenfassung |
| The hot-water extractable organic nitrogen is well known as a laboratory index of
mineralizable nitrogen. This available nitrogen is indispensable for growth of plants because
of being absorbed in crops. We measured the composition of the amino acid and amino sugar
for molecular weight fractions in hot-water extractable organic matters to understand the
source of the available nitrogen in soils inserted a compost. Two soil samples were
collected from fields (Soil Type; Andosol) in National Agricultural Research Center in
Tsukuba, Japan. A plant residue compost of 2 kga-1y-1 during 25 year has been
applied to a soil and another soil was under the mineral fertilization. Organic matters
were extracted from the soils of 3 g in the water of 50 ml at 80 degree centigrade
for16 hours. The molecular size distribution of the hot-water extractable organic
matters was analyzed by HPSCE (column YMC Diol-120, elution; 50mM phosphate
buffer under pH=7.0, flow rate 1 mlmin-1), and 20 fractions were collected at
regular intervals in the retention time. The chromatograms were monitored under
the absorbance at 280 nm and fluorescence intensity at Ex.280 nm: Em.330nm.
The concentrations of the 15 amino acids and three amino sugars (muramic acid,
glucosamine, and galactosamine) for the molecule weight fractions were measured by
HPLC as o-phthaldialdehyde (OPA) derivatives after the vapor HCl hydrolysis.
Organic nitrogen concentrations of the hot-water extractable organic matters in the
soil inserted the compost (C-soil) and the mineral fertilization soil (M-soil) were
133 and 35 mgkg-1, respectively. The extracted organic matters had the variable
molecule weight (103- 104 Da). The concentrations of the amino acid and amino
sugar of organic nitrogen in the C-soil were higher than those in the M-soil in all
fractions. The fractions were classified into 3 groups (LW, MW, and SW) based
on the molecule weight and spectroscopic characteristics. Each group had unique
composition of the amino acid and amino sugar, regardless of fertilization. The LW
with the largest molecule weight was characterized from the low UV absorbance
and the highest concentration of glucosamine and galactosamine. Thus, the LW
must be originated mainly from the microbial products, because glucosamine and
galactosamine are the biomarkers of the fungi chitin and bacterial products, respectively. The
MW was characterized from the high UV absorbance, low fluorescence, and the
highest concentration of total amino acids nitrogen. The percentages of the aspartic
and gultamic acids to the total amino acids in the MW were higher than those of
the other groups. The concentration of the muramic acid, which is a biomarker of
peptideglycan, was also highest in the MW. Thus, the MW includes an organic matter
originated from the cell wall of bacteria. SW showed the less UV absorbance and strong
fluorescence. The percentage of alanine, glysine, and valine in the SW were higher than
in the LW and MW. Amino sugars did not existed in the SW. Thus, the SW may
consist of some refractory organic matters. The above things reveal that the hot-water
extractable organic matters had variable composition of the amino acids and amino
sugars resulting from the different microbial origin of the soil organic nitrogen. |
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