
TY  - JOUR
A1  - M&ouml;ller, A. 
A1  - Kaiser, K. 
A1  - Amelung, W. 
A1  - Niamskul, C. 
A1  - Udomsri, S. 
A1  - Puthawong, M. 
A1  - Haumaier, L. 
A1  - Zech, W. 
T1  - Forms of organic C and P extracted from tropical soils as assessed by liquid-state <emph type="7">13</emph>C- and <emph type="7">31</emph>P-NMR spectroscopy
JF  - Soil Research
JO  - Soil Res.
Y1  - 2000
VL  - 38
IS  - 5
SP  - 1017
EP  - 1036
KW  - soil organic matter, P transformations, charred organic matter matter.
UR  - https://doi.org/10.1071/SR99111 
N2  - Transformation of soil organic phosphorus (SOP) is linked with the transformation of soil organic carbon (SOC). Yet, it is uncertain to which SOC structures the cycling of SOP is related, especially in tropical environments. To clarify this issue, we determined the vertical distribution of extractable C and P chemical structures in 4 soil profiles using solution 13C- and 31P-nuclear magnetic resonance (NMR) spectroscopy after extraction with 0.1 M NaOH/0.4 M NaF (1 : 1). Soils were from a cabbage cultivation with annual burning of weeds, a Pinus reforestation, a secondary forest, and a primary forest in northern Thailand. For all profiles, signals due to O-alkyl and carbonyl C dominated the 13C-NMR spectra (up to 50 and 22% of total spectral area, respectively). The proportions of alkyl and aryl C decreased, whereas carbonyl and O-alkyl C increased with soil depth. Sharp resonances at 135 and 177 ppm appeared in spectra of subsoil horizons. They indicated mellitic acid, an end-product of the oxidation of charred plant residues. The SOP forms comprised mainly orthophosphate diesters in the organic layer of the forests, whereas in the mineral horizons orthophosphate monoesters dominated the chemical composition of extractable SOP. The relationships between SOC and SOP forms in the organic floor layers of the forests were clearly different from those in the mineral soil horizons, indicating changed SOM dynamics upon contact with soil minerals. In the forest mineral soils, significant correlations between monoester-P and O-alkyl C (R = 0.84, P &#60; 0.001) were found. Diester-P, teichoic acids, and phosphonates were positively correlated with aromatic C and negatively with O-alkyl C. At the same time, teichoic acids and phosphonates were positively correlated with short range-ordered Al and Fe oxide phases. These findings can be explained through an increasing microbial decay of aryl C and diester-P compounds that may be less effectively stabilised at lower depths. 
ER  -

