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Interactions between peat and sodium acetate, ammonium sulphate urea or wheat straw during incubation studied by 13 C and 15 N NMR spectroscopy
Author(s) -
BenzingPurdie L.,
Cheshire M. V.,
Williams B. L.,
Ratcliffe C. I.,
Ripmeester J. A.,
Goodman B. A.
Publication year - 1992
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1992.tb00123.x
Subject(s) - chemistry , urea , straw , ammonium , nuclear chemistry , magic angle spinning , sodium , sodium acetate , nuclear magnetic resonance spectroscopy , ammonium acetate , organic matter , chromatography , inorganic chemistry , organic chemistry , high performance liquid chromatography
SUMMARY Transformations of sodium acetate, ammonium sulphate, urea and wheat straw in peat have been studied by determining the distribution of 15 N‐labelled material, and by 13 C and 15 N nuclear magnetic resonance spectroscopy (NMR) using cross polarization (CP) and magic‐angle spinning (MAS). Samples of an oligotrophic blanket peat were incubated for 6 months at 15°C with 15 N ammonium sulphate, 15 N urea, 13 C 15 N urea, 15 N‐labelled wheat straw or 13 C sodium acetate. The incubated samples were separated into fractions of >1 mm, 1–0.5 mm, 0.5–0.25 mm, 0.25–0.15 mm, 0.15–0.05 mm, 0.05–0.005 mm and a water‐soluble fraction by wet sieving, and were then freeze‐dried. The distribution of 15 N between the fractions was obtained after isotope‐ratio analysis by mass spectrometry, and the 0.5–0.25 mm, 0.05–0.005 mm and water‐soluble fractions from the incubations were examined by 13 C and 15 N NMR. 13 C‐labelled acetate increased carbohydrate resonances in the 0.05–0.005 mm and soluble material, but an organic acid derived from the substrate was still present 6 months later. Incorporation of 15 N from ammonium sulphate into the peat was low, and more than 50% of the added N was detected in the soluble fraction still present as 15 NH+ 4 . As carbohydrate and soluble organic matter were detected in the peat, it was concluded that microbial activity and N immobilization were restricted by poor aeration and low pH. Urea, in contrast, interacted with all the fractions examined, with some 15 N being incorporated into a range of compounds that included protein, peptides, amides, amino acids and carbamates or lactam derivatives. A small proportion of labelled 15 N from wheat straw, orginally present in the > 1 mm and 14.5 mm fractions, had moved into the 0.05–0.005 fraction during incubation and sieving. The 13 C spectra suggested that the presence of the straw may have stimulated decomposition of the peat components.