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CSIRO Publishing, Australian Journal of Soil Research, 5(45), p. 333

DOI: 10.1071/sr06133

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Labile soil organic matter pools under a mixed grass/lucerne pasture and adjacent native bush in Western Australia

Journal article published in 2007 by A. J. Macdonald ORCID, D. V. Murphy, N. Mahieu, I. R. P. Fillery
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Data provided by SHERPA/RoMEO

Abstract

Total C and N were measured in whole soils (0–0.15, 0.15–0.35, and 0.35–0.65 m), light organic matter fractions (<1 g/cm3 (LF 1.0) and 1.0–1.7 g/cm3 (LF 1.7)) in surface soils, and in leaf litter collected from a mixed grass/lucerne pasture and adjacent native bush at Moora, Western Australia. The C content of the plant material and light fractions was characterised by 13C cross-polarisation/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectroscopy. Water-extractable organic C (WEOC) and N (WEON) were measured in soil, and dissolved organic C (DOC) and N (DON) were measured in soil solutions. In addition, both NO3-N and NH4-N (SMN) were measured in soil solutions and water extracts. Total soil C (0–0.65 m) did not differ significantly between land uses, but there was clear evidence of N enrichment under the pasture system, which contained significantly (P < 0.05) more total N in the surface soil (0–0.15 m) compared with that under native bush. The significantly (P < 0.05) smaller C/N ratios of the surface soil, plant litter, and light fractions (LF 1.0 and 1.7) under the pasture provided further evidence of N enrichment. The 13C CP/MAS NMR spectra for plant material and light fractions did not differ greatly between landuses, but in both cases the O-alkyl : alkyl carbon ratio declined with increasing density. The decomposition and subsequent mineralisation of the relatively N-rich organic matter fractions in the pasture system may have contributed to the significantly (P < 0.05) greater DOC, DON, and SMN concentration measured in soil solutions under pasture compared with those under native bush.