Nitrogen and carbon mineralization in soil amended with d- and l-leucine

The rates of gross C mineralization over short-term (0–6 h) and longer-term (0–6 d) incubation of soil amended with the l- and d-enantiomers of leucine have been determined from the CO 2 production. The rates of N mineralization over 6 d incubations of similarly amended soils were determined by 15N...

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Bibliographic Details
Published in:Soil biology & biochemistry 1999-10, Vol.31 (11), p.1573-1578
Main Authors: O'Dowd, R.W, Barraclough, D, Hopkins, D.W
Format: Article
Language:English
Subjects:
15N isotope dilution
Agronomy. Soil science and plant productions
Amino acid enantiomers
Biological and medical sciences
Chemical, physicochemical, biochemical and biological properties
Fundamental and applied biological sciences. Psychology
Gross nitrogen mineralization
Organic matter
Physics, chemistry, biochemistry and biology of agricultural and forest soils
Soil science
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Summary:The rates of gross C mineralization over short-term (0–6 h) and longer-term (0–6 d) incubation of soil amended with the l- and d-enantiomers of leucine have been determined from the CO 2 production. The rates of N mineralization over 6 d incubations of similarly amended soils were determined by 15N isotope pool dilution for gross N mineralization and both α-amino N disappearance and NH 4 + accumulation for net N mineralization. The rates of net and gross N mineralization and of C mineralization from d-leucine were all significantly less than those from l-leucine and we present the first data for mineralization of N from a d-amino acid in soil. The hypothesis that the onset of rapid utilization of d-leucine by microorganisms was delayed whilst deamination occurred to yield an achiral keto-acid was not supported because the pulse in gross N mineralization following d-leucine addition to the soil was coincident with that of C mineralization and occurred later than the pulse of gross N mineralization in soil amended with l-leucine. By the time all the added amino acid had disappeared from the extractable pool, 26% of the N added as l-leucine had been taken up and possibly assimilated by the soil microorganisms compared with 47% for d-leucine. Based on these estimates of N assimilation, the C:N ratio of the microorganisms assimilating l-leucine could have been nearly twice that of the microorganisms assimilating d-leucine.
ISSN:0038-0717
1879-3428
DOI:10.1016/S0038-0717(99)00083-8