Premium
Nitrogen in particle size fractions of soils incubated for five years with 15 N‐ammonium and 14 C‐hemicellulose
Author(s) -
CHRISTENSEN B. T.,
SØRENSEN L. H.
Publication year - 1986
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.1365-2389.1986.tb00025.x
Subject(s) - silt , organic matter , soil water , chemistry , loam , nitrogen , ammonium , soil organic matter , mineralogy , environmental chemistry , soil science , geology , organic chemistry , paleontology
SUMMARY Four soils with a range of clay and silt contents were incubated for 5 a with 15 N‐labelled (NH 4 )SO 4 and 14 C‐labelled hemicellulose and then fractionated according to particle size by ultrasonic dispersion and sedimentation. The distribution of labelled and native N between clay, silt and sand fractions was determined and elated to previous results on the C distributions. Between 29% and 48% of the added N was found in organic form. The 15 N atom percentage excess decreased in the order: clay > whole soil > silt > sand. For both clay and silt, the enrichment factor for labelled and native N decreased with increasing fraction weight. Clay enrichment was higher for labelled than for native N, the converse being true for silt. The distribution of whole soil labelled organic N was: clay 77–91%, silt 4–11%, and sand <0.5%. Corresponding values for native N were 69–74%, 16–22%, and 1–2%, respectively. All soils had higher proportions of labelled than of native N in the clay, the converse was true for the silt. The C/N ratio of the native silt organic matter was higher and that of clay organic matter lower than whole soil C/N ratios. Differences between the C/N ratio distributions of native and labelled organic matter were small. The relative distribution of labelled N and C was very similar confirming that the turnover of C and N in soil organic matter is closely interrelated.