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Plant use of soluble organic N



Here is a link to an interesting review of soluble organic nitrogen.

D. V. Murphy, A. J. Macdonald, E. A. Stockdale, K. W. T. Goulding, S.
Fortune, J. L. Gaunt, P. R. Poulton, J. A. Wakefield, C. P. Webster, W. S.
Wilmer:
<review article> Soluble organic nitrogen in agricultural soils

Biol Fertil Soils 30 (2000) 5/6, 374-387
URL:
http://link.springer.de/link/service/journals/00374/bibs/0030005/00300374.ht
m
or
URL:
http://link.springer-ny.com/link/service/journals/00374/bibs/0030005/0030037
4.htm

A few surprising (to me) quotes:

SON is soluble organic nitrogen, TSN is total soluble nitrogen

"Our  data  (Table 1)  show,
for a wide range of  soil types (0 to 30-cm layer), a KCl-extractable
SON-N content of  generally  20–30 kg SON-N
ha –1  and  a  very  constant  ratio  between  mineral  N
and  SON  in  arable  soils,  with  SON  comprising  about
40–50% TSN."

"Our  measurements  of   SON  in  the  0  to  5-cm
layer of  a range of  soils on an organic  farm showed that
it  accounted  for  80%  of   TSN  and  ranged  from  24  to
46 kg SON-N ha –1"

"It is well established
that  some  plants  are  capable  of   utilising  SON
either directly (Chapin et al. 1993; Kielland 1994) or in
association  with  mycorrhiza  and  ectomycorrhizae  (At-kin
1996; Kielland 1994; Michelsen et al. 1996)."

"It  is  not clear whether agricultural
crops benefit  from SON either by direct uptake or
via  microbial  immobilisation  of   organic  molecules  and
then  re-mineralisation  of   NH4-N."

 Andy McGuire
 Lauzier Agricultural Systems Educator
 Washington State University Cooperative Extension
 Center for Sustaining Agriculture and Natural Resources
 PO Box 37, Courthouse
 Ephrata  WA 98823
 509-754-2011, Ext. 412
 Fax: 509-754-0163


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