From amcguire@coopext.cahe.wsu.edu Tue Feb 29 20:20:38 2000 Date: Tue, 29 Feb 2000 15:42:34 -0800 From: Andy McGuire Reply-To: amcguire@wsu.edu To: "SANET (E-mail)" Subject: Plant use of soluble organic N [ The following text is in the "iso-8859-1" character set. ] [ Your display is set for the "US-ASCII" character set. ] [ Some characters may be displayed incorrectly. ] 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: 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^Ö30 kg SON-N ha ^Ö1 and a very constant ratio between mineral N and SON in arable soils, with SON comprising about 40^Ö50% 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 ^Ö1" "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 To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail