The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 246

Contribution of DON to N in surface waters

Concentrations of DON in the soil leachate ranged from < 0.01 to 1.8 mg
Nl −1 , with larger concentrations in leachates from the core with vegetation
(mean = 0.93 mg N l −1 ) than without vegetation (mean = 0.26 mg N l −1 ).
These are generally larger than concentrations of DON observed in drain-
age waters from peatland in northern Scotland, which varied with season
and were largest, up to 0.56 mg N l −1 , in the autumn (Anderson et al .,
1991). In a study of upland streams in the UK, concentrations of DON
ranged between < 0.01 and 0.78 mg N l −1 , although the majority of stream
samples (80%) contained between 0.05 and 0.325 mg N l −1 (Chapman
et al ., 1998). Chapman et al . (1998) also reported that DON contributed to
between 14 and 69% of TDN in upland streams, with the proportion
increasing in upland areas dominated by peat soils. The lower concentra-
tions of DON in stream waters compared with soil leachates may be
explained by a combination of factors such as: (i) dilution with different
source waters of a lower DON content; and/or (ii) mineralization of DON
within the stream; and/or (iii) uptake of DON by stream biota.

Acknowledgements

The authors would like to thank Miriam Young and Yvonne Cook for
their assistance with the laboratory work. This research was funded
by

the Scottish Office, the Natural Environment Research Council

(GT5/96/2/FS) and the European Community.

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