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Keywords:

  • dissolved organic carbon;
  • dissolved organic matter;
  • agricultural land use;
  • subsurface drainage;
  • stream;
  • river

[1] Dissolved organic carbon (DOC) exported from agricultural lands can affect watershed carbon budgets and aquatic ecosystem functions. Agricultural practices, especially enhanced drainage, which is widespread in the midwestern United States and expanding, can influence how much DOC is exported from an area. Dalzell et al. compared fields that drained water at conventional rates (13 millimeters per day) with fields with intense drainage (51 millimeters per day). They found that intense drainage resulted in 55% more DOC exported per year. This was primarily due to increased water export but also due to increased DOC concentration. The researchers observed that DOC export from drained fields depended strongly on precipitation rates and varied considerably from year to year. DOC concentrations increased in stream networks in the drained watershed and shifted from microbial sources in farm field drainage to more terrestrially derived and higher molecular weight DOC at downstream sites. (Journal of Geophysical Research-Biogeosciences, doi:10.1029/2010JG001540, 2011)