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Denitrification in Subsoils of the North Carolina Coastal Plain as Affected by Soil Drainage
Author(s) -
Gambrell R. P.,
Gilliam J. W.,
Weed S. B.
Publication year - 1975
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1975.00472425000400030005x
Subject(s) - denitrification , subsoil , soil horizon , environmental science , soil water , drainage , topsoil , hydrology (agriculture) , soil science , geology , nitrogen , chemistry , ecology , geotechnical engineering , organic chemistry , biology
In a tiled moderately well‐drained soil, over 200 kg NO 3 ‐N/ha were generally found distributed throughout the top 3 m. However, in a poorly drained soil, relatively low levels of NO 3 were found in the top m and very little NO 3 persisted in the saturated zone beneath 1 m. Oxidation‐reduction potential (Eh) measurements in the tiled moderately well‐drained soil indicated well‐oxidized conditions (500–700 millivolts) to 3 m. The Eh measurements beneath 1 m in the poorly drained soil consistently indicated favorable conditions for denitrification. A marked decrease in the NO 3 ‐N/Cl ratio with depth in the poorly drained soil supported the contention that denitrification was occurring in the soil. The water‐soluble C content of the subsurface soil water was 2–5 mg/liter in the moderately well‐drained soil and 10–15 mg/liter in the poorly drained soil. The absence of saturated conditions for extended periods of time and lack of an adequate energy source apparently limited denitrification in the moderately well‐drained soil and much of the fertilizer N not utilized by crops moved into shallow aquifers and surface water. However, sufficient available organic C was present in the subsoil of the saturated, poorly drained soil to bring about a reducing soil environment and subsequent denitrification of the residual NO 3 . Thus, little NO 3 moved from this soil into surface waters.