Nitrification in paleocene shale.

Exchangeable ammonium nitrogen is present in Paleocene (Fort Union) shale below a depth of 10 meters in North Dakota and eastern Montana. Above 10 meters, exchangeable ammonium nitrogen is nitrified in situ. The lack of viable nitrifying organisms and the probable lack of oxygen prevent in situ nitrification below 10 meters. Shale samples incubated at 27 degrees C under nonsterile conditions or shales exposed to atmospheric contamination exhibited active nitrification without additional treatment.