Availability of Urea, Ammonium, and Nitrate Applied to Pine Bark

Initial availability of NO 3 , NH 4 , and urea applied to limed or unlimed pine bark as well as the form of N available over a period of 21 days was determined. Nitrate was not present in significant amounts when N was supplied as either urea or NH 4 , and the extractable amounts of both urea and NH 4 declined significantly over the course of the experiment. Urea was the least effective of the N forms in supplying N in an extractable form. With NO 3 as the N source, addition of lime to pine bark resulted in significant reductions in extractable NO 3 . Applications of NH 4 gave relatively equal amounts of extractable N as NH 4 from limed and unlimed pine bark after 21 days. It was concluded that N interaction and N transformations with these N forms in pine bark would influence total available N as well as the form of N available for plant growth.