Nitrogen Release from Urea and Sulfur-coated Urea in Jack Pine Forest Humus1
- N. W. Foster and
- E. G. Beauchamp2
Urea and sulfur-coated urea (SU) were each applied in the spring at a rate equivalent to 200 kg N ha−1 to a separate set of replicated 1-m2 plots in a 50-yr-old boreal jack pine (Pinus banksiana Lamb.) forest. Fertilizer N recovery in L, F, and H horizons was determined periodically over 4 yr. Urea was completely hydrolyzed in soil within 10 d, whereas incompletely dissolved SU pellets, containing N equivalent to approximately 10% of the amount added, were recovered from the humus horizons 447 d after fertilization. In urea-treated humus, NH+4-N concentrations significantly greater than those in controls were observed for 57 d. In SU-treated humus, NH+4-N concentrations significantly greater than those in a control were maintained for 477, 336, and 115 d in L, F, and H horizons, respectively. Initial (3 d) NH3 volatilization from SU-treated soil was only 17% of that observed in the urea treatment, presumably because slower release from SU granules resulted in lowere initial pH increases in L and F horizons.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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