Transformation and Losses of Applied Nitrogen-15 Labeled Ammonium in a Flooded Organic Soil
- Michael L. Meyer ,
- Paul R. Bloom and
- John Grava
Ammonia volatilization, denitrification, and mineralization-immobilization turnover rates (MIT) in a flooded organic soil were estimated using 15N-labeled NH4Cl fertilizer. The soil was placed in 15-cm columns either under dark or illuminated conditions. Volatilization of NH3-15N was 8 and 4% of the initial fertilizer N added to the dark and illuminated columns, respectively. The rates of fertilizer N and total N denitrification in the dark columns were constant over the experiment at 1.2 and 2.1 mg N kg−1 d−1, respectively. After 74 d 22% of the initial amended fertilizer N had been denitrified. The rate of net mineralization of N in the anoxic zone was constant with time at 1.5 mg N kg−1 d−1. Mineralization and immobilization turnover fit the model y = ymax (1 − e-kt), where y is the quantity of N mineralized or immobilized and k is the rate coefficient. For gross mineralization ymax = 480 mg N kg−1 d−1 and k = 0.00914 d−1. For immobilization ymax = 160 mg N kg−1 d−1 and k = 0.025 d−1. Mineralization and immobilization were not affected by the concentration of extractable NH4-N. Algae increased immobilization in illuminated columns. No priming effect of added NH+4 on N mineralization was found. The impact of MIT on calculation of fertilizer efficiency is illustrated.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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