Isotopic Tracer Techniques for Identification of Sources of Nitrate Pollution1
- A. P. Edwards2
A comparison was made of the use of natural variations in 15N-abundance vs. 15N-enriched and 15N-depleted fertilizers in determining the contribution of inorganic ammonium fertilizers to the NO3-N extracted from a Webster soil following a 30C aerobic incubation for 2.5 weeks. The natural abundance approach was unsatisfactory even in this simplified system and its lack of success is shown to be due in part to replicate variability. The fluctuations in 15N-content of the nitrate from carefully replicated samples of each fertilizer treatment were of the same order of magnitude as the mean difference between the 15N-contents of natural fertilizer-N and the soil-derived NO3-N. Therefore, the use of labeled fertilizers with 15N-contents substantially higher or lower than the natural abundance figure is the only valid approach to the measurement of fertilizer contribution to the NO3-N appearing in tile drains under field condition.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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