The Agricultural Department at New Mexico State University, Las Cruces, New
Mexico did a study involving 15N as a tracer of plant uptake in an
irrigated plot.

At 06:29 PM 3/5/1999 +0100, you wrote:
>Dear listmembers,
>
>We will do this summer an experiment with clover and grass to study
>N-cycle. For this we will use 15N-enriched fertilizer. Now, part of the
>differences found between species may be due to inhomogeneity of the
>fertilizer distribution in the soil (depth-trend) and species-dependent
>rooting depth.
>
>My first question: Did somebody already study the distribution of
>N-fertilizer in the soil?
>
>To partly reduce this problem, we thought of measuring delta15N of
>plants grown under natural 15N conditions (no enriched fertilizer).
>
>My second questions: Did anybody already such a study? How large are
>natural 15N variations, 15N difference between air-N2 and soil N? How
>large are the fractionations by built-in of N2, NO3,...?
>
>Any help, references, ... would be helpful.
>
>Thanks in advance,
>
>Silvio Borella
>
>
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