If memory serves, rates for N-uptake by plants as ammonia N and as nitrate N are 66 % and 34 % respectively.
Assuming plant samples (as freeze-dried, milled plant matter) are being analysed for total 15N by EA-IRMS, fertilizer with an enrichment level of 10 % APE 15N should be ample.
Assuming further your colleagues are interested in comparing N-uptake from ammonium N to N-uptake from nitrate-N, they would need to run a side-by-side study of at least three plots all but identical for fertilizer application, e.g. plot 1 has X kg of ammonium nitrate (10 % APE ammonium 15N) applied; plot 2 has X kg of ammonium nitrate (10 % APE nitrate 15N) applied; plot 3 has no fertilizer applied and serves as control (no N fertilizer; up-take of soil background 15N).
BTW, a fertilizer study on tomato plants has shown better N-uptake if fertilizer was applied in liquid form (solution) as compared to applying fertilizer is solid form (e.g. pellets).
Here are a few papers / book chapters on this subject.
D. Barraclough published a paper in Plant and Soil (1991; 131: 89-96) on 15N tracer experiments and how to interpret them.
The tomato study was published by Nakano und Uehara in Japan Agricultural Research Quarterly (2007; 41: 219-226).
Nadelhoffer, K.J. & Fry, B. contributed a chapter on "Nitrogen isotope studies in forest ecosystems" to the book Stable Isotopes in Ecology and Environmental Studies (1994; Eds K. Lajtha & R.H. Michener), pp. 22-44.
H. Dinkelmeyer et al. published a study if N-take from 15N labelled ammonium sulphate in Agroforestry Systems (2003; 57: 231-224).
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Jose Manuel Moreno Rojas
Sent: 27 September 2018 13:11
To: [log in to unmask]
Subject: [ISOGEOCHEM] Attempt to mark plants with fertilizers
Some colleagues are trying to convince to work on plants by marking them with fertilizers. They explained me that find several options in the webpage they checked:
AMMONIUM NITRATE (NITRATE-15N, 10%)
AMMONIUM NITRATE (NITRATE -15N, 98%)
AMMONIUM NITRATE (AMMONIUM-15N, 10%)
AMMONIUM NITRATE (AMMONIUM-15N, 98%)
AMMONIUM NITRATE (15N2, 10%)
AMMONIUM NITRATE (15N2, 98%)
AMMONIUM SULFATE(15N2, 99%)
AMMONIUM SULFATE(15N2, 10%)
Since they do not use to work with isotopes and I do not use to work with this type of products I am worried about how to manage that experimental work (and the later analysis). They provide me with this
Anybody out there with experience in this kind of works could help me?.
I would need which procedure is more convenient to mark the plants, formulations, etc. I do not know if there are other webs providing this kind of materials since they seems to be expensive.
Any advice would be wellcome.
José Manuel Moreno Rojas, PhD
Head of the Department of Food Science and Health IFAPA Centre "Alameda del Obispo"
Avda. Menéndez Pidal, s/n. 14071 Córdoba, Spain.
tel.: +34 671532758 (632758); fax: +34957016043
email: [log in to unmask]
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