Different 15N-based shoot-labelling protocols have been utilised to quantify the below-ground transfer of N between pasture or crop species. The most straight forward and effective 15N-labelling technique appears to be shoot labelling via leaflets or petioles. This paper reports a time-course study following 15N-shoot labelling of pasture legumes to ascertain whether a pulse-feeding of 15N labelled urea to the leaf resulted in induced exudation of highly 15N enriched compounds from the roots into the surrounding soil. Such an occurrence could confound interpretation of 15N data used to measure transfer of N between legume and non legume species. Small quantities of highly enriched 15N (99.8 atom% 15N) urea were fed to leaves of subterranean clover (Trifolium subteraneum; 0.22ml/plant of 1% urea solution) and lucerne (Medicago sativa; 0.45ml of 1% urea solution) over a period of 3 days. On days 1, 2, 4, 8, 16 and 32 after labelling, the plants were harvested and the 15N enrichment of shoots, roots and soil was determined. Soil analyses showed that the 15N enrichment of soil N was significantly higher in the lucerne treatment (12.3 '; parts per thousand 15N relative to the 15N content of atmospheric N2, 0.3663 atom% 15N) than subclover (11.3 ') (P<0.05), and both levels were significantly higher than, but very close to, the background level in the soil (10.7 '). The results could be explained if <10% of the lucerne root N or 12-27% of the subclover roots remained unrecovered in the soil following the sieving process. It was concluded that pulse-feeding of high concentrations of 15N labelled urea in the leaf did not induce substantial exudation of highly 15N enriched compounds from the roots into the surrounding soil.
|Title of host publication||16th AAC|
|Subtitle of host publication||Capturing opportunities and overcoming obstacles in Australian agronomy|
|Place of Publication||Australia|
|Publisher||The Regional Institute|
|Number of pages||4|
|Publication status||Published - 2012|
|Event||16th Australian Agronomy Conference - University of New England, Armidale, Australia|
Duration: 14 Oct 2012 → 18 Oct 2012
Conference number: 16th
http://agronomyaustraliaproceedings.org/index.php/2012-conf-proc-homepage (Conference proceedings 2012 homepage)
|Conference||16th Australian Agronomy Conference|
|Abbreviated title||Capturing Opportunities and Overcoming Obstacles in Australian Agronomy|
|Period||14/10/12 → 18/10/12|
Gardner, M., Peoples, M., Condon, J., Li, G., Conyers, M., & Dear, B. (2012). Evaluating the importance of a potential source of error when applying shoot 15N labelling techniques to legumes to quantify the below-ground transfer of nitrogen to other species. In I. Yunusa (Ed.), 16th AAC: Capturing opportunities and overcoming obstacles in Australian agronomy (pp. 1-4). The Regional Institute.