HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Magarian, D. M. Articles by Blumenthal, J. M. Search for Related Content PubMed Articles by Magarian, D. M. Articles by Blumenthal, J. M. Agricola Articles by Magarian, D. M. Articles by Blumenthal, J. M.

Bromide as a Tracer for Nitrate-N Uptake in Alfalfa Herbage

1319 West Oakes Dr., St. Cloud, MN 56303
USDA-ARS U.S. Dairy Forage Res. Ctr. (Minnesota Cluster) and Dep. of Soil, Water, and Climate, 439 Borlaug Hall, Univ. of Minnesota, St. Paul, MN 55108-6028
USDA-ARS and Dep. of Agronomy and Plant Genetics, 411 Borlaug Hall, Univ. of Minnesota, St. Paul, MN 55108
Panhandle Res. & Ext. Ctr., Univ. of Nebraska, 4502 Avenue I, Scottsbluff, NE 69361-4939

^* Corresponding author (russelle{at}soils.umn.edu).

The ¹⁵N isotope is a reliable way to measure nitrate-N (NO^-₃-N) uptake in N₂-fixing legumes, but is too expensive for plant breeding programs. Our goal is to develop an affordable method of selecting alfalfa (Medicago sativa L.) for NO^-₃-N uptake under field conditions. In this research, we tested whether the anion bromide (Br^-), which is used to trace NO^-₃-N movement in soils and is inexpensive to analyze, reflects NO^-₃-N uptake in alfalfa. ‘Webfoot’ (1994 and 1995), ‘Agate’ (1995), and ‘Ineffective Agate’ (1995) alfalfa were established in pots in the greenhouse. After removing herbage, daily additions of solutions containing Br^- and ¹⁵N-labeled NO^-₃-N were made to the pots. Uptake of Br^- and N derived from NO^-₃-N was determined in herbage regrowth sampled after 15, 25, and 35 d and the molar ratio of NO^-₃-N-derived N:Br^- was calculated. In both years, when a constant molar ratio in solution was provided at variable tracer concentrations, NO^-₃-N uptake and Br^- uptake both increased with increasing applied tracer concentration, but ratios in herbage were not constant for treatment, germplasm, or days of regrowth. These results imply that selection must be carried out under well-controlled tracer supply and crop management. At a constantNO^-₃-N concentration, but increasing solution Br^- concentration,NO^-₃-N uptake remained constant and Br^- uptake increased. Molar ratios of NO^-₃-N-derived N:Br^- in herbage directly reflected applied solution ratios in a soil-sand mixture (1994), but were less responsive in sand (1995) above molar ratios of 100:1 in solution. Individual plant analysis showed close agreement in Br^- and NO^-₃-N uptake among plants in all germplasms across a wide range of tracer supply, and indicated that selection for NO^-₃-N uptake using Br^- uptake would result in minimal error. We conclude that Br^- is a promising alternative tracer for use in selecting alfalfa for NO^-₃-N uptake.

Received for publication February 4, 1998.

This article has been cited by other articles:

				J. F. S. Lamb, M. P. Russelle, and D. M. Fenton Field-based Selection Method Creates Alfalfa Populations That Differ in Nitrate Nitrogen Uptake Crop Sci., March 19, 2008; 48(2): 450 - 457. [Abstract] [Full Text] [PDF]