Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 1997
Publication Date: N/A
Technical Abstract: Deeply rooted legumes, like alfalfa (Medicago sativa L.), provide the opportunity to remediate contaminated sites by removing leached nitrate from the subsoil. The objectives of this study were to evaluate the ability of alfalfa germplasms differing in root system architecture and symbiotic effectiveness to remove nitrate from subsoil and to assess the use of bromide as an indicator for nitrate absorption in alfalfa. At Becker, MN, on a sandy, mixed, Udorothentic Haploboroll, 20 mM nitrate labeled with 15N and Br was supplied to eight alfalfa germplasms through a subsoil irrigation system installed at the 50 cm depth. During the summer regrowth of the first production year, Ineffective Agate, an ineffectively nodulated, non-N2-fixing germplasm, removed 41% more subsoil NO3 than the N2-fixing germplasms. We observed a strong correlation between 15N and Br uptake in the herbage [mg excess Br in herbage = 25.2 X mg excess 15N in herbage, P < 0.0001, R2 = 0.97]. These results indicate that Br could be used as a reliable and cost effective tracer for NO3-N uptake.