African Journal of Biotechnology Vol. 5 (12), pp. 1210-1214, 16 June 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Appraisal of the ¹⁵N-isotope dilution and ¹⁵N natural abundance methods for quantifying nitrogen fixation by flood-tolerant green manure legumes

Eklou A. Somado^1* and Ronald F. Kuehne²

¹Africa Rice Center (WARDA), 01 Bp 2031 Cotonou, Benin Republic.

²University of Goettingen, Department of Crop Science, Tropical Agronomy Division, Grisebachdtr. 6, D-37077 Goettingen Germany.

*Corresponding author. E-mail: somado@hotmail.com. Phone: +229.21.35.01.88.

Abbreviations: BNF, Biological N fixation; %Ndfa, percent of N derived from the atmosphere; ¹⁵NE, ¹⁵N enriched isotope dilution technique; and ¹⁵NA, ¹⁵N natural abundance.

Accepted 12 May, 2006

Quantification of biological nitrogen fixation (BNF) is fundamental to identifying potential green manure legumes for their enhanced nitrogen contribution to sustained crop production. A screenhouse experiment compared BNF by Aeschynomene afraspera L. as affected by phosphorus, using the ¹⁵N-isotope dilution and the ¹⁵N methods. Rice (Oryza sativa L.) was grown as a non-fixing plant. Phosphorus significantly increased the percent N derived from the atmosphere (% N_dfa), whereby the ¹⁵N method tended to overestimate BNF contribution on average by 20% compared to the ¹⁵N dilution. Data confirmed rice as a non-fixing plant for estimation of BNF by flood-tolerant legumes.

Key words: Aeschynomene afraspera, Biological nitrogen fixation, ¹⁵N-isotope dilution, ¹⁵N natural abundance.