Abstract

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 the¹⁵N 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.

Abbreviation

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