International Journal of Manures and Fertilizers

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.

Accepted 12 January, 2021

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 (% Ndfa), 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.