Comparison of ¹⁵n natural abundance and difference methods for estimating n₂fixation of soybeans grown in a tropical soil

Creator

Ireneo J. Manguiat, University of the Philippines Los Banos
Danilo M. Mendoza, University of the Philippines Los Banos
Arnel M. Perez, University of the Philippines Los Banos
Tadakatsu Yoneyama, University of the Philippines Los Banos

Abstract

A study was carried out to compare the difference or N-yield method with the 15N natural abundance method for the estimation of the fractional contribution of biological N2fixation in the different plant parts of nodulating and non-nodulating isolines of soybeans. The results indicated that the δ15N values of most plant parts of soybeans were significantly lower (p <0.05) in the nodulating than in the non-nodulating isoline. However, in the case of the root+nodule component, the δ15N value was higher in the nodulating than in the non-nodulating isoline possibly due to isotopic discrimination of 15N over 14N which may have occurred in the nodules. Inoculation of soybeans with the Bradyrhizobium japonicum strain CB 1809 increased significantly (p <0.05) the δ15N value of the root+nodule component implying that the effectiveness of the soybean-rhizobium symbiosis had increased by inoculation. Percentage of plant N derived from atmospheric N2fixation (%Ndfa) estimated by the 15N natural abundance method was highly correlated (r =0.762, p <0.01) with that by the difference or N-yield method and the differences between the two methods were not statistically significant. The agreement between the two methods was closer at maturity than at the early reproductive stage. The %Ndfa obtained by the difference method ranged from 48.4 to 92.6% whereas the %Ndfa obtained by the 15N natural abundance method ranged from 43.2 to 92.4% in the different plant parts. Based on the 15N natural abundance method, approximately 15% of the N in pod, shoot, grain, and shell was derived from the soil but in the case of stover, this fraction was about 55%. © Taylor & Francis Group, LLC.

Source or Periodical Title

Soil Science and Plant Nutrition

ISSN

380768

Page

593-604

Document Type

Article

Subject

15 N natural abundance, N fixation 2, Soybean, Tropical soil

Recommended Citation

Manguiat, Ireneo J.; Mendoza, Danilo M.; Perez, Arnel M.; and Yoneyama, Tadakatsu, "Comparison of ¹⁵n natural abundance and difference methods for estimating n₂fixation of soybeans grown in a tropical soil" (2021). Journal Article. 3723.
https://www.ukdr.uplb.edu.ph/journal-articles/3723