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The Use of Nitrogen‐15‐Depleted Ammonium Sulfate for Estimating Nitrogen Fixation by Leguminous Trees 1
Author(s) -
Kessel Christopher,
Nakao Patty
Publication year - 1986
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1986.00021962007800030034x
Subject(s) - leucaena leucocephala , leucaena , shoot , nitrogen fixation , ammonium , nitrogen , botany , biology , horticulture , chemistry , organic chemistry
The feasibility of using 15 N‐depleted (NH 4 ) 2 SO 4 for assessing biological N 2 fixation of leguminous trees was investigated. A slowgrowing species, lebbeck [ Albizia lebbeck (L.) Benth], and a fastgrowing species, leucaena [ Leucaena leucocephala (Lam.) de Wit] were inoculated with appropriate Rhizobium strains and grown under four different levels of N. Each week, 0, 5, 12.5, or 25 mg of 15 N depleted (NH 4 ) 2 SO 4 was applied to the upper chamber of the Leonard assembly. After 10 and 18 weeks growth for leucaena and lebbeck respectively, plants were separated into shoots, roots, and nodules for analysis. The atom% 15 N in shoots and roots was linearly correlated to the amount of applied 15 N‐depleted (NH 4 ) 2 SO 4 . Significant differences in atom% 15 N and percentage N derived from N 2 fixation were measured in lebbeck and leucaena when, respectively, more than 8.3 and 2.9% of the total N was derived from (NH 4 ) 2 SO 4 . Nodules derived a larger portion of their total N from N 2 fixation than did the roots or shoots, indicating that most of the N present in the nodules was derived from N 2 fixation. Nodules of both species at the no N treatment showed slightly higher atom% 15 N values than the 15 N‐natural abundance level of atmospheric N 2 .