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N2‐Fixation in Field Beans Quantified by 15N Isotope Dilution. I. Effect of Strains of Rhizobium phaseoli 1
Author(s) -
Rennie R. J.,
Kemp G. A.
Publication year - 1983
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/agronj1983.00021962007500040015x
Subject(s) - nitrogen fixation , phaseolus , cultivar , biology , microbial inoculant , rhizobium , horticulture , inoculation , agronomy , bacteria , genetics
Most soils sown to field beans ( Phaseolus vulgaris L.) contain indigenous Rhizobium phaseoli ; thus, few studies have evaluated the effect of different strains of R. phaseoli on N 2 fixation and yield of bean cultivars. Since western Canadian soils contain no indigenous R phaseoli , strains were screened for their ability to fix N 2 in two bean cultivars, Aurora and Kentwood. Initially, the N 2 ‐fixing ability of 19 strains of R phaseoli was determined in vitro. The best were then compared with 16 superior Centro Internacional de Agricultura Tropical strains in a 2‐ year International Bean Inoculation Trial in the field in association with the same two small white bean cultivars. 15 N isotope dilution at levels of 15 N natural abundance in the field showed the % Ndfa (percentage plant N derived from the atmosphere) averaged 50% for Aurora but only 32% for Kentwood over all 16 strains. The % Ndfa did not vary between the two experimental years, but due to different levels of soil N, yield and actual amounts of N 2 fixed did vary. Aurora averaged 70 kg N ha −1 and Kentwood 37 kg N ha −1 fixed. Some strains fixed more than 100 kg N ha −1 in Aurora, resulting in dry matter and N yields in excess of uninoculated treatments receiving 40 or 100 kg fertilizer N ha −1 . Strains of R phaseoli from high temperature soils of Latin America fixed high amounts of N 2 in association with temperate bean cultivars under conditions of low temperature growth (10 to 23°C). CIAT strains 632,899, 640, and 904 and commercial Nitragin were highly efficient N 2 fixers with Aurora as were CIAT strains 952, 161, 166, and commercial Nitragin with Kentwood. Thus, R. phuseoli are as efficient as other rhizobia in supplying fixed N 2 to their host plant and, in N 2 ‐fixing mode, certain bean cultivars can meet their genetic yield potential in the field without the addition of fertilizer N.