Abstract

VALLES DE LA MORA, Braulio  and  CADISCH, Georg. Assessment of N₂ fixation by three forage peanut ecotypes using ¹⁵N natural abundance technique. Rev. mex. de cienc. pecuarias [online]. 2010, vol.1, n.2, pp.99-114. ISSN 2448-6698.

The percentage of nitrogen derived from N₂ fixation was measured by the ¹⁵N natural abundance method, in three Arachis pintoi (Ap) ecotypes: CIAT 17434, 18744 and 18748, using an improved Bradyrhizobium strain CIAT 3101 (BS), and a mixing of native strains (NS). As reference plants, a non-nodulating Arachis hypogaea, Brachiaria arrecta, B. brizantha and Cynodon nlemfuensis were used. The experiment was set up under greenhouse conditions, and five harvests were done. Dry matter yield was highest in Ap ecotypes and BS (98.3 ± 10.0 g pot^-1), vs plants with NS (19.9 ± 1.4 g pot^-1). Values of δ (delta) ¹⁵N in the ecotypes 17434, 18744 and 18748 were, 8.4, 5.7, 7.7 ‰, and 1.2, 1.0 and 3.5 ‰ for NS and BS, revealing for the later group more N₂ dependence to grow. All reference plants showed positive effects of the BS on the percentage of N₂ fixed: 92.7 ± 1.8 vs 6.5 ± 7.6 with ecotypes inoculated with NS. It was concluded that the N₂ fixed was highly dependent of the Rhizobium strain, and Bradyrhizobium CIAT 3101 strain was more efficient to fix N_2. The Arachis pintoi ecotypes CIAT 17434 and 18744 showed the highest N₂ fixing values. A. hypogaea highlighted as reference plant considering its growth pattern similar to A. pintoi.

Keywords : Arachis pintoi; Reference plants; Bradyrhizobium strain; ¹⁵N natural abundance method.

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