Determinación de la fijación biológica de N2 usando la técnica de abundancia natural del N15 en tres ecotipos de cacahuate forrajero

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 n2. 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.