'Universidad Autonoma de Yucatan Facultad de Economia'
Abstract
The nitrogen derived from N2 fixation was measured by the 15N isotope dilution method, in three Arachis pintoi (Ap) ecotypes: CIAT 17434, 18744 and 18748, using a Bradyrhizobium strain (BS) CIAT 3101, and native strains (NS) from Veracruz, Mexico, on greenhouse conditions. The reference plants were: a non-nodulating Arachis hypogaea, Brachiaria arrecta, Brachiaria brizantha and Cynodon nlemfuensis. Plant material received a 15N-enriched solution at 5 atom % 15N. Five harvests were done, where dry matter yield was highest (Pï‚£0.001) in Ap ecotypes+BS (53.9 ±5.2 g pot-1), vs Ap ecotypes+NS (19.7 ± 0.7 g pot-1). N yield (mg pot-1) of Ap ecotypes+NS was: 439 ± 19.6 mg pot-1 vs 1538 ± 117.0 mg pot-1 (Pï‚£0.001) from Ap ecotypes+BS. Values of atom% 15N in excess of legume shoots were lower (0.027 ± 0.01) with BS, compared to NS group (0.052 ± 0.002). The proportion of N2 fixed was greater than 0.5 in the three Ap ecotypes+ BS, using grasses as reference plant. Arachis pintoi ecotypes CIAT 17434 and CIAT 18744 fixed more N than ecotype CIAT 18748; and the improved Bradyrhizobium strain CIAT 3101 was more efficient to fix N2 than the native strains