Response of field-grown bean (Phaseolus vulgaris L.) to Rhizobium inoculation and nitrogen fertilization in two Cerrados soils |
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Authors: | M A T Vargas Ieda C Mendes Mariangela Hungria |
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Institution: | (1) BIOAGRI-Laboratorios, Cx. Postal 08.287, 73301-970, Planaltina, DF, Brazil e-mail: mtvargas@uol.com.br, BR;(2) EMBRAPA-Cerrados, Cx. Postal 08.223, 73301-970, Planaltina, DF, Brazil e-mail: mendesi@cpac.embrapa.br, BR;(3) EMBRAPA-Soja, Cx. Postal. 231, 86001-970, Londrina, PR, Brazil e-mail: hungria@cnpso.embrapa.br, BR |
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Abstract: | Most soils sown with field beans (Phaseolus vulgaris L.) contain indigenous rhizobia which might interfere with the establishment of inoculated strains. As a consequence, the
benefits of bean inoculation are usually questioned, and the use of N fertilizer is gradually becoming a common practice.
The present study had the objective of evaluating the effectiveness of inoculation and N fertilization in field soil with
(site 1) and without (site 2) a previous bean-cropping history. At site 1, which had a rhizobial population of 7×102 cells g–1 soil, inoculation had no effect on nodulation or yield, whereas at site 2 (<10 cells g–1 soil) inoculation increased nodulation, nodule occupancy by the inoculated strain and grain yield. N fertilizer decreased
nodulation at both sites, but increased grain yield at site 1 but not at site 2, indicating that the response to inoculation
and N fertilization depends on the cropping history. When bean was cultivated for the first time, indigenous populations of
rhizobia were low and high yields were accomplished solely with seed inoculation, with no further response to N fertilizer.
In contrast, previous cultivation of bean increases soil rhizobia, preventing nodule formation by inoculated strains, and
N fertilizer may be necessary for maximum yields. A significant interaction effect between N fertilizer and inoculation was
detected for serogroup distribution only at site 2, with N fertilizer decreasing nodule occupancy by the inoculated strain
and increasing the occurrence of indigenous strains. Consequently, although no benefits were obtained by the combination of
inoculation and N fertilizer, this practice may be feasible with the selection of appropriate N-tolerant strains from the
indigenous rhizobial population.
Received: 26 May 1999 |
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Keywords: | Rhizobial competitiveness Inoculation Dinitrogen fixation Nodulation Phaseolus vulgaris |
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