In-Furrow Inoculation and Selection for Higher Motility Enhances the Efficacy of Bradyrhizobium japonicum Nodulation

LÓPEZ-GARCÍA SL; PERTICARI, A; PICCINETI, C; VENTIMIGLIA, L; ARIAS, N; DE BATTISTA, JJ; ALTHABEGOITI, MJ; MONGIARDINI, EJ; PÉREZ-GIMÉNEZ, J; QUELAS, JI; LODEIRO, AR

AGRONOMY JOURNAL

American Society of Agronomy

Lugar: Madison; Año: 2008 vol. 101 p. 357 - 363

0002-1962

 ABSTRACT The issue of competition for nodulation has received much attention in studies on soybean [Glycine max (L.) Merr.] crops becausenative soil rhizobia oft en preclude nodulation of inoculated high-quality strains. In this work, soil placement and enhancedmotility of Bradyrhizobium japonicum were investigated as strategies to improve the competitiveness of soybean inoculantsapplied in the presence of large populations of native (or indigenous) soybean-nodulating rhizobia. The first strategy might allowfor the enhanced distribution of inoculant rhizobia in the surface soil, compared with inoculant that is directly applied to soybeanseed, while the second strategy is expected to enhance root colonization. The effects of soil placement and enhanced bacterialmotility on percentage nodule occupation, grain yield, and grain N contents were examined during the 2004–2005 soybeanseason at three locations in Argentina, comprising soils classifi ed as entic hapludol, argillic pelludert, and typical argiudol.Th e experimental design was a randomized complete block design, and main eff ects and interactions were also analyzed with afactorial design. Strain LP 3008, previously selected for increased motility, was more eff ective than the commonly inoculatedstrain E 109. While E 109 occupied, on average, 13.2% of nodules with seed inoculation, LP 3008 occupied 28.2%. In comparison,in-furrow inoculation yielded 24.2 and 37.2% average nodule occupancies for E 109 and LP 3008, respectively. However,these gains in nodulation effi cacy lead to a modest, nonsignifi cant yield increase, and grain N content was unaffected.