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Agronomy Journal Abstract -

Early Maturing Soybean Nodulation and Performance with Selected Bradyrhizobium japonicum Strains


This article in AJ

  1. Vol. 84 No. 3, p. 449-458
    Received: Apr 3, 1991

    * Corresponding author(s):
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  1. J. V. Wiersma  and
  2. J. H. Orf
  1. U niv. of Mennesota, Northwest Exp. Stn., Crookston, MN 56716
    D ep. of Agronomy and Plant Genetics, Univ. of Minnesota, St. Paul, MN 55108



Seed inoculation with Bradyrhizobium japonicum (Kirchner) Jordan is a common production practice for most soybean [Glycine max (L.) Merr.] growers in northwest Minnesota; however, plants seldom are well-nodulated. Our objectives were to (i) identify strains of B. japonicum that enhance nodulation and agronomic performance of Maturity Group 00 soybean cultivars grown on soils having a range of NO3−N concentrations; and (ii) assess cultivar-by-strain specificity. Six cultivars and five B. japonicum strains were evaluated in six field trials during 1988 to 1990. Nonfertilized (1988–1990) and N fertilized (1990), uninoculated controls were included. Soil NO3−N concentrations (0-60 cm) at planting ranged from 52 to 175 kg N ha−1. Residual soil NO3−N values were low and substantially less than initial values in only three environments. Nonetheless, significant increases in response to inoculation were observed for grain yield, seed weight, and grain N concentration in 17 of 18 comparisons. In 1990 trials, fertilizer N (168 kg ha−1) increased seed weight and grain N concentration significantly more than inoculation. Nodule number (r = −0.89; significant at P = 0.05) and dry weight (r = −0.97; significant at P = 0.01) were inversely correlated with soil NO3−N (0-60 cm) at planting. Estimated (difference method) N2 fixation (r = −0.93; significant at P = 0.05) and relative increases in grain yield (r = −0.93; significant at P = 0.05), seed weight (r = −0.97; significant at P = 0.01) and grain N concentration (r = −0.95; significant at P = 0.05) were inversely correlated with soil NO3−N (0-60 cm) at harvest. Although similar responses were observed among all cultivars, B. japonicum strains 61A152 and 61A212 generally outperformed other strains. Cultivar-by-strain specificity could not be detected. Soybean producers in northwest Minnesota should realize significant increases (10% or greater) in grain yield in response to inoculation of rhizobia-free soils, provided initial soil NO3−N concentrations (0-60 cm) are less than 110 kg N ha−1 and N mineralization during the growing season is minimal.

Published as Minnesota Agric. Exp. Stn. Scientific J. Paper no. 18 886. Research supported in part by the Minnesota Soybean Research and Promotion Council, and the Agricultural Research and Utilization Institute of the Greater Minnesota Corporation, Minneapolis, MN 55402.

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