ABSTRACT
Evaluation of soybean (Glycine max L.) genotypes for iron (Fe) deficiency can be influenced by zinc (Zn) deficiency. Post-harvest analysis for seed-Zn concentration [Zn] is one way to assess the likelihood that Zn deficiency interfered with genotype assessment. A greenhouse study was conducted on a calcareous soil low in available Zn to determine the influence of ZnSO4 (0, 1, 2, 4, and 8 mg Zn kg−1) on growth and seed [Zn] of three soybean genotypes differing in seed size (BS-8920H—large; MK1009HP—intermediate; and EX9228N—small). Maximum seed yields were obtained with 2 mg ZnSO4-Zn kg−1 for all three genotypes. Severity of Zn-deficiency symptoms in the absence of Zn fertilizer was less pronounced in BS-8920H than in MK1009HP and EX9228N. The relative response to Zn fertilizer was also least with BS-8920H, the large-seeded genotype. However, critical seed [Zn] values were similar for the three genotypes. Seed [Zn] of 31 to 33 mg Zn kg−1 or greater indicated that seed yield was not affected by Zn deficiency. This adequacy range for seed [Zn] was markedly lower than a reportedly critical seed [Zn] value for soybean of 43 mg Zn kg−1. Seed [Zn] was determined in 27 soybean genotypes from two yield trials conducted on calcareous soils with 0.60 and 0.45 mg DTPA-Zn kg−1, respectively. Seed [Zn] data indicated that Zn deficiency had possibly affected seed yields of some genotypes at the lower soil-Zn site.
Notes
a Number of days from emergence until 75% of the final number of pods were mature
a Numbers in parentheses are standard errors for the mean seed [Zn] values. Data were recalculated on a dry-weight basis