Mobilization of leaf N in soybean genotypes with varying durations of seedfill

D. B. Egli, J. C. Swank, T. W. Pfeiffer

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7 Scopus citations


Soybean (Glycine max (L.) Merrill) genotypes differing in seedfill duration were grown in the field for two years to characterize the mobilization of leaf N during fruiting. The duration of seedfill was estimated as the time from growth stage R5 (beginning seedfill) to R7 (physiological maturity) and as the effective filling period (EFP) calculated from seed growth rate and final seed mass estimated from seeds in fruits tagged at the beginning of seedfill. Nitrogen was measured in the last fully expanded leaf on the main stem at weekly intervals during seed development. There were significant genotypic differences in both estimates of the duration of seedfill in both years. The length of the R5 to R7 period ranged from 18 to 48 days in 1983 (7 genotypes) and from 30 to 52 days in 1984 (8 genotypes). The range in EFP across all genotypes was 17-40 days in 1983 and 16-35 days in 1984. Leaf N concentration declined steadily during seedfilling, reaching a minimum level of approximately 2.0-2.5% at R7. The leaf N concentration declined more rapidly in genotypes with shorter durations of seedfill; however, when leaf N concentration was expressed as a function of the stage of seed development the changes in leaf N were constant across genotypes. The data indicate that the long-filling-period characteristics was associated with a slower rate of leaf senescence rather than with a later initiation of senescence.

Original languageEnglish
Pages (from-to)251-258
Number of pages8
JournalField Crops Research
Issue number3-4
StatePublished - Feb 1987

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science


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