Determinate soybean [Glycine max (L.) Merr.] has been
characterized by few detailed nitrogen and phosphorous partitioning
studies. Knowledge of the variation in N and P concentrations with
plant part, nodal position, and plant age is needed for a better
understanding of plant functions. In this field study, 'Bragg'
soybean was grown on an Aquic Paleudult soil (series Goldsboro loamy
sand). Plants were sampled at 10 to 14 day intervals beginning 44
days after planting (July 7) until harvest. Maximum observed N
concentrations were 3.1, 2.8, 5.8, and 5.4% for stem internodes,
petioles (+branches), leaf blades, and pods, respectively. Maximum
observed P concentrations were 0.34, 0.48, 0.78, and 0.52 for the
same respective plant parts. Nodal and temporal mean N and P
concentrations varied considerably with plant age and nodal position
in all plant parts. These data show that mean N and
concentrations in all four plant parts can vary several fold,
depending upon plant age and nodal position for the sample. This
suggests caution should be exercised in tissue sampling and
interpretation of plant analysis. Concentrations of N and P
generally decreased with time for stem internode, petioles
(+branches), and leaf blades, but increased with time for pods.
Except for N concentration in stem internodes, which increases with
internode number, the N and P concentrations remain nearly constant
throughout the growing season. The relationships provide insight
for developing accurate plant models depicting N and P
concentrations and translocations over time and among plant parts
in determinate soybean
