Abstract:
Poinsettia (
Euphorbia pulcherrima
cv. 'Premium Red') as an ornamental pot plant is
widely grown in peat-based substrates with high pho
sphorus (P) fertilization. The aim of
the current study was to evaluate the P demand of p
oinsettia according to its P depletion
ability during the growth stages by using a mechani
stic simulation model. For this
purpose, rooted poinsettia cuttings were grown in t
he medium with 80: 20 (V:V %)
peat+mineral component (generally called as clay) a
nd treated with different P levels of
zero, 10, 35, 100, and 170 mg P [L substrate]
-1
. The yield and quality performance of the
plants were evaluated thoroughly. Also, depletion o
f P around the root surface and the
effect of buffering power on the depletion profile
were assessed by means of mechanistic
simulation model. The results showed that, in peat-
based substrates, P was transported to
the root surface mainly by mass-flow. The simulatio
n approach also revealed that the well
supplied plants cultivated in the peat-substrates n
eeded a higher concentration gradient
(30-50 μM) to drive the necessary flux and that the
amount of plant available P (
C
s
) was
limiting at later growth stages. The optimum yield
and quality of poinsettia was obtained
at the P application rate of 35 mg L
-1
substrate, with
C
s
of 11-12 and 15-16 mg [L
substrate]
-1
at planting and 53 days after planting. It was conc
luded that, to ensure a
sufficiently high concentration gradient, P had to
be supplemented by frequent fertigation
at later growth stages, but not at the early growin
g stage.
Keywords:
Concentration gradient, Fertigation, Modeling, Upt
ake.