Table
2
.
The
effect
of
starter
phosphorus
and
nitrogen
on
yield
and
incidence
of
powdery
mildew
of
tomato
Means
followed
by
different
letters
are
significantly
different
according
to
Duncuns
Multiple
range
test
at
P
=
0
.
01
.
The
results
obtained
show
that
plant
vigor
generally
increases
with
fertilizers
.
The
vegetative
growth
is
mainly
affected
by
the
dose
of
phosphorus,
also
there
is
no
interaction,
between
the
phosphorus
and
the
nitrogen
.
This
finding
is
in
full
agreement
with
those
obtained
by
other
workers
.
White
(1938),
found
that
plant
height,
leaf
area
and
the
number
of
flowers
produced
increased
in
response
to
added
nitrogen
.
Both
growth
and
development
may
be
restricted
by
an
inadequate
level
of
phosphorus
applied,
particularly
at
the
high
pH
(Massey
and
Winsor,
1969)
.
Phosphorus
deficiency
also
reduced
the
number
of
flower
buds
formed
and
delayed
antithesis
(Menary
and
Staden
-
Van,
1976)
.
In
our
results,
high
levels
of
phosphorus
were
found
to
be
associated
with
more
vigorous
growth
and
higher
disease
levels
.
The
increased
vigor
was
reflected
by
the
greater
number
of
branches
and
higher
early
yields
.
The
adverse
effects
of
the
disease
on
crop
yield
were
clearly
indicated
by
the
lack
of
significant
differences
between
fertilizer
treatments
in
late
-
season
yields
.
Incidence
of
powdery
mildew
is
found
to
be
affected
by
both
phosphorus
and
nitrogen
.
At
40
P,
which
is
the
highest
phosphorus
dose,
addition
of
N
-
nitrogen
seem
to
reduce
the
disease
incidence,
suggesting
that
it
is
not
only
the
phosphorus
that
affects
the
disease
build
-
up
but
also
the
ration
of
P:N
.
Literature
cited:
Massey,
D
.
M
.
,
Windsor,
G
.
W
.
1969
.
Ann
.
Rep
.
Glasshouse
Crops
Res
.
Inst
.
1968:70
-
81
.
Menary,
R
.
C
.
,
Staden,
J
.
Y
.
1976
.
Aust
.
J
.
Pl
.
Physiol
.
3:201
-
205
.
Mohamed,
Y
.
F
.
,
Eljack,
AE
.
1994
.
T
.
G
.
C
.
Report
#44:27
-
28
.
Wheeler,
B
.
E
.
T
.
1978
.
An
introduction
to
plant
diseases
.
John
Wiley
&
Sons,
London
&
New
York
.
White,
H
.
L
.
1938
.
Ann
.
Appi
.
Biol
.
,
25:544
-
557
.
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