.ancaster
arming,
Potassium Critical Component In Maintaining Healthy Vines
ANDY ANDREWS
Editor
LANCASTER (Lancaster
Co.) You say your grapes
don’t look healthy? Harvest
may be down?
The answer could be a sim
ple lack of potassium in the
vine’s diet, noted several
grape-growing specialists.
According to Dr. Tim Mar
tinson, entomologist with the
Finger Lakes Grape Program,
and Hans Walter-Peterson,
Cornell University Fredonia
Vineyard Lab, vines are a
major “sink” for potassium.
Potassium hunger signs can
make themselves seen readily
in the plant.
Both spoke in mid-Novem
ber this year at the Pennsylva
nia Association of Winegrow
ers (PAW) annual meeting at
the Farm and Home Center in
Lancaster. They spoke to
about 70 PAW members and
agri-industry representatives.
According to Martinson,
waiting to see signs for potas
sium deficiency may not the
appropriate time, since the
damage may already be done.
Cornell focuses on maintain
ing potassium levels
at optimum levels as
the most critical
component for fruit
set and yield
Growers who ob
serve symptoms, in
cluding a scorched
look on the leaf mar
gin, marginal yel
lowing, and inter
veinal scorching
could be seeing signs
of potassium defi
ciency.
However, accord
ing to Walter-Peter
son, a balance of
proper soil pH and
critical nutrients
such as nitrogen
could also improve
plant vitality and
fruit set.
Cornell bases its
nutrient recommen
dation programs on
potassium. They
look at the standard
components of a nu
trient program for
grape crops, starting
with nitrogen (N),
potassium (K),
boron (B), calcium
(Ca), magnesium
(Mg), zinc, and
other elements.
A magnesium de
ficiency could show
up as yellowing at
the edges of leaves
or brownshots at
leaf edge.
Iron deficiency,
usually manifest in
standing water prob
lems, includes yel
lowing of the leaves
and shoots. Boron
deficiency could
show up as chlorosis
of the leaves. Boron
is critical because
without it, there
could be poor fruit
set.
ter 7, 2002
latun
leceml
Boron is critical for the flo
ral parts of the plant. “Boron
is inexpensive and easy to
apply and easy to monitor,”
said Martinson. “It could have
a huge difference in the type
of crop you get.”
Other problems could be
pest- or fungus-related, in
cluding European Red Mite
(yellowing or browning of
leaves), Foliar Botrytis
(browning of leaves), viral dis
eases such as tomato ringspot,
stylet oil injury from applica
tion, drought stress, basil leaf
sublethal tissue injury, herbi
cide injury, Paraquat drift,
oxidant stippling on Ives, or
other factors.
Diagnosing the problems is
difficult simply because of
other factors, such as the
vine’s inability to transport
nutrients, for reasons that
leave plant specialists mysti
fied.
Also, the critical ratio of po
tassium to magnesium and
calcium plays a huge role dur
ing the interaction of other
nutrients. The target ratio on
K-Mg-Ca should be 1.2:1:10.
That relationship “will dictate
Speakers at the PAW annual meeting included, from left, Sam Coburn, USDA
Risk Management Agency; Hans Walter-Peterson, Cornell University Fredonia
Vineyard Lab; Terry Bates, Cornell Fredonia Vineyard Lab; Jim Travis, extension
fruit pathologist, Penn State Fruit Research and Extension Center; Richard
Cronce, Science Applications International Corporation program manager; and
Tim Martinson, Cornell University Finger Lakes Grape Program.
Photo by Andy Andrews, editor
potassium use,” said Martin-
son. available in the soil also is . . f ,
.... . , . . mimic foliar or pest problems.
Growers should take regu- transferred to plant tissue.
lar soil and petiole samples to During a dry weather season, (Turn to Page E 8)
ensure that what the plant has simple drought stress could