April 2019 - 7

Micronutrients for stress reduction
in potatoes - and for growers
Micronutrients tend to fall by the
wayside, but their importance should not
be overlooked. A comprehensive nutrition
plan is paramount. To find out more about
what this means
for growers, we
talked to Jimmy
Ridgway, Potato
Crop Manager
for Yara North
America.
Jimmy Ridgway
In comparison
with nitrogen
and potassium,
potatoes don't
need a lot of
zinc, copper,
manganese, boron or magnesium, but that
doesn't mean they don't perform vital roles
in potato growth.
Why micronutrients?
Micronutrients such as zinc, copper
and manganese are vital for a plant's
autoimmune system. This means that
keeping zinc, copper and manganese at
optimal levels in the plant can assist in
disease prevention and management.
As part of a comprehensive plan with
topical and curative fungicides when
pressure is higher, proper levels of these
micronutrients can make a big difference,
much like proper human health. " We
might need medicine when we are sick,
but there is less of a chance to become sick
when we take our vitamins and have a
good diet, " Ridgway said. One of the ways
that micronutrients function in disease
tolerance and resistance is that the level of
the nutrients that is required for the potato
plant is actually often toxic to the microbe.
Manganese is a well-documented example
of this particular function. The level of
manganese a potato plant needs is roughly
100 times what Streptomyces scabies (the
organism that causes common scab) needs.
So when soil is fertilized with the right level
of manganese, the toxicity is overwhelming
to the microbe and can reduce the incidence
of scab. Calcium, boron and copper work
to strengthen cell walls, which make it
more difficult for microbes to penetrate and
therefore damage or destroy cells. " The
calcium in cell walls acts like glue to hold
them together, so an opportunistic bacterium
or fungus can't invade as easily, " Ridgway
said. Other secondary and micronutrients
have specific roles as well. Magnesium and
boron, for example, facilitate the movement
of carbohydrates from leaves to tubers; if
their levels aren't correct, bulking of tubers
can be slowed or stop altogether. Boron is
also important for cell division as well as
promoting cell strength.
What are the best practices for
testing micronutrient levels?
Ridgway recommends growers take
petiole samples weekly from about
tuber initiation through late bulking.
" Progressive growers are also taking soil
samples during the season in addition to
pre-season samples, " he said. The problem
with only taking soil samples though, is
that the nutrients in the soil may not be
available due to pH, chemical tie-up, or
antagonism with each other. Calcium, for
example, which needs to be in a soluble
form for the potato plants to take it up, is
often bound up as highly insoluble gypsum
or calcium carbonate. " There isn't really
a way to over-apply soluble calcium, for
example, " Ridgway said, " and I've never
heard of a calcium toxicity problem. "
What rules of thumb does
Ridgway recommend?
1. Crop nutrition is a season-long
marathon. Demands change based on
the stage of growth, so nutrition needs
to be monitored and fertilization
needs to be adjusted as needed from
planting to tuber maturity.
2. Testing helps. Knowing the soil in the
local area goes a long way towards
getting the best results - and not
wasting applications. Use tissue
samples to identify trends in the plant's
nutrition status, not just as verification
tool for a suspected deficiency. Crop
nutrition programs that work in one
region may not necessarily be the
best options for another.
3. Understand product formulation.
" Growers often believe that if they
are using fungicides that contain zinc
Yara is committed to helping
farmers grow their toppotato
in terms of yield and quality,
having an impact on their
profitability. Crop knowledge,
application competenceincluding
technology tools
and services - and the most
comprehensive crop nutrition
portfolio on the market make
up the core of Yara's Crop
Nutrition Solution for potatoes.
To learn more visit
https://www.yara.us/cropnutrition/potato/.
For
more information, growers can view Yara's webinar on micronutrients at
http://bit.ly/YaraSpudmanWebinar2019 or visit
https://www.yara.us/crop-nutrition/fertilizer-products/yaravita/procote-learn-more/
ADVERTISEMENT | © 2019 Yara
and manganese that those products
are delivering zinc and manganese
nutrition; however, the formulation
of the fungicides is designed to keep
the zinc and manganese on the leaf
surface to combat the disease. Foliar
fertilizers, however, are designed to
get into the plant and improve its
nutrition status, " Ridgway said.
4. Follow up with analysis. Proactively
sample petioles to watch trends in
nutrient levels. It is possible to have
nutrient deficiency without any
visible symptoms. This could mean a
loss of yield down the line.
Finally, growers should adjust their plans
based on the market the tubers will enter;
nutritional requirements change based on if
potatoes are used for the fresh market, for
processing or for seed. " If a grower goes
into the season with a solid plan based on
these things, the grower - and plants -
will feel less stress. "
https://www.yara.us/crop http://www.bit.ly/YaraSpudmanWebinar2019 https://www.yara.us/crop-nutrition/fertilizer-products/yaravita/procote-learn-more/
April 2019

Table of Contents for the Digital Edition of April 2019
