August 2020 - 14

CONTROLLED ENVIRONMENT AGRICULTURE
Multi-year rotation in high tunnels curbs soil pathogens
By Dean Peterson
VGN Correspondent
Tomatoes are the high revenue crop in
high tunnels but growing tomatoes after
tomatoes can build up soil pathogens and
affect soil fertility. Carefully planned crop
rotations can minimize these issues and
provide long term benefits.
" A high tunnel is the most valuable
acreage on the farm but it's a long-term
investment. Long term sustainability is an
issue, " said Cary Rivard, associate professor
and Extension specialist at Kansas State
University (KSU).
Innovation is key to planning a rotation
and diversifying crops, grafting, and
selecting cover crops to match fallow
periods are all part of the mix.
Grafting tomatoes with disease resistant
or disease tolerant rootstocks can offer
some rotational benefit when alternated
with susceptible cultivars. The goal is to
keep the disease inoculum at low levels.
Cut flowers are a rotation option that's
short season and has a unique marketing
window. " Their income is similar to
tomatoes, " Rivard said.
KSU researchers gathered data on
rotation crops not traditionally grown
in high tunnels such as watermelon,
strawberries and sweetpotato slips.
Cucurbits like watermelon are a
good option but take space and require
a pollinator. " Space is a challenge with
cucurbits, " Rivard said. Trellising can help
with smaller cucurbits like cucumbers.
Indeterminate (day-neutral) strawberries
produce all summer and into October. " We
grow them as an annual in our system, "
Rivard said.
The sweetpotato slips are grown to sell to
other growers for transplanting.
Using this information, KSU researchers
developed and evaluated a series of threeyear
rotations for tomatoes in high tunnels.
spread by air movement. " Most of these
soil-borne pathogens don't move that far in
the soil in a high tunnel, " Rivard said.
The most common way soil pathogens
are spread in a high tunnel is by
contaminated tools which - as always -
makes sanitation an issue.
Cover crops fit in a rotation during
As a 2010 doctoral graduate of North Carolina State University's Department of Plant
Pathology, Cary Rivard's research with Dr. Frank Louws helped popularize the use of
tomato grafting as a propagation method in the United States. Photo: North Carolina
State University Communications
Two rotations were alternating tomatoes
with grafted tomatoes or strawberries.
Other rotations alternated tomatoes with
shorter season crops like melons, brassicas
or sweetpotato slips preceded or followed
by a summer cover crop. In all of the
three-year rotations, a winter green or
overwintering cover crop was also used.
KSU researchers also used published,
enterprise budgets to estimate the gross
revenue per square foot of the rotation
crops in their studies.
Tomatoes topped the list at $3.66 per
square foot. A salad mix came in at $2.40
per square foot, bell peppers at $2.30, beets
at $1.92, cucumbers at $1.62, lettuce at
$1.30 and spinach at $1.09.
Strawberries came in at $1.76 per square
foot, seedless watermelon at $0.89, and
sweetpotato slips at $4.30 per square foot.
" What we're really trying to do is
document opportunity, " Rivard said.
" We're trying to give growers the data they
need to plan. We as researchers don't have a
good way to put a dollar value on the long
term benefit to the soil. "
KSU also combined its crops grown
in the three-year rotations into a six-year
rotation with tomatoes only grown in one
of the six years.
" If growers can put together a six-year
crop rotation, that will be more sustainable
in the long term, " Rivard said, with more
diversified labor needs and less pest and
disease pressure.
" Be proactive, " Rivard said. " Think about
structuring your rotation for the long term
and then tailor it to your situation. "
Planned rotations must be across entire
plant families and not just species within
a family.
There are several common vegetable
families. The Solanaceae family includes
eggplant, peppers and tomatoes. Beans and
peas are in the Fabaceae family and the
Cucurbitacae family includes vine crops
like cucumbers, cantaloupe, watermelons,
pumpkins and squash. Lettuce is in the
Asteraceae family and Brassicaeae include
crops like broccoli, cabbage, cauliflower,
collards and radish. " You want to follow
some basic principles of good rotation, "
Rivard said.
Growing several crops in a high tunnel
on a close spacing and rotating them can be
effective since soil pathogens aren't typically
fallow times of the year. " Think about cover
crops first as a partner for your cash crop, "
Rivard said. " Plan your cash crop strategy
and build your cover crop around the cash
crop. " Cover crops in high tunnels perform
similarly to cover crops grown in the field.
Growers targeting off season crops and
the early season market may have a fallow
season in the summer - after spring crops
and before planting fall greens.
Millet, sorghum - sudangrass or
buckwheat in combination with cowpea as a
legume are good options for summer cover
crops. " Have a termination plan, " Rivard
said. Sorghum-sudangrass and millet can
get really tall. " Buckwheat is good, " Rivard
said. " It has a dense canopy and has flowers
that are good for beneficials. "
Oilseed radish, oats, spring barley or
millet in combination with cowpea are
good options for a fall cover crop and will
all winterkill.
Rye, triticale, or wheat combined
with hairy vetch or Austrian winter pea
are options for a cover crop that will
overwinter in the central U.S. Austrian
winter pea is probably a better choice for
the winter legume because of hairy vetch's
growth habit and tendency to go dormant
in cold temperatures.
A mix of legumes and grasses is best for
a cover crop. " Grasses will pick up nitrogen
in the soil and store it; legumes are going
to fix nitrogen from the air, " Rivard said.
" The big factor is being proactive, "
Rivard said. " Find your market, figure
out something you can grow and sell, and
build your rotation from there. " VGN
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By Gary Pullano
Managing Editor
The global cider market size was
estimated at $4.33 billion in 2018, and
is anticipated to register an annual
growth rate of 3.1% through 2025.
Fruit growers remain intrigued by
the prospect of expanded outlets for
their products in the cider-making
market, but processes involved in
Food production
industry entering era of
automation expansion
10
14
New grower shares
struggles, successes in
starting new farm
22
Two generations of
Georgia's Dickey Farms
honored by peers
February 2020 | Volume 59 |
Issue 2
due diligence
Doing
Ground-harvested fruit,
with care, OK for cider use
Bri Ewing Valliere, clinical assistant professor, Washington State University's School of Food Science, outlines the guidelines for using ground-harvested cider apples. Photos: Bri Ewing Valliere
harvesting and marketing the fruit
require special care.
Using ground-harvested fruit for
cider production must be done in
compliance with the Food Safety
Modernization Act (FSMA) Produce
Safety Rule. Apples that have come
in contact with the ground outside of
normal harvesting methods may be
used for human consumption only if
there has been adequate processing to
reduce food safety concerns.
Bri Ewing Valliere, clinical
assistant professor, Washington State
University's School of Food Science,
stressed the importance of following
proper procedures in a presentation
to growers and hard cider producers
at the Northwest Michigan Orchard &
Vineyard Show in Acme, Michigan.
Cider can be made from any apple.
" Cider apples " refers to cider-specific
cultivars that are typically considered
either bittersweet or bittersharp.
These apples serve no alternative
purpose and are destined for alcoholic
fermentation for cider.
Because they are unlikely to be
consumed raw, as of January 2019,
cider apples, winegrapes and hops
were considered " raw produce destined
See KANTOR, page 6
Technology is on the move for growers
By Christine Corbett Conklin
FGN Correspondent
It sounds like science fiction:
Robotic vehicles moving up and down
orchard and vineyard rows, gathering
information to guide growers in
everything from harvesting to disease
detection and pruning.
Yet, that technology is under
development right now, according to
George Kantor, senior systems scientist
with Carnegie Mellon University in
Pittsburgh, Pennsylvania. Addressing the
Washington State Tree Fruit Association's
Annual Meeting & Horticultural Expo
in December in Wenatchee, Washington,
Kantor outlined how this cutting-edge
technology will help growers.
For a number of years, automated
vehicles have existed, sometimes
rigged with cameras and large lighting
equipment to take pictures of fruit.
A camera card would then be taken
back to the research lab for processing.
However, rapid advances in computer
technology now make it possible to
produce sophisticated 3D models, with
information directly available from
the field, said Kantor who works in
the Robotics Institute, a division of the
university's School of Computer Science.
" There's a special kind of computer
system - GPU (Graphics Processing
Unit) - that makes computer games
work so well, " he said. It's also really
good for work in the field because it is
See CIDER, page 8
GEORGE KANTOR
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August 2020

Table of Contents for the Digital Edition of August 2020