This document summarizes a study of 31 Maine high tunnel producers to identify best practices and areas for improvement. Soil samples found that 70% of tunnels had pH below the recommended minimum of 6.5. Drainage and irrigation were challenges for some, with 16% reporting drainage issues and 16% having difficulty supplying enough water. The primary crops grown were tomatoes, greens, cucumbers and peppers. Recommendations include selecting sites with good drainage and soils, planning drainage improvements in advance, considering water availability when siting tunnels, and using mulch and drip irrigation.

1. MAINE
HIGH
TUNNEL
PRODUCTION:
IDENTIFYING
AREAS
FOR
IMPROVEMENT
Caragh
B.
Fitzgerald,
Assistant
Extension
Professor,
University
of
Maine,
Kennebec
County
Extension
Office,
125
State
Street,
3rd
Floor,
Augusta,
ME,
04330;
cfitzgerald@maine.edu;
207-­‐622-­‐7546
Mark
HuTon,
Extension
Specialist
and
Associate
Professor
of
Vegetable
Crops,
University
of
Maine,
Highmoor
Research
Farm,
52
Route
202,
Monmouth,
ME,
04259;
mark.huUon@maine.edu;
207-­‐933-­‐2100
ABSTRACT
In
2011
and
2012,
three
interviews
or
visits
were
conducted
with
31
Maine
high
tunnel
owners
to
idenRfy
Poten>al
Areas
of
Improvement
pracRces,
benefits,
challenges,
and
areas
for
improvement.
Basic
data
was
collected
on
52
tunnels
and
detailed
Site
Selec>on
and
Soil
Drainage
producRon
data
was
collected
on
31
tunnels.
Soil
samples
were
collected
in
mid-­‐summer
and
analyzed
for
ObservaRons
RecommendaRons
nutrients
using
standard
soil
test
methods,
saturated
media
extract,
and
other
measures
of
soil
quality.
Twenty-­‐ • 35%
addressed
drainage
prior
to
construcRon
• Choose
site
well:
good
soils
with
good
drainage
four
tunnels
were
a
year
or
less
old
at
the
start
of
the
project.
Eight
farms
were
cerRfied
organic,
23
were
not.
• 16%
reported
problems
with
drainage
of
new
• Plan
well
in
advance
of
construcRon
The
primary
crop
grown
was
tomatoes
(81%),
followed
by
greens
(56%),
cucumbers
(47%),
and
peppers
(44%)
tunnel
(including
one
who
had
miRgated
problems
(n=31).
We
idenRfied
producRon
challenges
where
addiRonal
educaRon
is
warranted.
Forty-­‐eight
percent
of
prior
to
construcRon).
farmers
reported
addressing
site
or
soil
drainage
either
before
or
a_er
construcRon.
ExisRng
management
of
pH
Irriga>on
was
inadequate
with
70%
tunnels
having
soils
with
pH
of
less
than
the
recommended
minimum
of
6.5
(32%
had
ObservaRons
RecommendaRons
pH
less
than
6.0,
n=37).
Ninety-­‐four
percent
of
growers
applied
compost
or
manure
prior
to
the
cropping
• 16%
of
farmers
reported
challenges
supplying
• Consider
water
availability
when
siRng
a
tunnel.
season.
Some
farmers
did
not
wait
the
recommended
120
days
between
applying
uncomposted
manure
and
enough
water
to
tunnel
crops.
• Take
Rme
to
learn
and
understand
irrigaRon
harvesRng,
potenRally
increasing
food
safety
risks.
Organic
maUer
levels
over
8%
(the
upper
range
of
standard
• Many
farmers
did
not
already
use
drip
irrigaRon
in
opRons
and
tools.
for
Maine
soils)
were
found
in
54%
of
tunnels
sampled
(n=37).
In
addiRon
to
being
an
unnecessary
expense,
the
field.
• Use
mulch
to
conserve
soil
moisture.
these
high
applicaRon
rates
contributed
to
high
soil
salt
levels.
Thirty
percent
of
tunnels
had
salt
levels
above
2
• Some
farmers
did
not
use
mulch
in
the
tunnel.
mmohs/cm,
which
can
be
detrimental
to
some
crops.
Heavy-­‐weight
Trickle
irrigaRon
This
project
was
funded
by
NRCS
Agreement
No.
69-­‐1218-­‐0-­‐28.
plasRc
mulch
was
used
in
61%
Special
thanks
to
JusRne
Rushing
for
her
assistance
with
data
collecRon.
covering
enRre
of
high
tunnels
tunnel
floor
for
in
the
study
QuesRons
weed
control
(n=41).
and
moisture
What
are
common
pracRces
in
high
tunnel
construcRon
and
producRon
in
Maine?
conservaRon
What
areas
need
improvement?
Soil
Tes>ng:
pH
Methods
ObservaRons
RecommendaRons
• 31
farms,
from
14
of
Maine’s
16
counRes
• Asked
about
crops,
management,
Rming,
inputs,
• 70%
of
tunnels
had
pH
less
than
6.5.
32%
had
pH
• Begin
management
using
standard
soil
tesRng
• 3
interviews
(June
2011
–
March
2012)
challenges
less
than
6.0
(Fig.
2).
methods.
Repeat
tests
every
few
years.
• First
2
in
person
• Collected
soil
samples
June
–
August
• Tomato
growth
can
be
compromised
at
pH
<
6.5.
• Follow
recommendaRons.
• Final
in
person
or
by
phone
• Analyzed
using
standard
soil
test
methods,
4.50
8.0
• Data
from
52
tunnels
saturated
media
extract,
other
measures
4.00
Results
and
Discussion
7.0
3.50
Salt
(mmohs/cm)
3.00
Of
the
31
farms
visited,
8
were
cerRfied
organic;
23
were
not.
The
mean
age
of
the
tunnels
was
2.8
years.
6.0
2.50
pH
Twenty-­‐four
were
a
year
or
less
old;
15
were
from
2-­‐5
years
old;
5
were
more
than
six
years
old.
The
2.00
5.0
1.50
emphasis
on
new
tunnels
(a
requirement
of
the
funder)
allowed
this
study
to
highlight
issues
with
new
1.00
4.0
tunnel
managers.
0.50
3.0
0.00
Tunnel
Suppliers,
Style,
Size,
and
Orienta>on
Farm
Farm
Fig.
2.
Soil
pH
of
37
Maine
high
tunnels.
Recommended
Fig.
3.
Soil
salt
level
of
37
Maine
high
tunnels.
Number
of
Farms
level
for
vegetable
crops
(6.0
–
7.0)
indicated.
Recommended
level
for
high
tunnel
tomatoes
(
<4.0
Width
Length
mmohs/cm)
and
other
crops
(<2.0mmohs/cm)
indicated.
0
5
10
15
20
25
12’
to
48’
25’
to
200’
Ledgewood
• 19%
were
17’
• 21%
were
48’
Soil
Tes>ng:
Salt
Rimol
ObservaRons
RecommendaRons
Homemade
• 29%
were
30’
• 33%
were
96’
• 30%
of
tunnels
had
salt
levels
above
2
mmohs/cm.
• Test
for
salt
levels
at
least
by
the
third
year.
Supplier
Griffen
87%
Gothic
style
(Fig.
3).
Growth
of
carrot,
onion,
and
beans
can
be
• Use
moderate
amounts
of
manure
and
manure-­‐
Farmtech
Orienta>on
Haygrove
13%
Quonset
style
reduced
with
salt
levels
between
2.0
and
3.0.
based
compost.
E
–
W:
59%
Harnois
LeUuce
and
cabbage
growth
can
be
reduced
at
salt
• If
high
salt
levels
are
detected,
large
amounts
of
Golden
Pacific
N
–
S:
37%
levels
between
3.0
and
4.0.
water
can
leach
salts
from
soil.
This
can
be
done
NE
–
SW:
4%
Fig.
1.
Supplier
and
style
of
52
Maine
high
tunnels.
• No
tunnels
had
salt
levels
above
4
mmohs/cm,
the
by
leaving
tunnel
uncovered
through
the
winter.
maximum
recommended
for
tomatoes.
Crops
Grown
Managing
Manure
and
Compost
Applica>ons
Tomatoes:
81%
Greens:
56%
Cucumbers:
47%
Peppers:
44%
ObservaRons
RecommendaRons
• High
organic
maUer
(over
the
standard
range
of
• Moderate
the
use
of
compost
to
keep
salts
from
5-­‐8%)
was
found
in
54%
of
tunnels.
accumulaRng
and
to
minimize
cost.
• 94%
of
farmers
added
compost
and/or
manure
in
• Follow
recommended
waiRng
periods
a_er
using
the
2011
growing
season.
uncomposted
manure.
• AddiRons
of
large
amounts
of
compost
can
be
expensive
and
raise
salt
levels.
• Some
did
not
wait
the
recommended
120
days
Other
crops:
kale
(34%)
carrots
(26%),
onion
(25%),
melon
(25%),
peas
(22%),
beans
(19%),
herbs
(19%),
flowers
(19%),
broccoli
between
using
uncomposted
manure
and
harvest.
(16%),
radish
(16%),
strawberry
(9%),
eggplant
(16%),
potato
(3%),
summer
squash
(19%),
raspberries
(3%),
tree
fruit
(3%)