University of Minnesota
Day-neutral Low Tunnel
Strawberry Project
Steve Poppe, Horticulture Scientist
Emily Hoover, Dept Head/Professor
Andy Petran and Jack Tillman, Graduate Students
Emily Tepe, Research Associate
Esther Jordan, Communications Specialist
Background
• Strawberries are an important part of a healthy diet
• Short MN growing season
• Day-neutral cultivars available to extend strawberry
harvest
• Use of organic production methods
• Funding provided by the North American Strawberry
Growers Association (NASGA) and the
MN Dept. of Ag, MN Specialty Crop Block Grant
Long Term Impacts:
• Extend the harvest
season and increase
yields
• Aim to enhance
profits
• Increase supply of
locally produced
organic strawberries
• Fruit available during
a non-traditional time
Why Low Tunnels instead
of High Tunnels
In high tunnels:
• Space not used
efficiently due to
strawberry plant stature
• Increased incidence of
diseases and insects
• Wind and snow damage
• Temperature gradient
high between inside and
outside
2015-2016 Project Objectives
• Grow Albion day-neutral
strawberry plants on a raised
bed in an open field vs. in a low
tunnel system
• Develop recommendations for
nitrogen requirements
• Evaluate production, fruit
quality, pest, weed and disease
management throughout the
season
• Educate and develop more
strawberry growers in the
upper Midwest region
2015 Summary: Morris
Albion yield and berry weight
Treatment
Low Tunnel
No Low
Tunnel
Fertility Rate
Average
Yield/Plant (lb)
Average
Yield/Acre (lb)
Average Berry
Weight (g)
0x
1 ab
18450 ab
11.4 ab
0.5x
0.75 c
13710 c
9.2 c
1x
0.82 bc
14991 bc
9.8 bc
1.5x
1.12 a
20446 a
11.9 a
1-0x
0.94 abc
17228 abc
10.5 abc
0x
0.95
17278
10.1
0.5x
0.86
15687
10.1
1x
1
18414
10.3
1.5x
0.92
16828
9.7
1-0x
0.9
16467
9.4
2015 Summary: St. Paul
Albion yield and berry weight
Treatment
Low Tunnel
No Low
Tunnel
Fertility Rate
Average
Yield/Plant (lb)
Average
Yield/Acre (lb)
Average Berry
Weight (g)
0x
0.78
13263
10.1
0.5x
0.76
13933
10.9
1x
0.71
12991
8.8
1.5x
0.79
14393
10.7
1-0x
0.91
15493
9.6
0x
0.55 b
9933 b
10.3
0.5x
0.79 ab
14330 ab
10.4
1x
0.61 ab
11081 ab
9.7
1.5x
0.61 ab
11164 ab
9.6
1-0x
0.85 a
15493 a
9.8
Harvest
• Strawberry flowers
removed 3 times
• Removed strawberry
runners 3 times during
the growing season
• Typically, harvest begins
around the 3rd or 4th week
of July
• Picked fruit until mid
October
A Noticeably Sweet Berry
• Brix is a measure of total
soluble solids
• Albion has relatively high brix
compared to other dayneutrals
• Our 2013 June-bearing variety
trial had an average brix level
of 7.7
• Brix content more influenced
by harvest date than fertility of
tunnel presence (St Paul)
Brix Content, St Paul 2015
LT
8.20.15
PL
0x
0.5x
1x
1.5x
1-0x
0x
0.5x
1x
1.5x
1-0x
6.45
8.01
7.15
6.73
6.63
6.96
7.24
7.31
7.01
6.45
LT
9.10.15
PL
LT
10.19.15
PL
0x
0.5x
1x
1.5x
1-0x
0x
0.5x
1x
1.5x
1-0x
10.68
11.08
10.51
9.52
10.33
10.33
9.24
10.89
9.93
10.92
0x
0.5x
1x
1.5x
1-0x
0x
0.5x
1x
1.5x
1-0x
5.40
5.45
5.75
5.54
5.55
5.11
5.83
5.68
6.06
5.88
Temperature and Humidity
• Temperature and
humidity recorded in the
low tunnel and non-low
tunnel beds
• Data loggers suspended
12 inches above both
beds
Temperature and Humidity
2013
2014
2015
Low tunnel
Non-low
tunnel
Low
tunnel
Non-low
tunnel
Low
Tunnel
Non-low
Tunnel
Average
temperature
71.3 F
68.2 F
64.6 F
63.6 F
67.3 F
66.2 F
Average
relative
humidity
82.4%
74.1%
78.2%
70.7%
81.7%
56.1%
63.5
57.8
56.4
51.8
60.3
54.9
Average due
point
Expenses (labor not included)
Variable costs
Total low tunnel
Treatment
per 100'
Fertilizer
$70
$11.67
Pesticides
$17
$2.78
Plants
$125/1000 (w/o
shipping)
Irrigation - drip tape
$13/acre
$2.22
Mulch - Plastic (white on black)
$112.00/9600’ of row
$5.00
1.5 mil Clear Film Roll
$176.00/1640”
$11.00
Galvanized Steel Hoops placed
every 5” (Quantity: 20)
$3.98
$79.60
Straw (for walkways)
$56.00
$9.33
approx. 17,500
plants/acre
Hoops for beginning and end of
each row, anchor pipe, steel stakes
to anchor hoops and elastic bungee
Tractor Fuel (tillage, bed prep,
plastic laying)
1 lb. plastic qt. containers
Total costs (variable + fixed)
$25.00
53.44
approx. 1 gallon/hour
approx. 20 hours
per acre,
$3.50/gallon
$3.50
$0.05
approx. 1 lb per
plant & 200 plants
per 100' row
$10.00
$213.54
Projected Profit
Projected profit based on 2015 data
Average total yield/plant
0.831 lbs
Estimated marketable yield/plant (15% loss)
0.706 lbs
Average marketable yield/100’ row
141.2 lbs
Average selling price/pound
X $5.00
Gross profit/100’ row
= $706.00
10 hrs labor to pick 100’ row x $9.50/hr
- $95.00
Total costs (variable and fixed, from last slide)
- $213.54
Net profit/100’ row
= $397.46
1 acre (660’ x 66’) ≈ 72.6 100’ rows*
Net profit/acre
* 6’ row spacing
$28,855.60
Low Tunnel Construction and
Planting Steps- 2015
Materials needed:
• Bed shaper
• Mulch machine
• 4 foot wide, 1 mil
white on black plastic
mulch
• Drip tape irrigation
• Dormant day-neutral
strawberry plants
Creating a Raised Bed
Creating a Raised Bed
• Once the bed is
created, a 4 foot wide 1
mil white on black
plastic mulch is placed
on top of the bed
• The dry wheel puncher
makes small holes in
the plastic to act as a
guide for proper plant
spacing
Creating a Raised Bed
Planting
• Row spacing was 14
inches between rows,
and 12 inches between
plants in a staggered
row
• Use a 1 inch x 12 inch
wooden plant stake to
transplant
• Place the blunt end of
the wood plant stake at
the tip of the roots and
insert the transplant into
the ground
Low Tunnel Support
Use pipe to anchor plastic hoop at the
beginning and end of each row
Installing hoops and anchor stakes
Installing Tunnel Plastic
1.5 mil clear film roll
Securing Plastic Hoop with Elastic
Bungee
Fertilizer Injector
• At grower sites, fertilizer
applied through Ez-Flo
injector
• Applied AgGrand 4-3-3
water soluble organic
fertilizer through drip tape
Fertilizer Treatments
• Chilean Nitrate, organic
fertilizer, 16-0-0
• Perforated centrifuge tubes
‘planted’ in the soil next to
each plant
• Fertilizer solutions were
mixed for each treatment in
another centrifuge tube
• One ounce of solution is
poured into each perforated
tube beside each plant using
this funnel device
Spotted Wing Drosophila (SWD)
• Very few, if any, SWD were
detected in our traps at
the Morris or St. Paul sites
in 2013, 2014, or 2015.
• Applied Oxidate (OMRI
Approved) for control at 1
oz./1 gallon water on a
weekly basis at the Morris
site
Spotted Wing Drosophila Traps
•
•
•
•
•
•
Clear plastic quart-size cup, with
lid
Drilled 3/16” holes around the cup
Wire handle inserted into the sides
Yellow sticky traps inside the lid
Trap cups monitored weekly
New bait each week
•
•
•
•
•
Recipe for SWD trap bait:
12 fl oz water
4 T sugar
1 T active dry yeast
1 T apple cider vinegar
1-2 T whole wheat flour
Tarnished Plant Bug
• Damage occurs when the insects use • Pressure was noticeably higher in
their sucking mouthparts to “drink”
2015 than in 2013-2014 leading
the sugars out of developing fruit
to a reduction in total and
marketable yields
• Results in distorted, cat-faced
berries at maturity
• Present in both low tunnel and
non-low tunnel treatments,
however the damage was more
severe in the non-low tunnel in
early season at St. Paul
• At both sites a variety of organic
insecticides were applied on a
weekly basis
• Insecticides used were Mycotrol,
Purespray Green, Pyganic and
Oxidate
Strawberry Leaf Spot
• Infection is a continuous
process with older lesions
producing spores to infect
young leaves during each
season
• Spores are carried to new
leaves by rain splash causing
the disease cycle to begin again
• More prevalent on the non-low
tunnel plant leaves versus the
low tunnel
Strawberry Leaf Spot Control
•
•
•
•
Most organic fungicides and
biocontrol agents are not highly
effective against overall disease
complex on strawberry
Products containing sulfur or
copper have little or no activity
against most leaf spot diseases
In order to apply sufficient copper
to obtain control, the potential for
plant injury is probably
unacceptable
Emphasis for controlling these
diseases should be placed on
selection and use of disease
resistant cultivars
New alternative disease control
materials for strawberries.
• Messenger
• Oxidate
• Trilogy
• Trichodex
Many of these products have great
potential but under moderate to high
disease pressure effectiveness is
uncertain.
Information taken from Organic Small
Fruit Disease Management GuidelinesOhio State University
Iron Chlorosis Issue
•
•
•
•
Chlorosis in day-neutral cultivars
due to high soil pH
Yellow foliage indicates a lack of
chlorophyll, the green pigment
responsible for photosynthesis
(sugar production) in plants
This photo shows chlorosis on
plants that are planted in a soil
that measured 7.6 pH
We have determined that these
newer day-neutral cultivars will
grow successfully in soils that have
a pH of 7.3 or lower
Dubois Retractable Tunnel System
Advantages
• No wind damage issues
• Faster/simpler to install as
compared to our original
system
• Less costly than original system
Concerns
• Slight tearing of hoop plastic
• Our original 4 mil thick plastic
provided better heat retention
in October
• Sides tend to roll down
What We Learned
• Skillful management
required throughout entire
growing season
• Fertility: Need 2nd year of
data to make conclusions
• Multiple cultivars is better
• Faster installation of Dubois
retractable tunnel system
• Insect and disease
pressures posed significant
challenges in 2015
… this has the potential as a real
production system
Portola
Special thanks to Nourse Farms for donating strawberry plants for the 2015 trial season
University of Minnesota
West Central Research and Outreach Center
Morris, MN
Steve Poppe
Horticulture Scientist
[email protected]
Andy Petran
Graduate Student
[email protected]
Albion
For more information visit
our low tunnel blog
http://fruit.cfans.umn.edu