High tunnels and drip irrigation can work well together for efficient crop production. Drip irrigation applies water and nutrients directly to the root zone, allowing for uniform moisture levels. Proper system design considers the water supply, emitter spacing, soil characteristics, and crop water needs. Sensors can monitor soil moisture to guide irrigation scheduling. Regular maintenance is needed to prevent emitter clogging. With efficient watering, high tunnels can produce higher yields than field production.

1. High Tunnels and Drip Irrigation
Making a Difference in Minnesota

2. Drip Irrigation Considerations
with
High Tunnel Production Systems
Jerry Wright, Retired Extension Engineer
Associate Professor Emeritus
University of Minnesota Extension
Bioproducts & Biosystems Engineering Dept
West Central Research & Outreach Center - Morris, Mn
High Tunnel Workshop – 2012
jwright@umn.edu or wrightsj@charter.net
Making a Difference in Minnesota

3. Reasons for Using Drip/Trickle
Irrigation
in High Tunnel Production System
•Efficiently & Uniformly Applies Crop Water
as Needed
– to maintain optimum growing conditions
– for transplant establishment
– for uniform plant/produce development
• by enhancing INPUT use efficiency
– to protect & enhance yield and quality
•Effectively Applies Some Nutrients in Water

4. Irrigation System Needs!!!
• Water supply
• System performance
– Uniform water application
– Flexible & crop specific control
– Fertigation??
– Frost protection??
– Cooling??
• System Options
• Operating Labor
• Cost????
• Consult Local Experts

5. Water Supply!!!
3 to 10 gallons per minute per tunnel
Dependent on Drip Flow Rate
and Tubing Layout

6. Estimated Daily Crop Water Use “ET”
Typical Annual Crop
0.30
0.25
ET - Inches per day
0.20
0.15
0.10
0.05
0.00
9-
23
14
28
11
25
6-
20
3-
17
Ju
Au
Se
-J
-M
-J
-A
-S
-M
-J
ul
l
un
u
g
ug
p
ep
ay
ay
n
Annual water use = 8 to 18 inches

7. Irrigation Water Applied in 2005
Average Inches per Day
High Tunnel Tomatoes at Staples, MN
m ·
may = 5–10 inches more than outside
m
m Y
Inches of water per day
m ª
m ü
m M
m ž
m ï
m @

8. IRRIGATION WATER USE
PERMIT
Minnesota Rules
www.dnr.state.mn.us/permits/water/index.html
IN EXCESS OF 10,000 GALLONS PER DAY(= 7 gpm)
GREATER THAN ONE MILLION GALLONS / YEAR
WITHDRAWAL LIMITS ON SURFACE WATER
 6 ACRE-INCHES PER ACRE with STREAM FLOW MINIMUM
GROUND WATER LIMITS
 12-15 ACRE-INCHES PER ACRE
 CANNOT CREATE ANY INTERFERENCE WITH DRINKING WELLS
WELL CONSTRUCTION FEE $235 (Mn Dept Health)
IRRIGATION APPLICATION FEE $150 - $300(after the fact)
ANNUAL REPORT ($140 minimum fee) for 50M Gallons

9. Water Quality Concerns??
• Iron–Calcium-Sand (groundwater)
• Algae – Sand – Silt (surface water)
• Water Treatment
– Screen/Disc Filters,
– Sand filter Tanks
– Chemical treatment?????

10. What are the soil characteristics
in the proposed site???
• Rooting potential
– Restrictive layer
• Drainage limitations
• Soil texture
• Water holding capacity
• Consult local experts
– NRCS & Extension

11. Know Your Soil
Rooting Depth
and
How Will Water
Re-Distribute!

12. Drip Irrigation System Options!!!

13. Drip Irrigation System
Characteristics!!!
• Low pressure & small water supply
• High water application efficiency
• Solid-set management
– variety of emitter spacings
– Irrigate crops separately
• Moderate Labor
– easily automated
• Works well with mulches – plastic
• No frost protection
• Emitters’ plug easily
• Tube damage

14. Drip Irrigation Wetted Pattern
Design!!!

15. Line Source Drip Tape
• Tape
– Emitters manufactured within the tape wall
– Common spacings: 4”, 8", 12", 16", 18", 24’’
– Flow rates (GPH) @ 8 psi: .16, .21, .33, .53
• .45GPM/100feet = 27 GPH/100ft or .67GPM = 40GPH/100ft.
– Wall thickness (mil): 6, 8, 10, 15
• One to two year of usage
– Maximum operating pressures: • 6 mil @ 10 psi
– • 8 mil @ 12 psi • 10 mil @ 14 psi •15 mil @ 25 psi
– ?? Pressure compensated drippers for more uniformity of
water and fertilizer applications
• Surface or sub-surface installations

16. Line Source Drip Tubing
• Tubing (in-line emitter devices)
– heavy wall thickness: 2-3 times tape
– Variable spacings: 9, 12, 18, 24, 48”
– multi-seasonal use
• 6 to 10 times more costly
– pressure compensated dripper options for best uniformity of
water and fertilizer applications and self-flushing: dirt and
debris during operation
• Surface or sub-surface installations

17. Drip Irrigation System
Water application rate!!!
Table 4: Average Application Rate from Drip Irrigation Systems
by Jerry Wright, Extension Engineer, University of Minnesota
Email: jwright@umn.edu (April 2005)
Drip Tube Flow ********** Wetted Soil Width in Inches *************
GPM GPH 8 12 16 20 24
per 100ft per 100ft Average Application Rate - Inches per Hour
0.200 12 0.29 0.19 0.14 0.12 0.10
0.250 15 0.36 0.24 0.18 0.14 0.12
0.300 18 0.43 0.29 0.22 0.17 0.14
0.350 21 0.51 0.34 0.25 0.20 0.17
0.450 27 0.65 0.43 0.32 0.26 0.22
0.670 40 0.97 0.64 0.48 0.39 0.32
0.850 51 1.23 0.82 0.61 0.49 0.41
1.700 102 2.45 1.64 1.23 0.98 0.82
Appl. Rate inches/hour = 12 in/ft * (GPH/100ft)/(7.48 gal/cuft * 100 * wetted width in feet)
file: irrigation gallons per ET version 3e.xls

18. Drip Irrigation System Design ??
One or Two Lateral Lines per Row

19. Drip Tube Placement
Plants off-set down
the row

20. Drip Tube Placement
• Tube should be installed at same time/prior to mulch
• Single-row crops:tomatoes,cucumbers, muskmelons
– Place tube 4 to 5 inches from the center or in the center
• Double-row crops: eggplant, peppers and strawberries
– tube should be placed directly on the center of the bed
• Placement: keep emitters up and place in a shallow
groove or buried (1-2”) to aid in keeping from shifting
in the bed or fasten each end of tubing to keep straight
•Caution – avoid puncturing tube during planting/staking

21. Drip Installation Prior to Plastic Mulch
Hand or Mechanical Installation

22. Drip Installation Prior to Plastic Mulch
On a smooth soil surface & slightly buried

23. Header Options

24. Water S upply & Pump
Pressure G auges
Filter
Control Timer Valve
Filter
B ackf low De vice
Chemical Sub-main
Air - Flushing
Injector Release Valve
Pressure Regulator
Tee Adapter
To Drip Tube Drip Tubes
with Shu t of f
Shut of f
Valve
Valves
High Tunnel House
2004 Jerry Wright, University of Minnesota

25. Drip Irrigation System
Operation & Maintenance!!!
• Easily damaged
– Rodents, hoe,
• Emitters’ easily plugged
– Iron and calcium
– Sand, algae
– Some fertilizers

26. Drip Irrigation Control Assembly

27. Water S upply & Pump
Pressure G auges
Filter
Control Timer Valve
Filter
B ackf low De vice
Chemical Sub-main
Air - Flushing
Injector Release Valve
Pressure Regulator
Tee Adapter
To Drip Tube Drip Tubes
with Shu t of f
Shut of f
Valve
Valves
High Tunnel House
Drip Irrigation Control Assembly
2004 Jerry Wright, University of Minnesota

28. Drip Irrigation Control Assembly
Cost: $300–600 + water supply system

29. Trickle Irrigation System
Zone - Design!!!

30. FERTIGATION
Nutrient "spoon-feeding"
• Check out chemical compatibility with irrigation water
• Provide backflow protection – MDA Fertigation permit?

31. CHEMIGATION - Fertigation
Nutrient "spoon-feeding"
• Calibration to a daily or weekly feeding program
• Assess backflow protection between water source – ?MDA Permit?

32. When & How Much Should I Water????

33. Average Irrigation Applied in High Tunnel Tomatoes
Gallons per Plant per inDay - Tomatoes
Average Irrigation Applied High Tunnel
Staples 2005
field observations Gallons per Plant per Day - Staples 2005 use more water
indicate cucumbers can
1.00
Plt/dy in 18" spacing Plt/dy in 24" spacing
0.90
Poly. (Plt/dy in 18" spacing) Poly. (Plt/dy in 24" spacing)
0.80
0.70
0.60
Gallons per Plant per day
0.50
0.40
0.30
0.20
0.10
0.00
3-Jul
5-Jun
2-Oct
9-Oct
10-Jul
17-Jul
24-Jul
31-Jul
12-Jun
19-Jun
26-Jun
4-Sep
7-Aug
15-May
29-May
22-May
18-Sep
11-Sep
25-Sep
14-Aug
21-Aug
28-Aug

34. In-Field Soil Water Assessment

35. Soil Water Monitoring Sensors

36. Sensors Installation Steps
• Soak sensors in water 2-3 hours
& air dry – repeat cycle 2/3 Xs
• Place in soil profile within plant
row at 2 to 3 depth locations
• Mark sensor depths and site
• !!! Read Sensors Frequently !!!!

37. SOIL WATER DEFICITS
for
Typical Soils & Soil Water Tensions
Good Range for High Tunnels - 25 to 40 centibars
Soil water tension in centibars, cbs
Soil Texture
10 30 50 70 100 200 1500**
Soil water deficit – inches per foot of soil
Coarse sand 0 0.1 0.2 0.3 0.4 0.6 0.7
Fine sand 0 0.3 0.4 0.6 0.7 0.9 1.1
Loamy sand 0 0.4 0.5 0.8 0.9 1.1 1.4
Sandy loam 0 0.5 0.7 0.9 1.0 1.3 1.7
Loam 0 0.2 0.5 0.8 1.0 1.6 2.4
**1500 cbs is approximately the permanent wilting point for most plants and the
soil water deficit values equal the soil’s available water holding capacity

38. Soil Water Monitoring Sensors
Installation Tips
• Soak sensors in water 2-3 hours
& air dry – repeat cycle 2/3 Xs
• Place in soil profile within plant
row at 1 to 2 depth locations
• Mark sensor depths and site
• !!! Read Sensors Frequently !!!!

39. Soil Water Monitoring
Irrometer Co - http://www.irrometer.com/
Spectrum Technologies - http://www.specmeters.com

40. Automatic Soil Moisture Monitoring
Save 10 to 20 minutes Each Day
$500-650
Hansen AM400 Soil Moisture Data Logger
Watermark Soil Moisture Date Logger

41. Extension Materials
Minnesota High Tunnel Production Manual
http://www.extension.umn.edu/distribution/horticulture/M1218.html or
http://www.mfvga.org/
Handbook –“Trickle Irrigation in the Eastern United States” NRAES #4
http://www.nraes.org
High Tunnels for the Central Great Plains - Kansas
http://www.hightunnels.org/
High Tunnel Production in Pennsylvania
http://plasticulture.cas.psu.edu/H-tunnels.html
Plastic Mulches & Drip for Vegetable Production
North Carolina State University Extension
http://www.ces.ncsu.edu/hil/hil-33.html
Micro irrigation in Mulched Bed Production Systems: Irrigation Depths
Florida Cooperative Extension
http://edis.ifas.ufl.edu/AE049 Making a Difference in Minnesota

42. *** Time for Questions ***