drip irrigation in high tunnels, 2015
TRANSCRIPT
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Using Drip Irrigation in High Tunnels
State Wide High Tunnel ConferenceWednesday, February 17, 2015
Baxter, MinnesotaKarl Foord
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Outline
• Advantages of drip irrigation
• Plant water use
• Soil characteristics–Water holding capacity
–Water movement
• Drip systems–Equipment & assembly
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Outline cont.
• Monitor–Water quality
–Application timing
• Fertigation–Regulations
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Drip irrigation advantages
• Efficient & uniform application of water
• Establish transplants
• Maintain optimum growing conditions• Maximize yield & quality
• Effective application of some nutrients
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PLANT WATER USE
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Soil moisture• Generally the most limiting
element in maintaining uniform plant growth & high quality produce• This deficiency can occur even
before visible wilting occurs
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Impact of water deficiencies
• Even small amounts of water deficiency can be detrimental – causing:–Slowed growth rate–Lighter weight fruit–Blossom end rot in tomato
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Soil water availability
• The amount of soil water available to a plant is a function of:• Plant's potential rooting zone • The soil texture and organic
matter content within that rooting zone
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Rooting zone
• The majority of the roots of most vegetable crops are generally no deeper than 10 to 12 inches
• For some crops like onions & strawberries, the depth is closer to 6 inches.
• 6 in. is a good level at which to measure water for root use
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Goal for top foot of soil moisture
• To achieve optimum growth:
• Maintain water levels the between 60 and 100% of the soil's available water holding capacity
• Especially during pollination and fruit development
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System design & needs
• System needs to meet anticipated plant needs under maximum stress• 3 – 10 gallons per minute per
tunnel
• Dependent on drip flow rate & tubing layout
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SOIL CHARACTERISTICS
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Soil characteristics
• Drainage• Compaction layer limiting root
growth• Soil texture–Water holding capacity–Water movement
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inches of water per foot of soil
Range
Coarse sand 0.24 - 0.48Fine sand 0.60 - 0.96Loamy sand 0.84 -1.44Sandy loam 0.96 - 1.80Loam-clay 1.68 - 2.40
Ranges in available water capacity for soil textures
Soil texture
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Water movement in soil
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Wetting patterns with drip irr igation
Distance between emitters
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DRIP SYSTEMS
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DRIP TAPE CHARACTERISTICS &
PLACEMENT
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Drip irrigation systems
• Low pressure & small water supply• Moderate labor–Easily automated
• Works well with plastic mulches
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Drip tape characteristics
• Emitters manufactured in the tape wall
• Common spacings: 8” & 12”
• Wall thickness: 10 & 15 mm• Maximum operating pressures:
–10 mm @ 14 psi
–15 mm @ 25 psi
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Drip tape flow rates
• Goal: wetted soil width 16 – 20 in.
• Flow rate of .67 gpm /100 ft.– 40 gph /100 ft.
• @ 12 psi• Low flow pressure regulator
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Irrigation system design
• 1 or 2 lateral lines per row
• When to use 2 rows?
–Strawberries with limited root systems – one drip per row on double row
• Install prior to mulch
• Run two drip tape lines
–one for insurance if have had plugging pbms
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Drip tube placementSingle-row crops: tomatoes, cucumbers, muskmelons
Place tube in center off-set from plant 4 – 5 in.
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Drip tube placement
Plants off-set down the row
Double-row crops: eggplant , peppers, strawberries
Place tube in center of bed
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Drip tube placement
• Place tube EMITTER SIDE UP!
• to keep tape from shifting
–Bury 1 – 2 in. –Secure tape at ends
• Avoid puncturing tube during:
–Planting
–Staking
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Drip tube installation prior to plastic mulch
To keep tape from shift ing:bury 1 – 2 in.
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Apply mulch after drip tube installation
Hand application of plastic mulch
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Apply mulch after drip tube installation
Mechanical application of plastic mulch
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MONITORING THE SYSTEM
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Water Quality• Groundwater (Chemical clogging)– Iron
–Calcium
• Surface water (Biological & Physical clogging)–Algae
–Sand & silt
–Bacterial slime
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Constituent Level of Concern Low Moderate High pH <7.0 7.0-8.0 >8.0 Iron (Fe) mg/L <0.2 0.2-1.5 >1.5 Manganese (Mn) mg/L <0.1 0.1-1.5 >1.5 Hydrogen Sulfide (H2S) mg/L <0.2 0.2-2.0 >2.0 Total Dissolved Solids (TDS) mg/L <500 500-2000 >2000 Total Suspended Solids (TSS) mg/L <50 50-100 >100 Bacteria Count (#/ml) <10,000 10,000-50,000 >50,000
http://www.smart-fertilizer.com/articles/emitter-clogging
http://edis.ifas.ufl.edu/ae032
Have your water analyzed by a laboratory that is qualified to evaluate emitter plugging hazards
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IRRIGATION TIMING
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Irrigation Water Applied in 2005Average Inches per Day
High Tunnel Tomatoes at Staples, MN
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Critical nature of irrigation timing
• Significant fluctuation from day to day based on weather conditions
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Tensiometer descriptor
• A tensiometer is a hollow tube with a porous ceramic cup at one end.
• The tube is filled with water, sealed with a cap and has an attached vacuum gauge.
• Tensiometers read in centibars (cb)
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Soil water monitoring
SensorsTensiometers
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Sensors
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Tensiometer function• As plants use water and the soil dries out, water
is drawn out of the tensiometer through the ceramic cup. Because the tube is sealed, a vacuum is created and is measured on the gauge.
• Low readings (10 cb) - relatively easy for plants to extract water from the soil
• Higher readings (35 cb) drier the soil - harder for plants to extract water
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Soil water assessment
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Good Range for High Tunnels - 25 to 40 centibars
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Summary
• When 6“ root zone tensiometer reads 30 cb begin watering (buffer incase gets to 40 cb)
• When 12” deep or below root zone tensiometer begins to decrease stop watering ~ 20 cb
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CHEMIGATION / FERTIGATION
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Chemigation / Fertigation
• Application of nutrients via drip system
• Understand safety requirements– Install anti-pollution and safety devices
• Fertilizer requirements of crop grown
• Fertilizer is compatible with water – Calcium and phosphorus fertilizer should not
be mixed with sulfates
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Fertigation system safety
• Install injection unit as bypass upstream from filter and pressure regulator and downstream of anti-pollution equipment
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Fertigation system operation
• Bring total drip system to operating pressure before beginning injection
• Conduct test runs to observe performance
• Test time for complete irrigation meeting water needs relative to injection time
• Avoid over irrigation & leaching of nutrients
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Fertigation systems
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Fertigation tank
Fertigation bypass
Control t imer Pressure
regulatorFilters
Backflow device
Pressure gauge
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REGULATIONS
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Water use & fertigation permits
• Most water and fertigation permits and rules apply to larger field situations
• If you go beyond your traditional homestead hose rate of 7 gpm – take a closer look at irrigation and fertigation regulations
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Resources• http://hightunnels.cfans.umn.edu/
• http://hightunnels.cfans.umn.edu/resources/irrigation-resources/
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Extension Materials
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Author
• Karl Foord Ph.D. MBA
• Regional Educator, Horticulture
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Handouts
• PowerPoint handout
• Extension Materials
• Drip irrigation and extension information for high tunnels
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References
• Irrometer Co - http://www.irrometer.com/
• Spectrum Technologies - http://www.specmeters.com
• Nutrient Management for Commercial Fruit & Vegetable Crops in Minnesota
• http://www.extension.umn.edu/distribution/cropsystems/DC5886.html
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• Plant tissue analysis performed by a qualified analytical lab can help you determine crop nutrition needs during the season and tailor the N fertilizer applications to actual crop needs.
• Fertilizers containing sulfate, phosphate, calcium, or anhydrous or aqua ammonium can lead to solid chemical precipitation inside the drip lines, which can block emitters