Pasture / Hay Irrigation options and Management

Chris Henry, Ph.D., P.E. Assistant Professor and Water Management Engineer

Special thanks to Phil Tacker for inspiration and assistance with this presentationSpecial thanks to Phil Tacker and KSU Extension for inspiration and assistance with this presentation

Micro-Irrigation for High Tunnels

Contact Information:E-mail: cghenry@uark.eduOffice: 870-673-2661

Micro-Irrigation (drip/trickle)

The slow, low pressure, precise, application of water and nutrients directly to plants’ roots in

a predetermined pattern.

What is irrigation and why do we irrigate?

• The watering of land by artificial means to foster plant growth (Merriam Webster Dictionary).

• Food security

Drip Irrigation

• Efficiency 95 – 100%• Less disease problems • Reduced weed growth • Fertilizer injection is possible

Types of Micro Irrigation

- Point Source (includes bubblers)

- Line Source

- Micro Spray

Point Source

Application: Individual plantings like orchard trees, grapes etc.

Point source emitters

‘Drippers’

Mini sprinklers

Spaghetti tubes and drippers

Each is rated for dripping at a pre-determined rate usually expressed in Gallons Per Hour (GPH)

1-3 GPH are common sizes

2 GPH emitter

Emitters

• Pressure: 1 psi minimum (2.3 ft, 0.7 meter elevation)• Typical output: ½, 1, 2 gallons per hour

– (2, 4, 8 liters per hour) • Outlet spacing is almost unlimited 2 – 12 feet is most common (0.6 – 3.6 meters)• Run length will be limited at low pressure (1 psi)

approx. 15 feet (5 meters) • 5-15 psi on larger systems (> 15 ft)

½” Polyethylene Tubing

Emitter

Punch Hole

Insert Emitter

Emitter Installed

Slow application Covers 12 – 16 inch diameter circle

Can be hidden under mulch – don’t bury emitter in the ground!!!

Wire Staple hold in place

End Closure

Line Source Application:

Irrigation in vegetable garden and/or rowed plants

Drip Tape• Pressure 1psi minimum (2.3 ft, 0.7 meter elevation)• Flow: approx. 0.5 gpm/100 ft (2 lph/42 meter)• Hole spacing: usually 12 inches (30 cm)• Covers about 12 inch (30 cm) wide strip

Concept introduced in England after WWII

Adopted in Israel for irrigating crops in the desert

American ‘invented’ the modern drip-tape concept

Tube in a tube…

Built in ‘pressure compensation’ over 5-15 PSI. Allows long runs with uniform water distribution

Line source emitters

Drip tape or drip tube

‘Leaky’ pipe

Weep hose

Line can be for dripping at a pre-determined rate usually expressed in Gallons Per Length Hour (GPH) - 25 G/100’/Hr is the most common drip capacity.

Drip Tape Wall Thickness

10 to 12 mil

Probably best for cost and durability

Header line with drip tape connected at each row

Fittings connect to header line and to drip tape

End of tape is easily sealed

Surface water supplies and well water supplies will probably require filtration for micro-irrigation.

Micro SprayApplication: Solid or close plant spacing

Micro Sprays• Pressure: 5 psi minimum (12 feet, 3.6 meters elevation) probably require

pump • Flow: 1.5 – 65 gallons per hour (6 – 250 liters per hour) 10 to 15 gph (38 to 57 lph) common• Coverage distance: 2 – 25 feet (0.6 – 7.6 meter)• Various wetting coverage patterns

Drip Irrigation

• Irrigations are usually frequent since applying low amounts of water

• Every 1 to 2 days is common

1 meter minimum

Homemade Drip LineOrifice Discharge (gph)

Nominal Operating Head

Hole Diameter

3 ft 4 ft 5 ft 6 ft 7 ft 8 ft

1/16 in 7.3 8.5 9.5 10.4 11.2 12.0

3/32 in 16.5 19.1 21.3 23.2 25.2 27.0

1/8 in 29.3 33.9 37.9 41.5 44.8 47.9

http://sowingshalom.blogspot.com/2009/11/simple-bucket-drip-irrigation-system.html

Mulching Combined With Irrigation

Large Scale Micro-irrigation

30 “ wide

1 ½” rise

Plastic mulch= 48” wide

Rolls are 2,000 to 4,000 ft long

Cost $110-130/acre

Drip Tape or Tube

8 mil (annual)

15 mil (several years)

Rolls or spools

8 mil- 7,500 ft (acre spool)

15 mil- 4,000 ft

$130-140/roll

1.6c/ft.

Offset

Tomatoes

Melons

Large flowers

Nursery stock

Centered

Peppers

Cole crops

Strawberries

Small Flowers

Single rows or double rows planted on beds

Hand planting

Mechanical or ‘punch’ planter

Remove a crop and plant another so that the beds are used 2-3 times per season.

Components of a drip system

( backflow preventer) Filter

150 mesh screen Pressure regulator

5 to 15 PSI Manifolds Drip tubing or drip line

Optional

Pressure gauges

Injectors

Controllers

Screen or mesh filters for well or municipal systems (closed water source)

150 or greater mesh

flush valve to clean

(pressure gauge to indicate filter clogging)

Sand or media filters for open water sources (stream, pond, or lake)- usually need 2-3 filters side by side

inlet at top

clean by backflushing

Pressure regulation between 5 and 15 PSI

Adjustable or ‘preset’

Considerations for Tunnel

• Set up tunnel with good drainage around building

• Raise area above grade and level• Loam soil types are ideal for tunnel, sand ok,

clays are least preferrable• Organic matter is good for irrigation• Micro-irrigation minimizes humidity in

building

Water Source

• Most alluvial wells in AR are high in iron, very bad for micro-irrigation.

• Rural water is probably best option, surface water may be better than groundwater.

• Know your water pressure • Obtain a water sample before buying anything

Iron or Sulfur bacteria (ochre) buildup on filter

elements

Fe > 1.5 ppm

Mn > 1.5 ppm

(Sulfate) ‘rotten egg smell’ – not common in Ks.

Injections of chlorine or a ‘drip maintenance product’

to the water

Shallow wells, where water turns things orange. Not usually a problem in municipal systems.

Water Quality Analysis

Suspended solids –’turbidity’ Iron Manganese Hardness (Hydrogen sulfides) Coliform bacteria (if used for drinking or

washing produce)

Potential for Clogging

Suspended solids

50 50-100 100

Chemical

Fe .1 .1-.5 >.5

Mn .1 .1-.5 >.5

Hardness

<150 150-300 >300

Hydrogen sulfide

.5 .5-2 >2

pH <7 7-7.5 >7.5

Slight Moderate Severe

All chemical values in ppm or mg/l (except pH)

Drip Irrigation Design ConsiderationsDrip Irrigation Design ConsiderationsDetermine the number of emitter lines/bed and emitter spacing

based on soil type and bed width. Determine the number of emitter lines/bed and emitter spacing

based on soil type and bed width.

Sand-low capillaritySand-low capillarity Loam-medium capillarityLoam-medium capillarity

Clay-high capillarityClay-high capillarity

Use 2 dripper lines on wide beds with sandy soil

Use 2 dripper lines on wide beds with sandy soil

Typical 12 inches between emitters

Short wetting period

Long wetting period

Short operation

Long operation

Filter

Pressure regulator

Manifold

tape

Typical layout in the field

Determining flow and pump requirements

You have 4 rows, 100’ long. How much water is required to operate the system?

4 X 100’=400’

25 gal/100 ft/hr

4/100’ X 25gph= 100 GPH= 1.6 GPM

Note: 5-10 gal/min through a garden hose

30 gal/min- household well

Most common brands of drip tape flow at 25 GPH/100 ft

Determining water requirements for a point source system

You have 500 ‘drippers’ in a system each dripping at a 2 GPH rate. What water flow do you need.

500 X 2 GPH= 1000 GPH or 16 GPM

Note: A garden hose will supply about 5-10 GPM

A household well will supply about 30 GPM

Most drip times are 1-2 hours for shallow rooted crops (average about 45 min/day over a summer)

Irrigation Fundamentals

Soil Water Balance Equation

Irrigation + Precipitation – Evapotranspiration +-Drainage +-Runoff = Water Balance

Available Water Holding Capacity and the Root Zone

Root Zone2’ to 4’

Vegetative RegionWater Use by ET

Storage of water for irrigationAvailable Water Holding Capacity

Deep Percolation BelowRoot Zone

Crop Water Use changes with Maturity

Kc ini Kc mid Kc end

Soybeans 0.3 0.95 0.2

Soil Texture Available Water Holding Capacity (in/ft)

Sand 0.5-1.0

Sandy loam 1.0-1.5

Loam 2.0-2.5

Silt loam 2.5

Clay 2.0-2.5

6-12 in 18-24” >36”

Broccoli, greens, onion, snap beans, peppers

Cabbage, cucumber, muskmelon, eggplant, potato, tomato

Asparagus, lima bean, watermelon

Rooting Depth

Loam soil, 2.0 in/ft of soil in cucumber. When roots are, 6”, AWC at 30% deficit is 1.4” (0.6”), when at 24 inches, 2.8” (1.2”)

Safety factor

Tensiometer functions as an artificial root- measuring soil matric potential or how ‘hard’ the root must work to remove water from the soil

010

20

3040

Saturated

Field Capacity

Irrigation range in sandy soils

60

Irrigation range in clays

Soil Type Field Capacity, cbars

Trigger, cb

Sand 7-12 30

Loam, silt loam

12-20 40

clay 20-35 55

Irrigation range in loams

0 centibar

200 centibar

Manual read Watermark

Wireless Watermark

Wired WatermarkWatermark soil

moisture sensors and dataloggers

Tend to be less slightly less responsive and less reliable, but much easier to use

6/1 6/15 6/29 7/13 7/27 8/10 8/24 9/7 9/21 10/50

40

80

120

160

200

240

012345678910

Rain Rip 30 Irrig Conv 30 Irrig rip 30 Avg 6" conv 30 Avg 6"

Soil

moi

stur

e (c

b)

Rain

, Irr

ig. (

in.)

6/1 6/8 6/156/226/29 7/6 7/137/207/27 8/3 8/108/178/248/31 9/7 9/149/219/2810/50

20406080

100120140160180200220240

012345678910

rip 30 Avg 18" conv 30 Avg 18"

6/1 6/8 6/156/226/29 7/6 7/137/207/27 8/3 8/108/178/248/31 9/7 9/149/219/2810/50

40

80

120

160

200

240

012345678910

rip 30 Avg 30" conv 30 Avg 30"

89 cb is 30% deficit Watermark threshold

30%

6” 18” 30”

6”

18”

30”

Subsoil did not recharge until irrigation and 3” rain

Sensors took guesswork out of whether or not irrigation was needed

V2 V4 V6 V8 V11 R2 R3 R4 R5 R6 R7 R8

Tips

• Tensiometer or watermarks should be soaked in water twice for 24 hrs

• Do not use a slurry, make hole with ½ inch conduit/pipe/soil probe and insert sensor

• Install after emergence• Use more than one sensor location• Watermarks cost $35 each, reader $250,

tensiometers $75 each.

Tensiometer ‘Station’

One long (12”)

One short (6”)

Turn the system on when the long tensiometer indicates a need to water.

Turn the system off when the short tensiometer drops to <5.

Fertigation=Fertilization & Irrigation

Add a concentrated fertilizer solution to the drip flow

Adjust dilution ratio from 1:64 to 1:400

No electrical required-operates on water flow (internal piston)

Usually operate at 1:100 or 1:200 dilution

Water Piston Injector

Dosatron or Dosamatic

Siphon into water flow

Injector set so that you can ‘bypass’

injector if you don’t want to use it.

Suggested application of fertilizer through drip

• All of the P and K needed applied before planting

• ¼ to 1/3 of the N required applied before planting

• Remainder applied through drip

Significant growth Full development

1 lb N per acre per day (watering)

Maintenance of Drip Systems

Applying water on a frequent (usually daily) basis

A drip system must be reliable each time you use it

Poor maintenance will ‘catch up with you’

You will use it often

Reliability is essential

It will quit when you need it most

Maintenance of Drip Systems:

Clogging by particles or algae

filters to remove particles and algae

Calcium deposits on drippers and lines

acid to dissolve calcium deposits

Slime or Ochre deposits on filters/drippers

Iron or Sulfur in water- chlorine or oxidize

A water quality test to determine hardness, total solids, iron, manganese, sulfate, (coliform bacteria)

Injecting for Maintenance

Acid (sulfuric or phosphoric) for calcium deposits from hard water (as needed)

Chlorine (from bleach) for bacterial slime caused from Iron or Manganese- daily or ‘shock’

Daily= 1 ppm free chlorine in the lines as you shut down. ( 2 teaspoons in 100 gal water)

‘Shock’= 30 ppm free chlorine in the lines as you shut down (1/2 cup in 100 gal water)

“Drip Maintenance Product”- a commercial preparation of anti-bacterial agents and weak acids to be used on a daily basis with

watering. Shut down system with ‘drip maintenance product’ in the

system.

Drip-A/-Tron

Sure Drip

s

inlet

outlet

An open tank will allow iron and manganese to oxidize, form a sludge that will settle to the bottom, and can be periodically removed

Suggested Reading

Thank you for your time

• Micro-irrigation is a different mindset• Know your pressures and water quality source• Pick a good location, drainage and soil