irrigation technology and design 1. why do we irrigate? of...kpu small farm sessions 2/13/2016...

KPU Small Farm Sessions 2/13/2016

Irrigation technology & Design -

Stephanie Tam (Ministry of Agriculture) 1

Irrigation Technology and Design

Stephanie Tam, P.Eng.

Water Management Engineer

Andrew Petersen, P. Ag

Regional Resource Specialist

B.C. Ministry of Agriculture

1. Why do we irrigate?

2. How much water can the soil store?

3. How much water can be applied at one time?

4. Irrigation Efficiencies

5. How much do you apply?

6. How often do we irrigate?

7. Irrigation Scheduling

1. Why do we Irrigate?

To grow a productive crop

To replenish Soil Moisture

Soil is our storage tank for water

Soil structure

How do we apply irrigation water?

Sprinklers systems Trickle / Drip systems

Soil Structure Saturated Soil




Naturally Drains Stored Water – Field Capacity

Available Water Storage Capacity(AWSC) Effective Rooting Depth

50 %

Table Error! No text of specified style in document..1 Effective Rooting Depth of Mature Crops

Shallow

0.45 m (1.5 ft)

Medium Shallow

0.6 m (2 ft)

Medium Deep

0.9 m (3 ft)

Deep

1.2 m (4 ft)

Cabbages

Cauliflowers

Cucumbers

Lettuce

Onions

Radishes

Turnips

Grass

Beans

Beets

Blueberries

Broccoli

Carrots

Celery

Peas

Potatoes

Spinach

Strawberries

Tomatoes

Tree Fruits (3’ x 10’)

Brussels Sprouts

Cereal

Clover (red)

Corn (sweet)

Eggplant

Kiwifruit

Peppers

Squash

Saskatoons


Alfalfa

Asparagus

Blackberries

Corn (field)

Grapes

Loganberries

Raspberries

Sugar beets


Effective Rooting Depth 2. How much water can the

soil store?Depends on soil texture and crop rooting depth.

Alfalfa = 4.0 foot root depth

Sandy loam = 1.5 inch water / foot

Total AWSC = 4.0 x 1.5

= 6.0 inch




Grass Crop

If Grass is grown instead of alfalfa:

Grass = 1.5 foot root depth

Sandy loam = 1.5 inch water / foot

Total AWSC = 1.5 x 1.5

= 2.2 inch

Compare Crops on

‘Sandy Loam Soil’

For a ALFALFA crop:

Total AWSC = 6.0 inch

For a GRASS crop:

Total AWSC = 2.2 inch

BUT!

Availability Coefficient, (AC)

• Maximum percentage of the total AWSC that the

crop can remove before irrigation should occur

again.

• Alfalfa and Grass 50 %

• Not all the water in the soil is readily available to

the crop.

3. How much water can be

applied at one time?

Maximum Soil Water Deficit (MSWD)

MSWD = AWSC x AC

MSWD (Alfalfa) = 6.0 x 0.50

= 3.0 inch

What if it was a Grass Crop?

Maximum Soil Water Deficit for a grass crop is:

MSWD (Grass) = 2.25 x 0.50

= 1.1 inch

MSWD (Alfalfa) = 6.0 x 0.50

= 3.0 inch

Peak Evapotranspiration

Vancouver = 0.18 in/day

Vernon = 0.22 in/day

Kelowna = 0.24 in/day




Maximum Irrigation Interval

Max Irrigation Interval = MSWD / ET

Vernon Alfalfa = 14 days

Vernon Grass = 5 days

Vancouver Alfalfa = 17 days

Vancouver Grass = 6 days

Irrigation Scheduling

1. Efficiency: Select the most

efficient type of irrigation

system possible

2. Uniformity: Design the system

to obtain the best uniformity

3. Scheduling: Schedule

irrigation timing according to

soil moisture or climate data

Certified Irrigation Designer

Certification in:

• Ag sprinkler

• Ag Drip

Being developed:

• Agriculture Technician

• Irrigation scheduling

• Application Efficiency is an indication of the percentage of water applied by an irrigation system that is actually available to the crop.

• Affected by:

– Wind, operating pressure, sprinkler trajectory, time of day and hot or cool weather

– Design, operation, and maintenance

– System type

4. Irrigation Efficiencies

Micro Sprinkler




Water Management Goals

• Sprinkler– Irrigate to fill the root zone

– Schedule to irrigate when soil moisture = 50% field capacity

• Trickle (Drip)– Maintain soil moisture content at optimum level

– Reduce plant moisture stress

– Apply frequent but low flow of water

5. How much do you apply?

On a sandy loam soil the maximum soil

water deficit (MSWD)

Alfalfa = 3.0 inch

Grass = 1.1 inch

Infiltration Rate, (AR)

Maximum infiltration rate of the soil

Different for each soil type

If it is exceeded:

Ponding, Runoff, and Erosion

Potential environmental concerns

Maximum Application Rates

Application Rate, (AR)

AR = 96.3 x Q

SS x LS

AR = application rate (in/hr)

Q = nozzle flow rate (gpm)

SS = sprinkler spacing (ft)

LS = lateral spacing (ft)

Example - Wheel line AR•Standard Wheel line with 40 foot sections

•60 ft move and 9/64 nozzle @ 50 psi

AR = 96.3 x Q

SS x LS

AR = 96.3 x 4.1

40 x 60

= 0.165 in/hr

PSI 9/64 5/32 11/64 3/16

30 3.10 3.90 4.70 5.60

40 3.60 4.50 5.40 6.40

50 4.10 5.00 6.10 7.20

60 4.40 5.50 6.50 7.90

70 4.80 5.90 7.20 8.50

80 5.10 6.30 7.70 9.10

Nozzle Flow Rate (Usgpm)




6. How often do we Irrigate?Depends on EVAPOTRANSPIRATION and

amount applied by the irrigation system

Effective Roots

Wind

RelativeHumidity

Temperature

Solar Radiation

Evaporation

Transpiration

Gross Water Applied (GWA)

• Amount of water applied to the soil.

GWA = AR x Set Time (hr)

GWA = 0.165 x 23.5

GWA = 3.87 inch

Net Water Applied (NWA)

• Amount of water that enters the soil.

NWA = GWA x AE

NWA = 3.87 x 0.72

NWA = 2.8 inch

Actual Irrigation Interval

• Net Amount Applied divided by the

ET (Vancouver)

Irr Interval = NWA / ET

Irr Interval = 2.8 in / 0.18 in/day

Irr Interval = 15 days

Trickle Water Requirement

• For point source trickle systems

– water requirement is calculated per plant

– Water / Plant / Day

• For linear tape systems

– water requirement is calculated per row

– Water / Row / Day

Plant Water Requirement

• For both designs need to calculate plant water requirement.

G/P/D= 0.623 x ET x S x A x K

ET - Peak evapotranspiration

S - Soil water storage factor

A - Area per plant

K - Crop coefficient factor




Soil Water Storage Factor, S

MSWD Peak ET (in/day) S Factor

0.3 0.8

0.25 0.75

0.2 0.75

0.3 0.85

0.25 0.8

0.2 0.75

0.3 0.95

0.25 0.9

0.2 0.85

3.0 inches +

2.0 inches

1.0 inches

Effective Soil Water Storage Factor

• Based on rooting depth of crop and evapotranspiration.

Crop Coefficient Factor, K

Crop Crop Coefficient

Apples 0.9 Grapes 0.7

Apricots 0.8 Blueberries 0.8

Cherries 0.9 Blackberries 0.6

Peaches 0.8 Kiwi Fruit 1

Pears 0.8 Logan Berries 0.6

Plums 0.8 Raspberries 0.7

Strawberries 0.75

Tomatoes 0.9

Vegetables 0.75

Crop Coefficient Factor (K)

Approximate Spacing

Tree Fruits – High

Density1

• Field area utilized by the plant root area.

Drip Irrigation Design

Blueberry field in Abbotsford

Spacing 2.5’ x 10’

Loam Soil (MSWD = 2.1)

Peak ET of 0.16 in/day

Plant Water Requirement

Blueberries in Abbotsford.

G/P/D = 0.623 x ET x S x A x K

= 0.623 x 0.16 x 0.75 x 25 x 0.8

= 1.5 USgpd (5.7 lpd)

Plant Water Requirement (Abbotsford)

Blueberries = 1.50 USgpd (5.7 lpd)

Raspberries = 1.00 USgpd (3.8 lpd)

Strawberries = 0.25 USgpd (1 lpd)

Trickle System Design Capacity

TC = G/P/D x L

E x Eu

• GPD - gallons per plant per day

• L - leaching factor

• E - application efficiency

• Eu - emission uniformity




Trickle System Design Capacity (Abbotsford)

Blueberries = 1.80 Usgpd (6.8 lpd)

Raspberries = 1.27 Usgpd (4.8 lpd)

Strawberries = 0.31 Usgpd (1.2 lpd)

Daily System Operating Time (Abbotsford)

Emitters supplying 0.5 USgph per plant (1.9 lph)

Blueberries = 3.6 hours

Raspberries = 2.5 hours

Strawberries = 0.6 hours

7. Irrigation Scheduling

• Irrigate according to crop requirement not to a fixed date.

• Irrigate only when necessary

• Apply only what the soil can hold

• Requires knowledge on climate, soil and irrigation system

Irrigation Scheduling

www.Irrigationbc.com

http://agricultural-calculator.irrigationbc.com/?date=Thu Dec 15 15:39:10 2011




Irrigation System Assessment

• Peak flow rate

• Annual water use

• System assessment/conversion

– Existing irrigation system

– min. 15% efficiency improvement

– Certified Irrigation Designer

Irrigation Management

• Irrigation scheduling equipment

– Weather station

– Soil moisture sensors

– Valves, controllers

• Provide data to www.Farmwest.com

– Pacific Field Corn Association

– Free climate data and calculators

– Over 100 climate stations in BC

irrigation technology and design 1. why do we irrigate? of...kpu small farm sessions 2/13/2016...

Documents