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Irrigation Management of Strawberry. Dr. John R. Duval Asst. Professor of Horticulture University of Florida http://strawberry.ifas.ufl.edu. Importance of proper Irrigation. Optimization of resources Minimization of inputs Social issues. Irrigation (The Basics).

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irrigation management of strawberry

Irrigation Management of Strawberry

Dr. John R. Duval

Asst. Professor of Horticulture

University of Florida

http://strawberry.ifas.ufl.edu

importance of proper irrigation
Importance of proper Irrigation
  • Optimization of resources
  • Minimization of inputs
  • Social issues
irrigation the basics
Irrigation (The Basics)
  • When is irrigation needed?
  • How much water should be applied at each irrigation?
things to know
Things to know
  • Pumping capacity
  • Irrigation efficiency
  • Soil characteristics
pumping capacity irrigation efficiency
Pumping Capacity / Irrigation Efficiency
  • How much water can be applied with available irrigation equipment?
  • How much water is lost in the system?
    • Typically 10-30% loss in drip system with an average of 15%
    • 20-30% loss with solid set overhead with an average of 25%
typical soil water holding capacities

Soil

Texture

Inches of Water per 12" of Soil

Sands

very coarse

0.4 to 0.8

Sands

coarse

0.8 to 1.7

Fine sandy loams

moderately coarse

1.2 to 1.8

Loams, silt loams

medium

1.7 to 2.3

Sandy clay loams

moderately fine

2.0 to 2.5

Clay, silty clay

fine

2.0 to 3.0

Peats and mucks

2.0 to 3.0

Typical soil water holding capacities
determining plant water needs
Determining Plant Water Needs
  • Gravimetric
  • Tensiometers
  • Resistive Sensors
  • TDR
  • Crop water balance models
  • Other
gravimetric techniques
Gravimetric Techniques
  • Oven drying of soil
  • Measures absolute water content
  • Used to calibrate other soil moisture determination techniques
  • Very accurate
tensiometers
Tensiometers
  • Measures soil water tension
tensiometers1
Advantages

Inexpensive

Works well in saturated range

Easy to install and maintain

Can operate for extended periods

Can be used in an automated system

Disadvantages

Difficult to translate data into water volume content

Requires regular maintenance

Subject to breakage

Automated system costly

Limited range

Tensiometers
resistive sensors gypsum block watermark
Resistive Sensors(Gypsum block, Watermark)
  • Measures soil water tension
resistive sensors
Advantages

Inexpensive

High level of precision when ion concentration in soil constant

Function over entire range of soil moisture

Disadvantages

Needs calibration

Limited life of sensor

Calibration changes over time (Gypsum blocks)

Resistive Sensors
water tension measurements
Water Tension Measurements
  • General recommendations on when to water:

Soil Type Tension (cbars)

Sand 20-30

Silt 30-50

Clay 50-60

60 cbars limit of readily available water.

water tension measurements1
Water Tension Measurements
  • Need to be calibrated
  • Need to know field capacity of the soil and the amount water needed to bring soil back to field capacity from a given tension
time domain reflectometer tdr
Time Domain Reflectometer(TDR)
  • Measures volumetric water content
time domain reflectometer tdr1
Advantages

Independent of soil texture, temperature and ion content

Useful for long term measurements

Can be automated

Responds quickly to change

Disadvantages

Costly

Time Domain Reflectometer (TDR)
other sensors
Other Sensors
  • Capacitive Sensors

-Measures soil water content, measures at any depth, high precision

-Costly, stability questionable

  • Neutron Probes

-Measures soil water content non- destructive, can make real time measurements

-Costly, dangerous, dependent on soil characteristics

crop water balance models check book method
Advantages

Doesn’t rely on soil moisture readings

Inexpensive

Takes into account climatic conditions

Disadvantages

Time consuming

Crop water balance models(check book method)
crop water balance
Crop Water Balance
  • Class A pan evaporation is used to estimate crop Evapotranspiration
  • Basic equation taking into account stage of plant growth

Example

DWU = R + I – (CF X ETo) – (D + RO)

CF=0.15 + 0.018DAT + 0.0001DAT2

water balance
Water Balance

Assume a sandy loam with a soil water holding capacity of 1.5 inches of water

Water use estimate

Day 1 0.28 in.

Day 2 0.37 in.

Day 3 0.15 in.

Day 4 0.30 in.

Total 1.00 in. (2/3 Soil water)

So irrigate to replace 1 inch of water on the 5th day

so how much water do we put out
So how much water do we put out?

Example:

Plasticulture system

4 ft bed spacing (10,890 linear bed feet)

2 ft bed top

Emitter rate of 0.38 GPH

Emitter spacing of 18 in (1.5ft)

example continued
Example (Continued)

So determine total number of emitters and multiply by discharge rate

(10,890 ft / 1.5 ft) X 0.38GPH =

2759 GPH

1 acre inch of water = 27,154 Gallons

So:

27,154 Gal / 2759GPH = 9hrs 50 min

but wait
But Wait!

We only want to water the bed. Which is only 2 ft wide.

So:

2 ft bed / 4ft bed spacing = 0.5

And therefore we water for:

9hrs 50 min X 0.5 =4hrs 55 min

overhead irrigation
Overhead Irrigation

Flow rate Acre-In. water GPM/Acre applied in 1hr.

100 0.22

300 0.66

500 1.10

to determine run time
To determine run time

Assume flow rate of 300 GPM/A

1 inch of water needed divided by the Acre inches of water put out in a hour by the system 0.66 and multiply by 1 + the % loss in the system (25%)

So:

(1 A/in / 0.66 A/in/hr) X 1.25 = 1hr 54 min

irrigation scheduling for strawberry
Irrigation Scheduling for Strawberry
  • When is irrigation needed?
  • How much water should be applied at each irrigation?