Water-Plant-Soil Relations - ag.arizona.edu

Soil-Water Def

• Soil Moisture Tension
• Saturation
• Field Capacity (FC)
• Permanent Wilting Point

(PWP)
• Available Water Holding

Capacity (AWHC)

• Readily Available
Water (RAW)

finitions

t
g

Soil-Water Def

• Soil Moisture Tension
• Saturation
• Field Capacity (FC)
• Permanent Wilting Point
• Available Water Holding

(AWHC)
• Readily Available Water

• Management Allowed
Depletion (MAD)

– 40% MAD = 40% of
available water is
to be used before
irrigating

finitions

t (PWP)
g Capacity

(RAW)

d

allowed

Typical Water-

Soil Texture
Sandy
Sandy Loam
Loam
Clay Loam
Silty Clay
Clay

-Holding Capacities

Capacity (inches/ft)
1.0
1.4
2.0
2.3
2.5
2.7

Low-Volu
Irri

ASM/SW

ume Landscape
igation

WES 404/504

Low-Volume L
Irrigation

Drip irrigation or lo
method of applyi
plants.

„ Benefits are:

– healthier plants
– greater efficiency

• water conservati
• compliance with

– enhanced flexibi

Landscape

ow-volume irrigation is a
ing water slowly to

y

ion
h local ordinances

ility









Low-Volume La
Design Process -

1. Start with a landsca
2. Determine plant-wa
3. Irrigate “base” plan
4. Calculate system r
5. Irrigate “non-base”
6. Lay out system
7. Calculate system h

andscape Irrigation
- Rain Bird

ape plan & gather site data
ater requirements
nts
run time
” plants

hydraulics

Low-Volume La
Design Process

Rain Bird Approach
[http://www.rainbird.co

1. Start with a landscape
& gather site data

2. Determine plant-water
requirements

3. Irrigate “base” plants
4. Calculate system run t
5. Irrigate “non-base” pla
6. Lay out system
7. Calculate system hydr

andscape Irrigation

h
om]

e plan
r

time
ants
raulics

Step 1: The La

„ Develop plot
plan

andscape Plan

Step 1: The La

„ Site data workshe

1. Site information
2. Water source
3. Soil type
4. Climate & PET
5. Hydrozones

andscape Plan

eet - Rain Bird





Rain Bird Workshe
Source

„ Condition

– chemistry

• hard water
• total dissolved

– particulates

• filtration

– chlorination

„ Supply

– flow rate
– pressure

eet, Block 2 - Water

solids Emitter Flow Minimum

Rate Filtration

0.5 GPH 200 mesh

1.0 GPH and 150 mesh
larger





Rain Bird Workshe
Properties

„ Determining soil tex

– Coarse, medium, o

„ Soil texture is impo
how fast water will
and how much wat

– Coarse

– Medium

– Fine

eet, Block 3 - Soil

xture

or fine

ortant for determining
move through the soil
ter will be held.

Wetted Diameter a

and Infiltration Rate

Rain Bird Workshe
and PET

„ Determining clim
„ How hot does it g

summer days?
„ How humid does

summer days?
„ What do you thin

climate througho

eet, Block 4 - Climate

mate and PET
get on the warmest

s it get on the warmest

nk is the most common
out the United States?

Step 2: Plant-W

„ Need to adjust P
requirements

– Need to adjust fo
– Need to adjust fo
– Need to adjust fo

Water Requirement

PET to plant’s

or species
or density of plantings
or microclimate

Sparsely/Dens

„ Individual, sparsely-
arranged plants

– individual emitters or mi
bubblers

– water requirement meas
in gal/d

„ Groups of densely-
arranged plants

– micro-sprays, dripline,
emitter tubing

– water requirement meas
in in/d

sely Planted Areas

icro-
sured

sured

Plants & Hydro

„ Make detailed plo

„ Then group plant

together hy

– plants irrigated o

– plants using the

– served by one co

– tip: zone large tr
surrounding plan

ozones

ot plan
ts that can be irrigated
ydrozones

on the same schedule
same irrigation method
ontrol valve
rees separately from any
nt life

PET adjustmen

Kc (crop coefficien

– accounts for spe
of the plant

„ Species factor
„ Density factor
„ Microclimate fact

Kc = SF

nt

nt, plant factor)

ecific conditions and needs

tor
F x DF x MF

Example

You’re designing fo
primarily planted
(groundcover). T
factor is ? The de
groundcover is p
of a building, nex
species, density,
What is the Kc?

or a hydrozone that is
d in Ice Plants
Therefore, the species
ensity factor is high and
planted on the east side
xt to a pool. What are the
, microclimate factors?

Plant Water Re

„ Densely-planted
Water Requirem
Kc

„ Sparsely-planted
Water Requireme
0.623 x Canopy a
Applicati

equirement

areas
ment (inches per day)=
c x PET

d areas
ent (gallons per day) =
area (sq ft) x Kc x PET
ion Efficiency

Example 1

You’re designing fo
hydrozone of dro
in Phoenix. The
the street and su
walkways. Calcu
requirement.

or a densely-arranged
ought-sensitive shrubs

shrubs are adjacent to
urrounded by cement
ulate the water

Example 2

You’re designing fo
hydrozone of tree
trees are planted
with a lawn within
Calculate the wa

or a sparsely-arranged
es in Flagstaff. The
d in front of a block wall
n 3 feet of the trunks.
ater requirement.