Water 4

1. Water and IrrigationWater and Irrigation
Jeff SchalauJeff Schalau
Associate Agent, ANRAssociate Agent, ANR
University of Arizona Cooperative ExtensionUniversity of Arizona Cooperative Extension
Yavapai CountyYavapai County

2. What do we hope to learnWhat do we hope to learn
about water and irrigation?about water and irrigation?
To Better Understand:To Better Understand:
 How water interacts with ourHow water interacts with our
environmentenvironment
 How plants utilize waterHow plants utilize water
 How, when, and where to irrigateHow, when, and where to irrigate
plantsplants

3.  One oxygen atomOne oxygen atom
 Two hydrogen atomsTwo hydrogen atoms
 HH22OO
 Not symmetricalNot symmetrical
 Electrons spend more time near the oxygenElectrons spend more time near the oxygen
and less near the hydrogenand less near the hydrogen
 Water molecule is polarWater molecule is polar
Molecular Structure ofMolecular Structure of
WaterWater
O
HH
++
-

4. Physical StatesPhysical States
Vapor

5. Solvent PropertiesSolvent Properties
 Interacts with other polar compoundsInteracts with other polar compounds
 Is repelled by non-polar compoundsIs repelled by non-polar compounds
 Small size allows it to saturate areasSmall size allows it to saturate areas
 Can convey other substances inCan convey other substances in
solutionssolutions

6. Sodium Chloride in SolutionSodium Chloride in Solution

7. CohesionCohesion
 The attraction waterThe attraction water
to itself – H bondsto itself – H bonds

8. AdhesionAdhesion
 The attraction ofThe attraction of
water to otherwater to other
surfaces/substancesurfaces/substance
ss

9. Surface TensionSurface Tension
 Interaction betweenInteraction between
hydrogen bonding and thehydrogen bonding and the
earth’s gravitational pullearth’s gravitational pull

10. Capillary ActionCapillary Action
 ““Wettable” surfaces causeWettable” surfaces cause
a film of water to partiallya film of water to partially
pull away from other waterpull away from other water
molecules and cling to themolecules and cling to the
surface.surface.
 Capillary action isCapillary action is
important in soil andimportant in soil and
plant/water relations.plant/water relations.

11. Useful Constants/ConversionsUseful Constants/Conversions
 Weight: 62.416 pounds per cubic foot at 32°FWeight: 62.416 pounds per cubic foot at 32°F
 Weight: 8.33 pounds/gallon, 0.036 pounds/cubicWeight: 8.33 pounds/gallon, 0.036 pounds/cubic
inchinch
 Density: 1 gram per cubic centimeter (cc) at 39.2°FDensity: 1 gram per cubic centimeter (cc) at 39.2°F
 1 gallon = 4 quarts = 8 pints = 128 ounces = 2311 gallon = 4 quarts = 8 pints = 128 ounces = 231
cubic inchescubic inches
 1 liter = 0.2642 gallons = 1.0568 quart = 61.021 liter = 0.2642 gallons = 1.0568 quart = 61.02
cubic inchescubic inches
 1 Acre-Foot = 325,851 gallons = 43,560 cubic feet1 Acre-Foot = 325,851 gallons = 43,560 cubic feet

12. DiffusionDiffusion
 The tendency of substances to move fromThe tendency of substances to move from
areas of high concentration to areas of lowareas of high concentration to areas of low
concentrationconcentration
 At equilibrium, they remain as far apart asAt equilibrium, they remain as far apart as
possiblepossible

13. OsmosisOsmosis
 Osmosis is the net movement of waterOsmosis is the net movement of water
across a selectively permeable membraneacross a selectively permeable membrane
driven by a difference in solutedriven by a difference in solute
concentrations on the two sides of theconcentrations on the two sides of the
membranemembrane
 The water moves from the area of higherThe water moves from the area of higher
solute concentration to the area of lowersolute concentration to the area of lower
solute concentration until equilibrium issolute concentration until equilibrium is
reachedreached

14. OsmosisOsmosis

15. pH: Alkalinity/AciditypH: Alkalinity/Acidity
 The measurement of the H+ ionsThe measurement of the H+ ions
found in that particular substancefound in that particular substance
 The scale goes from 0 to 14The scale goes from 0 to 14
 7 is neutral7 is neutral
 Below 7 is acidicBelow 7 is acidic
 Above 7 is alkaline (or basic)Above 7 is alkaline (or basic)
 One pH unit represents a ten-foldOne pH unit represents a ten-fold
change in H+ concentrationchange in H+ concentration

16. The pH ScaleThe pH Scale

17. Plant/Water RelationsPlant/Water Relations
 Transpiration is theTranspiration is the
water vapor given offwater vapor given off
plantsplants
 Evaporation is theEvaporation is the
water vapor lost fromwater vapor lost from
the soilthe soil
 Evapotranspiration isEvapotranspiration is
the sum of both (Et)the sum of both (Et)

18. IrrigationIrrigation
 Art and Science of providing to properArt and Science of providing to proper
quantity of water to plant roots when itquantity of water to plant roots when it
is neededis needed
 Plants and irrigation techniques shouldPlants and irrigation techniques should
be suited to:be suited to:
– Climate (macro and micro)Climate (macro and micro)
– TopographyTopography
– SoilSoil
– Available water (quality and quantity)Available water (quality and quantity)

19. Shrub and Tree RootShrub and Tree Root
SystemsSystems
In the arid southwest, tree roots canIn the arid southwest, tree roots can
extend horizontally 3 to 5 times theextend horizontally 3 to 5 times the
height of the tree.height of the tree.

20. Terry Mikel’s Law ofTerry Mikel’s Law of
PizzaPizza
 A=A=ππrr22
 10” pizza = 79 in10” pizza = 79 in22
 12” pizza = 113 in12” pizza = 113 in22
 20” pizza = 314 in20” pizza = 314 in22
 As the radius of the rootAs the radius of the root
system doubles, thesystem doubles, the
area of the root systemarea of the root system
increases by four timesincreases by four times
10”10”
12”12”
20”20”

21. Weight of water on/in soilWeight of water on/in soil
 Table is 3’ x 6’ (36 ftTable is 3’ x 6’ (36 ft22
))
 1 inch of water on that table weighs…1 inch of water on that table weighs…
 187 lbs187 lbs
 6 inches of water = 1,122 lbs6 inches of water = 1,122 lbs
 Soil compaction can occur during floodSoil compaction can occur during flood
irrigationirrigation
 Water also displaces air potentiallyWater also displaces air potentially
leading to plant stressleading to plant stress

22. Lysimeters are used toLysimeters are used to
measure actual watermeasure actual water
useuse

23. How does water behaveHow does water behave
in soil?in soil?
1.1. Gravity moves it in (infiltration)Gravity moves it in (infiltration)
2.2. Gravity + Capillary Action moves it downGravity + Capillary Action moves it down
and horizontally (percolation)and horizontally (percolation)
3.3. Evaporation and transpiration removesEvaporation and transpiration removes
water from soilwater from soil
4.4. Capillary action moves it upwardCapillary action moves it upward
5.5. Diurnal effectDiurnal effect
• Day - driesDay - dries
• Night - equilibratesNight - equilibrates

24. Irrigation PrinciplesIrrigation Principles
 1 inch of water will:1 inch of water will:
– Go 12” deep in a sandy loamGo 12” deep in a sandy loam
– 8-10” deep in a loam8-10” deep in a loam
– 4-6” deep in a clay loam4-6” deep in a clay loam
 To irrigate each soil to a three footTo irrigate each soil to a three foot
depth, you need to apply:depth, you need to apply:
– 3” on a sandy loam3” on a sandy loam
– 4” on a loam4” on a loam
– 6” on a clay loam6” on a clay loam

25. More IrrigationMore Irrigation
PrinciplesPrinciples
 1 gallon of water will irrigate roughly 11 gallon of water will irrigate roughly 1
ftft33
of soilof soil
Sandy Loam
Clay Loam
Loam

26. One, Two, Three Rule - IOne, Two, Three Rule - I
Annual or
Perennial
Shrub
Tree

27. One, Two, Three Rule -One, Two, Three Rule -
IIII
Annual or
Perennial
Shrub
Tree
Irrigate plants to the
proper depth and
check with a probe
1 foot 2 feet 3 feet
Annual or
Perennial
Shrub
Tree
Irrigate plants to the
proper depth and
check with a probe

28. One, Two, Three Rule - IIIOne, Two, Three Rule - III
Annual or
Perennial
Shrub
TreeAllow plants to utilize the
water until the soil surface
dries to a depth of (early
morning):
1 inch 2 inches 3 inches
Annual or
Perennial
Shrub
Tree

29. One, Two, Three Rule - IVOne, Two, Three Rule - IV
Annual or
Perennial
Shrub
TreeThis is the irrigation
frequency for that soil at
that time of year!
Annual or
Perennial
Shrub
Tree

30. Irrigation Methods-DripIrrigation Methods-Drip
 Easy to install, but does not keep upEasy to install, but does not keep up
with growth on large woody plantswith growth on large woody plants
 You can use multiport heads for theseYou can use multiport heads for these
situationssituations
 I think of it as a “disposable system”I think of it as a “disposable system”
which works for some natives (i.e. bywhich works for some natives (i.e. by
the time the system disintegrates,the time the system disintegrates,
natives may be able to survive onnatives may be able to survive on
natural precipitation.natural precipitation.

31. Irrigation Methods-SprayIrrigation Methods-Spray
headsheads
 Excellent for turf and ground coversExcellent for turf and ground covers
 Not as good for trees and shrubsNot as good for trees and shrubs
 Need a good design (consider hiring aNeed a good design (consider hiring a
professional to design the system)professional to design the system)
 Still need repair and maintenanceStill need repair and maintenance
 Do not mix and match incompatibleDo not mix and match incompatible
nozzles and head types or brands.nozzles and head types or brands.

32. Irrigation Methods-Irrigation Methods-
BubblersBubblers
 Great for shrubs and trees in basinsGreat for shrubs and trees in basins
 Need to have level ground and a bermNeed to have level ground and a berm
 Do not put on same station (valve) asDo not put on same station (valve) as
turf or dripturf or drip

33. Irrigation Methods-Irrigation Methods-
Automatic TimersAutomatic Timers
 Reset times for different times of yearReset times for different times of year
 Check system periodically to makeCheck system periodically to make
sure it is working correctlysure it is working correctly
 Turn off after rainsTurn off after rains

34. Irrigation Methods-OtherIrrigation Methods-Other
 Soaker hoses work great for trees,Soaker hoses work great for trees,
shrubs, vegetables, and annualsshrubs, vegetables, and annuals
 Oscillating sprinklers can work well forOscillating sprinklers can work well for
those on a budget, but there will bethose on a budget, but there will be
dry spotsdry spots
 Good, old fashioned hose sprayingGood, old fashioned hose spraying
works well for natives that only needworks well for natives that only need
periodic watering during droughtperiodic watering during drought

35. Irrigation Wrap-UpIrrigation Wrap-Up
 Do not overwater or fertilize nativeDo not overwater or fertilize native
and/or drought tolerant plants andand/or drought tolerant plants and
cause them to grow too muchcause them to grow too much
 Do not assume that just because aDo not assume that just because a
plant is native and/or drought tolerantplant is native and/or drought tolerant
that it does not need irrigationthat it does not need irrigation
 Plants need some water in winter,Plants need some water in winter,
evergreens also need adequate waterevergreens also need adequate water
in winterin winter