Water and Irrigation Jeff Schalau Associate Agent, ANR University of Arizona Cooperative Extension Yavapai County.

Water and Water and IrrigationIrrigation

Jeff SchalauJeff SchalauAssociate Agent, ANRAssociate Agent, ANRUniversity of Arizona Cooperative University of Arizona Cooperative ExtensionExtensionYavapai CountyYavapai County

What do we hope to learn What do we hope to learn about water and irrigation?about water and irrigation?

To Better Understand:To Better Understand: How water interacts with our How water interacts with our

environmentenvironment How plants utilize waterHow plants utilize water How, when, and where to irrigate How, when, and where to irrigate

plants plants

One oxygen atomOne oxygen atom Two hydrogen atomsTwo hydrogen atoms HH22OO Not symmetricalNot symmetrical Electrons spend more time near the Electrons spend more time near the

oxygen and less near the hydrogenoxygen and less near the hydrogen Water molecule is polarWater molecule is polar

Molecular Structure of Molecular Structure of WaterWater

O

HH

++

-

Hydrogen BondingHydrogen Bonding

++ attracted to attracted to –– Each HEach H22O is O is

bonded to its bonded to its nearest neighbornearest neighbor

Physical StatesPhysical StatesVapor

Solvent PropertiesSolvent Properties

Interacts with other polar Interacts with other polar compoundscompounds

Is repelled by non-polar Is repelled by non-polar compoundscompounds

Small size allows it to saturate Small size allows it to saturate areasareas

Can convey other substances in Can convey other substances in solutionssolutions

Sodium Chloride in SolutionSodium Chloride in Solution

CohesionCohesion The attraction The attraction

water to itself – H water to itself – H bondsbonds

AdhesionAdhesion

The attraction of The attraction of water to other water to other surfaces/substansurfaces/substancesces

Surface TensionSurface Tension

Interaction between Interaction between hydrogen bonding and hydrogen bonding and the earth’s gravitational the earth’s gravitational pullpull

Capillary ActionCapillary Action

““Wettable” surfaces Wettable” surfaces cause a film of water to cause a film of water to partially pull away from partially pull away from other water molecules other water molecules and cling to the surface.and cling to the surface.

Capillary action is Capillary action is important in soil and important in soil and plant/water relations.plant/water relations.

Useful Useful Constants/ConversionsConstants/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 Weight: 8.33 pounds/gallon, 0.036

pounds/cubic inchpounds/cubic inch Density: 1 gram per cubic centimeter (cc) at Density: 1 gram per cubic centimeter (cc) at

39.2°F39.2°F 1 gallon = 4 quarts = 8 pints = 128 ounces = 1 gallon = 4 quarts = 8 pints = 128 ounces =

231 cubic inches231 cubic inches 1 liter = 0.2642 gallons = 1.0568 quart = 1 liter = 0.2642 gallons = 1.0568 quart =

61.02 cubic inches61.02 cubic inches 1 Acre-Foot = 325,851 gallons = 43,560 1 Acre-Foot = 325,851 gallons = 43,560

cubic feetcubic feet

DiffusionDiffusion The tendency of substances to move The tendency of substances to move

from areas of high concentration to from areas of high concentration to areas of low concentrationareas of low concentration

At equilibrium, they remain as far At equilibrium, they remain as far apart as possibleapart as possible

OsmosisOsmosis

Osmosis is the net movement of water Osmosis is the net movement of water across a selectively permeable across a selectively permeable membrane driven by a difference in membrane driven by a difference in solute concentrations on the two sides solute concentrations on the two sides of the membraneof the membrane

The water moves from the area of The water moves from the area of higher solute concentration to the area higher solute concentration to the area of lower solute concentration until of lower solute concentration until equilibrium is reachedequilibrium is reached

OsmosisOsmosis

pH: Alkalinity/AciditypH: Alkalinity/Acidity

The measurement of the H+ ions The 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-fold One pH unit represents a ten-fold

change in H+ concentrationchange in H+ concentration

The pH ScaleThe pH Scale

Plant/Water RelationsPlant/Water Relations

Transpiration is the Transpiration is the water vapor given water vapor given off plantsoff plants

Evaporation is the Evaporation is the water vapor lost water vapor lost from the soilfrom the soil

Evapotranspiration Evapotranspiration is the sum of both is the sum of both (Et)(Et)

Evapotranspiration Evapotranspiration (Et)(Et)

http://croptechnology.unl.edu/animationOut.cgi?anim_name=transpiration.swf&width=0&height=0http://croptechnology.unl.edu/animationOut.cgi?anim_name=transpiration.swf&width=0&height=0

Transpiration Transpiration AnimationAnimation StartStart

Et PredictionEt Prediction

air temperatureair temperature relative humidityrelative humidity soil temperaturesoil temperature solar radiationsolar radiation precipitationprecipitation wind speedwind speed wind direction wind direction

AZMET Station

IrrigationIrrigation

Art and Science of providing to Art and Science of providing to proper quantity of water to plant proper quantity of water to plant roots when it is neededroots when it is needed

Plants and irrigation techniques Plants and irrigation techniques should be suited to:should be suited to:– Climate (macro and micro)Climate (macro and micro)– TopographyTopography– SoilSoil– Available water (quality and Available water (quality and

quantity)quantity)

Shrub and Tree Root Shrub and Tree Root SystemsSystems

In the arid southwest, tree roots In the arid southwest, tree roots can extend horizontally 3 to 5 can extend horizontally 3 to 5 times the height of the tree.times the height of the tree.

Terry Mikel’s Law of Terry Mikel’s Law of PizzaPizza A=A=rr22

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 As the radius of the root system doubles, root system doubles, the area of the root the area of the root system increases by system increases by four timesfour times

1010””

1212””

2020””

Weight of water on/in Weight of water on/in soilsoil Table is 3’ x 6’ (36 ftTable is 3’ x 6’ (36 ft22)) 1 inch of water on that table 1 inch of water on that table

weighs…weighs… 187 lbs187 lbs 6 inches of water = 1,122 lbs6 inches of water = 1,122 lbs Soil compaction can occur during Soil compaction can occur during

flood irrigationflood irrigation Water also displaces air potentially Water also displaces air potentially

leading to plant stressleading to plant stress

Lysimeters are used to Lysimeters are used to measure actual water measure actual water useuse

How does water How does water behave in soil?behave in soil?1.1. Gravity moves it in (infiltration)Gravity moves it in (infiltration)2.2. Gravity + Capillary Action moves it Gravity + Capillary Action moves it

down and horizontally (percolation)down and horizontally (percolation)3.3. Evaporation and transpiration Evaporation and transpiration

removes water from soilremoves water from soil4.4. Capillary action moves it upwardCapillary action moves it upward5.5. Diurnal effect Diurnal effect

• Day - driesDay - dries• Night - equilibratesNight - equilibrates

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 To irrigate each soil to a three foot depth, you need to apply:foot 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

More Irrigation More Irrigation PrinciplesPrinciples 1 gallon of water will irrigate 1 gallon of water will irrigate

roughly 1 ftroughly 1 ft3 3 of soilof soil

Sandy Loam

Clay LoamLoam

One, Two, Three Rule - One, Two, Three Rule - II

Annual or

Perennial

Shrub

Tree

One, Two, Three Rule - One, Two, Three Rule - IIII

Annual or

Perennial

Shrub

TreeIrrigate plants to the proper depth and check with a probe

1 foot 2 feet 3 feet

Annual or

Perennial

Shrub

TreeIrrigate plants to the proper depth and check with a probe

One, Two, Three Rule - One, Two, Three Rule - IIIIII

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

One, Two, Three Rule - One, Two, Three Rule - IVIV

Annual or

Perennial

Shrub

TreeThis is the irrigation frequency for that soil at that time of year!

Annual or

Perennial

Shrub

Tree

Irrigation Methods-Irrigation Methods-DripDrip Easy to install, but does not keep up Easy to install, but does not keep up

with growth on large woody plantswith growth on large woody plants You can use multiport heads for You can use multiport heads for

these situationsthese situations I think of it as a “disposable system” I think of it as a “disposable system”

which works for some natives (i.e. which works for some natives (i.e. by the time the system by the time the system disintegrates, natives may be able disintegrates, natives may be able to survive on natural precipitation.to survive on natural precipitation.

Irrigation Methods-Irrigation Methods-Spray headsSpray heads 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 Need a good design (consider hiring

a professional to design the system)a professional to design the system) Still need repair and maintenanceStill need repair and maintenance Do not mix and match incompatible Do not mix and match incompatible

nozzles and head types or brands.nozzles and head types or brands.

Irrigation Methods-Irrigation Methods-BubblersBubblers Great for shrubs and trees in Great for shrubs and trees in

basinsbasins Need to have level ground and a Need to have level ground and a

bermberm Do not put on same station Do not put on same station

(valve) as turf or drip(valve) as turf or drip

Irrigation Methods-Irrigation Methods-Automatic TimersAutomatic Timers Reset times for different times of Reset times for different times of

yearyear Check system periodically to Check system periodically to

make sure it is working correctlymake sure it is working correctly Turn off after rainsTurn off after rains

Irrigation Methods-Irrigation Methods-OtherOther Soaker hoses work great for trees, Soaker hoses work great for trees,

shrubs, vegetables, and annualsshrubs, vegetables, and annuals Oscillating sprinklers can work well Oscillating sprinklers can work well

for those on a budget, but there will for those on a budget, but there will be dry spotsbe dry spots

Good, old fashioned hose spraying Good, old fashioned hose spraying works well for natives that only need works well for natives that only need periodic watering during droughtperiodic watering during drought

Irrigation Wrap-UpIrrigation Wrap-Up

Do not overwater or fertilize native Do not overwater or fertilize native and/or drought tolerant plants and and/or drought tolerant plants and cause them to grow too muchcause them to grow too much

Do not assume that just because a Do not assume that just because a plant is native and/or drought plant is native and/or drought tolerant that it does not need tolerant that it does not need irrigationirrigation

Plants need some water in winter, Plants need some water in winter, evergreens also need adequate evergreens also need adequate water in winter water in winter