Water and IrrigationWater and IrrigationJeff SchalauJeff SchalauAssociate Agent, ANRAssociate Agent, ANRUniversity of Arizona Cooperative ExtensionUniversity of Arizona Cooperative ExtensionYavapai CountyYavapai County

What do we hope to learn What do we hope to learn about water and irr igation?about water and irr igation?

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 oxygen Electrons spend more time near the oxygen

and less near the hydrogenand 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 bonded O is bonded

to its nearest to its nearest neighborneighbor

Physical StatesPhysical StatesVapor

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 in Can convey other substances in

solutionssolutions

Sodium Chloride in SolutionSodium Chloride in Solution

CohesionCohesion The attraction water The attraction water

to itself – H bondsto itself – H bonds

AdhesionAdhesion

The attraction of The attraction of water to other water to other surfaces/substancesurfaces/substancess

Surface TensionSurface Tension

Interaction between Interaction between hydrogen bonding and the hydrogen bonding and the earth’s gravitational pullearth’s gravitational pull

Capil lary ActionCapil lary Action

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

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

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/cubic Weight: 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 = 231 1 gallon = 4 quarts = 8 pints = 128 ounces = 231

cubic inchescubic inches 1 liter = 0.2642 gallons = 1.0568 quart = 61.02 1 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

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

areas of high concentration to areas of low areas of high concentration to areas of low concentrationconcentration

At equilibrium, they remain as far apart as At equilibrium, they remain as far apart as possiblepossible

OsmosisOsmosis

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

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

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 off water vapor given off plantsplants

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

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

Evapotranspiration (Et)Evapotranspiration (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 AnimationTranspiration Animation

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

Irr igationIrrigation

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

Plants and irrigation techniques should Plants 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)

Shrub and Tree Root Shrub and Tree Root SystemsSystemsIn the arid southwest, tree roots can In the arid southwest, tree roots can extend horizontally 3 to 5 times the extend horizontally 3 to 5 times the height of the tree.height of the tree.

Terry Mikel’s Law of Terry 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 root As the radius of the root system doubles, the system doubles, the area of the root system area of the root system increases by four timesincreases by four times

10”10”

12”12”

20”20”

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 flood Soil compaction can occur during flood

irrigationirrigation 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 behave How 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 down Gravity + Capillary Action moves it down

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

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

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

Irr igation 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 foot To 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

More Irr igation More Irr igation PrinciplesPrinciples 1 gallon of water will irrigate roughly 1 1 gallon of water will irrigate roughly 1

ftft3 3 of soilof soil

Sandy Loam

Clay LoamLoam

One, Two, Three Rule - IOne, Two, Three Rule - I

Annual or

Perennial

Shrub

Tree

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

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 - I IIOne, Two, Three Rule - I II

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 - 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

Irr igation Methods-DripIrrigation Methods-Drip

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

Irr igation Methods-Spray Irrigation 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 a Need 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 incompatible Do not mix and match incompatible

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

Irr igation 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) as Do not put on same station (valve) as

turf or dripturf or drip

Irr igation Methods-Irrigation Methods-Automatic TimersAutomatic Timers Reset times for different times of yearReset times for different times of year Check system periodically to make Check system periodically to make

sure it is working correctlysure it is working correctly Turn off after rainsTurn off after rains

Irr igation 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 for Oscillating sprinklers can work well for those on a budget, but there will be those on a budget, but there will be dry spotsdry 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

Irr igation 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 tolerant plant 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 water evergreens also need adequate water in winter in winter