Soil Water: Characteristics and Behavior. Chapter 5 – NR 200.

Soil Water: Soil Water: Characteristics and Characteristics and

BehaviorBehavior

Chapter 5 – NR 200Chapter 5 – NR 200

Water UsesWater Uses

How the plant uses water. How the plant uses water. 60-90% of plant mass is water60-90% of plant mass is water When a plant has a full complement of water it is When a plant has a full complement of water it is

said to be turgid, loss of turgidity results in wilting.said to be turgid, loss of turgidity results in wilting. Is essential for cell functionsIs essential for cell functions PhotosynthesisPhotosynthesis Transpiration helps cool the leafTranspiration helps cool the leaf Plant nutrients are in solutionPlant nutrients are in solution Carries carbohydrates in phloemCarries carbohydrates in phloem

Improper amount of waterImproper amount of water Stress – too littleStress – too little

WiltingWilting Permanent wilting pointPermanent wilting point Water stress weakens plantWater stress weakens plant

Too much waterToo much water No air spaceNo air space Anaerobic conditions exist when no oxygen Anaerobic conditions exist when no oxygen

availableavailable

Water UsesWater Uses

Water Molecule structureWater Molecule structure

StructureStructure Two hydrogen atoms one oxygen atomTwo hydrogen atoms one oxygen atom

this attachment is held at 105this attachment is held at 105 this hydrogen side is positively chargedthis hydrogen side is positively charged

Creating a polar moleculeCreating a polar molecule Causing it to be attracted strongly to itself, Causing it to be attracted strongly to itself,

cohesioncohesion Also attraction towards other material, Also attraction towards other material, adhesion.adhesion.

The force that attracts water to other objectsThe force that attracts water to other objects In small spaces this force can move waterIn small spaces this force can move water In large spaces the affect is minimalIn large spaces the affect is minimal Responsible for the surface tension of waterResponsible for the surface tension of water

Water Molecule StructureWater Molecule Structure

Capillary waterCapillary water The ability of water to move upward against The ability of water to move upward against

gravity or outward.gravity or outward. This ability is directly related to adhesion and This ability is directly related to adhesion and

cohesioncohesion The meniscus is pulled up a small tube by The meniscus is pulled up a small tube by

adhesion properties of the tube and the cohesion adhesion properties of the tube and the cohesion pulls the other water molecules with it. The pulls the other water molecules with it. The height of travel is related to the size of the tube. height of travel is related to the size of the tube. h = .15/r with the radius in cm h = .15/r with the radius in cm

Water Molecule StructureWater Molecule Structure

Soil Water Energy forms: Soil Water Energy forms: The energy that acts on soil waterThe energy that acts on soil water

Matric forceMatric force is the soil solid’s attraction is the soil solid’s attraction (adhesion) to water which causes adsorption (adhesion) to water which causes adsorption and movement of water through the soil and movement of water through the soil (capillarity) not counting the force of gravity.(capillarity) not counting the force of gravity.

Osmotic forceOsmotic force is the movement of a high is the movement of a high concentration of ions to a lower concentration of ions to a lower concentration.concentration.

GravityGravity

Water movement and Water movement and retentionretention

MovementMovement Texture and the wetting patternTexture and the wetting pattern Clay soils produce a more round ball patternClay soils produce a more round ball pattern Sandy soils produce a more oblong pattern; Sandy soils produce a more oblong pattern;

water percolates more quickly into the soilwater percolates more quickly into the soil

Types of water movementTypes of water movement Gravitational Water or Saturated flowGravitational Water or Saturated flow

Water that moves through the root zone and Water that moves through the root zone and belowbelow

Water movement varies as to the soil textureWater movement varies as to the soil texture Water movement in the soil changes when water Water movement in the soil changes when water

moves from one different/unmixed texture soil to moves from one different/unmixed texture soil to anotheranother

Water movement and Water movement and retentionretention

Types of water movement (cont’d)Types of water movement (cont’d) Capillary movementCapillary movement

Small pores water moving laterallySmall pores water moving laterally Conditional on texture and structureConditional on texture and structure Large poresLarge pores

Little water retentionLittle water retention SandSand

Small poresSmall pores Great water retentionGreat water retention ClayClay

Water movement and Water movement and retentionretention

Types of water movement (cont’d)Types of water movement (cont’d) Capillary movement (Cont’d)Capillary movement (Cont’d)

Medium poresMedium pores Fine sand and silt hold the most available waterFine sand and silt hold the most available water

Infiltration - the process in which water moves Infiltration - the process in which water moves into the Soilinto the Soil

Percolation is the downward movement of water Percolation is the downward movement of water through through

the soil the soil soil texturesoil texture CompactionCompaction Soil stratifications affect the soil how?Soil stratifications affect the soil how?

Water soil terms of Water soil terms of wetnesswetness

Maximum retentive capacity Maximum retentive capacity Water has filled all pore spacesWater has filled all pore spaces Can only be maintained by more water or no Can only be maintained by more water or no

percolationpercolation

Field CapacityField Capacity After gravitational water has moved out and After gravitational water has moved out and

the soil is holding the waterthe soil is holding the water Sometimes called capillary waterSometimes called capillary water

Water soil terms of Water soil terms of wetnesswetness

Permanent Wilting Point (PWP) or wilting Permanent Wilting Point (PWP) or wilting coefficient.coefficient. That point of no return for a plant wiltingThat point of no return for a plant wilting Water in the soil is no longer available to the plantWater in the soil is no longer available to the plant Available water is the difference between Field Available water is the difference between Field

capacity and PWPcapacity and PWP A fine sand or silt loam will have the highest available A fine sand or silt loam will have the highest available

waterwater

Hygroscopic water - water held so tightly it is Hygroscopic water - water held so tightly it is unavailable to the plantunavailable to the plant

Water removal by the Water removal by the plantplant

Removal of water from the surface area Removal of water from the surface area first then the lower areasfirst then the lower areas

Water around the soil particle is removed Water around the soil particle is removed by the root hair and used by the plant. by the root hair and used by the plant.

The root must be in contact with the soil The root must be in contact with the soil to remove its water.to remove its water.

Measuring soil water Measuring soil water

Gravimetric MeasurementsGravimetric Measurements Weight difference between soil and oven Weight difference between soil and oven

dried soil = percentage of weight of the dried soil = percentage of weight of the water.water.

TensiometersTensiometers Measures the moisture pull of the soil in a Measures the moisture pull of the soil in a

tube or the measures the water potential of tube or the measures the water potential of the soilthe soil

TensiometersTensiometers

Measuring soil waterMeasuring soil water

Electrical Resistance blockElectrical Resistance block Measures the conductivity through a block of Measures the conductivity through a block of

gypsum or other buffering material. More gypsum or other buffering material. More water the less resistance. This device can water the less resistance. This device can easily be hooked to a watering device to easily be hooked to a watering device to automatically water a given field.automatically water a given field.

Electrical Resistance Electrical Resistance blockblock

Time Domain Time Domain ReflectometryReflectometry

May be automatedMay be automated Requires wave guidesRequires wave guides Expensive instrumentExpensive instrument

Time Domain Time Domain ReflectometryReflectometry

Neutron Scattering ProbeNeutron Scattering Probe

Radiation permit requiredRadiation permit required Expensive equipmentExpensive equipment Requires access tubeRequires access tube Not good in high-organic soilsNot good in high-organic soils

Neutron Scattering ProbeNeutron Scattering Probe

How does water move How does water move around on this planet? around on this planet?

97% of our world’s water is in the ocean97% of our world’s water is in the ocean our ground water only makes up our ground water only makes up

another .7%another .7% of the .05% of the other water, 60% is in of the .05% of the other water, 60% is in

lakes and 33% trapped in the soillakes and 33% trapped in the soil

How does water move How does water move around on this planet?around on this planet?

Most of the clouds are therefore formed form the Most of the clouds are therefore formed form the oceans by evaporation and transpiration together oceans by evaporation and transpiration together these two avenues of water into the atmosphere these two avenues of water into the atmosphere are called evapotranspiration (ET).are called evapotranspiration (ET). This rain then falls on areas we call watersheds This rain then falls on areas we call watersheds

usually defined as river area bounded by mountains or usually defined as river area bounded by mountains or hills that divide the waters movement from one hills that divide the waters movement from one another.another.

We utilize the Tuolumne River watershed with Don We utilize the Tuolumne River watershed with Don Pedro the primary storage site with Modesto and Pedro the primary storage site with Modesto and Turlock reservoirs the secondary storage site.Turlock reservoirs the secondary storage site.

How does water move How does water move around on this planet?around on this planet?

Reducing ET and EvaporationReducing ET and Evaporation Remove unwanted vegetationRemove unwanted vegetation Fallow periods for water replenishingFallow periods for water replenishing Vegetative mulches and crop residuesVegetative mulches and crop residues Plastic mulchesPlastic mulches ????

How does water move How does water move around on this planet? around on this planet?

Water infiltration and percolationWater infiltration and percolation If water does not move into the soil, then run-If water does not move into the soil, then run-

off occursoff occurs Water that is in the soil moves downward into Water that is in the soil moves downward into

least water potential area.least water potential area. If the downward movement is impeded then the If the downward movement is impeded then the

water backs up until it forms a lake or moves into water backs up until it forms a lake or moves into another lower area.another lower area.

Drainage can reclaim high water saturated areasDrainage can reclaim high water saturated areas Surface draining – Ditches and slopeSurface draining – Ditches and slope Sub-surface -Sub-surface -

DrainageDrainage

What do we do with What do we do with our tail water?our tail water?

What is the problem What is the problem with tail water?with tail water?

How does water move How does water move around on this planet? around on this planet?

Water infiltration and percolation (cont’d)Water infiltration and percolation (cont’d) Water and the dissolved elements move with the Water and the dissolved elements move with the

water to lowest areawater to lowest area Applications for septic tanksApplications for septic tanks

Enough percolation to have water move into the soilEnough percolation to have water move into the soil But not too fast as the soil cannot filter out the solids But not too fast as the soil cannot filter out the solids

(150cm per hour)(150cm per hour)

How does water move How does water move around on this planet? around on this planet?

Irrigation methodsIrrigation methods Water is getting scarcer and more people Water is getting scarcer and more people

want it we must use the present water in a want it we must use the present water in a more efficient manner.more efficient manner.

IrrigationIrrigation 1. How do we measure water?1. How do we measure water? 2. How do we decide what method to 2. How do we decide what method to

use?use? A. ClimateA. Climate B. Type of cropB. Type of crop C. Cost of water (availability)C. Cost of water (availability) D. Slope of fieldD. Slope of field E. Physical properties of soilE. Physical properties of soil F. Drainage capabilityF. Drainage capability G. Salinity or other problemsG. Salinity or other problems

IrrigationIrrigation

1. Flood - Surface1. Flood - Surface 2. Sprinkler2. Sprinkler 3. Drip - Microirrigation3. Drip - Microirrigation

Flood - TypesFlood - Types

1. Checks1. Checks 2. Furrow2. Furrow

A. Plastic or Alum. PipesA. Plastic or Alum. Pipes

B. Gated PipeB. Gated Pipe

C. Poly PipeC. Poly Pipe

D. Permanent pipe (valves)D. Permanent pipe (valves)

Sprinkler - TypesSprinkler - Types

1. Hand Set1. Hand Set 2. Permanent Set2. Permanent Set 3. Wheel Line3. Wheel Line 4. Center Pivot4. Center Pivot 5. Hose Drag5. Hose Drag

Drip - TypesDrip - Types

1. Micro Emitters1. Micro Emitters 2. In-Line Emitters2. In-Line Emitters 3. Adjustable Emitters3. Adjustable Emitters 4. Drip Tape4. Drip Tape 5. Many more types5. Many more types

Soil Moisture BehaviorSoil Moisture Behavior

1. Saturation (1/10 Atmosphere)1. Saturation (1/10 Atmosphere)

2. Field Moisture Capacity (1/3 2. Field Moisture Capacity (1/3 Atmosphere) ½ saturationAtmosphere) ½ saturation

3. Permanent Wilting Percentage (15 3. Permanent Wilting Percentage (15 Atmosphere) ¼ saturationAtmosphere) ¼ saturation

How does water enter How does water enter the soil?the soil?

through pores in the soilthrough pores in the soil sandy soils have the largest pores, but are sandy soils have the largest pores, but are

often filled with other materialoften filled with other material medium textured soils (loamy) have good medium textured soils (loamy) have good

water entry propertieswater entry properties clays, pores swell shut when they get wetclays, pores swell shut when they get wet

How does water move How does water move around on this planet? around on this planet?

Use of water for management of high salt Use of water for management of high salt soilssoils Perhaps improved drainage to remove Perhaps improved drainage to remove

excess waterexcess water Use more water to leach out the salts as Use more water to leach out the salts as

long as there is a good clean source of long as there is a good clean source of water is available.water is available.

Salt movement in soil.Salt movement in soil.

Salt movement in soil.Salt movement in soil.