Tree/Soil Tree/Soil Relations & Relations & Water Water ManagementManagement

Scott KillpackScott KillpackAgronomy/Natural Agronomy/Natural ResourcesResources

IntroductionIntroductionThe relationship between The relationship between tree root systems and the tree root systems and the soils in which they grow soils in which they grow has a greater influence on has a greater influence on tree health than any other tree health than any other single factor.single factor.

IntroductionIntroductionUnderstanding soil is vital Understanding soil is vital to arboriculture because to arboriculture because soil is, quite literally, the soil is, quite literally, the foundation within which a foundation within which a tree grows.tree grows.

Soil Soil GenesisGenesis

How it How it All All StartedStarted

Factors of Soil Formation

Time

Climate

Parent Material

Topography

Plants

Significant Missouri Parent Materials

Alluvial - river, stream deposits

Alluvial - river, stream deposits

Glacial Till - deposits associated with the advance and retreat of glacial ice flows

Significant Missouri Parent Materials

North America Glacial Periods

Nebraskan - 1.5 million to 900,000 B.C.

Kansan - 700,000 to 600,000 B.C.

Illionian - 325,000 to 225,000 B.C.

Wisconsin - 100,000 to 10,000 B.C.

Alluvial - river, stream depositsGlacial Till - deposits associated with the

advance and retreat of glacial ice flowsLoess - wind blown materials comprised

primarily of silt with some fine sand and clay

Significant Missouri Parent Materials

Distribution of Loess in the Midwest

deposition occurred around

14,000 to 10,000 B.C.

Loess Thickness in Missouri

West

East

glacial till

loess

Mis

sour

i Riv

er

Mis

siss

ippi

Riv

er

prevailing wind

Alluvial - river, stream depositsGlacial Till - deposits associated with

the advance and retreat of glacial ice flows

Loess - wind blown materials comprised primarily of silt with some fine sand and clay

Residuum - mostly limestone

Significant Missouri Parent Materials

Factors of Soil Formation

Time

Climate

Parent Material

Topography

Plants

The Soil Profile - The Master Horizons

AA top most mineral horizon - varying levels of organic matter - .5 to 4% in Missourizone of maximum leaching/weathering - clay along with iron & aluminum oxides - light in color

EEzone of maximum accumulation - clay along with iron & aluminum oxidesBBzone where the soil forming processes that are active in the A, E, & B horizons are essentially non-existent

CC

The Soil Profile - The Master Horizons

OO highly decayed organic material, not much mineral (sand, silt or clay)

Present in some soils

Might find O horizon in heavy undisturbed forest or undisturbed prairie.

Physical Physical PropertiePropertiess

Four Major Components of SoilsAir20 - 30%

Mineral

45%Water20 - 30%

Organic

3-5%

An ideal soil is 50% solids 50% pore space

Relative Size of Sand, Silt and Clay

Silt0.05 0.002

mm

Clay< 0.002

mm

Sand2.0 - 0.05

mm

Approximate Surface Area

Course Sand – Half DollarFine Clay – Basketball Court

1 gram samples (= 0.035 ounces)

External surfaces

Diagram of a Silicate Clay Crystal

K+

Ca+2

Mg+2

Ca+2

Internal surfaces

Surfaces have negative charge

Negatively Charged Colloids Attract Positively

Charged Ions Cations

K+

Ca+2

Na+

Ca+2

H+

Mg+2

-

---

- -

---

Soil Colloid

Soil Textural Class NamesClasses based on relative proportions of sand, silt and clay

Moderately Finesandy clay loam, clay loam & silty clay loamFinesandy clay, silty clay & clay

Coarsesand and loamy sandModerately CoarseSandy LoamMediumsilt, loam and silt loam

Sand Silt and Clay Content of Selected Soil Textural Classes

sand silt clay

loamy sandsandy loam

loamsilt loam

clay loamclay

85

65

45

2028 25

10

25

40

60

3730

510

1520

3545

Soil Textural Determinatio

n35 % sand45 % silt20 % clay

Pore Pore SpaceSpace

Four Major Components of SoilsAir20 - 30%

Mineral

45%

Water20 - 30%

Organic3%

Total Pore Space - Two Types

Macro - allow the ready movement of air and percolating water.

Micro - does not generally provide much air movement under moist soil conditions.

Soil Pore Space - Graphical Visualization

Total Pore Spacemacro pore micro pore

Virgin Tilled

MicroMacro

Influence of Tillage on Pore Size

34%

26%35%

17%

Soil Soil StructurStructur

ee

Soil StructureThe combination of soil particles and pore space

Types of Soil Structure

Plate-likeColumnarBlocky (cube like and subangular)

Granular

Soil Structure/Aggregation Factors

freezing and thawing wetting and drying Root growth soil organisms organic matter adsorbed cations

Influence of Cropping Practices on Water Stable Aggregates

continuouscorn

corn inrotation

meadow inrotation

continuousbluegrass

9%23%

42%57%

Bulk DensityThe mass of a given volume of dry soil - a combination of the mineral, organic matter, and pore space.What

happens when soil volume is compressed?

Urban Soils • Altered

profile• Reduced

organic matter• Soil structure degraded• High bulk density or

compaction

OrganiOrganic c MatterMatter

Organic Matter

primary sources - vegetative tops, seeds and roots of plants

secondary sources - animal wastes and animal tissues

Humus - essentially the stable fraction of organic matter that remains after thorough decomposition .

Organic Matter

Composition of Organic Matter

water

75%

dry matter

25%

Composition of Organic Matter

water

75%dry

matter25% carbohydr

ates60%

lignins

25%

protein 10%other 5%

Type ofCompound

s

water

75%dry

matter25%

carbon

44%

oxygen

40%

other 8%

hydrogen 8%

carbohydrates60%

lignins

25%

protein 10%

other 5%

ElementalComposition

Type ofCompounds

nitrogenphosphoruspotassium

sulfurcalcium

magnesium

Composition of Organic Matter

Organic Matter in Missouri Soils

height of bars = to % of soil samples

north

bootheel

< 1.0 1.0 to 1.9 2.0 to 2.9 3.0 to 3.9 > 3.9

4

40 42

12

3

12

55

26

62

Organic Matter - Importance

improves soil structure

provides plant nutrients

improves cation exchange capacity

Organic Matter Factors that Affect Levels

temperaturemoisturelandscape positionLand management

Carbon:Nitrogen Ratios

The relative composition of carbon and nitrogen within plant material

Carbon:Nitrogen Ratios

Important in controlling:

• available nitrogen• total organic

matter• rate of decay

Carbon:Nitrogen Ratios

animal manurelegume residuewheat strawcorn stalkssawdustsoil

15:120:180:155:1

200:110:1

Soil Soil WaterWater

Saturation - when the entire pore volume of soil (both macro and micro) is filled with water.

Field Capacity - when water has moved out of the macro pores - gravitational water - leaving essentially the micro pores filled with water.

Wilting Point - water remaining in micro pores that is held too tightly to be absorbed by plant roots.

Soil Water Terms

Available Water - water held in the soil that is between field capacity and wilting point

Unavailable Water - water held in the soil at or beyond the wilting point

Soil Water Terms

Infiltration - the movement of water into the soil.

percolation – water movement within the soil profile.

Soil Water Terms

General Relationship Between Soil Moisture and Soil Texture

0

10

20

30

40

sand sandyloam

loam siltloam

clayloam

clay

FieldCapacity

Available Water

WiltingPoint

Unavailable Water

Soil Water Fundamentals

The polarity of the water molecule results in the adsorption to negatively

charged clay particles

positive

negative

oxygen atom

hydrogen atoms

adsorption - the attractive forces of water to the channels through which it moves

cohesion - the attraction of water molecules for each other (surface tension)

Soil Water Capillary Fundamentals

loamysand

siltloam

loamysand

siltloam

loamysand

siltloam

water moves into the loamy sand only after the silt loam becomes saturated

clay

siltloam

clay

siltloam

perched water table

upon reaching the silt loam-clay interface water immediately moves into the clay layer due to the high attractive forces associated with clay-type soils

clay loamArmstrong

silt loamCotter

loamy sandSarpy

silty clayLevasy

Available Water for Several

Selected Soils2.4 - 2.6

2.8 - 3.1

0.6 - 1.0

1.4 - 2.4

Bars = inchesof water/ft of soil

Soil Soil BiologyBiology

large - gophers, moles, mice . . .

small - ants, beetles, grubs, slugs, snails earthworms . . .

micro - nematodes, protozoa and rotifers

Soil Organisms - Fauna

Soil Organisms - Floraalgae - are chlorophyll-bearing

organisms and thrive in wet or moist soils - important groups include green and blue-green

fungi - includes molds and mushrooms - some have a symbiotic association with the roots of plants (mycorrhizae)

actinomycetes - are filamentous, but are unicellular like bacteria.

Soil Organisms - FloraBacteria - one of the simplest, smallest and most important forms of soil microbial life

– obtain their energy from organic matter (heterotrophs) or from inorganic substances such as ammonium, sulfur and iron (autotrophs)

Benefits of Soil Organisms

decomposition of organic matter - Natures "Recycle Crew”

transformation of plant unavailable organic nitrogen to plant available inorganic nitrogen – “nutrient cycling”

Mycorrhizae – “Fungus Roots” • Fungi infected

roots• Symbiotic

relationship• Increase water

nutrient update• > 2,500 different fungi

Rhizosphere • Zone surrounding roots

where intense biological/chemical processes take place

Soil Soil ChemistChemistryry

Cation ExchangeThe "exchange" between a cation in the soil solution and another cation on the surface of negatively charged material such as clay or organic matter.

Negatively Charged Colloids Attract Positively

Charged Ions Cations

K+

Ca+2

Na+

Ca+2

H+

Mg+2

-

---

--

---

soil colloidH+

H+

K+

Ca+2

NH4+

soil solution

soil solution

soil solution

Fe+2

- --Al+3

H+H+

Common Soil Cations

Ca

2+ Mg

2+Al

3+

Na

+

H+

K+

NH

+

Fe

3+

Negatively Charged Ions

Are Called AnionsChemical Ionic

Nutrient symbol form

Chloride Cl Cl-

Nitrate N NO3-

Sulfate S SO4-2

Borate B BO4-3

Phosphate P H2PO4-

Cation Exchange Capacity

The total of exchangeable cations that a soil can adsorb or hold.

Sometimes called "total exchange capacity" or "base exchange capacity”

expressed in centimoles per kilogram of soil - specific quantity of electrical charges

sand sandy loam loam silt loam clay loam

36

1418

27

Relationship Between Soil Texture and Cation Exchange Capacity

height of bars = millieq./100g of soil

Clay and Organic Matter Clay and Organic Matter have Greatest Influence have Greatest Influence

on CECon CEC

Clay - 10 to 150 meq/100gOM – 200 to 400 meq/100g

Cation Exchange Capacity of Missouri Soils

height of bars = to % of soil samples

north

bootheel

< 5 5 to 10 10 to 18 18 to 24 > 24

0

16

70

12

211

3629

1410

Soils and pH Two cations largely responsible for acidity

hydrogenaluminum

Understanding pH•results on a “log” scale

6 vs 7 = factor of 10

5 vs 7 = factor of 100

3 4 5 6 7 8 9 10 11

verystrong strong

verystrong

mod-erate

mod-erateslight slight strong

NeutralAlkalinityAcidity

pH Scale

common range for Missouri soils

pH and Plant pH and Plant NutritionNutrition• low pH can increase

toxicity• high pH can reduce

availability• influence soil organisms

pH & Nutrient Availability

pH Preferences of Some Common Plants

Alkaline loving

>7.0

Pin Oak, MagnoliaPine, JuniperHolly, Birch

Sweet Gum, Spruce

Ash, Beech Dogwood, Maple Spruce, Yew

Cedar, ElmJuniper, PoplarRedbud, Willow

Tuliptree

Poplar, WillowBlack Walnut

Junipers, RedbudElm, Maple

Hickory

Medium Range

6.0 - 7.0

Acid Loving

<6.0

Alter Soil pH• determine need by soil test• Lime to raise pH• Sulfur to lower pH

pH Can be Difficult to Alter

• Roots occupy large soil volume

• High clay or organic matter

Resistance to change - buffering capacity

Plant Water Needs• Varies with species and size• Influenced by soil & climate

factorsWhat part of the plant plays a role in water loss or transpiration rate?

Leaf stomatas

The The LeafLeaf

Leaf Stomata

applecornblack oak

sunflower

None39,00

0None55,00

0

250,000

64,000375,00

0100,00

0

Number of stomata per square Number of stomata per square inchinch plant upperplant upper lower lower

Irrigation Principles• Vary by age and species• Transplants - more frequent

(especially within the root ball)

• Mature - less frequent• Infrequent, deep soakings

best

Irrigation Principles• Match output with

infiltration rates (soil type/texture)

• Keep off of lower trunk• Pre-dawn - early morning

(lower ET or evapotranspiration )

Irrigation Principles• Mulches - various

advantages• Use of antitranspirants (can

be phytotoxic• Drainage - surface and

subsurface∙Grade and slope∙Tile drains

Irrigation Methods• Sprinkler• Drip irrigation• Soaker hoses• Pressure injection• Basin irrigation

Irrigation MethodsMinimum irrigation• plants with similar water

requirements• efficient watering system (drip

methods)• monitor soil moisture

(tensiometers)• mulches

Irrigation MethodsRecycled water• Excess salts (phytotoxicity)• Likely pH increase• Increase nitrogen, phosphorus &

sulfur• Clogged irrigation emitters

Drainage

• Consider grade/slope (avoid low spots)

• Drain tiles (approx 3 ft. deep)• Amending soil

with organic material

Let’s review some Let’s review some test questionstest questions