basic soils arborist version - 2010
TRANSCRIPT
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