This document summarizes key topics related to soil science and tree nutrition. It discusses the components and properties of soil, including texture, structure, pH, and moisture content. Soil provides nutrients, water, and gas exchange for plant growth. The document also covers urban soil challenges, irrigation methods, and water conservation. Maintaining proper soil conditions is important for tree health.

1. James Wagner

2. What Will Be Covered?
 Chapter 3: Soil Science
 Chapter 4: Water Management
 Chapter 5: Tree Nutrition and Fertilization

3. Soil
 Substrate of Rock, Sand, Silt and Clay
 Organic Matter
 Water & Air

4. Soil
Soil is a balanced ecosystem
inhabited by:
 Insects
 Earthworms
 Nematodes
 Bacteria
 Fungi
 Other Microbes
http://ecomerge.blogspot.com/2010_06_0
1_archive.html

5. Soil
Soil provides plants with:
 Root support
 Nutrients
 Water
 Gas exchange (O2 & CO2)

6. Soil
Soil ecology can differ due to:
 Underlying geology
 Geographic location
 Climate
 What types of plants grow there

7. Physical Properties
 Soils are the result of the weathering of parent
material over a long period of time.
 Geology influences soil. Weathered rock–Sediment
from waterways.

8. Physical Properties
An ideal soil consists of:
 50% pore space (water &
air)
 50% solid (45% mineral
and 5% organic matter)
Bryan Kotwica, Bugwood.org

9. Physical Properties
Soil Profile
Weathering events over time, such as:
 Leaching
 Temperature fluctuations
 Chemical reactions
 Biological activity
 Accumulation of different elements and materials
Cause the soil to develop horizontal layers called
horizons

10. Physical Properties
Soil Profile
Soil horizons are:
 O-Decomposing organic
matter (great amount of
biological activity)
 A-Rich in organic matter
and biological activity.
Fine roots of trees
 B-Accumulates leached
nutrients (few to no fine
roots)
 C-Partially weathered
parent material http://soils.usda.gov/education/resources/le
ssons/profile/

11. Physical Properties
Soil Texture is the
fineness or coarseness of
a soil determined by
relative amounts of
minerals.
Sand>Silt>Clay
Coarse  Fine
Loam- “Ideal” mineral mix
of sand silt and clay.

12. Physical Properties
Soil Structure is the
arrangement, shape and size
of clumps of soil particles,
called aggregates.
 Determined by physical soil
properties, chemical changes
and biological activity
 Modified by root growth,
temperature fluctuations,
burrowing insects and animal
activity.
 Organic matter improves soil
structure and increases pore
space.

13. Physical Properties
 Soil structure helps determine the amount of macropores
(air movement or gas exchange) and micropores (water
retention) a soil contains because pore space occurs within
and between aggregates.
 Soil Texture influences pore space due to particle size.
Sandy soils tend to have more macropores and less
micropores than soils with more clay.
 Bulk Density measures the mass of the soil per unit of
dried soil volume. Bulk density can be used as an indicator
of pore space and soil compaction.
 Greater bulk density=more micropores than macropores
 Different soil textures have different ranges of bulk density

14. Physical Properties
Soil Compaction is the
disruption and
destruction of soil
aggregates. It can be
caused by foot and
vehicle traffic, high
levels of sodium in the
soil and watering.

15. Physical Properties
Soil compaction
 Reduces water infiltration and availability
 Root growth
 Gas exchange
 Biological activity

16. Chemical Properties
Soil pH
 Measure of soil acidity or alkalinity
 Many effects on soil ecology and soil chemistry
 Greatly affects the availability of soil mineral nutrients
to plants
 Difficult to alter due to soil buffering capacity

17. Chemical Properties
 Soil particles have varying
negative charges which attract
soil mineral nutrients that exist
as ions in the soil solution.
Positively charged ions are called
cations.
 Cation Exchange Capacity (CEC)
measures the soil’s ability to
hold on to cations.
 Soils high in clay and/or organic
matter have higher CECs.
 Soil texture, soil structure and
CEC should be considered when
determining fertilizer needs.
Bryan Kotwica, Bugwood.org

18. Chemical Properties
 Saline soils occur when a soil have excess levels of
soluble salts which can be toxic to plants
 Sodic soils have excess levels of sodium which raises
the soil pH and destroys the soil structure.

19. Biological Activity
 Animals, insects, bacteria, fungi and other organisms help
cycle nutrients through the soil and help decompose
organic matter.
 The rhizosphere is a microzone of intense biological
activity surrounding actively elongating roots. This
environment can be very different from the surrounding
soil.
 Mycorrhizae-certain fungi can form beneficial symbiotic
relationships with tree roots
 Actinomycetes are soil-dwelling bacteria that play a critical
role in the decomposition of organic matter
 Certain atmospheric nitrogen-fixing soil bacteria form
beneficial relationships with certain tree roots

20. Soil Moisture and Plant Growth
 Soil pore space helps
determine the water
holding capacity of a soil.
A greater amount of
micropores means a higher
water holding capacity.
 Well-aggregated soil
structure aids aeration and
drainage.
 Tree roots need adequate
Andrew Koeser, International Society of Arboriculture, Bugwood.org
gas exchange as well as
adequate water to thrive.

21. Urban Soils
Urban soils are often
altered in such a way as
to inhibit tree growth
and development.
 Highly compacted soils
 Little to no organic
matter
 Little biological activity
 Suffer greater
temperature fluctuations
Craul, Urban Soils, 1985
 can contain pollutants

22. Urban Soil Improvement
Before planting: Site contains existing trees:
 Till compacted soils  Use air excavation to
 Remove soil and replace break up compacted soil
with better soil around root zone (radial
 Improve drainage
trenching) and
(French drains, drain incorporate organic
tile) matter.
 Incorporate organic
matter

24. Water and Trees
 Water is vital to trees.
 Large trees can absorb hundreds of gallons of water from
soil in a day.
 Up to 95% of the water taken up by trees can be lost
through transpiration.
 Water use varies due to tree species, size, soil, air
temperature, humidity, light and wind.
 Inadequate soil moisture can lead to root loss, leaf
abscission, twig dieback and tree death.
 Too much water can result in poor nutrient uptake, poor
root development, disease and death.

25. Irrigation
 Trees generally need less water than turf
 Proper tree selection and planting may reduce
irrigation needs.
 Irrigation is most important for newly transplanted
trees, which can need frequent irrigation

26. Irrigation
If irrigation is needed,
water trees infrequently
and deeply.
 Promotes well developed
roots
 Promotes better soil
structure
 Reduces development of
pathogens

27. Irrigation
 Shallow, frequent watering can lead to poor root
development, soil compaction and disease.

28. Irrigation Systems
 Sprinklers-When properly used they can be very
efficient and economical. Higher potential for water
loss due to evaporation.
 Drip-Delivers water to plant more precisely than
sprinklers with less potential for runoff. Drip systems
can plug so they need to be monitored.
 Other systems include soil injection, soaker hose,
basin irrigation and temporary, portable drip systems.

29. Water Conservation
 Drought tolerant landscaping (Xeriscaping)
 Minimum irrigation-provides just enough water to
maintain plant health, growth and appearance.
 Group plants with the same water requirements
together on the same irrigation schedule
(hydrozones).
 Requires an understanding of water budgets, soil and
plant water loss, water-holding capacity, application
rates, infiltration rate and irrigation system efficiency.
 Water needs can also be determined using soil probes,
tensiometers and electronic moisture sensors.

30. Water Conservation
Recycled water used in irrigation can be effective but
salinity, phytotoxicity and increases in soil pH are
potential problems.

31. Water Conservation
The use of mulch around the base of trees can reduce
soil moisture evaporation, as well as:
 Improve soil structure
 Improve water infiltration
 Moderate soil temperature
 Reduce weed competition
 Reduce soil compaction and erosion
 Organic mulches increase soil organic matter as they
decompose

32. Water Conservation
 Soil amendments to increase water hold capacity
 Limit turf plantings
 Reduce or eliminate fertilizer applications during
drought conditions
 Antitranspirants-for temporary use only. Long term
use can be toxic to some plants

33. Flooding and Drainage
 For some tree species only a short period of flooding can be
harmful as photosynthesis shuts down.
Drainage
 Best to establish proper drainage before planting.
 Improving the soil structure works best
 French drains, drain pipe/tiles will remove gravitational water,
but do not make up for poor soil structure.
 With after planting drainage improvements care must be taken
not to damage the root system.
 When irrigating, water application rate should not exceed the
infiltration rate of the soil.
 Soil aeration can relieve some drainage problems caused by soil
compaction.

34. Flooding and Drainage
 Water flow over impervious surfaces (parking lots,
roads) can cause flooding and carry pollutants.
 “Rain gardens” to catch drainage from impervious
surfaces can reduce storm water runoff. However
plantings must be tolerant of flooding, pollutants and
drought conditions.

36. Introduction
 Trees require certain essential elements to function
and grow.
 An essential element (or nutrient) is a chemical
constituent that is involved in the metabolism of the
tree or that is necessary for the tree to complete its life
cycle.
 In nature these elements are present, replenished and
recycled by the decomposition of organic matter.

37. Introduction
In urban setting, the soil may be different because of:
 Removal of soil
 Removal of fallen leaves or other potential organic
matter
 Lack of beneficial soil-dwelling organisms

38. Tree Requirements
 Trees take up essential elements dissolved in water
through their roots. Each element plays a specific role
and cannot be substituted by another element.
 Essential elements are divided into:
 Macroelements-needed in larger amounts
 Microelements-needed in smaller amounts
 Trees and other plants can only utilize essential
nutrients in the form of specific ions.

39. Essential Elements
Macronutrients Micronutrients
O-Oxygen B-Boron
H-Hydrogen Cl-Chlorine
C-Carbon Cu-Copper
N-Nitrogen Fe-Iron
P-Phosphorus Mn-Manganese
K-Potassium Mo-Molybdenum
Ca-Calcium Ni-Nickel
Mg-Magnesium Zn-Zinc
S-Sulfur

40. Essential Elements
C Hopkins Café Managed by My Clever Cousin Mo.
C HOPKNS CaFe Mg Ni B Mn Cl Cu Zn Mo

41. Tree Requirements
 Growth and development
of trees is dependant on
the most limiting of
nutrients.
 Nitrogen is often the
most limiting of the
macronutrients due to
leaching, volatilization
and, in urban
environments, due to
lack of nutrient cycling.
 P,K and S are mostly in
adequate amounts in
soil.

42. Tree Requirements
 Fe, Mn and Zn are
usually the most limiting
micronutrients in urban
soils
 Micronutrients can be
phytotoxic at higher
levels

43. Tree Requirements
Soil pH is important
because nutrients may
be present in the soil but
not available to the tree
or present in toxic
amounts.

44. Fertilizer
 Available in many forms
 Complete fertilizer
contains N, P and K.
 Fertilizer analysis on the
label- composition as a
% by weight of total N,
available P (P2O5)
phosphoric acid and K
(K2O) soluble potash
 Always in the order of N-
http://www.butlerswcd.org/Homeowner/Soils.html
P-K

45. Fertilizer
 Because phosphoric acid contains 44% P and soluble
potash contains 83% K, the percent P and K on the
label must be multiplied by .44 and .83, respectively to
calculate the percent amount of P and K. For example:
A 50 lbs. bag of 10-6-4 fertilizer contains
 5 lbs. N
 3 lbs. P
 2 lbs K
 Complete fertilizers are not always needed

46. Fertilizer
 May be organic or inorganic
 Inorganic fertilizers release their elements quickly so
they are available to plants quickly
 They may “burn” the plants and are susceptible to
leaching and volatilization.
 Organic fertilizers are composed of naturally occurring
or synthetic carbon-based molecules that must
decompose in the soil to release their elements.

47. Fertilizer
Slow release fertilizers are a preferred choice for
fertilizing trees, either with organic fertilizers or
coated inorganic fertilizers.

48. Fertilizer
Application rates
Depends on age, health, species, form of fertilizer,
application method, site conditions and desired goal.

49. Fertilizer
Prescription fertilization
 Based on soil tests and foliar analysis
 Determines the amount and availability of essential
nutrients in the soil and how deficient the tree is in
specific nutrients.

50. Fertilizer
Timing
Timing of fertilizer applications depend on the tree,
fertilizer type, soil conditions and CEC.

51. Fertilizer
Application techniques
Beneficial to apply fertilizer
beyond the drip line.
Surface application
 Requires less time
 Doesn’t require
sophisticated equipment
 Can deliver nutrients to
upper soil, closer to feeder
roots
 Susceptible to
volatilization and runoff

52. Fertilizer
Subsurface application
 Drill hole
 Soil injection
Foliar, implants and injection can be used to correct
minor deficiencies, but do not provide long-term
impact

53. Fertilizer
Over application of fertilizer can result in
 Burning-higher solute content in soil than in root
draws water out of the root
 Runoff and leaching-nutrients can pollute waterways
and ground water
 Fertilizer salts can raise soil pH affecting the
availability of nutrients