3. Plant roots need gases
•Oxygen - burns (respires) sugars provided by the
canopy (leaves) for energy
•Release carbon dioxide in the process
•If the two gases cannot freely exchange with the
atmosphere…
• respiration shuts down
• roots die off
• Plants can’t get water or nutrients.
•Many root- and wood-rotting organisms (fungi)
thrive in low oxygen soil conditions.
4. Composition of a typical soil
Water
Air
Mineral
fraction
Organic matter
6. The effect of particle size
Sand particles Clay particles
Water flow
Air flow
7.
8. Texture effects on soil physical properties
Texture Available water Aeration Drainage Compaction
Sand
Loam
Silt loam
Clay loam
Clay
9. Soil texture and drainage
Sand
Silt Loam Clay Loam
Coarse
Texture
Medium
Texture
Fine
Texture
Can’t I just add Sand or Clay
to balance the condition of
the soil?
10. Answer: No…!
•Why? It’s a problem of scale:
• Soil weighs about 90 lbs per cu. ft.
• Soil from a hole 3 ft. in diameter by 2 ft deep is
about 18 cu. ft., and weighs 1600 lbs.
• To change the texture by 10 to 20% would require
160 to 320 lbs of material (sand or clay)
• Requires considerable expense and effort
• Could just be creating cement!
19. Excavation and Fill Soils
•Needed to provide proper grade and
surface drainage, but…
•Generally low in organic matter
•Excavated subsoils (basement, grade cut…)
•Often stockpiled for extended periods (much of
the organic matter decomposed in 2 to 6
months)
•Thoroughly disturbed, mixed and broken
up, structure has been reduced, even
eliminated.
21. Excessive drainage problem
•Very sandy soil
•Coarse soils are naturally droughty within
hours after rain.
•Add extra organic matter (but not to tree
planting holes)
•Precise water management (frequent, low
volume – like drip/trickle systems)
22. Amending soils with organic matter
•Improves drainage and aeration of clay soils
•Improves water-holding capacity of sandy soils
•Reduces compaction
•Provides/retains nutrients
•Locally lowers soil pH
•NOTE: Add no more than 25% by volume
• Higher levels can cause significant soil settling as OM
breaks down
24. Water and mineral nutrition
• Water action helps release minerals into the soil
solution (dissolving, freeze-thaw breakdown—
weathering of rock)
• Water is the medium by which mineral nutrients travel
to, into, and through the roots
25. Soil chemical properties greatly affect the
release of nutrients or the movement of water
•Soil texture
•pH affects mineral form and release
•Accumulation of salts: carbonates, sodium,
chloride and sulfates, etc.) can restrict water and
nutrient uptake, or alter soil structure
26. What is pH?
• pH is measured as the “activity” or concentration of
hydrogen ions (H+) in the solution.
• The higher the concentration of hydrogen ions, the
lower the pH (more acidic).
2 4 6 8 10 12
Neutral
(7.0)
acidic alkaline
27. •Why worry about soil pH?
•Affects the dissolution of
soil minerals
•Generally, higher pH =
lower mineral availability
29. •Why? Another problem of scale:
•Western soils have VERY large reservoirs of pH
buffers in the soil (solid carbonates and other
minerals, ex. “free lime”)
• 1% CaCO3 in an acre-foot of soil weighs 40,000 lbs
• Nevada soils frequently contain 20-30%
•All buffering compounds would have to be
dissolved and neutralized before the pH will
drop.
Answer: No
30. Buffering reactions:
CaCO3 + CO2 (in water) Ca2+ + 2 HCO3
(Calcium Carbonate) (Bicarbonate)
HCO3 + H+ (in water) CO2 + H2O
(this is just one acid neutralization reaction -- no
change in pH, i.e., no increase in free H+)
Added acid (H+) is consumed until all Carbonates
are dissolved, or other cations leached from the
system (i.e., Total Alkalinity is neutralized).
32. pH tolerant = iron-efficient plants
Iron-inefficient Intermediate Iron-efficient
Quaking aspen Red maple Ash
Sugar maple European beech Linden
Sweetgum Horsechestnut Scotch pine
Silver maple Baldcypress Ginkgo
Pin oak Quaking aspen Burr oak
34. “Typical” Nevada soils
•Arid/Droughty conditions
•Low precipitation
•Coarse, sandy soils
•High pH (alkaline – 7 to 8+)
•Reduced mineral nutrient release (especially
Iron)
•May not be able to “fix” the conditions.
35. IF I CAN’T FIX THE
SOIL, WHAT DO I
DO?
• Choose species adapted
to the conditions at hand
• Prepare soils for best
possible condition
36. Soil Organic Matter
• Originates from living organisms,
consisting mostly of carbon and nitrogen.
• Includes living organisms (bacteria, fungi,
earthworms) and decaying plant matter.
• Soil organisms use decaying plant matter
as a food source.
37. Humus
• An organic component of soil, formed by the
decomposition of leaves and other plant material
by soil microorganisms.
• “Stable” vs. “active” (compost)
• Stable humus does not add nutrients, but it does
bind and store nutrients.
• Presence of stable humus can prevent leaching
of nutrients from the soil.
38. Cation exchange capacity (CEC)
The degree to which cations can be held by
soil particles and exchanged with soil water.
Cation Anion
positively charged negatively charged
ex. Mg2+ ex. SO42-
Positive ions attract negative ions.
39.
40. Essential Nutrients
Chemical elements involved in the
metabolism of the plant or necessary
for the plant to complete its life cycle
Fertilizers are mineral salts.
44. Fertilizers
Inorganic
•Release elements
quickly in water
•Excess can “burn”
plants
•Urea is treated as
inorganic because of
“quick release” of N
•Solubility not affected
by temperature
•May leach from soil
Organic
•Release inorganic
ions slowly
Examples:
•Urea formaldehyde
•Isobutylidene diurea
(IBDU)
•Manures
•Sewage sludge
•Blood
•Bone meal
46. Slow-release: urea aldehydes
•Urea formaldehyde
• 36-38% nitrogen
• Slowly released
• Relies on microbial
breakdown
•IBDU – isobutylidene
diurea
• Slowly released
• Not dependent on microbial
activity.
47. Slow-release: sulfur-coated
•Prills of various
fertilizers (urea, triple
superphosphate,
potassium sulfate,
potassium chloride)
•Coated with sulfur and
wax-like sealant
•Not dependent on
microbial activity
Sulfur-coated urea
48. Water-Insoluble Nitrogen (WIN)
GUARANTEED MINIMUM ANALYSIS
Total Nitrogen (N) 12.0 %
Water Insoluble Nitrogen (N) 10.8%
Iron (Fe) 0.2%
Organic Matter 80.0%
Look for WIN that is at least 50% of total Nitrogen.
49. Forms of Nitrogen
•Ammonium (NH4+)
•Potential toxicity
•Acidifying
•Should be no more
than 40% of total N for
container plants
•Urea – broken down
to ammonium
•Nitrate – less chance
of toxicity but greater
chance of leaching
Ammonium toxicity symptoms
51. pH adjustment for turfgrass?
•Use of regular sulfur applications can deteriorate
soil structure and cause build-up of soluble salts.
•Hard water used for irrigation can negative the
acidifying effects.
•Acidifying fertilizers are a better option for western
soils
• Offset alkalinity of irrigation water
• Temporarily low soil pH at time of fertilization.
52. N is most important for turfgrass fertility
•Elicits the strongest growth response
•Enhances green color
•Absorbed primarily in NO3− form
•Can be translocated to leaf tissue within 24 hours.
53. Analysis of quick-release N fertilizers
N carrier Analysis Burn
potential
Soil reaction
Ammonium
nitrate
33-0-0 High Acidic
Potassium
nitrate
13-0-44 High Basic
Ammonium
sulfate
21-0-0 High Acidic
Urea 45-0-0 High Slightly acidic
Monoammonium
phosphate
11-50-0 Moderate Slightly acidic
Diammonium
phosphate
20-50-0 Moderate Basic
54. Analysis of slow-release N fertilizers
N carrier Analysis Burn
potential
Activity at
low
temperatures
IBDU 31-0-0 Moderately
low
Moderate
Sulfur-coated
Urea (SCU)
22 to 38-0-0 Low Moderate
Resin-coated
urea
24 to 35-0-0 Low Moderate
Urea
formaldehyde
36 to 38-0-0 Low Very low
Manures Variable Very low Very low
Activated 4 to 6-4-0 Very low Very low
55. Turfgrass N requirements by species
Grass species Lbs. N per 1,000 sq. ft. per
year
Creeping bentgrass 3 to 8
Kentucky bluegrass 2 to 4
Perennial ryegrass 2 to 4
Red fescue 1 to 3
Chewings fescue 1 to 3
Tall fescue 1 to 2
Dwarf fescue 1 to 2
No more than 1 lb. N in any one application.
56. Phosphorus requirements of turf
•Greatest response to phosphorus seen with
turfgrass seedlings.
•Deficiencies rarely observed in established turf
• Exceptions include low soil P levels or pH above 7.8
•Applications should be based on soil tests.
•High soil P levels increase potential for annual
bluegrass (weed) infestation.
58. Potassium requirements of turf
•K involved stress resistance, wear tolerance,
disease resistance
•Factors that affect requirements:
•Clipping removal, irrigation, soil texture
•Application should be based on soil tests.
59. “Winterizers”
•Only good for warm-
season grasses.
•Cool-season grasses
need nitrogen in the
fall.
•When? -mean daily
temperature for three or
more consecutive days
is below 50 degrees F.
60. Turf Fertilization Schedule
Maintenance
level
Spring
April/May
Summer
June July
Fall
Sept Nov
Total
Pounds of N per 1,000 square feet
Low 1 - - 1 - 2
Medium 1 - - 1 1 3
High 1 0.5 0.5 1 1 4
Fertilization may be reduced by as much as
one half if clippings are consistently recycled
back into the lawn.
61. Iron deficiency
•Most common micronutrient deficiency for
turfgrass
•Intervienal chlorosis of leaf blades and thinning of
turf
•More serious problem when pH above 7.5 or high
soil phosphorus.
•Spray every two weeks with 1 to 2 ounces ferrous
sulfate per 1,000 sq. ft. until corrected.
62. Fertilizer calculations
•You have a 50-lb bag of 26-5-10 fertilizer that you
want to apply to a lawn at a rate of 1.0 lb nitrogen
per 1000 sq ft. How much of the 26-5-10 fertilizer
will you need to apply per 1000 sq ft?
•Ignore the weight of the fertilizer bag and divide
the amount of nitrogen desired (1.0 lb nitrogen per
1000 sq ft) by the percentage of nitrogen in the
bag (26%). 26% = 0.26.
•(1.0 lb nitrogen per 1000 sq ft) ÷ 0.26 = 3.8 lb of a
26-5-10 fertilizer is needed to supply 1.0 lb
nitrogen per 1000 sq. ft.
67. Shift towards soilless potting mixes
•Do not need to be
pasteurized
(sterilized)
•Lighter in weight
(lower shipping
costs)
•Mixes are more
consistent – you
know what to expect
68. Properties of soilless potting mixes
•Water retention
•Aeration
•Drainage
The goal is to increase aeration without decreasing water
retention.
69. •Perlite
• Volcanic origin
• Low bulk density
• Good drainage and aeration
• Low CEC and water-holding
•Vermiculite
• Heat-expanded mica
• Low bulk density
• Use coarse grades for best
aeration and drainage
• High CEC and water-holding
Coarse mineral components
Vermiculite
pH 7.5
pH 7.5 (U.S.), 9.0 (African)
70. Sand
•Coarse concrete-grade
(washed)
•High bulk density
•Excellent drainage and
aeration
•Increases water-holding
when mixed with bark
•Decreases water-
holding when mixed
with field soil
•Low CEC
71. Calcined Clays
• Good water- and nutrient-holding capacity
• Excellent drainage qualities
• Provides Coarse Texture and Aggregated
Structure
• Little influence on pH of a mix
• Bulk density 30 to 40 lbs/ft3
72. Bulk Density
•How heavy per unit
volume
•Acceptable range:
40 to 60 lb/ft3
•Too heavy: not
economical to ship
•Too light: pots with
plants topple
Material
Bulk density at
CC
(lbs/ft3
)
Field soil 106
Sand 107
Sphagnum peat 54
Coir (coconut
fiber)
46
Vermiculite 46
Pine bark 51
Perlite 32
Rock wool 54
CC = Container Capacity
73. Peats
•Sphagnum moss - a moss that grows in
acid bogs in North America, Canada, and
northern Europe
•Sphagnum peat moss - the partially
decomposed remains of Sphagnum moss
•Peat moss (or moss peat) – partially
decomposed Sphagnum or hypnum
•Reed-sedge peat – reeds, sedges,
marsh grasses and cattails (variable in color
and other properties)
•Peat humus – highly decomposed; low
water-holding capacity
Less decomposed
More
decomposed
74. Sphagnum moss Sphagnum moss peat – pH 3.0 to 4.0
Hypnum moss peat– pH 5.2 to 5.5
Reed-sedge peat – pH 4.0 to 7.5
75. Peat-based mixes
•Common formulations:
•Sphagnum peat moss / vermiculite (1 : 1)
•Sphagnum peat moss / perlite (1 : 1)
•Excellent water- and nutrient-holding, good
drainage.
•Very difficult to re-wet if allowed to dry out.
•Must be careful not to over-fertilize and
water enough to leach out excess nutrients.
•Breaks down over time.
76. Bark-based products
•Cheaper than
Sphagnum peat
• pH 4.5, increases
over time
•Excellent aeration and
wettability
•Poor water-holding
•Often mixed with sand
and vermiculite or
peat moss (3 bark : 1
sand : 1 vermiculite or
peat moss)
pH of softwoods 3.0 to 4.0
pH of hardwoods 6.0 to 7.0
78. •Dolomitic limestone
• Correct the pH or acidity of a
mix
•Phosphate
• Superphosphate (0-45-0)
•Nitrogen and
potassium
• Enough to last 2 weeks
•Micronutrient mix
• Enough to last the growing
season
•Wetting agent
• Gel granules help media hold
water longer
Other Pre-plant Additives
Hydrogel crystals used as a
wetting agent
79. Organic mixes
• OMRI –
• Organic Materials Review
Institute
• Assures products are
consistent with the
requirements of the National
Organic Standard.
• Challenge is not finding
ingredients but in getting
consistency.
• May not use wetting agents
in certified organic
products.
80. Summary – container substrates
•Stable product that will not shrink in volume during
plant production / shelf time.
•Bulk density low enough for shipping and handling
but high enough to prevent toppling of plants.
•At least 10 to 20% air by volume at CC (container
capacity) in a 6.5-inch pot
•High cation exchange capacity (CEC) for nutrient-
holding.
•pH of 6.2 to 6.8 (soil-based) or 5.4 to 6.5 (soilless)
– crop dependent
