Introduction to Soils for the Master Gardener

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Introduction to Soils for the Master Gardener
Dick Wolkowski Extension Soil Scientist Departme
nt of Soil Science University of Wisconsin -
Madison
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• 700
• different
• soils
• in Wis.

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Productive soil must be fertile

• physical fertility
• texture, structure, drainage, tilth
• chemical fertility
• nutrient supply
• soil testing
• nutrient additions
• biologically fertile
• microorganisms
• organic materials
• soil environment

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Soil formation-weathering

• physical
• freezing, thawing, wetting, drying, organisms
• chemical
• dissolved minerals moved in water
• soil horizons formed
• 1 inch - 100 years

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Soil f (Climate, Parent material, Living
organisms, Topography, Time )
Deciduous
Coniferous
Prairie
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Soil texture

• classes - sand, silt, clay
• names based on proportions
• loam, silty clay, loamy sand
• changing proportions not recommended
• clay also group of minerals
• montmorillinite, kaolinite.
• nutrient storehouse

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Textural classes
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Soil organic matter

• plants, animals, microorganisms
• living, dead, decay products
• humus
• complex, dark-colored, reactive
• soil acidity reservoir
• nutrient storehouse
• difficult to significantly increase

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Soil structure

• particles glued into aggregates
• organic matter, clay, bacterial secretions, Fe/Al
  oxide coatings
• granular, platy, blocky
• finer aggregates in topsoil, massive in subsoil
• improve by adding organic residues
• decay 90 CO2 H2O

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Problem heavy soil

• aggregates tightly packed
• small pores
• poor drainage, roots suffocate
• cloddy if tilled wet
• compact easily
• improve with organic residues
• better crumb stability
• larger pores
• sand clay cement

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Problem light soil

• aggregates too big to pack tightly
• large pore spaces
• droughty
• improve with organic residues
• sponge
• better water holding capacity

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Organic residues

• compost, grass clippings, crop residues
• annual gardens - 1 bu / 20 sq ft
• perennial gardens - 1 bu / 10 ft
• do not add to tree/shrub planting hole
• green manure, fall cover crops
• green topgrowth tilled under
• extra N needed for high C residues
• microorganisms tie-up N
• wood chips, sawdust, oat straw

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Organic residues

• provides food for microorganisms
• for every 100 lb. added, 90 lb. converted to
  water, carbon dioxide
• 10 lb. stable 1st year
• 1 lb. stable 2nd year
• microbial decay process
• more glue for better crumb stability
• nutrients released
• fresh surfaces for nutrient holding

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How to remember the 17 essential elements

• C HOPKINS CaFe is Mighty
• Nice, But Many More
• Prefer Claras Zany Cup
• Required for the plant to complete life cycle
• Directly involved in metabolism
• Can not be substituted by another nutrient
• Essential for a wide range of plants

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Food for plants?

• plant, animal nutrition very different
• plants manufacture basics
• protein, carbohydrate, sugar.
• framework with C, H, O
• 14 essential soil elements
• N, P, K - primary
• Ca, Mg, S - secondary
• B, Cl, Ni, Cu, Fe, Mn, Mo, Zn trace or micro
• animals (we) eat basics

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Nutrient supply

• clay main nutrient storehouse
• negative charge
• attracts, holds positive ions
• Ca , Mg , K , NH4
• easily displaced, exchanged
• plant uptake
• some leaching on sandy soils
• negative ions remain in soil solution
• NO3-, Cl-, SO4

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Nutrients must be soluble
plant root
pore space
soil solution
Nutrient exchange between clay and soil solution
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Would Calvin be a good master gardener?
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Soil testing is the only preplant method of
knowing nutrient need!

• WHAT SOIL TESTING TELLS US
• Crop N need
• Plant available P and K
• Crop P and K need
• Soil organic matter
• Soil pH and lime requirement
• Other tests if requested

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A shovel is OK too, mix a small amount in a clean
bucket
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Soil test

• rapid chemical analysis
• index of potential nutrient supply
• deficiency
• excess
• sample to show true variation
• Composite
• UWEX lab in Madison

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Sampling soils

• sample depth
• established turf - 4 inches
• new turf, gardens - 6 inches or tillage depth
• raised beds - depth of bed
• probe best, spade OK
• combine 5 subsamples composite

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Avoid unusual areas backfill, wet spots, etc.
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Sampling soils

• when
• annual gardens, new turf
• fall, spring before tillage
• perennials, problems, established turf
• anytime
• suspected salt damage
• very early spring
• sample each area separately
• repeat every 2-3 yrs

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Useful laboratory tests

• routine
• soil pH, buffer pH
• organic matter
• available P and K
• other
• Ca, Mg, S, Zn, B, Mn
• no good test/need
• N, Fe, Cu, Cl, Mo, Ni
• problem solving
• texture, soluble salts
• Cl, Pb, As,...

UW Soil and Plant Analysis Lab 8452 Mineral Point
Rd, Verona 53593 (West Madison Ag. Research
Station)
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Soil test report

• potential for deficiency
• which nutrient needed
• how much to apply
• fertilizer for nutrient need
• lime, sulfur amendments for pH change
• when to apply
• when to STOP!

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Soil test results

• excessively high
• common for residential areas
• not detrimental
• adding more not beneficial
• avoid balanced blends, most organics
• low
• build to optimum
• turf fertilizer blends

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Soil test results - pH

• measure of acidity, alkalinity
• scale 1 - 14, optimum 6 - 7
• add lime only if recommended
• incorporate 6 - 8 inches
• add aluminum sulfate to acidify
• new turf
• if strongly alkaline
• blueberry, rhododendron

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Effect of soil pH on nutrient availability
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Optimum pH for turf and gardens

• depends on species pH range
• kentucky bluegrass 6.0 - 7.6
• creeping red fescue 5.3 - 7.5
• sweet corn 6.0
• potato 5.4 6.0
• green bean 6.8
• tomato 6.0

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Soil test results - organic matter

• 2 - 4 most soils
• impractical and difficult to change
• nutrient reservoir
• used for calculating N and lime recommendations

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Soil test results - N

• no direct measures on report
• N rec from crop need, organic matter
• promotes leaf growth
• excess N
• delays maturity
• moves below root zone and may contaminate ground
  water

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Soil test results - P

• stimulates root growth and flowering
• shallow rooted greater need
• optimum soil test P for turf and gardens
• - established turf 11 - 15 ppm
• - sweet corn 16 - 25 ppm
• - green bean 16 - 25 ppm
• - tomato 31 - 45 ppm
• - potato 161- 200 ppm

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Soil test results - K

• promotes disease resistance, winter hardiness
• root crops require most
• optimum soil test K for turf
• - established turf 41 - 60 ppm
• - sweet corn 101 - 120 ppm
• - green bean 101 - 120 ppm
• - tomato 121 - 180 ppm
• - potato 121- 160 ppm

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Inorganic fertilizer

• sold on a percent by weight basis
• N P2O5 K2O
• chemically simple
• N in air plus natural gas
• rock phosphate, potash mined, sized and cleaned
• very soluble salts
• easily blended
• must be careful with rates

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Inorganic fertilizer

• Nutrient
• Type N P2O5 K2O
• -------------- ---------------
• urea 46 0 0
• ammonium nitrate 33 0 0
• triple super P 0 46 0
• ordinary super P 0 20 0
• muriate of potash 0 0 60
• potassium sulfate 0 0 50
• di-ammonium phos. 18 46 0

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Recommended fertilizer

• Gardens
• avoid high N fertilizers for most crops
• sweet corn, potato are exceptions
• uniform, low grade (e. g.10-10-10)
• does not match plant need
• over supply P and K
• micronutrients generally not needed
• adjust pH as necessary

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Organic fertilizer

• chemically complex, contains C
• naturally occurring
• byproducts
• microorganisms must degrade
• slow release, rate ???
• improve structure with long-term use

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Organic fertilizer

• Nutrient
• Type N P2O5 K2O
• -------------------------------
• blood meal 13.0 1.5 0.6
• bone meal 2.2 27.0 0
• seaweed 1.5 1.0 4.9
• tree leaves 0.7 0.1 0.8
• greensand 0 1.4 6.3
• activated biosolid 6.0 3.0 0.2

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Organic fertilizer

• may contain
• unnecessary nutrients, compounds
• nonessential elements
• does not add nutrition, improve flavor, enhance
  food safety and quality
• often more expensive per pound of nutrient

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Foliar sprays fruits, sensitive ornamentals

• trace, secondary elements
• soil Fe, Mn fixed at high soil pH
• supply by spraying leaves
• temporary fix, requires repeating
• emergencies
• no substitute for soil applied nutrients
• leaf burn, expensive, extra work
• most spray falls on soil

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Recommended fertilizer

• Turf blends
• regular or maintenance - high N
• soil test P, K optimum, above
• starter - high P2O5
• soil test P below optimum
• winterizer - high K2O
• soil test K below optimum
• use a Holiday schedule
• sweep off driveways and sidewalks

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Other turf management considerations

• Mowing
• no shorter than 2.5 in.
• cut no more than 1/3 at any time
• normal height in fall
• Thatch
• natural buildup
• verti-cut, power-rake, core
• Water
• 1 in. per week in summer, less in spring and fall
• soak rather than sprinkle
• Shade
• seed fescue
• prune trees
• mow higher
• less water and fertilizer

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Compost
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What is Compost ?

• Material left after the aerobic decomposition of
  organic material(s)

Organic Material bugs O2 ? Compost
CO2 H2O
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General Characteristics

• N availability much lower than fresh materials
  like manures, biosolids, food processing wastes
  (lt10 of TN)
• Diverse array of feedstocks used to make
  compost
• Variability in quality of finished compost
• Comes with lots of things besides
  macro-nutrients

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Assessment of maturity

• High concentrations of ammonium-N indicate
  immature compost
• - should be less than 40 ppm
• Measure microbial respiration under optimal
• moisture, temperature conditions
• - High respiration high activity unstable
• - Low respirationlow activity stable
• Test compost or compost blend BEFORE using

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Fresh Vs. Composted Organic Matter

• Fresh Wastes
• High biological activity
• Some have high nutrient availability
• Can immobilize nutrients during early stages of
  decomposition
• Highly variable in physical traits
• Instability can increase Pythium damping off of
  certain crops

• Compost
• Already gone through decomposition, stable
• Mature compost should provide some nutrients
• Improves drainage and other physical properties
• Provides for biological control of Phytophthora
  root rot

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Making Your Own Compost

• Build a bin 5 x 5 x 5 ft.
• Add organic materials and adjust to 40-60 water
  content
• Use bulking agent for wet materials, add water to
  dry materials
• High CN materials take longer
• Maintain aeration by frequent turning
• Compost is finished when pile doesnt re-heat and
  it is difficult to distinguish initial materials

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