s oil test interpretation Weston Miller OSU Extension Service Preview of presentation Safety precautions General soil quality assessment How to take a soil test What to test for Interpreting results ID: 784255
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Slide1
Assessing soil quality,soil testing procedures,soil test interpretation
Weston Miller,
OSU Extension Service
Slide2Preview of presentationSafety precautionsGeneral
soil quality assessment
How to take a soil test
What to test for
Interpreting results
Slide3Safeair.Oregon.gov
Based on soil data collected by DEQ in late February 2016, OHA concludes that the levels of metals in soil around Bullseye Glass in SE Portland and
Uroboros
Glass in N Portland are
too low to harm the health of people in the surrounding community.
As a precaution for urban food gardeners in general, State agencies are advising that gardeners perform soil tests for metals in urban areas regardless of proximity to air pollution sources.
Slide4How to interpret results of soil test for heavy metals in urban areas
Slide5Safety first with metals!
Slide6How to minimize exposure to heavy metals through vegetable gardening
Research inherent hazard of site
Old paint on/near buildings, industries like gas stations/plumbing shops, air pollution from roads/industry, etc.
Increase soil pH by adding lime to the soil
Add compost and other forms of organic matter
Avoid root crops and greens in suspect areas
Wash produce thoroughly
Take off shoes before entering home
Wash hands after gardening, even if you use gloves
Slide7Questions to assess soil quality Does soil have good structure and
tilth
?
Is the soil free of compacted layers?
Is the soil easily worked?
Is the soil full of living organisms?
Are earthworms abundant in the soil?
Is plant residue present and decomposing?
Do crops/weeds appear healthy and vigorous?
Do roots grow well?
Does water infiltrate quickly?
Is water available for plant growth?
Slide8DrainageAvoid low areas
Raised beds
Organic matter
Slide9Look for signs of life
Look for response of plants to flush of nutrients in early summer
Slide10Soil Texture How coarse or fine a mineral
soil is.
The
proportion
of sand, silt, and clay.
Slide11Soil Triangle
Slide12Laboratory texture analysis
Slide13Soil texture by feel
Slide14Relative Size of Soil Particles
(University of Nebraska, Lincoln)
Slide15Slide16General properties of sandy soilsSandy
soils tend to
be:
Low
in
organic
matter content
Low native fertility
Low water holding capacity
Low cation exchange
and buffer
capacities
R
apidly permeability of air and water
Slide17General properties of finer soilsFiner soils tend to be:
H
igher
in organic matter content
H
igher
native fertility
Higher
water holding capacity
Higher
cation exchange and buffer capacities
Slower
permeability of air and water
Good up to a point, then…
Slide18(CA Fertilizer Association)
Ideal soil structure
Slide19OM helps to aggregate particles, creating pore spaces
Slide20Slide21OSU soil testing resourcesKeyword search “OSU small farms soil test”
How to take a sample
List of labs
How to interpret results
Slide22Why do
chemcial
analysis of soils?
Establish baseline nutrient status
Determine application rates
Assess pH and need for liming
Measure changes over
time
Avoid excess nutrient application or build up of salt
Slide23How to take a soil test
Slide24Determine management units
Slide25Sample where the crop will be planted
Slide26Slide27Slide28Slide29What to test forpH (acidity-basicity)
SMP
buffer (ease of change of pH)
Organic matter (OM)
Cation
Exchange Capacity (CEC)
Phosphorus (P)
Potassium (K)
Calcium (Ca)
Magnesium (Mg)
Sodium (Na)- salts
Texture?
Slide30Date
Slide31Organic matter
Slide32Organic Matter (OM)Tests not so accurate, tend to overestimateLook for 5-8% OM for veggies
Slide33Soil Organic Matter (SOM) fractions
Slide34Slide35Organic Matter
Key to long term fertility
Improves quality of most soils
Breaks down to form humus (natural glue)
Strengthens aggregates
Improves water holding capacity
Releases plant nutrients
Provides food for beneficial
organisms
Slide36Too much of a good thing?High Organic Matter (OM) content leads to:High rates of mineralization of soil leading to potential excess available nutrients (P and K)
Excess nutrients can lead to plant problems
High P can
affect micronutrient
and N
absorption
Potential for excess nutrients to leach into groundwater or surface water as non-point source of pollution
Slide37Cation
Exchange Capacity
Slide38A soil’s capacity to hold cations is called its cation exchange capacity
or CEC.
CEC is a calculated value
Slide39CEC determines availability of cations
Higher in clay soils because negative charge
Organic
matter and increase pH can increase effective CEC
Slide40Slide41Slide42Slide43pH
Slide44pH Scale
pH 6-7 is best for vegetable production
Slide45Soil pH determines if lime is needed
Slide46Soil pH and nutrient availability
Soil bacteria abundance
Slide47Courtesy John Hart, OSU Crop & Soil Science
Soil pH is Key
Slide48Courtesy John Hart, OSU Crop & Soil Science
Slide49SMP Buffer pH
Slide50SMP Buffer tells how much lime to apply
Slide51To Increase Soil pH
Lime (Calcium carbonate)
Per soil test recommendations
Or
5-10
# / 100 sq. ft.
Dolomite also has Mg
Apply in fall, if possible
Slide52Phosphorus soil test
Slide53Potassium
Slide54Calcium
Slide55Magnesium
Slide56Trace minerals: B and Zn
Zn =
6
.8ppm, which is high, but Zn rarely causes toxicity except in saline soils
Consider tissue analysis to test for B if noticing signs of deficiency (
chlorotic
young leaves; death of main growing point; stunted growth)
Slide57What about nitrogen?Forms available for plant uptake
Nitrate (N0
3
-
)
Ammonium (NH
4
+
)
Concentrations depend on bio activity
Vary widely with temp and moisture
Difficult to interpret soil test results
Slide58Nitrate nitrogen
Slide59Residual soil nitrate
Slide60General recommendation: Apply 3 # actual N per 100ft
2
over course of season in splits with. No more than ½
in
initial application
Slide61Review of presentationSafety precautionsGeneral soil assessment
How to take a soil test
Safety first!
What to test for
Interpreting results