Readying the soil for spring-summer planting is one of the most important tasks gardeners face at this point in the year. But what is soil made of, and what does it need to benefit the plants we want to grow? This class will provide an overview of soil types and basic soil ecology, give gardeners tools for assessing their soils, and provide suggestions on when and how to use various soil amendments.

1. Garden Soil &
Amendments
Independence Gardens
Portland, OR
January 2012
© Independence Gardens LLC
Download the
handout that goes
along with this
slideshow!
http://bit.ly/y4K4ru
Tuesday, January 31, 2012

2. Topics We’ll Cover
• What is soil?
• Soil issues worldwide
• Soil issues in your garden
• Soil components
• pH
• Nutrients
• Soil testing
• Amendments
What We’ll Cover TodayPreview
Got Questions?
Please ask as we go along.
Tuesday, January 31, 2012

3. What is soil?
• Soil is an edge
– Microorganisms + minerals
• Soil is the basis of a
diverse ecosystem
– Broader base  more room for
everything else
• Soil is a process
– Anything but static!
• Soil is a relationship
– Between components,
conditions, inhabitants,
and YOU
http://
www.extension.um
n.edu/distribution/
cropsystems/
images/
M1272-4.jpg
http://www.hylandseeds.com/images/
soil%20photo.jpg
Tuesday, January 31, 2012

4. Soil worldwide
http://www.utafoundation.org/soil_loss.jpg
Tuesday, January 31, 2012

5. Soil in your garden
• Top 6-8 in.
– Where plants do most of their feeding
• You can look for
– Structure
– Texture
– pH
– Nutrient presence/availability
– Organic matter
– Biological activity
• A single acre of good soil can support 2000 lbs.
of animal life above the soil surface and
4000-6000 lbs. below (“microherds”)
http://www.gardenvisit.com/assets/madge/shovel/600x/
shovel_600x.jpg
Tuesday, January 31, 2012

6. Soil components
• Mineral components
and organic matter =
“solid”
• Air and water = “space”
– Soil microorganisms live
in this part of the soil,
and they are what make
nutrients available to
plants
http://courses.soil.ncsu.edu/resources/physics/
composition/compo3b.png
Tuesday, January 31, 2012

7. http://school.discoveryeducation.com/schooladventures/soil/
images/particle_sizes1.gif
Soil particles
• Clay
– Less than 0.002 mm
• Silt
– 0.002 mm – 0.05 mm
• Sand
– 0.05 mm – 2.00 mm
• Fine pebbles
– 2.00 mm – 5.00 mm
• Medium pebbles
– 5.00 mm – 20.00 mm
• Coarse pebbles
– 20.00 mm – 75.00 mm
Tuesday, January 31, 2012

8. http://www.omafra.gov.on.ca/english/engineer/facts/
vfss_manual/vfssman37f1.png
Soil layers
• O (organic)
• A (assimilation)
• E (elluviation)
• B (banking)
• C (chemical/
constitution)
• R/D (durable)
Tuesday, January 31, 2012

9. Soil types
• Not just “dirt”
– Dirt is soil where it’s
not supposed to be
• Loam is ideal for
garden soil
– 40% silt
– 40% sand
– 20% clay
http://www.dirtguytopsoil.com/images/soiltriangle.gif
Tuesday, January 31, 2012

10. Soil food web
• This is
who/what
shares your
soil with
your plants
http://www.magicsoil.com/MSREV2/Soil_Food_Web_Soil_Biology_Primer.jpg
Tuesday, January 31, 2012

11. pH
• Logarithmic scale, 0 (acid)-14 (base)
http://packerpedia.wiki.packer.edu/file/view/pH_Scale.jpg/31722773/pH_Scale.jpg
Tuesday, January 31, 2012

12. Nutrient availability
• Soil nutrient supermarket
• Our soils are generally ~5.5
• Ideal garden soil is 6.8-7.0
• Other factors affecting availability
include:
– Soil texture
– Soil temperature
– Amount of organic matter
– Microbial activity
– Interactions with other nutrients
• Competition for sites on soil
particles
• Forming insoluble compounds
http://attra.ncat.org/images/organic_soil/chart.jpg
Tuesday, January 31, 2012

13. Nutrient availability
• Soil nutrient supermarket
• Our soils are generally ~5.5
• Ideal garden soil is 6.8-7.0
• Other factors affecting availability
include:
– Soil texture
– Soil temperature
– Amount of organic matter
– Microbial activity
– Interactions with other nutrients
• Competition for sites on soil
particles
• Forming insoluble compounds
http://attra.ncat.org/images/organic_soil/chart.jpg
Tuesday, January 31, 2012

14. Nutrient availability
• Soil nutrient supermarket
• Our soils are generally ~5.5
• Ideal garden soil is 6.8-7.0
• Other factors affecting availability
include:
– Soil texture
– Soil temperature
– Amount of organic matter
– Microbial activity
– Interactions with other nutrients
• Competition for sites on soil
particles
• Forming insoluble compounds
http://attra.ncat.org/images/organic_soil/chart.jpg
Tuesday, January 31, 2012

15. Nutrients
Tuesday, January 31, 2012

16. Essential plant nutrients
• From air and water
– Carbon (C) Hydrogen (H) Oxygen (O)
• Macronutrients
– Nitrogen (N) Phosphorus (P) Potassium (K)
• Secondary macronutrients
– Sulfur (S) Calcium (Ca) Magnesium (Mg)
• Micronutrients
– Boron (B) Chlorine (Cl) Copper (Cu)
– Iron (Fe) Manganese (Mn) Molybdenum (Mo)
– Zinc (Zn)
Tuesday, January 31, 2012

17. How to learn more
• Shake test
– “Layer Away”
• Perc test
• Watering test
• pH test
• Soil test
• “Weed”
observation
• Bug’s eye view
Tuesday, January 31, 2012

18. Soil testing: Do it...if:
• Nutrient testing
– You plan to grow most or all of your own food
yourself
– You’re growing in a small, homogenous,
contained space
– and/or you’ve been experiencing problems
• Toxics testing (esp. Pb)
– You are aware of previous uses of your land that
were “dirty” or sources of pollution in the ‘hood
– You don’t know how your land has been used in
the past
– You’re growing within 6 ft. of a house built before
1978
– Small children/elders/animals will eat the harvest
http://www.thegardenerseden.com/wp-content/uploads/2009/10/Soil-
Sample-for-Testing.jpg
Tuesday, January 31, 2012

19. What to do with your new info
• Awareness...attention...and amendments!
– Organic matter
• Adding it is the most important thing you can do for your soil!
• 1-2 times a year, add 1-2 in. of compost, mixed into the top 8 in. of soil
– Soil conditioners improve structure and/or provide nutrients
• Examples: coffee grounds, bloodmeal, kelp, peat moss, coco coir, lime,
etc. (some are organic matter, some are not)
• Apply as needed
– Mulches have many benefits but are not soil conditioners
– Fertilizers aren’t designed to help your soil
Tuesday, January 31, 2012

20. Adding organic matter
• Increases infiltration of water from soil surface
• Increases water-holding capacity in sandy soils and
drainage in clay soils
• Improves nutrient retention (reduces leaching)
• Improves nutrient availability
• Examples: garden/household compost,
(composted) manure, mushroom compost, cover
crops/green manure, worm castings
Tuesday, January 31, 2012

21. Changing pH
• Test first
– DIY kits
– Professional/lab test
• To raise pH
– Add lime (maximum: 5 lbs./100 sq. ft.)
– Add wood ash (maximum: 1.5 lbs./100 sq. ft./yr.)
• To lower pH
– Add organic matter
– Add sulfur (maximum: 5 lbs./100 sq. ft.)
Tuesday, January 31, 2012

22. Ongoing nutrition
• Know what’s there already
• Conserve what is present
– Maintain pH
– Reduce erosion and leaching
– Recycle nutrients! (compost/mulch)
• Add nutrients
– Commercial/packaged fertilizers
• Avoid fertilizing dry soil
• Always follow instructions on the label
– Organic matter
• Include cover crops/green manures to protect and enhance soil
Tuesday, January 31, 2012

23. Organic fertilizer N-P-K values
Thanks to Naomi Montacre for this chart.
Tuesday, January 31, 2012

24. A few more pointers
• Define your garden space
– One way to do this: use raised beds
– Or…you can use containers
• This is a whole different kind of soil and soil-building
• Avoid compaction
– Including mechanical tilling
• Avoid unnatural layering
– For example, infilling a raised bed and not incorporating the
new soil into the native soil
• A note on toxins
– Know where the risk is and the common pathways for exposure
Tuesday, January 31, 2012

25. And finally...
• To get neglected soil into shape for
THIS season
– Incorporate 1-6” of compost
– Add kelp meal (K), bone meal or
a mineral mix (P), and an organic
N source (alfalfa meal, blood
meal, or fish meal/emulsion)
according to package instructions
• To protect your soil for next year
– Mulch regularly
– Sheet mulch or cover crop
through the winter
Tuesday, January 31, 2012

26. Questions?
Tuesday, January 31, 2012