This presentation will teach you what soil is, how to find out what type of soil you have, how soil feeds plant, and how to improve your soil's health.

1. BASICS OF SOIL FERTILITY FOR
URBAN (AND NON-URBAN)
GROWERS
Anne Pfeiffer
UW-Madison
Thanks to Erin Silva for some slide content

2. PLANTS NEED…

3. OVERVIEW
• A Quick Intro to Soils
• Finding your Soil Type
• How Soils Feed Plants
• What It All Means: Growing Healthy
Plants
• Fertilizer Calculation Example

4. BY THE TIME YOU LEAVE…
• Have a clear understanding of the essential soil
considerations for locating a garden or farm
• Know how, when and why to conduct a soil test
and how to interpret the results
• Gain a basic understanding about how to make
soil and fertility management decisions.
• Access resources for non-biased, straightforward
information about soil management

5. A QUICK OVERVIEW OF
SOILS

6. SOILS: MORE THAN “JUST DIRT”
• Hold up plants
• Provide air and water to plants
• Supply nutrients
–Plants need sufficient quantity but not too
much
• Provide habitat for soil organisms

7. CHARACTERISTICS OF AN IDEAL
SOIL
• What are characteristics of ideal soils?
–Fertile
–Deep
–Well drained/aerated
–High in organic matter
–Friable
• soil is easily worked

8. WHAT IS SOIL?
2-5% Organic Matter
50% Solid Matter 50% Pore Space

9. MINERAL AND ORGANIC
•
COMPONENTS
Broken down rock particles
– Depends on parent material
– Clay particles hold nutrients
• Organic matter (containing carbon)
– Decomposed plant and animal matter
– Ideal soil is about 5% organic matter
– Complex molecular structure plays special role:
• Source of food for soil microorganisms
• Source of nutrients for plants
• Holds minerals against loss due to leaching
– May or may not be plant available

10. PORE SPACE
• Air (~25% of total soil volume)
–Oxygen supports soil life
• Roots
• Microbes
–Air can be displaced by water
• Water (~25% of total soil volume)
–Carries nutrients to plants

11. SOIL PROFILE
• Topsoil (A horizon)
– It is the darkest layer of the soil
because it contains organic
matter and humus.
– Contains majority of feeding
roots of plants
• Subsoil
– Low in nutrients
– Contains few microorganisms
– Structure of subsoil is important
for drainage
• Often disturbed in urban
settings

12. EXAMPLE OF A SOIL PROFILE
• Note the dark organic
horizon at the surface
and changes in color
and structure down
the profile

13. SOIL TEXTURE
• Determined by mineral component
• Coarseness or fineness of soil
• Why is texture important?
–The texture will determine how much air is in
soil and how well water flows through the soil
–Determines how easily the soil is worked and
under what conditions

14. SOIL TEXTURE: CLAY
• Soil particles are less
than 0.002 mm in size
• Does not drain easily
and is difficult to
work
• Root growth is poor
due to small spaces
between soil particles

15. SOIL TEXTURE: SILT
• Particle size is
between 0.002 to
0.05 mm
• Feels silky to the
touch

16. SOIL TEXTURE: SAND
• Sand particles range in
size from 0.2 mm for
the very finest sand to
2 mm for the coarsest
• Feels gritty if rubbed
between your fingers
• Warms up and dries
early in spring
• Low in nutrients

17. SOILS ARE A MIX OF SAND, SILT
AND CLAY

18. SOIL TYPES
• Most soils are a mixture of different soil textures
– Often a soil type will be dominated by a particular texture
• Can group soil types by how well drain and major
texture class they contain
– Heavy soils
• Contain a high proportion of clay
– Light soils
• Contain a high proportion of sand
• Important to know the soil type because it will
determine the management practices you need to
use

19. FINDING YOUR SOIL TYPE

20. http://websoilsurvey.nrcs.usda.gov/

24. SOILS AND PLANT
NUTRITION

25. ESSENTIAL ELEMENTS FOR PLANT
NUTRITION
• Must be required for the completion of the life cycle of the plant.
• Must not be replaceable by another element.
• Must be directly involved in plant metabolism, that is, it must be
required for a specific physiological function.
• The element must be required by a substantial number of plant
species, not just a single species or two.

26. 16 ESSENTIAL ELEMENTS
• C, H, and O are not considered minerals
• Macronutrients:
– Primary macronutrients: N, P, and K
• Needed in relatively large amounts
– Secondary macronutrients: Ca, Mg, S
• May be supplied in smaller quantities
• Micronutrients: Cl, Fe, B, Mn, Zn, Cu, Mo
– Required in small amounts but still essential
– Deficiencies lead to severe depression in growth, yield, and
quality
• If any one is missing or low, plant productivity is limited

27. ELEMENTS REQUIRED IN PLANT
NUTRITION

28. SOIL NUTRIENTS
• Ability of a soil to hold nutrients and release
them to plants depends on
– Presence and availability of nutrients
– Soil texture
– Organic matter
• Clay size particles and organic matter both hold
nutrients but make them available to different
degrees
• …HOW?

29. SOIL ACTS AS A MAGNET
• Attracts and retains positively charged
ions in soil solution
• Prevents them from moving downward
with water (leaching)

30. AN ION?

31. IONS ATTRACTED TO SOIL
PARTICLE
Brady & Weil, 2004. Elements of the Nature and Properties of Soils

32. CATION EXCHANGE CAPACITY
•
(CEC) and humus to attract
The ability of clay, organic matter,
positive ions
– Clay, organic matter, and humus all have negative charges on
their surfaces
– Most nutrients (P, K, Ca, etc) are cations or have positive
charges
– “Opposites attract”
• The higher the cation exchange capacity, the more closely
the nutrients are held and the less likely they are to be lost
to leaching
• (soils also have anion exchange and it works the same way)

33. HOW DOES CEC DIFFER IN
• In general…
SOILS?
– Sand- low CEC
– Clay – high CEC
• Soil with low CEC– generally has low clay and organic matter, low
water holding capacity, requires more frequent fertilizer and lime
amendments, and is prone to leaching
• Soils with CEC greater than 20 may have high clay content,
moderate to high organic matter content, high water holding
capacity, less frequent need for lime and fertilizers (except N),
and low leaching potential for cationic nutrients.
• On the other hand, their physical properties may make it difficult for a farmer to
cultivate, irrigate or maintain good aeration

34. GROWING HEALTHY PLANTS

35. SOIL TESTING
• Soil tests can assess nutrient levels
• Available in most states for a minimal fee

36. http://uwlab.soils.wisc.edu/ OR, search “WI soil testing”

37. NUTRIENT REQUIREMENTS
• The correct nutrient balance …
–Depends on soil type and texture
–Varies by plant
–Is affected by climate

38. Approximate nutrient removal (lb/unit of yield) in the harvested portion
PLANTS HAVE DIFFERENT NEEDS
of several Michigan vegetable crops. 11 ton=20 cwt
Source: Fertilizer Recommendations for Vegetable Crops in Michigan (Warneke et al. 1992)
Crop N P2O5 K2O N P2O5 K2O
-lb/ct1- -lb/ton1-
Asparagus 0.67 0.20 0.50 13 4.0 10
Beans, snap 1.2 0.12 0.55 24 2.4 11
Broccoli 0.20 0.05 0.55 4.0 1.0 11
Cabbage 0.35 0.08 0.35 7.0 1.6 7.0
Carrots 0.17 0.09 0.34 3.4 1.8 6.8
Cauliflower 0.33 0.13 0.33 6.6 2.6 6.6
Celery 0.25 0.10 0.80 5.0 2.0 16
Cucumbers 0.10 0.06 0.18 2.0 1.2 3.6
Lettuce 0.24 0.10 0.45 4.8 2.0 9.0
Muskmelon 0.42 0.10 0.55 8.4 2.0 11
Onions 0.25 0.13 0.24 5.0 2.6 4.8
Peas, shelled 1.0 0.23 0.50 20 4.6 10
Peppers 0.20 0.07 0.28 4.0 1.4 5.6
Pumpkins 0.20 0.06 0.34 4.0 1.2 6.8
Sweet 0.42 0.14 0.28 8.4 2.8 5.6
Squash 0.18 0.08 0.33 3.6 1.6 6.6
Tomatoes 0.20 0.04 0.35 4.0 0.8 7.0

39. Guide to the Mineral Nutrient Value of Organic Materials Percent (%)
Materials: Nitrogen Phosphorus Potassium Relative Nutrient Availability
FERTILIZERS ACT DIFFERENTLY
(%N) (%P2O5) (%K2O)
Bone Meal(raw) 2 to 6 15 to 27 0 Slow
Bone Meal(steamed) 0.7 to 4 10 to 34 0 Slow Med.
Cocoa Shell Meal 2.5 1 2.5 Slow
Compost(not fortified) 1.5 to 3.5 0.5 to 1 1 to 2 Slow
Cotton Seed Meal(dry) 6 2.5 1.7 Slow Med.
Dried Blood(dry) 12 1.5 0.57 Med. Rapid
Fish Meal(dry) 10 4 0 Slow
Manure(fresh)
Cattle 0.25 0.15 0.25 Medium
Horse 0.3 0.15 0.5 Medium
Sheep 0.6 0.33 0.75 Medium
Swine 0.3 0.3 0.3 Medium
Poultry(50%water) 2 2 1 Med. Rapid
Milorganite(dry) 5 2 to 5 2 Medium
Mushroom Compost .4 to.7 1 .5 to 1.5 Slow
Peat and Muck 1.5 to 3 .25 to .5 .5 to 1 Very Slow
Sawdust 4 2 4 Very Slow
Sewage Sludge(digested) 1 to 3 .5 to 4 0 to .5 Slow
Urea 42 to 5 0 0 Rapid
Wood Ashes* 0 1 to 2 3 to 7 Rapid
* Wood ashes may raise pH
Cornell gardening resources A Guide to the Nutrient Value of Organic Materials, Ecogardening Factsheet #8, Spring 1993

40. PH MATTERS

41. MORE ISN’T BETTER
• Too much of any nutrient can be
negative
– Poor fruit set
– Run-off or leaching resulting in
environmental pollution
– Soil acidification through reaction with
nitrogen

42. FERTILIZER CALCULATION
EXAMPLE

43. CALCULATING AMENDMENTS
• http://www.caes.uga.edu/publications/pubD

44. ADDITIONAL RESOURCES
• Basic Soil Science:
– Chapter 3. Concepts of Basic Soil Science, W. Lee Daniels and Kathryn
C. Haering, Department of Crop and Soil Environmental Sciences,
Virginia Tech
– www.mawaterquality.org/capacity_building/mid.../chapter3.pdf
• Calculating organic amendments:
– How to Convert an Inorganic Fertilizer Recommendation to an Organic
One, Revised by Julia Gaskin, David Kissel, Glen Harris and George
Boyhan. Original manuscript by Wayne McLaurin, retired Horticulture
Professor, and Water Reeves, retired Horticulture Educator
– http://www.caes.uga.edu/Publications/displayPDF.cfm?pk_ID=7170

45. Anne Pfeiffer
UW-Madison
Community and Regional Food Systems
www.community-food.org