by Peter Bierman and Carl Rosen. Presented at the 2012 MN Statewide High Tunnel Conference.

1. Soils 101:
Soil Physical & Chemical Properties
Peter Bierman and Carl Rosen
Department of Soil, Water, and Climate
University of Minnesota
MFVGA Beginning Grower Workshop
January 18, 2012

2. Physical Properties
l Texture, structure, organic matter
l Controls drainage, water-holding capacity
l Suitability for vegetable/fruit production
l Often the most difficult to manage

3. Soil Testing and Soil Fertility
l Essential plant nutrients
l Managing fertility
l Soil acidity and liming
l Types of soil tests
l Soil sampling/sample handling
l Fertilizer sources

4. Soil Composition
Soil is composed of solids, water, and air
 Solids (50%)
 Sand, silt, clay (90-99%)
 Organic matter (1-10%)
 Water (25%)
 H 2O
 100-1000 ppm soluble salts
 Air (25%)
 High CO2 (10-20 times as high
as the atmosphere)

5. Importance of Soil Physical Properties
l Healthy crop root growth
q roots require both air and water
l Determines infiltration, drainage,
aeration, water-holding capacity
q control the balance
between air and water
in the root zone

6. Soil Texture
l Relative proportions of sand-, silt-, and
clay-sized particles
q sand > silt > clay
l Soil “textural class”
q loamy sand, silt loam, clay
l Texture is a fixed
soil property
q not altered by management under ordinary
conditions

7. Soil Texture
l Coarse-textured soils
q dominated by sand
• well-drained/aerated
• low water and nutrient holding capacity
l Fine-textured soils
q dominated by clay
• poorly drained/aerated
• high water and nutrient holding capacity
l Loams
q intermediate texture and properties

8. Textural Triangle Feel

9. Soil Structure
l Sand, silt, clay combined into
aggregates
l Aggregates arranged with pore spaces
between them
l “Good” structure
q ~50% solids and 50% pore space
q pore space evenly distributed
• large, air-filled pores (drain readily)
• smaller, water holding pores

10. Soil Structure
Soil Air & Water
Tightly Held
Water Film
Water-filled
Pore Space
Air-filled
Macropore
Soil
Aggregate

11. Soil Structure
l Soil structure can be altered by
management
q improved or degraded
Granular aggregation promoted Compaction reduces pore space
by organic matter

12. Soil Organic Matter
Organic matter affects most soil properties
 Forms of organic matter
• Plant/animal residues
• Various stages of
decomposition
• Humus
• Decomposition by-product
• Resistant to further
degradation

13. Soil Organic Matter
l Can improve aggregation and structure
l High water-holding capacity
l Improves physical condition of both
coarse- and fine-textured soils
l Retains and cycles
nutrients
l Drives soil biology

14. Soil Depth
l Determines potential rooting depth
l Zone of water and nutrient uptake
l Drainage restriction
l Gravel, bedrock, compacted layers

15. Finding Soil/Site Information
l County Soil Surveys
q soil maps
q soil types
q texture
q drainage
q topography
q water-holding
l NRCS, SWCD, Extension
l SoilWeb App
l http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

16. Soil Survey

17. Soil Survey

18. Site Preparation/Modification
l Ideally begins well before planting the
first vegetable crop Subsurface Drainage and
Crop Root Growth
l Drainage
improvements
Free water level
Free water level
Free water level Free water level
Spring Summer Spring Summer
Undrained Land Tile Drained Land

19. Site Preparation/Modification
l Increase soil
organic matter
q high residue
rotation crops
q cover crops
q manure, compost
l Soil test
q lime
q fertilizer

20. Soil Testing and Soil Fertility
l Essential plant nutrients
l Soil sampling/handling
l Types of soil tests
l Soil acidity and liming
l Cation exchange capacity
l Organic/inorganic fertilizers
l Value of soil testing
q example field

21. Essential Plant Nutrients
Nutrients derived from the soil and/or fertilizer
Macronutrients Micronutrients
Primary Zn – Zinc
N - Nitrogen B – Boron
P – Phosphorus Fe – Iron
K – Potassium
Mn – Manganese
Secondary
Cu – Copper
S – Sulfur
Mg – Magnesium Mo – Molybdenum
Ca – Calcium Ni – Nickel
Cl – Chlorine

22. Soil Sampling
l Collect representative samples
q Soil tests are only as accurate as
the samples you submit
q Sampling is often the weakest link
in a soil testing program
l Follow sampling and handling
guidelines of the laboratory you
submit samples to

23. Sampling Guidelines
l Divide fields into uniform areas
q soil type, slope, crop history, tillage,
previous lime, fertilizer, manure, compost
applications
l No more than 20 acres for a single
sample
l Collect 20-30 soil cores
q random, zig-zag pattern across the field
l Standard depth 6-8 inches
q 2 feet for soil nitrate test

24. Soil Sampling
l Thoroughly mix sub-samples in a clean,
plastic container
q submit about a pint of this composite
sample to a laboratory for analysis
l If soil is wet
q air dry
• spread in a thin layer on a
clean surface before mixing
q oven dry at <97° F

25. Soil Tests
l Standard series
q do on a regular basis
q P, K, soil pH, buffer pH, OM, texture
• lime requirements are based on a Buffer Index
l Additional tests
q first time a new site is sampled
• or when a problem is suspected
q Ca, Mg, Zn, B
• Cu and Mn on organic soils

26. Sherburne
Pine Hill Vineyard
123 Needle Lane
48
Big Lake, MN 55309
1 57 57 x x x
2 25 57 x x x xx

27. 03/20/2005

28. Soil Acidity
l Soil pH measures acidity/alkalinity
l Mineral soils
q pH 5.8 to 7.0
• optimum range for most vegetables
q pH of 5.4 or less reduces scab on potatoes
l Organic soils (peats and mucks)
q optimum pH is lower, 5.2 to 6.0

29. Soil pH
l Microbial
activity
l Nutrient
availability
q optimum pH
about 1 unit
lower for
organic
soils/media
Mineral soils

30. Liming
l Soil acidification
q rainfall and leaching, N fertilizers
l Western MN vs. eastern MN
l Soil pH
q do you need lime?
l Buffer index
q reserve acidity
q how much lime?

31. Nitrogen
l Recommendations based on
q crop grown
• expected yield
q soil organic matter level
q preceding legume crops
q manure or compost applications
q nitrate soil test
• measures residual N
• standard in western MN

32. Phosphorus and Potassium
l Recommendations based on
q crop grown
• expected yield
l Soil test level for P and K

33. Relative Nutrient Mobility
l Nitrogen moves much faster than
phosphorus and potassium in the
soil
l Phosphorus has very limited
mobility in the soil
l Implications:
q P and K should be
incorporated before planting
q Nitrogen can be topdressed or
sidedressed during the
growing season

34. Soil Cation Exchange Capacity
CEC is the amount of positively charged ions a
soil can hold – reduces leaching and buffers
the soil solution
Soil Solution
K+ Mg2+
Ca2+
H+

35. Sources of Plant Nutrients
Plant nutrients come from both organic and
chemical sources

36. Organic vs. Inorganic Fertilizers
l Organic
q Nutrients slowly released
q Low burn potential
q Improve soil structure
q May contain weed seeds
q Usually higher cost
q Acceptability for certified organic crop
production depends upon the certifying agency
l Inorganic (manufactured soluble fertilizers)
q Nutrients quickly available
q High burn potential
q Lower cost/unit of nutrient

37. Inorganic Fertilizers
Inorganic Fertilizer %N % P2O5 % K2O
___________________________________________________________________________________________________________
Ammonium sulfate 21 0 0
Ammonium nitrate 34 0 0
Urea 45 0 0
Calcium nitrate 15 0 0
Monoammonium phosphate 11 48 0
Diammonium phosphate 18 46 0
Rock phosphate 0 5 0
Superphosphate 0 20 0
Conc. superphosphate 0 46 0
Green sand 0 1 6
Muriate of potash 0 0 60
Potassium sulfate 0 0 50
Potassium – magnesium sulfate 0 0 22
Blends (N, P, K) 10 10 10
12 12 12
27 3 3
6 12 12
18 6 12
___________________________________________________________________________________________________________

38. Organic Fertilizers
Organic Fertilizer %N % P2O5 % K2O
___________________________________________________________________________________________________________
Manure (fresh)
bat 6.0 9.0 3.0
cattle 0.55 0.55 0.45
hog 0.50 0.35 0.45
horse 0.65 0.25 0.50
poultry 1.00 0.85 0.45
rabbit 2.4 1.4 0.6
sheep 0.9 0.5 0.8
Alfalfa hay 2.5 0.5 2.1
Bone meal (steamed) 1.0 15.0 0.0
Fish scraps 9.0 7.0 0.0
Lawn clippings 1.2 0.3 2.0
Leaves (sugar maple) 0.7 0.1 0.8
Milorganite * 5.0 3.0 2.0
Straw (wheat) 0.6 0.2 1.0
Grain straw 0.6 0.2 2.1
Sawdust 0.2 0.1 0.2
Wood ashes 0.0 2.0 6.0
___________________________________________________________________________________________________________
* Not acceptable for organic fruit and vegetable production

39. Value of Soil Testing

41. Sweet Corn Tissue Analysis
Element Conc. Interp. Element Conc. Interp.
(%) (ppm)
N 1.72 Def. Fe 79 Suff.
P 0.16 Def. Mn 860 Excess
K 2.01 Low Cu 8 Suff.
Ca 0.28 Def. Zn 22 Suff.
Mg 0.15 Def. B 4 Low
S 0.09 Def.

42. Sweet Corn Soil Test
pH P K Mg Ca S Zn Salts
------------------------ ppm ------------------- mmhos/cm
3.8 96 90 16 106 3 0.8 0.2
L H M L L L M L

43. Aluminum Toxicity – low pH
Al, Mn toxicity at pH <5 or 5.5 for many plants
43

44. Recommendation
l Lime to pH 6 in the fall with dolomitic lime
l Apply potassium-magnesium sulfate in the
spring preplant
l Soil test yearly to
monitor changes

45. Additional Information
l Nutrient Management for Commercial Fruit
and Vegetable Crops in Minnesota
BU-5886-E - 2005
 University of Minnesota Extension Service
q http://www.extension.umn.edu/
l University of Minnesota Soil Testing Lab
q http://soiltest.cfans.umn.edu/
q Phone: 612-625-3101