I shared this presentation on 1/21/2011 at the SSAWG conference in Chattanooga, TN

1. Basic Soil Improvement Techniques
for Sustainable Farmers
Dr. Joel Gruver
School of Agriculture
Western Illinois University
(309) 298 – 1215
j-gruver@wiu.edu

2. Useful Resources

3. http://www.sare.org/publications/soils.htm

4. Managing cover crops profitably, 3rd edition

5. http://www.sare.org/publications/handbooks.htm
Free
downloads

6. NRCS SOIL BIOLOGY PRIMER
http://soils.usda.gov/sqi/concepts/soil_biology/biology.html

10. Excellent comprehensive
soil science textbook
> $100
< $10

11. Are you Which factor
familiar with do you think is
the “disease most
triangle”? important?

12. Do you think agroecologically?

13. Continuous tomatoes
Managing crop
residues
All of these strategies are being used successfully
by some farmers/gardeners. Only you can
determine the best fit for you.

14. Growing under cover may be
the most effective organic
strategy for improving crop
health and productivity

15. Have any of you visited Monticello ?
Jefferson made good use of microclimates

16. Thomas
Jefferson
Garden in
Gruverland
Inspired by Monticello, my family decided
to make better use of microclimates

17. Understanding the soil environment

18. Sand and silt
are the bones of the
soil skeleton
http://www.ecogrowth.com.au/soil.htm
Soil skeletons

19. Clay and humus are the soil skin
and connective tissues
Brady and Weil (2002) http://www.ccma.csic.es/dpts/suelos/
clay minerals humus

20. Why is the soil skin important ?
 Adsorption of water films
 Adsorption of organic and
inorganic chemicals
 Ion exchange
 Catalysis of chemical reactions
 Habitat for bacteria

21. Get to
know your
soil’s body
parts !

22. The jar test

23. TEXTURE
BY FEEL

24. Textural 12
triangle textural
classes
http://www.oneplan.org/Images/soilMst/SoilTriangle.gif

25. Loamy soils
Loamy soils have the most favorable physical properties

26. Potting media criteria
High moisture retention and rapid drainage
It can be difficult toeffective for both
It is rarely cost optimize
moisturefarmers to change the texture
retention and drainage in
or other inherent properties of
real soils the soils on their farms

27. ≠
Understanding inherent differences in soil properties

28. WEB SOIL SURVEY
- a great source of info on
soil inherent properties

29. What are these
crazy people
trying to do ?
Location:
Laurenburg, NC
Date: 1961
Very deep plowing as
part of a futile effort to
create deep “Prairie”
soils in North Carolina

30. Good Tilth Poor Tilth
The soil fabric
http://www.grdc.com.au/growers/gc/gc48/conference1.htm

31. The soil pore
network serves
as a respiratory
and circulatory
system
http://www.mtm.kuleuven.ac.be/Research/NDT/IDO_SHerman_final.ppt

32. Understanding your soil’s respiratory and
circulatory system
Pore size Drainage pores
10- 30 μm
Field Capacity
Easily available
Plant available water
Permanent wilting point
0.2
μm
Unavailable water
Adapted from Buol (2000)

34. 1.0% CAfter adding water 1.4% C

36. Do you
scavenge and
hoard organic
materials from
far and wide?

37. This can be a good soil
building strategy but
should not be a
permanent strategy in a
world with finite organic
resources.
Is it time to reduce your
farm’s foot print?

38. What is happening on your farm?
There is a lot more to soil organic matter
management than just increasing OM
inputs !!

39. Why does
org anic matter
accumulate in soil?

40. Most soil microbes are
unculturable

41. ..and the soil microbes
that are culturable
can digest almost
everything organic
at rates hundreds of
times faster than
decomposition in field
soils

43. aka digestibility
Understanding organic resource quality
C:N ratio > ~ 20
(Giller, 2000)

44. Relationship between fine mineral fraction and SOM
Soils with more
fine particles
normally retain
more SOM
Magdoff and Weil (2004)

45. Weak relationship between clay content and SOC for 1261
agricultural soils in England and Wales
Clearly many factors
other than clay
affect C
accumulation
Webb et al.(2003)

46. Temperature affects SOM dynamics
Organic matter destruction by
aerobic organisms
Your farm
and consumption
in 50 yrs
Organic matter
Organic matter consumption
OM production production
synthesis by plants
~ 70 F
mean annual temp
Temperature
Brady and Weil (2002)

47. Landscape position affects SOM dynamics
Poorly
drained
Where does the most OM accumulate? Interstream divide
Somewhat
Moderately LANDSCAPE
poorly
well drained
drained POSITIONS
Well
drained
Poorly
Shoulder Interfluve
drained
Valley floor
SOIL Backslope
DRAINAGE
CLASSES

48. Agriculture normally accelerates loss of SOM
http://www.extension.umn.edu/distribution/cropsystems/components/7402_02.html

49. OM depleted
top soil
Erosion has caused major redistribution of OM
OM enriched
sediment

50. Artificial drainage has greatly increased the number of
days when soils are suitable for field operations
but has also
contributed
Pollution of to many
water resources environmental Loss of SOM
problems

51. 47
42
Identify 2
methods of
increasing
SOM.
Adapted from Magdoff and Weil (2003)

52. Small increases in OM can
improve macro-aggregation
Superior air/water relationships
Healthier root
growth and function (justification statement)
NC STATE UNIVERSITY DEPARTMENT of SOIL SCIENCE

54. There’s more than one way to collect a soil sample
but results have little value if the sample is not
representative
http://www.arlington.k12.va.us/schools/abingdon/programs/naturalistclub/pic%2012-04/good%20diggin%20shot.JPG

55. Composite
sampling
Multiple sub-
samples are
collected from
each management
unit and mixed
together

56. Recommendations
Analytical results
So what do the
numbers mean ???

57. Have any of you ever had to run a 40
as part of a try-out for a team?
How well does an
athlete’s 40 time
predict their ability
to play the game?

58. By themselves, extractable nutrient
levels are not informative.
Extractable nutrient levels provide an index of
nutrient availability that can be interpreted using
results from field experiments.

59. Meaningful interpretation of soil test results
requires field calibration
100 %
yield
50 %
yield
Soil test P concentration (ppm)
http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif

60. moisture temperature microbial activity
Soil test levels are not directly related to
most of the factors controlling nutrient
availability during a growing season.
Calibration experiments were not conducted
using organic management practices
rooting depth root health

61. Understanding nutrient uptake
Root
H20
exudates Transpirational
activate soil stream
microbes
H 20
Root growth

62. http://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htm
Nutrients that are not Nutrients that can be
easily redistributed easily redistributed

64. Sampling vegetable crops for tissue analysis
http://www.cahe.nmsu.edu/pubs/_a/a-123.html

65. Analytical results
Estimated Nutrients available for a single crop
Total nutrient content of DM is adjusted for moisture and availability
http://149.168.222.13/D:/2005/WASTES/Predicti/7000/WAW06343.PDF

66. Feed the soil vs. Feed the crop ?
Both strategies are important !
Unhealthy roots in soils with low SOM and poor structure
use nutrients inefficiently…
Healthy roots need
available nutrients !
Plants with poorly
developed roots
tend to have
nutrient deficiency Acute root
and drought stress disease
symptoms
Chronic root
malfunction

67. How often
do you
How often
look atlook
do you
roots ?
at roots?

68. http://www.tre.umn.edu/growers/nursery_nightmares/nightmares.htm

69. Raised beds promote healthy roots !!
Faster drainage and soil warming
Greater depth of fertile soil
Restricted traffic

70. No wheel
traffic on
beds

71. What happened to my soil??
Tillage when a soil is too
wet often creates clods
that require a period of
wetting and drying
and/or freezing and
thawing (in addition to
biological activity)
before good structure is
restored.

72. Are you familiar with the fence post principle?
Zone of maximum biological activity and
rapid residue decay

73. The soil stomach
 Bacteria Plant roots depend
 Fungi Microflora on an external
 Algae digestive system
 Protozoa Microfauna “ the soil food web”
 Nematodes
 Microarthropods Mesofauna
 Enchytraeids
 Earthworms
 Ants, termites, spiders
Macrofauna
 Mollusks
 Others: rodents, snakes, Megafauna
voles, amphibians, etc.

74. What do bacteria do in soil ?
 Colonize aerobic and anaerobic environments
 Decompose easily digested organics
 Mediate redox transformations
 Nourish bacterivores
 Fix N

75. Most N transformations in soil are
carried out by bacteria!!
Soil
Plant biomass

76. What do fungi do in soil ?
 Decompose less easily digested organics
 Penetrate residues
 Stabilize soil structure
 Nourish fungivores
 Form symbioses with plant roots and soil fauna
 Compete with plant pathogens
 Parasitize plants and soil animals
 Produce toxins e.g. aflatoxin produced by
Aspergillus flavus on peanut

77. Most plant pathogens are
fungi but most fungi are
not plant pathogens !!

78. Soil organisms in
are
concentrated HOT
SPOTS !
detritusphere rhizosphere
Adapted from Coleman et al. (19??)

79. Detritusphere
surface residue zone

80. Clean tillage
eliminates the
detritus layer
Many soil organisms prefer to feed
at the surface

81. Rhizosphere
< 10 % of soil volume
under prairie vegetation
< 1 % of soil volume under
most vegetable crops Zone of root
influence

83. Cover crops
Less loss
Less loss

84. Cover crops increase annual root production and function
Feed
livestock
Cover
Crops
Recent studies indicate that
CCs can have many root production is the best
other beneficial predictor of long-term
effects Adapted from Magdoff and Weil (2004) retention of SOM.