This is a slightly modified version of a presentation that I shared at the VA No-till Alliance meeting in Harrisonburg, VA on 2/7/2012

1. The science and management
of
soil biology
Joel Gruver
WIU Agriculture
j-gruver@wiu.edu
The Furrow

7. Is conventionally
managed soil a
biological ghost
town?

8. Microherd
Even soils receiving intensive tillage
and chemical inputs contain billions of
bacteria per gram of soil
Phil Brookes

9. The soil beneath our feet may be teeming with a hundred
times more species of bacteria than previously thought,
according to biologists in New Mexico, US.
Measuring the bacterial biodiversity of soil is difficult
because only a few species can be cultured, according to
Jason Gans of the Los Alamos National Lab.
Fortunately, biologists can also estimate biodiversity
using a technique called DNA reassociation. This involves
chemically unzipping the two strands of all the bacterial
DNA in a sample, mixing them up and seeing how long
they take to join up again with matching partners.

10. Their results reveal that there are a few
very common species in soil but lots of rare SSSA
species. "There is a very large number of
low abundance species," says Gans. So
many rare species, in fact, that the estimate
of bacterial biodiversity rises to ~ 1 million
species per gram of soil.

11. How much of the C in these corn stalks
will return to the atmosphere within 1
year?
> 75%
This is not possible without an active
microbial community

12. Which trajectory for
SOM is most common C
in the US?
B
A
150 b/a
How is it possible for
residue levels to
Corn yield
increase > 3x without
building SOM?
30 b/a
1950

13. Broadbalk continuous wheat experiment
Data modelled by RothC-26.3 (solid lines)
100
Organic C in soil NPK systems are both producing > 100 bu/a wheat
The manure and
(t C ha-1) Farmyard manure annually
80
Soil C (tons/ha)
60
Why has the NPK program
resulted in so little increase in
40
SOM? NPK
20 unfertilized
Unmanured
0
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020
Year

14. The current OM level in a soil is a
result of the long-term balance
between organic inputs and outputs

15. The current OM level in a soil is a
result of the long-term balance
between organic inputs and outputs
Organic outputs
Yield enhancing practices will not build
SOM if OM outputs increase at a
comparable rate to OM inputs

16. Drainage + Tillage + Lime + N + harvest = Accelerated loss of SOM
”But with the removal of water through furrows, ditches, and
tiles, and the aeration of the soil by cultivation, what the
pioneers did in effect was to fan the former simmering fires…
into a blaze of bacterial oxidation and more complete
combustion. The combustion of the accumulated organic
matter began to take place at a rate far greater than its annual
accumulation. Along with the increased rate of destruction of
the supply accumulated from the past, the removal of crops
lessened the chance for annual additions. The age-old process
was reversed and the supply of organic matter in the soil began
to decrease instead of accumulating.”
William Albrecht – 1938 Yearbook of Agriculture

17. How do these soils differ ??
manure
cover crops
crop residues crop residues
20 years of similar tillage and total organic
input but different types of organic inputs
Rodale Institute Farming Systems Trial

18. Granular crumb structure Poor structure
The development of
crumb structure is
a key step in
retaining SOM
http://www.grdc.com.au/growers/gc/gc48/conference1.htm

19. We are well aware that a poorly
balanced diet for humans results in
heart disease, tooth decay,
obesity… what are the
consequences of feeding soil a
“white bread” diet?
White bread diet for soil = very little diversity of organic inputs

20. Unfortunately this is the
norm in agriculture
today :-<
Acute
root
VS.
disease
Chronic root
malfunction

21. Dramatic effect of steam
sterilization and compost on
growth of pepper plants

22. The digestive
capacity of soil
microorganisms
greatly exceeds
organic inputs to
soils.
http://picturethis.pnl.gov/im2/8208417-5cn0/8208417-5cn.jpg

23. So
why does
organic matter
accumulate at all
in soil?

24. In the long run

25. Nature, October 2011
…it remains largely unknown why some SOM persists for
millennia whereas other SOM decomposes readily…
Recent analytical and experimental advances have
demonstrated that molecular structure alone does not
control SOM stability: in fact, environmental and biological
controls predominate…

26. Mined humate products may
have value but are not the
same as old soil organic matter
The traditional concept of
large stable humus
molecules has been
rejected by most scientists

27. Organic matter accumulates under anaerobic conditions
Blackland soils of
North Carolina
Lily (1981)
> 1 million acres

28. Impact of temperature on SOM accumulation
Organic matter accumulates
in climates that support high
biomass production but limit
Organic matter dynamics
decomposition
Temperature
Brady and Weil (2002)

29. Organic matter production Impact of temperature on plant growth
Temperature
Brady and Weil (2002)

30. Organic matter consumption Impact of temperature on decomposition
Temperature
Brady and Weil (2002)

31. Visualizing soil
habitat at biologically
relevant scales

32. Worm’s eye view?

33. Nematode’s eye view?

34. Bacteria occupy
< 5 % of soil surfaces
and < 0.1% of soil
porosity
Visualizing soil habitat at
relevant scales

35. Most of the pores where soil
microorganisms reside are either
environmentally suppressive or
lacking in suitable substrates.

36. Microorganisms have very limited ability to
move within the soil matrix.

37. As a result,
soil is a very sleepy place !
osmobiosis anhydrobiosis
thermobiosis
anoxybiosis
cryobiosis

38. Most soil microorganisms are
in a dormant state
waiting…

39. For their prince charmings
to arrive !

40. Roots
Rain
There are many types of prince charmings !
Tillage
Organic Amendments

41. Dormant earthworm
SSSAJ 69(3) cover

42. Earthworm cocoons
offer much more protection
http://soils.usda.gov/sqi/soil_quality/soil_biology/images/CE8a-cocoon_LR_small.jpg

43. Most plants in your
soils are in a state
of dormancy

44. Seed dormancy than
is much better microbial
understood dormancy

45. Who lives in the soil?
 Bacteria
Body size  Fungi Microflora
increasing  Algae
 Protozoa Microfauna
 Nematodes
 Microarthropods Mesofauna
 Enchytraeids
 Earthworms Macrofauna
 Ants, termites, spiders
 Mollusks
Megafauna
 Others: rodents, snakes,
voles, amphibians, etc.

46. Most soil organisms widely in size
Soil organisms vary are tiny !!!
 Bacteria
 Fungi Microflora aka microbes
 Algae
 Protozoa Microfauna
 Nematodes
 Microarthropods Mesofauna
 Enchytraeids
 Earthworms
 Ants, termites, spiders
Macrofauna
 Mollusks
 Others: rodents, snakes, Megafauna
Abundance voles, amphibians, etc.

47. Soil
microbes
carry out
> 90% of all
decomposition

48. Soil animals have a
disproportionate impact on
nutrient cycling, energy fluxes
and plant growth

49. Soil animals are mobile
but have limited digestive ability
Soil microbes are relatively immobile
but have almost unlimited
digestive ability
fungi bacteria

50. 3 main types of digestive interactions
occur between soil animals and microbes

51. Microbivory
+ NH4+
NH4
NH4+
NH4+ NH4+
NH4+ I want some
bacteria for
lunch !
Microfauna (e.g. protozoa and nematodes)
harness the microbes’s digestive abilities by
grazing on them

52. External
rumen
digestion
When mesofauna feed on fresh litter, their fecal
pellets contain shredded, moistened and mixed
but largely undigested residues
Reingestion of fecal pellets after a few days of
microbial activity greatly increases assimilation

53. Many
microarthropods
use this digestive
strategy

54. Leaf cutter ants are a more
well known example of
external rumen digestion

55. Internal rumen digestion
greatly enhances utilization
of complex substrates by
soil macrofauna

56. Macrofauna are also
ecosystem engineers

57. Do roots and
macrofauna play
similar ecological
roles?

58. Microbial activation Structural modification
bacteria
root hair
rhizoplane
Structural modification Microbial activation

59. Navigating the rhizosphere
Rhizoplane End of the rhizosphere
Endo- Root free soil
Rhizosphere Ecto-Rhizosphere
> 100 X
microbial
activity
(Lavelle and Spain, 2001)

60. Why do roots have a priming effect?
Aggregate Release of protected
Disruption organic matter
Growing Priming
Root Effect
Exudation Activation of
microorganisms
(Lavelle and Spain, 2001)

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

62. casts middens
Drilosphere
Zone of
earthworm
influence

63. Detritusphere
fungi
surface residue zone

64. Clean tillage
eliminates the
detritusphere
Many soil organisms prefer to
feed at the surface

65. 3 main
strategies for
Conservation managing soil Augmentation
biology
Activation

66. Not all earthworms are sensitive to tillage…
but the ones that make vertical burrows
that connect the topsoil and subsoil are…

67. Earthworm functional
continuum
Epigeic  Anecic  Endogeic
worms worms worms

68. Myco = fungus Mycorrhizal diversity
Rhiza = root
Ectomycorrhizae
Most woody plants
AM endomycorrhizae
Most herbaceous
Arbutoid plants including
mycorrhizae corn and soybeans
Ericoid
endomycorrhizae
Orchid endomycorrhizae
Lavelle and Spain (2001)

69. Mycorrhizal Networks: Connecting
plants intra- and interspecifically
•Many plants are
connected
underground by
mycorrhizal hyphal
interconnections.
•Mycorrhizal fungi
are not very host
specific.
Illustration by Mark Brundrett
Mycorrhizal inoculants are available
but conservation of established networks is more important

70. Increase nutrient uptake suppress pathogens
(especially P)
Mycorrhizae
Mediate plant competition Improve soil structure
Glomalin
Superglue
of the soil ??

71. Are you conserving the beneficial
fungi on your crop foliage?

72. Frogeye leafspot fungus resistance to strobilurin
chemistry a concern for Mid-South soybean growers
Hembree Brandon - Mar. 2, 2011 5:36am
Add another to the growing list of weeds, insects, and diseases that have
developed resistance to the chemicals that farmers rely on to control pests and
protect yields — strobilurin-resistant Cercospora sojina, the fungus that causes
frogeye leafspot in soybeans.
The strobilurin chemistry has been widely used as a first line of defense in
preventing yield loss from Frogeye leafspot.
―There was documentation in 2010 of strobilurin-resistant Cercospora in Illinois,
Kentucky, and Tennessee,‖ Tom Allen said at the annual conference of the
Mississippi Agricultural Consultants Association.

73. Roots
Rain
Irrigation
Biological activation strategies
Tillage
Organic Amendments

74. Innovative cover cropping
is a great way to activate
your soil biology!!

75. Bio-strip till
attempt #1
September 2008

76. Attempt #3
Radish planted on 30” rows using milo plates
in mid-August 2010

78. Corn following cover crop experiment in
2011 at the WIU Organic Research Farm
Relative
Cover crop system
corn yield
Volunteer oats 79%
Radishes planted on 30‖ 99%
Radishes drilled on 7.5‖ 91%
Corn planted on radish rows

79. Wheat + radish trial at the Allison farm
November 2010
3 lb/a = 2 lb/a = 1 lb/a > 0 lb/c
~ 2.5 bu/a yield boost
Is this an activation effect?

80. Have you tried any
biological seed
treatments?
Augmenting soil biology

81. Old school inoculation

82. http://www.beckerunderwood.com/en/pages/scienceofinoculation

85. VOTiVO contains a naturally occurring soil bacteria, or rhizobacteria, that live
and grow with the plant’s root system. The bacteria creating a biofilm that
becomes a living barrier limiting the number of receptor sites which could
otherwise be occupied by plant pathogens such as nematodes. Nematodes
use gaseous and solid exudates from the root as means to detect a root’s
proximity, so reduced levels of exudates can decrease the ability of the
nematodes to locate the receptor sites on the roots. The bacteria further
reduce viable nematode populations by consuming exudates, depriving
nematodes of an additional source of energy and nutrients.

87. competition parasitism
Ask vendors to explain specifically
how their product works!
antibiosis induced resistance

88. Do recognize this scene?
If you build it, they will come…
The most important biological management strategy