2nd lecture presentation of the semester for my Soil Fertility class

1. ROOTS
The hidden half of agriculture

2. How many of you regularly
look at crop roots ?
John McGillicuddy
IA crop scout

3. Bill Darrington (Persia, IA)
One of several readings
for this week

4. Read the attached article and submit answers using WO before the start of class
next Wednesday.
1)Describe several factors contributing to deep root growth on Bill Darrington's
farm.
2) The article refers to Ray Rawson as the guru of "vertical farming"... what is
"vertical farming" and what did Bill Darrington learn from Ray Rawson about soil
aeration?
3) Why does Bill Darrington dig so many soil pits and what does he look for?
4) What is Bill Darrington's perspective on anhydrous ammonia? Do you agree
with this perspective?
5) Have you ever looked at roots in a soil pit? If so, describe something you
observed. If not, when do you think you will have an opportunity to look at some
roots? What do you think you will see?

5. Ken Ferrie – Farm Journal

6. All you need to do to grow healthy roots
is use rootworm resistant genetics… right??
When rootworm pressure is high, rootworm resistant
genetics normally result in much healthier roots

7. Rootworm resistant genetics are not a silver bullet !
Severe damage by corn
rootworm larvae to roots of
a biotech corn rootworm
hybrid
http://www.ipm.iastate.edu/ipm/icm/2006/11-13/btcorn.html

8. We have witnessed the historically low densities of
European corn borers across Illinois and some nearby
states that are now believed to be linked to the widespread
adoption of Bt corn hybrids. Will we see a similar
phenomenon unfold with western corn rootworms? I
suspect we might be headed down this road. Will western
corn rootworms adapt as they have repeatedly done so in
the past? If we don't integrate management tactics, we
could have the answer sooner than we would like.

10. U of I Corn Borer survey results

11. The seed roots stop growing shortly after the coleoptile
emerges from the soil surface. The nodal root system
becomes visible at ~ V1. The nodal root system
becomes the dominant system by V6.

12. 16 weeks
8
4
7 feet deep !!

13. 1926

15. Sub-soil water
and nutrients
Brady and Weil (2002)

16. Sidewall compaction
?

17. Waiting for drier soil
is the most important strategy
Sidewall compaction
?

18. Tillage systems
affect root
architecture
Adapted from Hunt et al. (1986)

19. Long term no-till
(w/ healthy soil biology)
Intensive tillage
Network
Plow pan of
biopores
Ontario Ministry of Ag and Food

20. Which solution
would you use ?

21. WIU Allison Organic Research Farm – September 2007

23. January

24. February

25. Early May
Warmer and drier than soil
with other cover crops and
almost no weed growth

26. Visual evidence of biodrilling
Canola root
Rapeseed root

27. The experiment was planted to
corn on May 29 2008
Corn following radish
established well, had the lowest
in-row weed pressure and
yielded about 10 bu more.

28. Chemical toxicities
can inhibit root growth
Aluminum
toxicity
Aluminum
toxicity

29. Galled root system of tomato infected with root-knot
nematode, Meloidogyne sp., compared with non-
infected root system
Root pathogens can
inhibit root growth
http://www.agnr.umd.edu/users/nrsl/entm/nematology/images/eis143.jpg

30. Root knot juvenile penetrating a tomato root

31. You won’t know what is happening
underground unless you take a look…

32. All you need
is a shop-vac
and a hose!
Its just like going to the dentist!

33. Roots have many functions !

34. Absorptive network for limiting soil resources
of water and nutrients
Mechanical structures that support plants,
strengthen soil, construct channels, break
rocks, etc.
Hydraulic conduits that redistribute soil water
and nutrients
Habitats for mycorrhizal fungi, rhizosphere
and rhizoplane organisms

35. Carbon pumps that feed soil organisms and
contribute to soil organic matter
Storage organs
Chemical factories that may change soil pH,
poison competitors, filter out toxins,
concentrate rare elements, etc.
A sensor network that helps regulate plant
growth

36. Macro-
anatomy of roots

37. Micro-anatomy of roots
http://www.sparknotes.com/biology/plants/plantstructures/section2.rhtml

38. What is the function
of the root cap?

39. The cell wall of the endodermis (pink inner strip of cells) is waterproofed by the
Casparian strip, which forces water to enter the symplast before it can enter the
root xylem
phloem
root hair
xylem
epidermis
endodermis
cortex

40. Apoplast vs. symplast
The movement of fluids from the root hairs to the xylem
can occur through one of two conductive pathways–
the apoplast and the symplast.
The apoplast route consists of inter-cellular spaces
within the root cortex along which water and solutes
can diffuse.
The symplast route consists of channels through cells
along which water and solutes are actively transported.

41. http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/35.03.jpg

42. Water moves upward
through plants
whenever there is a
progressively more
negative gradient of
water potential along
the soil-plant-
atmosphere
continuum

43. H20
A continuous Solar energy
chain of water
drives the
molecules is process
pulled up
through the Plants provide
plant the conduit
H20
H20
H20

44. Understanding nutrient uptake
H20
Root exudates
N, S, P activate soil microbes Transpirational
Root growth
stream
H 20
Diffusion

45. Nutrient uptake is an active and selective process
outside cell
inside cell

46. Rhizosphere
Roots normally
occupy < 1% of topsoil
volume
The rhizophere is
normally < 10 % of soil
volume Zone of root
influence

47. Navigating the rhizosphere
End of the
Rhizoplane rhizosphere
Endo-
Rhizosphere Ecto-Rhizosphere
Microbial activity
> 90%
< 10% of soil
volume
of soil
volume
A few millimeters
(Lavelle and Spain, 2001)

48. Both strategies are important !
Feed the soil vs. Feed the crop???
Unhealthy roots use nutrients inefficiently…
Healthy roots need available nutrients !
Acute
root
disease
Chronic root
malfunction

49. How do you know if a crop has healthy roots?
extend into the
white color B horizon
proliferate in all minimal
directions evidence of
deformities

50. Healthy
cowpea
nodule
with a
pink
interior

51. Legume
nodules
come in
many shapes
and sizes

52. Lots of complicated biochemistry – very intensively studied!!
Legume
love
affair
Sarrantonio

53. Examples of rhizobia innoculant

54. Inoculation groups for commonly grown legumes
Alfalfa Group Alfalfa
(Rhizobium meliloti) Black medic
Bur clover
Button clover
White sweetclover
Yellow sweetclover
Clover Group Alsike clover
(Rhizobium trifolii) Arrowleaf clover*
Ball clover
Berseem clover
Crimson clover
Hop clover
Persian clover
Red clover
Rose clover*
Subterranean clover*
White clover
Cowpea Group Alyceclover
Soybean has its own inoculation group!!
(Bradyrhizobium japonicum spp.) Cowpea
Kudzu
Peanut

55. Mycorrhizal associations
Ectomycorrhizae
AM endomycorrhizae
Arbutoid
mycorrhizae
Ericoid
endomycorrhizae
Orchid endomycorrhizae
Lavelle and Spain (2001)

56. Ectomycorrhizal roots

57. Close up of ecto-mycorrhiza

58. Mycorrhizal Networks: Connecting
plants intra- and interspecifically
•Many plants are
connected
underground by
mycorrhizal hyphal
interconnections.
•Mycorrhizal (AM)
fungi are not host
specific.
Illustration by Mark Brundrett

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