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I shared this updated version of a class lecture on roots with a group of seed company reps on 2/9/2011
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Managing for
Healthy Roots
Joel Gruver
School of Agriculture
Western Illinois University
[email protected]://www.slideshare.net/jbgruver/
The hidden half of agriculture
ROOTS
The Furrow
Bill Darrington (Persia, IA)
Interesting example of a farmer with a
root-focused management program.
How many of you regularly
look at crop roots ?
What do you look for?
Healthy shoot
growth and good
yields
white color
proliferate in all
directions
extensive
growth into the
sub-soil
minimal
evidence of
deformities
Evidence of healthy roots
Efficient use of
soil resources
The nodal root system becomes visible at ~ V1.
The nodal root system becomes the dominant
system by V6.
Understanding corn root
development
The seed roots stop
growing shortly after
the coleoptile
emerges from the
soil surface.
1926
4 weeks
8 weeks
16 weeks
7 feet deep !!
Corn root developmentdocumented in the 1920s
If this was possible 90 years ago, just
think what is possible today?
Corn College TV Episode 8 - Wednesday, Oct 20 2010
This episode digs deep with crown root development
Dig up a root ball
Dig up a root ball
Remove brace roots
Dig up a root ball
Remove brace roots
Inspect crown roots
http://www.fontanelle.com/util/resources/news/real-word-agronomy
Evaluating
corn rootworm
damage
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
Severe damage by corn
rootworm larvae to roots of
a corn rootworm hybrid
http://www.ipm.iastate.edu/ipm/icm/2006/11-13/btcorn.html
Rootworm resistant genetics are not a silver bullet !
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.
U of I Corn Borer survey results
Sidewall compaction
?
Is this the solution?
Waiting for drier soil
is the most important strategy
Sometimes it is valuable
to dig a soil pit.
A pit will allow you to look deeper and see
how the soil volume is being explored
John McGillicuddy
IA crop scout
You won’t know what is happening
underground unless you take a look…
All you need
is a shop-vac
and a hose!
Its just like going to the dentist!
Adapted from Hunt et al. (1986)
Tillage systems
affect root
architecture
Long term no-till(w/ healthy soil biology)Intensive tillage
Ontario Ministry of Ag and Food
Plow pan
Network
of
biopores
Ken Ferrie – Farm Journal
As the root moves through the soil it tapers
down, but when it hits a sudden density
change, ‘it’s like a fly hit the screen. It’s too
tight and it twists, bends and runs
horizontally," said Ferrie.
Horizontal tillage creates loose soil on top and a
firm shelf underneath, and the density change
creates difficulties for roots which are trying to
penetrate the firmer layer.
"What causes the sudden density change?
Compaction. If it hits a compacted layer, it turns
and runs on top of it."
Ferrie added the drastic change is caused by a
farm in horizontal tillage. "You can’t use horizontal
tillage without putting in a horizontal layer"
Ken Ferrie’s perspective
Vertical
tillage tool
Brady and Weil (2002)Brady and Weil (2002)
Sub-soil water
and nutrients
Cotton plant’s perspective
My first wading pool
garden in July 2009
The watermelon root system on the title slide was exhumed from this pool in September.
Watermelon root system exhumed from a wading pool
Wading pools filled with compost are *not* an optimal rooting environment but
are an example of the plasticity of plant root systems. With limited rooting
volume but adequate water and nutrients, it is possible to grow abundant crops.
Does this look familiar?
Saturated soil is
less compressible
than wet soil
Compaction
probably extends
several feet deep
Which solution
would you use ?
Artificial drainage has greatly increased the
number of days when soils are suitable for deep
root growth
but has also
contributed
to many
environmental
problems
Pollution of
water resources Loss of SOM
Prevention through improved drainage maybe the most effective strategy
WIU Allison Organic Research Farm – September 2007
January
February
Early May
Warmer and drier than soil with other cover crops and
almost no weed growth
Visual evidence of biodrilling
Rapeseed root
Canola root
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.
Mechanism(s) of
yield enhancement??
Aluminum
toxicity
Aluminum
toxicity
Chemical toxicities
can inhibit root growth
Understanding aluminum toxicity
Toxic forms
of Al are
bioavailable
at pHs < 5.5
Aluminum toxicity
is minimal above
a water pH of 5.5
http://www2.ctahr.hawaii.edu/tpss/research_extension/rxsoil/alroot.gif
Fe and Mn toxicities also
occur at lower pHs
What damaged these corn roots?
B was included in
starter fertilizer
http://www.sdstate.edu/ps/soil-lab/loader.cfm?csModule=security/getfile&PageID=788496
http://www.agnr.umd.edu/users/nrsl/entm/nematology/images/eis143.jpg
Galled root system of tomato infected with root-knot
nematode, Meloidogyne sp., compared with non-
infected root system
Root pathogens can
inhibit root growth
Root knot juvenile penetrating a tomato root
Acute
root
disease
Feed the soil vs. Feed the crop???
Healthy roots need available nutrients !
Unhealthy roots use nutrients inefficiently…
Chronic root
malfunction
Both strategies are important !
Healthy roots grow
in soils with a
favorable balance
of air, water and
soil organic matter
Roots have many functions !
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
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
H20
H20
H20H20
A continuous
chain of water
molecules is
pulled up
through the
plant
Solar energy
drives the
process
Plants provide
the conduit
Understanding nutrient uptake
Transpirational
stream
H20
H20
Root exudates
activate soil microbes
Ro
ot g
row
th
N, S, P
Diffusion
Nutrient uptake is an active and selective process
insid
e c
ell
ou
tsid
e c
ell
Rhizosphere
Zone of root
influence
The rhizophere is
normally < 10 % of soil
volume
Roots normally
occupy < 1% of topsoil
volume
Navigating the rhizosphere
Rhizoplane
Endo-
Rhizosphere Ecto-Rhizosphere
End of the
rhizosphere
(Lavelle and Spain, 2001)
< 10% of soil
volume
> 90%
of soil
volume
Mic
rob
ial acti
vit
y
A few millimeters
Healthy
cowpea
nodule
with a
pink
interior
Legume
nodules
come in
many shapes
and sizes
Legume
love
affair
Sarrantonio
Lots of complicated biochemistry – very intensively studied!!
Examples of rhizobia innoculant
Alfalfa Group
(Rhizobium meliloti)
Alfalfa
Black medic
Bur clover
Button clover
White sweetclover
Yellow sweetclover
Clover Group
(Rhizobium trifolii)
Alsike clover
Arrowleaf clover*
Ball clover
Berseem clover
Crimson clover
Hop clover
Persian clover
Red clover
Rose clover*
Subterranean clover*
White clover
Cowpea Group
(Bradyrhizobium japonicum spp.)
Alyceclover
Cowpea
Kudzu
Peanut
Lespedeza
Inoculation groups for commonly grown legumes
Ectomycorrhizae
Arbutoid
mycorrhizae
Ericoid
endomycorrhizae
Orchid endomycorrhizae
AM endomycorrhizae
Mycorrhizal associations
Lavelle and Spain (2001)
Increase nutrient (P) uptake suppress pathogens
Mediate plant competition Improve soil structure
Glomalin
Superglue
of the soil ??
Trichoderma biofungicide product
4 modes of action
competition parasitism
antibiosis induced resistance
Like many emerging
technologies with real potential
- field results have been
inconsistent
Bio-strip till
September 2008
Radishes seeded with a push
planter in late August 2008
Attempt #2September 2009
Tillage radish on 30” rows with oats on 7.5” rows
November 2009
Radish planted on 30” rows using milo plates
in mid-August 2010
It is normal for the fleshy root of cover crop radishes to rise
3 or more inches out of the ground. This is not a sign of compaction!
Ontario, Canada
Large scale conventional grain producers
are starting to experiment with bio-strip-till.
Annual ryegrass
w/crimson clover
Annual ryegrass is a very deep rooted cover crop that has good
tolerance of wet soils, combines well with other species and
produces less above ground biomass than cereal rye