Managing for

Healthy Roots

Joel Gruver

School of Agriculture

Western Illinois University

j-gruver@wiu.eduhttp://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