Managing for Healthy Roots

Dr. Joel Gruver School of Agriculture

Western Illinois University j-gruver@wiu.edu

http://www.slideshare.net/jbgruver/

My first wading pool garden in July 2009

The watermelon root system on the title slide was exhumed from this pool in September.

Housing project garden in early June

~ 1 month after transplanting

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.

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

extend into the

B horizon

minimal

evidence of

deformities

Evidence of healthy roots

Efficient use of

soil resources

Feed the soil vs. Feed the crop ?

Acute root

disease

Chronic root

malfunction

Both strategies are important !

but healthy roots need available nutrients !

Unhealthy roots use nutrients inefficiently…

Plants with poorly

developed roots

tend to have

nutrient deficiency

and drought stress

symptoms

Corn 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.

4 weeks

8 weeks

16 weeks

7 feet deep !!

1926

I have not read this book but it looks interesting!

Brady and Weil (2002)

Brady and Weil (2002)

Sub-soil water

and nutrients

Cotton plant

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

Which option would you use ?

WIU Allison Organic Research Farm – September 2007

Early May

Warmer and drier than soil with other cover crops and

almost no weed growth

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 than

the no radish treatment.

Visual evidence of biodrilling

Rapeseed root

Canola root

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

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

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

Nematode diversity

Fungivore Bacterivore

Predatory Plant parasitic

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

What is the function

of the root cap?

Protection and lubrication

H20

H20

H20 H20

A continuous

chain of water

molecules is

pulled up

through the

plant

Solar energy

drives the

process

Plants provide

the conduit

Understanding the “ins and outs”

of root function

Transpirational

stream

Ro

ot g

row

th

H20

H20

Root

exudates

activate soil

microbes

NO3-1

Ca+2

Iess mobile nutrients like phosphorus

How many of you regularly plant transplants that look like this?

How many of you are familiar with this system of growing transplants?

My personal experience is that making and handling soil blocks can be a

tedious process but the quality of the transplants is excellent

Large scale automated soil block production and planting is common in Europe

Most important characteristic of potting media

High moisture retention and rapid drainage

It can be difficult to optimize both moisture retention and drainage in real soils

Raised beds promote healthy roots !!

Faster drainage and soil warming

Greater depth of fertile soil

Restricted traffic

No wheel traffic on

beds

Where is the party? Rhizoplane

Endo-Rhizosphere Ecto-Rhizosphere Root free soil

End of the rhizosphere

(Lavelle and Spain, 2001)

< 10% of soil volume

> 90% of soil

volume

Bio

logi

cal a

ctiv

ity

A few millimeters

N-fixing nodules on a cowpea plant

Pink is good!

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

Joint vetch

Lupine Group

(Rhizobium lupini)

Blue lupine

White lupine

Pea and Vetch Group

(Rhizobium leguminosarum)

Bigflower vetch

Common vetch

Hairy vetch

Roughpea

Winter pea

Other**

Bird’s-foot trefoil (Rhizobium loti)

Cicer milk vetch

Crown vetch

Sainfoin (Rhizobium)

Soybean (Rhizobium japonicum)

Kura clover

Leucaena

Inoculation groups for commonly grown legumes

3 broad goals of

ecological

management Activation

Augmentation Conservation

crop rotations Historically

revolved around LEGUMES

Typical amounts of nitrogen

fixed by legumes

Alfalfa 150-300+

Soybeans 150-250

Red clover 75-200

Hairy vetch 75-200

Other annual forage

legumes 50-150

(lbs/ac/yr)

Net loss

Inoculation of cover crops is low cost way to increase N fixation

Hairy Vetch 3,260 lbs of DM/ac

141 lbs of N/ac

133 lbs of K/ac

18 lbs of P/ac

52 lbs of Ca/ac

18 lbs of Mg/ac

Ectomycorrhizae

Arbutoid

mycorrhizae

Ericoid

endomycorrhizae

Orchid endomycorrhizae

AM endomycorrhizae

Mycorrhizal diversity

Lavelle and Spain (2001)

Most woody plants

Most herbaceous

plants including

corn and soybeans

Myco = fungus

Rhiza = root

Close up of an arbuscule (one way that mycorrhiza connect to the plumbing of plants)

Increase nutrient uptake

(especially P)

suppress pathogens

Mediate plant competition Improve soil structure

Glomalin

Superglue of the soil ??

Mycorrhizae

•Many plants are

connected

underground by

mycorrhizal hyphal

interconnections.

•Mycorrhizal fungi

are not host specific.

Illustration by Mark Brundrett

Mycorrhizal Networks: Connecting plants intra- and interspecifically

This is just an example of a product not an endorsement!

Trichoderma biofungicide product

Mixed Results

4 modes of action

competition parasitism

antibiosis induced resistance

Bio-strip till

September 2008

Radishes seeded with a push planter in late August 2008

Attempt #2 September 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