Dr. Joel GruverSchool of Agriculture

Western Illinois University(309) 298 – 1215

j-gruver@wiu.edu

Basic Soil Improvement Techniquesfor Sustainable Farmers

Useful Resources

http://www.sare.org/publications/soils.htm

Managing cover crops profitably, 3rd edition

http://www.sare.org/publications/handbooks.htm

Free downloads

http://soils.usda.gov/sqi/concepts/soil_biology/biology.html

NRCS SOIL BIOLOGY PRIMER

Excellent comprehensive soil science textbook

> $100

< $10

Are you familiar with the “disease

triangle”?

Which factor do you think is

most important?

Do you think agroecologically?

Managing crop residues

Continuous tomatoes

All of these strategies are being used successfully by some farmers/gardeners. Only you can

determine the best fit for you.

Growing under cover may be the most effective organic

strategy for improving crop health and productivity

Have any of you visited Monticello ?

Jefferson made good use of microclimates

Thomas

Jefferson

Garden in

Gruverland

Inspired by Monticello, my family decided to make better use of microclimates

Understanding the soil environment

Sand and silt

are the bones of the

soil skeleton

http://www.ecogrowth.com.au/soil.htm

Soil skeletons

Clay and humus are the soil skin

and connective tissues

humusclay minerals

http://www.ccma.csic.es/dpts/suelos/Brady and Weil (2002)

Why is the soil skin important ?

Adsorption of water films

Adsorption of organic and

inorganic chemicals

Ion exchange

Catalysis of chemical reactions

Habitat for bacteria

Get to

know your

soil’s body

parts !

The jar test

TEXTURE BY FEEL

Textural

triangle

12

textural

classes

http://www.oneplan.org/Images/soilMst/SoilTriangle.gif

Loamy soils

Loamy soils have the most favorable physical properties

Potting media criteria

High moisture retention and rapid drainage

It can be difficult to optimize both

moisture retention and drainage in

real soils

It is rarely cost effective for farmers to change the texture or other inherent properties of

the soils on their farms

≠

Understanding inherent differences in soil properties

WEB SOIL SURVEY- a great source of info on soil inherent properties

What are these

crazy people

trying to do ?

Location:

Laurenburg, NC

Date: 1961

Very deep plowing as part of a futile effort to create deep “Prairie” soils in North Carolina

http://www.grdc.com.au/growers/gc/gc48/conference1.htm

The soil fabric

Good Tilth Poor Tilth

The soil pore

network serves

as a respiratory

and circulatory

system

http://www.mtm.kuleuven.ac.be/Research/NDT/IDO_SHerman_final.ppt

Field Capacity

Permanent wilting point

Plant available water

Pore size

10- 30 μm

Drainage pores

Unavailable water

Adapted from Buol (2000)

Easily available

Understanding your soil’s respiratory and

circulatory system

0.2

μm

After adding water1.0% C 1.4% C

Do you scavenge and hoard organic materials from far and wide?

This can be a good soil building strategy but

should not be a permanent strategy in a world with finite organic

resources.

Is it time to reduce your farm’s foot print?

There is a lot more to soil organic matter management than just increasing OM

inputs !!

What is happening on your farm?

accumulate in soil?

Why does

matorganic ter

Most soil microbes are unculturable

..and the soil microbes that are culturablecan digest almost

everything organic at rates hundreds of

times faster than decomposition in field

soils

Understanding organic resource quality

(Giller, 2000)

aka digestibility

C:N ratio > ~ 20

Relationship between fine mineral fraction and SOM

Magdoff and Weil (2004)

Soils with more fine particles

normally retain more SOM

Weak relationship between clay content and SOC for 1261 agricultural soils in England and Wales

Webb et al.(2003)

Clearly many factors other than clay

affect C accumulation

Temperature affects SOM dynamics

Brady and Weil (2002)

Temperature

Organic matter destruction by aerobic organisms

Organic matter synthesis by plants

Org

anic

mat

ter

pro

du

ctio

nO

rgan

ic m

atte

r co

nsu

mp

tio

nO

M p

rod

uct

ion

an

d c

on

sum

pti

on

Your farmin 50 yrs

~ 70 F mean annual temp

Interstream divide

SOIL DRAINAGE CLASSES

Poorly drained

Somewhat poorly drained

Moderately well drained

Poorly drained

Well drained

Interfluve

Valley floorBackslope

Shoulder

LANDSCAPE POSITIONS

Landscape position affects SOM dynamics

Where does the most OM accumulate?

http://www.extension.umn.edu/distribution/cropsystems/components/7402_02.html

Agriculture normally accelerates loss of SOM

OM enriched sediment

OM depleted top soil

Erosion has caused major redistribution of OM

Artificial drainage has greatly increased the number of days when soils are suitable for field operations

but has also contributed

to many environmental

problems

Pollution of water resources Loss of SOM

Adapted from Magdoff and Weil (2003)

47

Identify 2 methods of increasing

SOM.

42

DEPARTMENT of SOIL SCIENCENC STATE UNIVERSITY

(justification statement)

Small increases in OM can

improve macro-aggregation

Superior air/water relationships

Healthier root

growth and function

http://www.arlington.k12.va.us/schools/abingdon/programs/naturalistclub/pic%2012-04/good%20diggin%20shot.JPG

There’s more than one way to collect a soil sample

but results have little value if the sample is not

representative

Composite

sampling

Multiple sub-

samples are

collected from

each management

unit and mixed

together

Recommendations

So what do the numbers mean ???

Analytical results

Have any of you ever had to run a 40

as part of a try-out for a team?

How well does an

athlete’s 40 time

predict their ability

to play the game?

By themselves, extractable nutrient levels are not informative.

Extractable nutrient levels provide an index of nutrient availability that can be interpreted using

results from field experiments.

Meaningful interpretation of soil test results

requires field calibration

100 % yield

50 %yield

http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif

Soil test P concentration (ppm)

Soil test levels are not directly related to most of the factors controlling nutrient

availability during a growing season.

moisture temperature microbial activity

rooting depth root health

Calibration experiments were not conducted using organic management practices

Understanding nutrient uptake

Transpirational

stream

Ro

ot g

row

th

H20

H20

Root

exudates

activate soil

microbes

http://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htm

Nutrients that can be easily redistributed

Nutrients that are not easily redistributed

Sampling vegetable crops for tissue analysis

http://www.cahe.nmsu.edu/pubs/_a/a-123.html

http://149.168.222.13/D:/2005/WASTES/Predicti/7000/WAW06343.PDF

Estimated Nutrients available for a single crop

Total nutrient content of DM is adjusted for moisture and availability

Analytical results

Acute root

disease

Feed the soil vs. Feed the crop ?

Chronic root

malfunction

Both strategies are important !

Healthy roots need

available nutrients !

Unhealthy roots in soils with low SOM and poor structure

use nutrients inefficiently…

Plants with poorly

developed roots

tend to have

nutrient deficiency

and drought stress

symptoms

How often

do you

look at

roots ?

How often do you look

at roots?

http://www.tre.umn.edu/growers/nursery_nightmares/nightmares.htm

Raised beds promote healthy roots !!

Faster drainage and soil warming

Greater depth of fertile soil

Restricted traffic

No wheel traffic on

beds

What happened to my soil??

Tillage when a soil is too wet often creates clods that require a period of

wetting and drying and/or freezing and

thawing (in addition to biological activity)

before good structure is restored.

Are you familiar with the fence post principle?

Zone of maximum biological activity and rapid residue decay

Bacteria

Fungi

Algae

Protozoa

Nematodes

Microarthropods

Enchytraeids

Earthworms

Ants, termites, spiders

Mollusks

Others: rodents, snakes,

voles, amphibians, etc.

Microflora

Mesofauna

Megafauna

Microfauna

Macrofauna

The soil stomachPlant roots depend

on an external digestive system

“ the soil food web”

What do bacteria do in soil ?

Colonize aerobic and anaerobic environments

Decompose easily digested organics

Mediate redox transformations

Nourish bacterivores

Fix N

Most N transformations in soil are carried out by bacteria!!

Plant biomass

Soil

What do fungi do in soil ?

Decompose less easily digested organics

Penetrate residues

Stabilize soil structure

Nourish fungivores

Form symbioses with plant roots and soil fauna

Compete with plant pathogens

Parasitize plants and soil animals

Produce toxins e.g. aflatoxin produced by Aspergillus flavus on peanut

Most plant pathogens are fungi but most fungi are not plant pathogens !!

Adapted from Coleman et al. (19??)

detritusphere rhizosphere

Soil organisms are

concentrated

in

HOT

SPOTS !

Detritusphere

surface residue zone

Clean tillage eliminates the detritus layer

Many soil organisms prefer to feed at the surface

Rhizosphere

Zone of root influence

< 10 % of soil volume under prairie vegetation

< 1 % of soil volume under most vegetable crops

Cover crops

Less lossLess loss

Cover

Crops

Adapted from Magdoff and Weil (2004)

Cover crops increase annual root production and function

Feed

livestock

Recent studies indicate that root production is the best

predictor of long-term retention of SOM.

CCs can have many other beneficial effects