SUSTAINABLE SOIL

MANAGEMENT

SOIL SYSTEMS GUIDE

National Sustainable Agriculture Information Service

www.attra.ncat.org

Abstract: This publication covers basic soil properties and management steps toward building and maintaining

healthy soils. Part I deals with basic soil principles and provides an understanding of living soils and how they work. In this section you will find answers to why soil organisms and organic matter are important. Part II covers management steps to build soil quality on your farm. The last section looks at farmers who have successfully built up their soil. The publication concludes with a large resource section of other available information.

By Preston Sullivan

NCAT Agriculture Specialist
May 2004

©2004 NCAT

Table of Contents

Part I. Characteristics of

Sustainable Soils ……….. …2

Introduction ………….. .2

The Living Soil: Texture

and Structure……….. ..2

The Living Soil: The Importance of

Soil Organisms……….. …3

Organic Matter, Humus, and the Soil

Foodweb ……….. .7

Soil Tilth and Organic Matter………….. .8

Tillage, Organic Matter, and Plant

Productivity ……….. 10

Fertilizer Amendments and

Biologically Active Soils ……….. 13

Conventional Fertilizers………….. 14

Top$oil ñ Your Farmí$ Capital ………….. 15

Summary of Part I………….. 18

Summary of Sustainable

Soil Management Principles ……….. 19

Part II. Management Steps to

Improve Soil Quality ……….. 20

Part III. Examples of Successful

Soil Builders (Farmer Profiles) ……….. 25

References………….. 27

Additional Resources ………….. 28

Photo by Preston Sullivan

Soybeans no-till planted into wheat stubble.

ATTRA is the national sustainable agriculture information service operated by the National Center for Appropriate Technology, through a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California.

PART I. Characteristics of SUSTAINABLE SOILS

Introduction

What are some features of good soil? Any farmer will tell you that a good soil:

ï feels soft and crumbles easily

ï drains well and warms up quickly in

the spring

ï does not crust after planting

ï soaks up heavy rains with little runoff ï stores moisture for drought periods ï has few clods and no hardpan

ï resists erosion and nutrient loss

ï supports high populations of soil

organisms

ï has a rich, earthy smell

ï does not require increasing inputs for

high yields

ï produces healthy, high-quality crops

(1)

All these criteria indicate a soil that functions
effectively today and will continue to produce
crops long into the future. These characteris-
tics can be created through management prac-
tices that optimize the processes found in na-
tive soils.

How does soil in its native condition function?
How do forests and native grasslands produce
plants and animals in the complete absence of
fertilizer and tillage? Understanding the prin-
ciples by which native soils function can help
farmers develop and maintain productive and
profitable soil both now and for future genera-
tions. The soil, the environment, and farm con-
dition benefit when the soilís natural produc-
tivity is managed in a sustainable way. Reli-
ance on purchased inputs declines year by year,
while land value and income potential increase.
Some of the things we spend money on can be
done by the natural process itself for little or
nothing. Good soil management produces crops
and animals that are healthier, less susceptible
to disease, and more productive. To understand
this better, letís start with the basics.

PAGE 2

Sustainable: capable of being maintained at

length without interruption, weakening, or losing in power or quality.

The Living Soil: Texture

and Structure

Soils are made up of four basic components:
minerals, air, water, and organic matter. In
most soils, minerals represent around 45% of
the total volume, water and air about 25% each,
and organic matter from 2% to 5%. The min-
eral portion consists of three distinct particle
sizes classified as sand, silt, or clay. Sand is the
largest particle that can be considered soil.

Sand is largely the mineral quartz, though other
minerals are also present. Quartz contains no
plant nutrients, and sand cannot hold nutri-
entsóthey leach out easily with rainfall. Silt
particles are much smaller than sand, but like
sand, silt is mostly quartz. The smallest of all
the soil particles is clay. Clays are quite differ-
ent from sand or silt, and most types of clay
contain appreciable amounts of plant nutrients.
Clay has a large surface area resulting from the
plate-like shape of the individual particles.
Sandy soils are less productive than silts, while
soils containing clay are the most productive and
use fertilizers most effectively.

Soil texture refers to the relative proportions of
sand, silt, and clay. A loam soil contains these
three types of soil particles in roughly equal pro-
portions. A sandy loam is a mixture containing
a larger amount of sand and a smaller amount
of clay, while a clay loam contains a larger
amount of clay and a smaller amount of sand.
These and other texture designations are listed
in Table 1.

Another soil characteristicósoil structureóis
distinct from soil texture. Structure refers to the
clumping together or ìaggregationî of sand, silt,
and clay particles into larger secondary clusters.

Table 1. Soil texture designations

ranging from coarse to fine.

Texture Designation

Coarse-textured Sand

Loamy sand

Sandy loam

Fine sandy loam

Loam

Silty loam

Silt

Silty clay loam

Clay loam

Fine-textured Clay

If you grab a handful of soil, good structure is
apparent when the soil crumbles easily in your
hand. This is an indication that the sand, silt,
and clay particles are aggregated into granules
or crumbs.

Both texture and structure determine pore space
for air and water circulation, erosion resistance,
looseness, ease of tillage, and root penetration.
While texture is related to the minerals in the
soil and does not change with agricultural ac-
tivities, structure can be improved or destroyed
readily by choice and timing of farm practices.

The Living Soil: The

Importance of Soil

Organisms

An acre of living topsoil contains approximately
900 pounds of earthworms, 2,400 pounds of
fungi, 1,500 pounds of bacteria, 133 pounds of
protozoa, 890 pounds of arthropods and algae,
and even small mammals in some cases (2).
Therefore, the soil can be viewed as a living com-
munity rather than an inert body. Soil organic
matter also contains dead organisms, plant
matter, and other organic materials in various
phases of decomposition. Humus, the dark-col-
ored organic material in the final stages of de-
composition, is relatively stable. Both organic
matter and humus serve as reservoirs of plant
nutrients; they also help to build soil structure
and provide other benefits.

The type of healthy living soil required to sup-
port humans now and far into the future will

be balanced in nutrients and high in humus,

with a broad diversity of soil organisms. It will
produce healthy plants with minimal weed, dis-
ease, and insect pressure. To accomplish this,
we need to work with the natural processes and
optimize their functions to sustain our farms.

Considering the natural landscape, you might
wonder how native prairies and forests func-
tion in the absence of tillage and fertilizers.
These soils are tilled by soil organisms, not by
machinery. They are fertilized too, but the fer-
tility is used again and again and never leaves
the site. Native soils are covered with a layer of
plant litter and/or growing plants throughout
the year. Beneath the surface litter, a rich com-
plexity of soil organisms decompose plant resi-
due and dead roots, then release their stored
nutrients slowly over time. In fact, topsoil is
the most biologically diverse part of the earth
(3). Soil-dwelling organisms release bound-up
minerals, converting them into plant-available
forms that are then taken up by the plants grow-
ing on the site. The organisms recycle nutrients
again and again with the death and decay of
each new generation of plants.

There are many different types of creatures that
live on or in the topsoil. Each has a role to play.
These organisms will work for the farmerís ben-
efit if we simply manage for their survival. Con-
sequently, we may refer to them as soil livestock.
While a great variety of organisms contribute
to soil fertility, earthworms, arthropods, and the
various microorganisms merit particular atten-
tion.

Earthworms

Earthworm burrows enhance water infiltration
and soil aeration. Fields that are ìtilledî by
earthworm tunneling can absorb water at a rate
4 to 10 times that of fields lacking worm tun-
nels (4). This reduces water runoff, recharges
groundwater, and helps store more soil water
for dry spells. Vertical earthworm burrows pipe
air deeper into the soil, stimulating microbial
nutrient cycling at those deeper levels. When
earthworms are present in high numbers, the
tillage provided by their burrows can replace
some expensive tillage work done by machin-
ery.

PAGE 3

Table 2. Selected nutrient analyses of worm casts compared to those of the surrounding soil.

Nutrient Worm casts Soil

Lbs/ac Lbs/ac

Carbon 171,000 78,500

Nitrogen 10,720 7,000

Phosphorus 280 40

Potassium 900 140

From Graff (6). Soil had 4% organic matter.

Earthworms thrive where there is no tillage.
Generally, the less tillage the better, and the shal-
lower the tillage the better. Worm numbers can
be reduced by as much as 90% by deep and fre-
quent tillage (7). Tillage reduces earthworm
populations by drying the soil, burying the plant
residue they feed on, and making the soil more
likely to freeze. Tillage also destroys vertical

Figure 1. The soil is teeming with organisms that cycle

nutrients from soil to plant and back again.

Worms eat dead plant material left on top of
the soil and redistribute the organic matter and
nutrients throughout the topsoil layer. Nutri-
ent-rich organic compounds line their tunnels,
which may remain in place for years if not dis-
turbed. During droughts these tunnels allow
for deep plant root penetration into subsoil re-
gions of higher moisture content. In addition
to organic matter, worms also consume soil and
soil microbes. The soil clusters they expel from
their digestive tracts are known as worm casts
or castings. These range from the size of a mus-
tard seed to that of a sorghum seed, depending
on the size of the worm.

The soluble nutrient content of worm casts is
considerably higher than that of the original soil
(see Table 2). A good population of earthworms
can process 20,000 pounds of topsoil per yearó
with turnover rates as high as 200 tons per acre
having been reported in some exceptional cases
(5). Earthworms also secrete a plant growth
stimulant. Reported increases in plant growth
following earthworm activity may be partially
attributed to this substance, not just to improved
soil quality.

PAGE 4

worm burrows and can kill and cut up the

worms themselves. Worms are dormant in the
hot part of the summer and in the cold of win-
ter. Young worms emerge in spring and falló
they are most active just when farmers are likely
to be tilling the soil. Table 3 shows the effect of
tillage and cropping practices on earthworm
numbers.

Table 3. Effect of crop management on earthworm populations.

Crop Management Worms/foot²

Corn Plow 1

Corn No-till 2

Soybean Plow 6

Soybean No-till 14

Bluegrass/

clover ó- 39

Dairy

pasture ó- 33

From Kladivko (8).

As a rule, earthworm numbers can be increased
by reducing or eliminating tillage (especially fall
tillage), not using a moldboard plow, reducing
residue particle size (using a straw chopper on
the combine), adding animal manure, and grow-
ing green manure crops. It is beneficial to leave
as much surface residue as possible year-round.

Cropping systems that typically have the most

earthworms are (in descending order) perennial
cool-season grass grazed rotationally, warm-
season perennial grass grazed rotationally, and
annual croplands using no-till. Ridge-till and
strip tillage will generally have more earthworms
than clean tillage involving plowing and disking.
Cool season grass rotationally grazed is highest
because it provides an undisturbed (no-tillage)
environment plus abundant organic matter from
the grass roots and fallen grass litter. Generally
speaking, worms want their food on top, and
they want to be left alone.

Earthworms prefer a near-neutral soil pH, moist
soil conditions, and plenty of plant residue on
the soil surface. They are sensitive to certain
pesticides and some incorporated fertilizers.
Carbamate insecticides, including Furadan,
Sevin, and Temik, are harmful to earthworms,
notes worm biologist Clive Edwards of Ohio
State University (4). Some insecticides in the
organophosphate family are mildly toxic to
earthworms, while synthetic pyrethroids are
harmless to them (4). Most herbicides have little
effect on worms except for the triazines, such
as Atrazine, which are moderately toxic. Also,
anhydrous ammonia kills earthworms in the
injection zone because it dries the soil and tem-
porarily increases the pH there. High rates of
ammonium-based fertilizers are also harmful.

For more information on managing earthworms,
order The Farmerís Earthworm Handbook: Man-
aging Your Underground Moneymakers, by David
Ernst. Ernstís book contains details on what
earthworms need to live, how to increase worm
numbers, the effects of tillage, manure, and live-
stock management on earthworms, how 193
chemicals affect earthworms, and more. See the
Additional Resources section of this publica-
tion for ordering information. Also visit the
earthworm Web sites listed in that section.

As a rule, earthworm numbers can be in-
creased by reducing or eliminating tillage.

Arthropods

In addition to earthworms, there are many
other species of soil organisms that can be seen
by the naked eye. Among them are sowbugs,

millipedes, centipedes, slugs, snails, and spring-

tails. These are the primary decomposers. Their role is to eat and shred the large particles of plant and animal residues. Some bury residue, bring-
ing it into contact with other soil organisms that further decompose it. Some members of this group prey on smaller soil organisms. The springtails are small insects that eat mostly fungi. Their waste is rich in plant nutrients released after other fungi and bacteria decompose it. Also of interest are dung beetles, which play a valu-
able role in recycling manure and reducing live-
stock intestinal parasites and flies.

Bacteria

Bacteria are the most numerous type of soil or-
ganism: every gram of soil contains at least a
million of these tiny one-celled organisms. There
are many different species of bacteria, each with
its own role in the soil environment. One of the
major benefits bacteria provide for plants is in
making nutrients available to them. Some spe-
cies release nitrogen, sulfur, phosphorus, and
trace elements from organic matter. Others
break down soil minerals, releasing potassium,
phosphorus, magnesium, calcium, and iron.
Still other species make and release plant
growth hormones, which stimulate root
growth.

Several species of bacteria transform nitrogen
from a gas in the air to forms available for plant
use, and from these forms back to a gas again.
A few species of bacteria fix nitrogen in the roots
of legumes, while others fix nitrogen indepen-
dently of plant association. Bacteria are respon-
sible for converting nitrogen from ammonium
to nitrate and back again, depending on cer-
tain soil conditions. Other benefits to plants
provided by various species of bacteria include
increasing the solubility of nutrients, improving
soil structure, fighting root diseases, and detoxi-
fying soil.

Fungi

Fungi come in many different species, sizes, and
shapes in soil. Some species appear as thread-
like colonies, while others are one-celled yeasts.
Slime molds and mushrooms are also fungi.
Many fungi aid plants by breaking down or-
ganic matter or by releasing nutrients from soil

PAGE 5

minerals. Fungi are generally quick to colonize Protozoa

larger pieces of organic matter and begin the

decomposition process. Some fungi produce Protozoa are free-living microorganisms that

plant hormones, while others produce antibiot- crawl or swim in the water between soil par-

ics including penicillin. There are even species ticles. Many soil protozoa are predatory, eat-

of fungi that trap harmful plant-parasitic nema- ing other microbes. One of the most common is

todes. an amoeba that eats bacteria. By eating and

digesting bacteria, protozoa speed up the cy-

The mycorrhizae (my-cor-ry¥-zee) are fungi that cling of nitrogen from the bacteria, making it

live either on or in plant roots and act to extend more available to plants.

the reach of root hairs into the soil. Mycorrhizae

increase the uptake of water and nutrients, es- Nematodes

pecially phosphorus. They are particularly im-

portant in degraded or less fertile soils. Roots Nematodes are abundant in most soils, and only

colonized by mycorrhizae are less likely to be a few species are harmful to plants. The harm-

penetrated by root-feeding nematodes, since the less species eat decaying plant litter, bacteria,

pest cannot pierce the thick fungal network. fungi, algae, protozoa, and other nematodes.

Mycorrhizae also produce hormones and anti- Like other soil predators, nematodes speed the

biotics that enhance root growth and provide rate of nutrient cycling.

disease suppression. The fungi benefit by tak-

ing nutrients and carbohydrates from the plant Soil organisms and soil quality

roots they live in.

All these organismsófrom the tiny bacteria up

Actinomycetes to the large earthworms and insectsóinteract

with one another in a multitude of ways in the

Actinomycetes (ac-tin-o-my¥-cetes) are thread- soil ecosystem. Organisms not directly involved

like bacteria that look like fungi. While not as in decomposing plant wastes may feed on each

numerous as bacteria, they too perform vital other or each otherís waste products or the other

roles in the soil. Like the bacteria, they help substances they release. Among the substances

decompose organic matter into humus, releas- released by the various microbes are vitamins,

ing nutrients. They also produce antibiotics to amino acids, sugars, antibiotics, gums, and

fight diseases of roots. Many of these same an- waxes.

tibiotics are used to treat human dis-

eases. Actinomycetes are respon- Roots can also release into the

sible for the sweet, earthy smell

noticed whenever a biologically active soil is tilled.

Algae

Research on life in the soil has

determined that there are
ideal ratios for certain key or-
ganisms in highly productive
soils.

soil various substances that

stimulate soil microbes. These
substances serve as food for se-
lect organisms. Some scientists
and practitioners theorize that

plants use this means to stimulate the specific

Many different species of algae live in the up-

per half-inch of the soil. Unlike most other soil
organisms, algae produce their own food
through photosynthesis. They appear as a
greenish film on the soil surface following a satu-
rating rain. Algae improve soil structure by pro-
ducing slimy substances that glue soil together
into water-stable aggregates. Some species of
algae (the blue-greens) can fix their own nitro-
gen, some of which is later released to plant
roots.

PAGE 6

population of microorganisms capable of releas-

ing or otherwise producing the kind of nutri-
tion needed by the plants.

Research on life in the soil has determined that
there are ideal ratios for certain key organisms
in highly productive soils (9). The Soil Foodweb
Lab, located in Oregon, tests soils and makes
fertility recommendations that are based on this
understanding. Their goal is to alter the makeup

of the soil microbial community so it resembles

that of a highly fertile and productive soil. There are several different ways to accomplish this goal, depending on the situation. For more on the Soil Foodweb Lab, see the Additional Re-
sources section of this publication.

Because we cannot see most of the creatures liv-
ing in the soil and may not take time to observe
the ones we can see, it is easy to forget about
them. See Table 4 for estimates of typical
amounts of various organisms found in fertile
soil. There are many Web sites that provide in-
depth information on soil organisms. Look for
a list of these Web sites in the Additional Re-
sources section. Many of these sites have color
photographs of soil organisms and describe their
benefits to soil fertility and plant growth.

Table 4. Weights of soil organisms in the top 7 inches of fertile soil.

Organism Pounds of liveweight/acre

Bacteria 1000

Actinomycetes 1000

Molds 2000

Algae 100

Protozoa 200

Nematodes 50

Insects 100

Worms 1000

Plant roots 2000

From Bollen (10).

Organic Matter, Humus,
and the Soil Foodweb

Like cattle and other farm animals, soil live-
stock require proper feed.

Understanding the role that soil organisms play
is critical to sustainable soil management. Based
on that understanding, focus can be directed
toward strategies that build both the numbers
and the diversity of soil organisms. Like cattle
and other farm animals, soil livestock require
proper feed. That feed comes in the form of
organic matter.

Organic matter and humus are terms that de-

scribe somewhat different but related things.
Organic matter refers to the fraction of the soil
that is composed of both living organisms and
once-living residues in various stages of decom-
position. Humus is only a small portion of the
organic matter. It is the end product of organic
matter decomposition and is relatively stable.
Further decomposition of humus occurs very
slowly in both agricultural and natural settings.
In natural systems, a balance is reached be-
tween the amount of humus formation and the
amount of humus decay (11). This balance also
occurs in most agricultural soils, but often at a
much lower level of soil humus. Humus con-
tributes to well-structured soil that, in turn, pro-
duces high-quality plants. It is clear that man-
agement of organic matter and humus is essen-
tial to sustaining the whole soil ecosystem.

The benefits of a topsoil rich in organic matter
and humus are many. They include rapid de-
composition of crop residues, granulation of soil
into water-stable aggregates, decreased crust-
ing and clodding, improved internal drainage,
better water infiltration, and increased water
and nutrient holding capacity. Improvements
in the soilís physical structure facilitate easier
tillage, increased water storage capacity, re-
duced erosion, better formation and harvesting
of root crops, and deeper, more prolific plant
root systems.

Soil organic matter can be compared to a bank
account for plant nutrients. Soil containing 4%
organic matter in the top seven inches has
80,000 pounds of organic matter per acre. That
80,000 pounds of organic matter will contain
about 5.25% nitrogen, amounting to 4,200
pounds of nitrogen per acre. Assuming a 5%
release rate during the growing season, the or-
ganic matter could supply 210 pounds of nitro-
gen to a crop. However, if the organic matter is
allowed to degrade and lose nitrogen, pur-
chased fertilizer will be necessary to prop up
crop yields.

All the soil organisms mentioned previously,
except algae, depend on organic matter as their
food source. Therefore, to maintain their popu-
lations, organic matter must be renewed from
plants growing on the soil, or from animal ma-
nure, compost, or other materials imported from

PAGE 7

off site. When soil livestock are

fed, fertility is built up in the soil,
and the soil will feed the plants.

Ultimately, building organic mat-
ter and humus levels in the soil is
a matter of managing the soilís

these aggregates become wet

Ultimately, building organic again, however, their stability

matter and humus in the soil is challenged, and they may

is a matter of managing the break apart. Aggregates can

soilís living organisms. also be held together by plant

roots, earthworm activity, and

by glue-like products pro-

living organismsósomething akin to wildlife

management or animal husbandry. This entails working to maintain favorable conditions of moisture, temperature, nutrients, pH, and aera-
tion. It also involves providing a steady food source of raw organic material.

Soil Tilth and Organic

Matter

A soil that drains well, does not crust, takes in
water rapidly, and does not make clods is said
to have good tilth. Tilth is the physical condi-
tion of the soil as it relates to tillage ease, seed-
bed quality, easy seedling emergence, and deep
root penetration. Good tilth is dependent on
aggregationóthe process whereby individual
soil particles are joined into clusters or ìaggre-
gates.î

Aggregates form in soils when individual soil
particles are oriented and brought together
through the physical forces of wetting and dry-
ing or freezing and thawing. Weak electrical
forces from calcium and magnesium hold soil
particles together when the soil dries. When

duced by soil microorganisms. Earthworm-cre-

ated aggregates are stable once they come out of the worm. An aggregate formed by physical forces can be bound together by fine root hairs or threads produced by fungi.

Aggregates can also become stabilized (remain
intact when wet) through the by-products of
organic matter decomposition by fungi and bac-
teriaóchiefly gums, waxes, and other glue-like
substances. These by-products cement the soil
particles together, forming water-stable aggre-
gates (Figure 2). The aggregate is then strong
enough to hold together when wetóhence the
term ìwater-stable.î

USDA soil microbiologist Sara Wright named
the glue that holds aggregates together
ìglomalinî after the Glomales group of common
root-dwelling fungi (12). These fungi secrete a
gooey protein known as glomalin through their
hair-like filaments, or hyphae. When Wright
measured glomalin in soil aggregates she found
levels as high as 2% of their total weight in east-
ern U.S. soils. Soil aggregates from the West
and Midwest had lower levels of glomalin. She
found that tillage tends to lower glomalin lev-
els. Glomalin levels and aggregation were

MICROBIAL AND FUNGAL

BYPRODUCTS GLUE

THE PARTICLES TOGETHER

DISPERSED STATE AGGREGATED STATE

Figure 2. Microbial byproducts glue soil particles into water-stable aggregates.

PAGE 8 //SUSTAINABLE SOIL MANAGEMENT

higher in no-till corn plots than in tilled plots

(12). Wright has a brochure describing glomalin
and how it benefits soil, entitled Glomalin, a Man-
ageable Soil Glue. To order this brochure see the
Additional Resources section of this publica-
tion.

A well-aggregated soil allows for increased
water entry, increased air flow, and increased
water-holding capacity (13). Plant roots occupy
a larger volume of well-aggregated soil, high in
organic matter, as compared to a finely pulver-
ized and dispersed soil, low in organic matter.
Roots, earthworms, and soil arthropods can
pass more easily through a well-aggregated soil

(14). Aggregated soils also prevent crusting of the soil surface. Finally, well-aggregated soils are more erosion resistant, because aggregates are much heavier than their particle compo-
nents. For a good example of the effect of or-
ganic matter additions on aggregation, as shown by subsequent increase in water entry into the soil, see Table 5.

Table 5. Water entry into the soil after 1
hour

Manure Rate (tons/acre) Inches of water

0 1.2

8 1.9

16 2.7

Boyle et al. (13).

The opposite of aggregation is dispersion. In a dispersed soil, each individual soil particle is free to blow away with the wind or wash away with overland flow of water.

Clay soils with poor aggregation tend to be
sticky when wet, and cloddy when dry. If the
clay particles in these soils can be aggregated
together, better aeration and water infiltration
will result. Sandy soils can benefit from aggre-
gation by having a small amount of dispersed
clay that tends to stick between the sand par-
ticles and slow the downward movement of
water.

Crusting is a common problem on soils that are
poorly aggregated. Crusting results chiefly from
the impact of falling raindrops. Rainfall causes
clay particles on the soil surface to disperse and

clog the pores immediately beneath the surface.

Following drying, a sealed soil surface results
in which most of the pore space has been dras-
tically reduced due to clogging from dispersed
clay particles. Subsequent rainfall is much more
likely to run off than to flow into the soil (Fig-
ure 3).

air water

Crusted

air water

Well-Aggregated

Figure 3. Effects of aggregation on water and air

entry into the soil.

Derived from Land Stewardship Project

Monitoring Toolbox (15).

Since raindrops start crusting, any management
practices that protect the soil from their impact
will decrease crusting and increase water flow
into the soil. Mulches and cover crops serve this
purpose well, as do no-till practices, which al-
low the accumulation of surface residue. Also,
a well-aggregated soil will resist crusting be-
cause the water-stable aggregates are less likely
to break apart when a raindrop hits them.

Long-term grass production produces the best-
aggregated soils (16). A grass sod extends a
mass of fine roots throughout the topsoil, con-

PAGE 9

tributing to the physical processes that help form

aggregates. Roots continually remove water
from soil microsites, providing local wetting and
drying effects that promote aggregation. Fine
root hairs also bind soil aggregates together.

Roots also produce food for soil

microorganisms and earth-

ï allowing the build-up of excess sodium from

irrigation or sodium-containing fertilizers

Tillage, Organic Matter, and

Plant Productivity

worms, which in turn generate

compounds that bind soil par-
ticles into water-stable aggre-
gates. In addition, perennial
grass sods provide protection

The best-aggregated soils are

those that have been in long-
term grass production.

Several factors affect the level

of organic matter that can be
maintained in a soil. Among
these are organic matter addi-
tions, moisture, temperature,

from raindrops and erosion. Thus, a perennial

cover creates a combination of conditions opti-
mal for the creation and maintenance of well-
aggregated soil.

Conversely, cropping sequences that involve
annual plants and extensive cultivation provide
less vegetative cover and organic matter, and
usually result in a rapid decline in soil aggrega-
tion. For more information on aggregation, see
the soil quality information sheet entitled Ag-
gregate Stability at the Soil Quality Instituteís
home page, <http://soils.usda.gov/sqi/files/
sq_eig_1.pdf>. From there, click on Soil Qual-
ity Information Sheets, then click on Aggregate
Stability.

Farming practices can be geared to conserve and promote soil aggregation. Because the binding substances are themselves susceptible to micro-
bial degradation, organic matter needs to be replenished to maintain microbial populations and overall aggregated soil status. Practices should conserve aggregates once they are formed, by minimizing factors that degrade and destroy aggregation. Some factors that destroy or degrade soil aggregates are:

ï bare soil surface exposed to the impact of
raindrops

ï removal of organic matter through crop pro-
duction and harvest without return of or-
ganic matter to the soil

ï excessive tillage

ï working the soil when it is too wet or too
dry

ï use of anhydrous ammonia, which speeds
up decomposition of organic matter
ï excess nitrogen fertilization

PAGE 10

tillage, nitrogen levels, cropping, and fertiliza-

tion. The level of organic matter present in the
soil is a direct function of how much organic
material is being produced or added to the soil
versus the rate of decomposition. Achieving this
balance entails slowing the speed of organic mat-
ter decomposition, while increasing the supply
of organic materials produced on site and/or
added from off site.

Moisture and temperature also profoundly af-
fect soil organic matter levels. High rainfall and
temperature promote rapid plant growth, but
these conditions are also favorable to rapid or-
ganic matter decomposition and loss. Low rain-
fall or low temperatures slow both plant growth
and organic matter decomposition. The native
Midwest prairie soils originally had a high
amount of organic matter from the continuous
growth and decomposition of perennial grasses,
combined with a moderate temperature that did
not allow for rapid decomposition of organic
matter. Moist and hot tropical areas may ap-
pear lush because of rapid plant growth, but
soils in these areas are low in nutrients. Rapid
decomposition of organic matter returns nutri-
ents back to the soil, where they are almost im-
mediately taken up by rapidly growing plants.

Tillage can be beneficial or harmful to a biologi-
cally active soil, depending on what type of till-
age is used and when it is done. Tillage affects
both erosion rates and soil organic matter de-
composition rates. Tillage can reduce the or-
ganic matter level in croplands below 1%, ren-
dering them biologically dead. Clean tillage in-
volving moldboard plowing and disking breaks
down soil aggregates and leaves the soil prone
to erosion from wind and water. The mold-
board plow can bury crop residue and topsoil
to a depth of 14 inches. At this depth, the oxy-

gen level in the soil is so low that decomposi-

tion cannot proceed adequately. Surface-dwell-
ing decomposer organisms suddenly find them-
selves suffocated and soon die. Crop residues
that were originally on the surface but now have
been turned under will putrefy in the oxygen-
deprived zone. This rotting activity may give a
putrid smell to the soil. Furthermore, the top
few inches of the field are now often covered
with subsoil having very little organic matter
content and, therefore, limited ability to support
productive crop growth.

The topsoil is where the biological activity hap-
pensóitís where the oxygen is. Thatís why a
fence post rots off at the surface. In terms of
organic matter, tillage is similar to opening the
air vents on a wood-burning stove; adding or-
ganic matter is like adding wood to the stove.
Ideally, organic matter decomposition should
proceed as an efficient burn of the ìwoodî to
release nutrients and carbohydrates to the soil
organisms and create stable humus. Shallow
tillage incorporates residue and speeds the de-
composition of organic matter by adding oxy-
gen that microbes need to become more active.

In cold climates with a long dormant season,

light tillage of a heavy residue may be benefi-
cial; in warmer climates it is hard enough to
maintain organic matter levels without any till-
age.

As indicated in Figure 4, moldboard plowing
causes the fastest decline of organic matter, no-
till the least. The plow lays the soil up on its
side, increasing the surface area exposed to oxy-
gen. The other three types of tillage are inter-
mediate in their ability to foster organic matter
decomposition. Oxygen is the key factor here.
The moldboard plow increases the soil surface
area, allowing more air into the soil and speed-
ing the decomposition rate. The horizontal line
on Figure 4 represents the replenishment of or-
ganic matter provided by wheat stubble. With
the moldboard plow, more than the entire or-
ganic matter contribution from the wheat straw
is gone within only 19 days following tillage.
Finally, the passage of heavy equipment in-
creases compaction in the wheel tracks, and
some tillage implements themselves compact the
soil further, removing oxygen and increasing the
chance that deeply buried residues will putrefy.

Organic Matter loss 19 days after Tillage

4000

3500

3000

2500

2000

1500

1000

500

0

Mb. plow Mb.+ 2

disc

Residue from wheat crop

Disc Chisel Pl. No-till

Tillage type

Reicosky & Lindstrom, 1995

Figure 4. Organic matter losses after various tillage practices (17).

Tillage also reduces the rate of water entry into

the soil by removal of ground cover and destruc-
tion of aggregates, resulting in compaction and
crusting. Table 6 shows three different tillage
methods and how they affect water entry into
the soil. Notice the direct relationship between
tillage type, ground cover, and water infiltra-
tion. No-till has more than three times the wa-
ter infiltration of the moldboard-plowed soil.
Additionally, no-till fields will have higher ag-
gregation from the organic matter decomposi-
tion on site. The surface mulch typical of no-till
fields acts as a protective skin for the soil. This
soil skin reduces the impact of raindrops and
buffers the soil from temperature extremes as
well as reducing water evaporation.

Table 6. Tillage effects on water infiltration and ground cover.

Water Infiltration Ground Cover

mm/minute Percent

No-till 2.7 48

Chisel Plow 1.3 27

Moldboard Plow 0.8 12

From Boyle et al., 1989 (13).

Both no-till and reduced-tillage systems provide
benefits to the soil. The advantages of a no-till
system include superior soil conservation, mois-
ture conservation, reduced water runoff, long-
term buildup of organic matter, and increased
water infiltration. A soil managed without till-
age relies on soil organisms to take over the job
of plant residue incorporation formerly done by
tillage. On the down side, no-till can foster a
reliance on herbicides to control weeds and can
lead to soil compaction from the traffic of heavy
equipment.

Pioneering development work on chemical-free
no-till farming is proceeding at several research
stations and farms in the eastern U.S. Pennsyl-
vania farmer Steve Groff has been farming no-
till with minimal or no herbicides for several
years. Groff grows cover crops extensively in
his fields, rolling them down in the spring us-
ing a 10-foot rolling stalk chopper. This rolling
chopper kills the rye or vetch cover crop and
creates a nice no-till mulch into which he plants
a variety of vegetable and grain crops. After
several years of no-till production, his soils are
mellow and easy to plant into. Groff farms 175
PAGE 12

acres of vegetables, alfalfa, and grain crops on

his Cedar Meadow Farm. Learn more about
his operation in the Farmer Profiles section of
this publication, by visiting his Web site, or by
ordering his video (see Additional Resources
section).

Other conservation tillage systems include ridge
tillage, minimum tillage, zone tillage, and re-
duced tillage, each possessing some of the ad-
vantages of both conventional till and no-till.
These systems represent intermediate tillage sys-
tems, allowing more flexibility than either a no-
till or conventional till system might. They are
more beneficial to soil organisms than a con-
ventional clean-tillage system of moldboard
plowing and disking.

Adding manure and compost is a recognized
means for improving soil organic matter and
humus levels. In their absence, perennial grass
is the only crop that can regenerate and increase
soil humus (18). Cool-season grasses build soil
organic matter faster than warm-season grasses
because they are growing much longer during
a given year (18). When the soil is warm
enough for soil organisms to decompose organic
matter, cool-season grass is growing. While
growing, it is producing organic matter and
cycling minerals from the decomposing organic
matter in the soil. In other words, there is a net
gain of organic matter because the cool-season
grass is producing organic matter faster than it
is being used up. With warm-season grasses,
organic matter production during the growing
season can be slowed during the long dormant
season from fall through early spring. During
the beginning and end of this dormant period,
the soil is still biologically active, yet no grass
growth is proceeding (18). Some net accumu-
lation of organic matter can occur under warm-
season grasses, however. In a Texas study,
switchgrass (a warm-season grass) grown for
four years increased soil carbon content from
1.1% to 1.5% in the top 12 inches of soil (19). In
hot and moist regions, a cropping rotation that
includes several years of pasture will be most
beneficial.

Effect of Nitrogen on Organic Matter

Excessive nitrogen applications stimulate in-
creased microbial activity, which in turn speeds
organic matter decomposition. The extra nitro-

gen narrows the ratio of carbon to nitrogen in

the soil. Native or uncultivated soils have ap-
proximately 12 parts of carbon to each part of
nitrogen, or a C:N ratio of 12:1. At this ratio,
populations of decay bacteria are kept at a stable
level (20), since additional growth in their popu-
lation is limited by a lack of nitrogen. When
large amounts of inorganic nitrogen are added,
the C:N ratio is reduced, which allows the popu-
lations of decay organisms to explode as they
decompose more organic matter with the now
abundant nitrogen. While soil bacteria can ef-
ficiently use moderate applications of inorganic
nitrogen accompanied by organic amendments
(carbon), excess nitrogen results in decomposi-
tion of existing organic matter at a rapid rate.
Eventually, soil carbon content may be reduced
to a level where the bacterial populations are
on a starvation diet. With little carbon avail-
able, bacterial populations shrink, and less of
the free soil nitrogen is absorbed. Thereafter,
applied nitrogen, rather than being cycled
through microbial organisms and re-released to
plants slowly over time, becomes subject to
leaching. This can greatly reduce the efficiency
of fertilization and lead to environmental prob-
lems.

Excessive nitrogen stimulates

increased microbial activity,

which in turn speeds organic

matter decomposition.

To minimize the fast decomposition of soil or-
ganic matter, carbon should be added with ni-
trogen. Typical carbon sourcesósuch as green manures, animal manure, and compostóserve this purpose well.

Amendments containing too high a carbon to
nitrogen ratio (25:1 or more) can tip the balance
the other way, resulting in nitrogen being tied
up in an unavailable form. Soil organisms con-
sume all the nitrogen in an effort to decompose
the abundant carbon; tied up in the soil organ-
isms, nitrogen remains unavailable for plant
uptake. As soon as a soil microorganism dies
and decomposes, its nitrogen is consumed by
another soil organism, until the balance be-
tween carbon and nitrogen is achieved again.

Fertilizer Amendments and

Biologically Active Soils

What are the soil mineral conditions that foster
biologically active soils? Drawing from the
work of Dr. William Albrecht (1888 to 1974),
agronomist at the University of Missouri, we
learn that balance is the key. Albrecht advocated
bringing soil nutrients into a balance so that none
were in excess or deficient. Albrechtís theory
(also called base-saturation theory) is used to
guide lime and fertilizer application by measur-
ing and evaluating the ratios of positively
charged nutrients (bases) held in the soil. Posi-
tively charged bases include calcium, magne-
sium, potassium, sodium, ammonium nitrogen,
and several trace minerals. When optimum ra-
tios of bases exist, the soil is believed to support
high biological activity, have optimal physical
properties (water intake and aggregation), and
become resistant to leaching. Plants growing
on such a soil are also balanced in mineral lev-
els and are considered to be nutritious to hu-
mans and animals alike. Base saturation per-
centages that Albrechtís research showed to be
optimal for the growth of most crops are:

Calcium 60ó70%

Magnesium 10ó20%

Potassium 2ó5%

Sodium 0.5ó3%

Other bases 5%

According to Albrecht, fertilizer and lime ap-
plications should be made at rates that will bring
soil mineral percentages into this ideal range.
This approach will shift the soil pH automati-
cally into a desirable range without creating
nutrient imbalances. The base saturation theory
also takes into account the effect one nutrient
may have on another and avoids undesirable
interactions. For example, phosphorus is known
to tie up zinc.

The Albrecht system of soil evaluation contrasts
with the approach used by many state labora-
tories, often called the ìsufficiency method.î
Sufficiency theory places little to no value on
nutrient ratios, and lime recommendations are
typically based on pH measurements alone.
While in many circumstances base saturation
and sufficiency methods will produce identical

PAGE 13

soil recommendations and similar results, sig-

nificant differences can occur on a number of
soils. For example, suppose we tested a corn-
field and found a soil pH of 5.5 and base satu-
ration for magnesium at 20% and calcium at
40%. Base saturation theory would call for lim-
ing with a high-calcium lime to raise the per-
cent base saturation of calcium; the pH would
rise accordingly. Sufficiency theory would not
specify high-calcium lime and the grower might
choose instead a high-magnesium dolomite lime
that would raise the pH but worsen the balance
of nutrients in the soil. Another way to look at
these two theories is that the base saturation
theory does not concern itself with pH to any
great extent, but rather with the proportional
amounts of bases. The pH will be correct when
the levels of bases are correct.

Albrechtís ideas have found their way onto
large numbers of American farms and into the
programs of several agricultural consulting com-
panies. Neal Kinsey, a soil fertility consultant
in Charleston, Missouri, is a major proponent
of the Albrecht approach. Kinsey was a stu-
dent under Albrecht and is one of the leading
authorities on the base-saturation method. He
teaches a short course on the Albrecht system
and provides a soil analysis service (21). His
book, Hands On Agronomy, is widely recognized
as a highly practical guide to the Albrecht sys-
tem. ATTRA can provide more information on
Albrecht Fertility Management Systems.

Several firmsómany providing backup fertilizer
and amendment productsóoffer a biological-
farming program based on the Albrecht theory.
Typically these firms offer broad-based soil
analysis and recommend balanced fertilizer
materials considered friendly to soil organisms.
They avoid the use of some common fertilizers
and amendments such as dolomite lime, potas-
sium chloride, anhydrous ammonia, and oxide
forms of trace elements because they are con-
sidered harmful to soil life. The publication How
to Get Started in Biological Farming presents such
a program. See the Additional Resources sec-
tion for ordering information. For names of com-
panies offering consulting and products, order
the ATTRA publications Alternative Soil Testing

PAGE 14

Laboratories and Sources of Organic Fertilizers and

Amendments. Both of these are also available on the ATTRA Web site located at <http:// www.attra.ncat.org>.

Conventional Fertilizers

Commercial fertilizer can be a valuable resource to farmers in transition to a more sustainable system and can help meet nutrient needs dur-
ing times of high crop nutrient demand or when weather conditions result in slow nutrient re-
lease from organic resources. Commercial fer-
tilizers have the advantage of supplying plants with immediately available forms of nutrients. They are often less expensive and less bulky to apply than many natural fertilizers.

Not all conventional fertilizers are alike. Many
appear harmless to soil livestock, but some are
not. Anhydrous ammonia contains approxi-
mately 82% nitrogen and is applied subsurface
as a gas. Anhydrous speeds the decomposition
of organic matter in the soil, leaving the soil
more compact as a result. The addition of an-
hydrous causes increased acidity in the soil, re-
quiring 148 pounds of lime to neutralize 100
pounds of anhydrous ammonia, or 1.8 pounds
of lime for every pound of nitrogen contained
in the anhydrous (22). Anhydrous ammonia
initially kills many soil microorganisms in the
application zone. Bacteria and actinomycetes
recover within one to two weeks to levels higher
than those prior to treatment (23). Soil fungi,
however, may take seven weeks to recover.
During the recovery time, bacteria are stimu-
lated to grow more, and decompose more or-
ganic matter, by the high soil nitrogen content.
As a result, their numbers increase after anhy-
drous applications, then decline as available soil
organic matter is depleted. Farmers commonly
report that the long-term use of synthetic fertil-
izers, especially anhydrous ammonia, leads to
soil compaction and poor tilth (23). When bac-
terial populations and soil organic matter de-
crease, aggregation declines, because existing
glues that stick soil particles together are de-
graded, and no other glues are being produced.

Potassium chloride (KCl) (0-0-60 and 0-0-50),

also known as muriate of potash, contains ap-
proximately 50 to 60% potassium and 47.5% chloride (24). Muriate of potash is made by re-
fining potassium chloride ore, which is a mix-
ture of potassium and sodium salts and clay from the brines of dying lakes and seas. The potential harmful effects from KCl can be sur-
mised from the salt concentration of the mate-
rial. Table 7 shows that, pound for pound, KCl is surpassed only by table salt on

Sodium nitrate, also known as Chilean nitrate

or nitrate of soda, is another high-salt fertilizer.
Because of the relatively low nitrogen content
of sodium nitrate, a high amount of sodium is
added to the soil when normal applications of
nitrogen are made with this material. The con-
cern is that excessive sodium acts as a dispers-
ant of soil particles, degrading aggregation. The
salt index for KCl and sodium nitrate can be
seen in Table 7.

the salt index. Additionally, some

plants such as tobacco, potatoes,
peaches, and some legumes are
especially sensitive to chloride.
High rates of KCl must be avoided

Protecting soil from erosion is

the first step toward a sustain-
able agriculture.

Top$oil – Your
Farm’$ Capital

on such crops. Potassium sulfate, potassium ni- Topsoil is the capital reserve of every farm. Ever

trate, sul-po-mag, or organic sources of potas- since mankind started agriculture, erosion of

sium may be considered as alternatives to KCl topsoil has been the single largest threat to a

for fertilization.

Table 7. Salt index for various fertilizers.

Material Salt Index Salt index per unit

of plant food

Sodium chloride 153 2.9

Potassium chloride 116 1.9

Ammonium nitrate 105 3.0

Sodium nitrate 100 6.1

Urea 75 1.6

Potassium nitrate 74 1.6

Ammonium sulfate 69 3.3

Calcium nitrate 53 4.4

Anhydrous ammonia 47 .06

Sulfate-potash-magnesia 43 2.0

Di-ammonium phosphate 34 1.6

Monammonium phosphate 30 2.5

Gypsum 8 .03

Calcium carbonate 5 .01

soilís productivityóand, consequently, to farm

profitability. This is still true today. In the U.S., the average acre of cropland is eroding at a rate of 7 tons per year (2). To sustain agriculture means to sustain soil resources, because thatís the source of a farmerís livelihood.

The major productivity costs to the farm associ-
ated with soil erosion come from the replace-
ment of lost nutrients and reduced water hold-
ing ability, accounting for 50 to 75% of produc-
tivity loss (2). Soil that is removed by erosion
typically contains about three times more nu-
trients than the soil left behind and is 1.5 to 5
times richer in organic matter (2). This organic
matter loss not only results in reduced water
holding capacity and degraded soil aggregation,
but also loss of plant nutrients, which must then
be replaced with nutrient amendments.

Five tons of topsoil (the so-called tolerance level)
can easily contain 100 pounds of nitrogen, 60
pounds of phosphate, 45 pounds of potash, 2
pounds of calcium, 10 pounds of magnesium,
and 8 pounds of sulfur. Table 8 shows the ef-
fect of slight, moderate, and severe erosion on
organic matter, soil phosphorus level, and plant-
available water on a silt loam soil in Indiana
(25).

Water erosion gets started when falling rainwa-

ter collides with bare ground and detaches soil
particles from the parent soil body. After
enough water builds up on the soil surface, fol-
lowing detachment, overland water flow trans-
ports suspended soil down-slope (Figure 5).
Suspended soil in the runoff water abrades and
detaches additional soil particles as the water
travels overland. Preventing detachment is the
most effective point of erosion control because
it keeps the soil in place. Other erosion control
practices seek to slow soil particle transport and
cause soil to be deposited before it reaches
streams. These methods are less effective at pro-
tecting the quality of soil within the field.

Commonly implemented practices to slow soil
transport include terraces and diversions. Ter-
races, diversions, and many other erosion ìcon-
trolî practices are largely unnecessary if the
ground stays covered year-round. For erosion
prevention, a high percentage of ground cover
is a good indicator of success, while bare ground
is an ìearly warningî indicator for a high risk
of erosion (27). Muddy runoff water and gul-
lies are ìtoo-lateî indicators. The soil has al-
ready eroded by the time it shows up as muddy
water, and itís too late to save soil already sus-
pended in the water.

Table 8. Effect of erosion on organic matter phosphorus and plant-available water.

Erosion level Organic matter Phosphorus Plant-available water

% Lbs./ac %

Slight 3.0 62 7.4

Moderate 2.5 61 6.2

Severe 1.9 40 3.6

From Schertz et al., 1984. (24)

When erosion by water and wind occurs at a

rate of 7.6 tons/acre/year it costs $40 per acre
each year to replace the lost nutrients as fertil-
izer and around $17/acre/year to pump well
irrigation water to replace the soil water hold-
ing capacity of that lost soil (26). The total cost
of soil and water lost annually from U.S. crop-
land amounts to an on-site productivity loss of
approximately $27 billion each year (2).

PAGE 16

Protecting the soil from erosion is the first step

toward a sustainable agriculture. Since water
erosion is initiated by raindrop impact on bare
soil, any management practice that protects the
soil from raindrop impact will decrease erosion
and increase water entry into the soil. Mulches,
cover crops, and crop residues serve this pur-
pose well.

Figure 5. Raindrops falling on bare ground initiate erosion.
Drawing from cropland monitoring guide (27).

Additionally, well-aggregated soils resist crust-

ing because water-stable aggregates are less
likely to break apart when the raindrop hits
them. Adequate organic matter with high soil
biological activity leads to high soil aggregation.

Many studies have shown that cropping sys-
tems that maintain a soil-protecting plant
canopy or residue cover have the least soil ero-
sion. This is universally true. Long-term crop-
ping studies begun in 1888 at the University of
Missouri provide dramatic evidence of this.
Gantzer and colleagues (28) examined the ef-
fects of a century of cropping on soil erosion.
They compared depth of topsoil remaining af-
ter 100 years of cropping (Table 9). As the table
shows, the cropping system that maintained the
highest amount of permanent ground cover
(timothy grass) had the greatest amount of top-
soil left.

Table 9. Topsoil depth remaining after 100 years of different cropping practices.

Crop Sequence Inches of topsoil

remaining

Continuous Corn 7.7

6-year rotation* 12.2

Continuous timothy grass 17.4

*Corn, oats, wheat, clover, timothy

From: Gantzer et al. (28).

The researchers commented that subsoil had

been mixed with topsoil in the continuous corn
plots from plowing, making the real topsoil
depth less than was apparent. In reality, all the
topsoil was lost from the continuous corn plots
in only 100 years. The rotation lost about half
the topsoil over 100 years. How can we feed
future generations with this type of farming
practice?

In a study of many different soil types in each
of the major climatic zones of the U.S., research-
ers showed dramatic differences in soil erosion
when comparing row crops to perennial sods.
Row crops consisted of cotton or corn, and sod
crops were bluegrass or bermuda grass. On
average, the row crops eroded more than 50
times more soil than did the perennial sod crops.
The two primary influencing factors are ground
cover and tillage. The results are shown in Table
10.

So, how long do fields have before the topsoil is
gone? This depends on where in the country
the field is located. Some soils naturally have
very thick topsoil, while other soils have thin
topsoil over rock or gravel. Roughly 8 tons/
acre/year of soil-erosion loss amounts to the
thickness of a dime spread over an acre. Twenty
dimes stack up to 1-inch high. So a landscape
with an 8-ton erosion rate would lose an inch
of topsoil about every 20 years. On a soil with a
thick topsoil, this amount is barely detectable
within a personís lifetime and may not be no-

PAGE 17

Table 10. Effect of cropping on soil erosion rates

Soil type Location Slope Row crop soil loss Sod soil loss

State % Tons/ac Tons/ac

Silt loam Iowa 9 38 .02

Loam Missouri 8 51 .16

Silt loam Ohio 12 99 .02

Fine sandy Oklahoma 7.7 19 .02

loam

Clay loam N. Carolina 10 31 .31

Fine sandy Texas 8.7 24 .08

loam

Clay Texas 4 21 .02

Silt loam Wisconsin 16 111 .10

Average Average 9.4 49 .09

Adapted from Shiflet and Darby, 1985 (29).

ticed. Soils with naturally thin topsoils or top-

soils that have been previously eroded can be transformed from productive to degraded land within a generation.

Forward-thinking researcher Wes Jackson, of
the Land Institute, waxes eloquent about how
tillage has become engrained in human culture
since we first began farming. Beating our
swords into plowshares surely embodies the tri-
umph of good over evil. Someone who creates
something new is said to have ìplowed new
ground.î ìYet the plowshare may well have
destroyed more options for future generations
than the swordî (30).

Tillage for the production of annual crops is the
major problem in agriculture, causing soil ero-
sion and the loss of soil quality. Any agricul-
tural practice that creates and maintains bare
ground is inherently less sustainable than prac-
tices that keep the ground covered throughout
the year. Wes Jackson has spent much of his
career developing perennial grain crops and
cropping systems that mimic the natural prai-
rie. Perennial grain crops do not require tillage
to establish year after year, and the ground is
left covered. Ultimately, this is the future of grain
production and truly represents a new vision
for how we produce food. The greatest research
need in agriculture today is breeding work to
develop perennial crops that will replace annual
crops requiring tillage. Farming practices us-
ing annual crops in ways that mimic perennial

PAGE 18

systems, such as no-till and cover crops, are our

best alternative until perennial systems are de-
veloped.

Summary of Part I

Soil management involves stewardship of the
soil livestock herd. The primary factors affect-
ing organic matter content, build-up, and de-
composition rate in soils are oxygen content, ni-
trogen content, moisture content, temperature,
and the addition and removal of organic mate-
rials. All these factors work together all the time.
Any one can limit the others. These are the fac-
tors that affect the health and reproductive rate
of organic matter decomposer organisms. Man-
agers need to be aware of these factors when
making decisions about their soils. Letís take
them one at a time.

Increasing oxygen speeds decomposition of or-
ganic matter. Tillage is the primary way extra
oxygen enters the soil. Texture also plays a role,
with sandy soils having more aeration than
heavy clay soils. Nitrogen content is influenced
by fertilizer additions. Excess nitrogen, with-
out the addition of carbon, speeds the decom-
position of organic matter. Moisture content af-
fects decomposition rates. Soil microbial popu-
lations are most active over cycles of wetting
and drying. Their populations increase follow-
ing wetting, as the soil dries out. After the soil
becomes dry, their activity diminishes. Just like

humans, soil organisms are profoundly affected

by temperature. Their activity is highest within a band of optimum temperature, above and below which their activity is diminished.

Adding organic matter provides more food for
microbes. To achieve an increase of soil organic
matter, additions must be higher than remov-
als. Over a given year, under average condi-
tions, 60 to 70 percent of the carbon contained
in organic residues added to soil is lost as car-
bon dioxide (20). Five to ten percent is assimi-
lated into the organisms that decomposed the
organic residues, and the rest becomes ënewí
humus. It takes decades for new humus to de-
velop into stable humus, which imparts the
nutrient-holding characteristics humus is
known for (20). The end result of adding a ton
of residue would be 400 to 700 pounds of new
humus. One percent organic matter weighs
20,000 pounds per acre. A 7-inch depth of top-
soil over an acre weighs 2 million pounds.
Building organic matter is a slow process.

It is more feasible to stabilize and maintain the
humus present, before it is lost, than to try to
rebuild it. The value of humus is not fully real-
ized until it is severely depleted (20). If your
soils are high in humus now, work hard to pre-
serve what you have. The formation of new
humus is essential to maintaining old humus,
and the decomposition of raw organic matter
has many benefits of its own. Increased aera-
tion caused by tillage coupled with the absence
of organic carbon in fertilizer materials has
caused more than a 50% decline in native hu-
mus levels on many U.S. farms (20).

Appropriate mineral nutrition needs to be present for soil organisms and plants to pros-
per. Adequate levels of calcium, magnesium, potassium, phosphorus, sodium, and the trace elements should be present, but not in excess. The base saturation theory of soil management helps guide decision-making toward achieving optimum levels of these nutrients in the soil. Several books have been written on balancing soil mineral levels, and several consulting firms provide soil analysis and fertility recommenda-
tion services based on this theory.

Commercial fertilizers have their place in sus-

tainable agriculture. Some appear harmless to
soil livestock and provide nutrients at times of
high nutrient demand from crops. Anhydrous
ammonia and potassium chloride cause prob-
lems, however. As noted above, anhydrous kills
soil organisms in the injection zone. Bacteria
and actinomycetes recover within a few weeks,
but fungi take longer. The increase in bacteria,
fed by highly available nitrogen from the anhy-
drous, speeds the decomposition of organic
matter. Potassium chloride has a high salt in-
dex, and some plants and soil organisms are
sensitive to chloride.

Topsoil is the farmerís capital. Sustaining agri-
culture means sustaining the soil. Maintaining
ground cover in the form of cover crops, mulch,
or crop residue for as much of the annual sea-
son as possible achieves the goal of sustaining
the soil resource. Any time the soil is tilled and
left bare it is susceptible to erosion. Even small
amounts of soil erosion are harmful over time.
It is not easy to see the effects of erosion over a
human lifetime; therefore, erosion may go un-
noticed. Tillage for production of annual crops
has created most of the erosion associated with
agriculture. Perennial grain crops not requir-
ing tillage provide a promising alternative for
drastically improving the sustainability of future
grain production.

Summary of Sustainable Soil
Management Principles

ï Soil livestock cycle nutrients and
provide many other benefits.

ï Organic matter is the food for the soil live-
stock herd.

ï The soil should be covered to protect it from
erosion and temperature extremes.

ï Tillage speeds the decomposition of organic
matter.

ï Excess nitrogen speeds the decomposition of
organic matter; insufficient nitrogen slows
down organic matter decomposition and
starves plants.

PAGE 19

ï Moldboard plowing speeds the decomposi-
tion of organic matter, destroys earthworm
habitat, and increases erosion.

ï To build soil organic matter, the produc-

tion or addition of organic matter must ex-
ceed the decomposition of organic matter.

ï Soil fertility levels need to be within accept-
able ranges before a soil-building program
is begun.

Photo by USDA NRCS

PART II. MANAGEMENT STEPS TO IMPROVE SOIL QUALITY

1. Assess Soil Health and Biological

Activity on Your Farm

A basic soil audit is the first and sometimes the
only monitoring tool used to assess changes in
the soil. Unfortunately, the standard soil test
done to determine nutrient levels (P, K, Ca, Mg,
etc.) provides no information on soil biology and
physical properties. Yet most of the farmer-rec-
ognized criteria for healthy soils (see p. 2) in-
clude, or are created by, soil organisms and soil
physical properties. A better appreciation of
these biological and physical soil properties, and
how they affect soil management and produc-
tivity, has resulted in the adoption of several
new soil health assessment techniques, which
are discussed below.

The USDA Soil Quality Test Kit

The USDA Soil Quality Institute provides a Soil
Quality Test Kit Guide developed by Dr. John
Doran and associates at the Agricultural Re-
search Serviceís office in Lincoln, Nebraska.
Designed for field use, the kit allows the mea-
surement of water infiltration, water holding
capacity, bulk density, pH, soil nitrate, salt con-
centration, aggregate stability, earthworm num-
bers, and soil respiration. Components neces-
sary to build a kit include many items commonly
availableósuch as pop bottles, flat-bladed
knives, a garden trowel, and plastic wrap. Also
necessary to do the tests is some equipment that

PAGE 20

is not as readily available, such as hypodermic

needles, latex tubing, a soil thermometer, an
electrical conductivity meter, filter paper, and
an EC calibration standard. The Soil Quality
Test Kit Guide can be ordered from the USDA
through the Soil Quality Instituteís Web page,
<http://soils.usda.gov/sqi/files/
KitGuideComplete.pdf>. The 88-page on-line
version of the guide is available in Adobe Acro-
bat Reader format through the above Web page
and may be printed out. A summary of the tests
is also available from the Web page. To order a
print version, see the Soil Quality Institute ref-
erence under Additional Resources.

A greatly simplified and quick soil quality as-
sessment is available at the Soil Quality Instituteís
Web page as well, by clicking on ìGetting to
Know your Soil,î near the bottom of the
homepage. This simplified method involves dig-
ging a hole and making some observations.
Here are a few of the procedures shown at this
Web site: Dig a hole 4 to 6 inches below the last
tillage depth and observe how hard the digging
is. Inspect plant roots to see whether there is a
lot of branching and fine root hairs or whether
the roots are balled-up. A lack of fine root hairs
indicates oxygen deprivation, while sideways
growth indicates a hardpan. The process goes
on to assess earthworms, soil smell, and aggre-
gation. Another useful, hands-on procedure for
assessing pasture soils is discussed in the ATTRA
publication Assessing the Pasture Soil Resource.

Early Warning Monitoring for Croplands

A cropland monitoring guide has been pub-
lished by the Center for Holistic Management
(27). The guide contains a set of soil health in-
dicators that are measurable in the field. No
fancy equipment is needed to make the assess-
ments described in this monitoring guide. In
fact, all the equipment is cheap and locally avail-
able for almost any farm. Simple measurements
can help determine the health of croplands in
terms of the effectiveness of the nutrient cycle
and water cycle, and the diversity of some soil
organisms. Assessments of living organisms,
aggregation, water infiltration, ground cover,
and earthworms can be made using this guide.
The monitoring guide is easy to read and un-
derstand and comes with a field sheet to record
observations. It is available for $12 from the
Savory Center for Holistic Management (see
Additional Resources).

Direct Assessment of Soil Health

Some quick ways to identify a healthy soil in-
clude feeling it and smelling it. Grab a handful
and take a whiff. Does it have an earthy smell?
Is it a loose, crumbly soil with some earthworms
present? Dr. Ray Weil, soil scientist at the Uni-
versity of Maryland, describes how he would
make a quick evaluation of a soilís health in just
five minutes (31).

Look at the surface and see if it is crusted, which
tells something about tillage practices used, or-
ganic matter, and structure. Push a soil probe-

down to 12 inches, lift out some soil and feel its
texture. If a plow pan were present it would have
been felt with the probe. Turn over a shovelful of

soil to look for earthworms and smell for actino-
mycetes, which are microorganisms that help com-
post and stabilize decaying organic matter. Their

activity leaves a fresh earthy smell in the soil.

Two other easy observations are to count the
number of soil organisms in a square foot of
surface crop residue and to pour a pint of wa-
ter on the soil and record the time it takes to
sink in. Comparisons can be made using these
simple observations, along with Ray Weilís
evaluation above, to determine how farm prac-
tices affect soil quality. Some of the soil quality
assessment systems discussed above use these

and other observations and provide record keep-

ing sheets to record your observations.

A Simple Erosion Demonstration

This simple procedure demonstrates the value
of ground cover. Tape a white piece of paper
near the end of a three-foot-long stick. Hold
the stick in one hand so as to have the paper
end within one inch of a bare soil surface (see
Figure 6). Now pour a pint of water onto the
bare soil within two to three inches of the white
paper and observe the soil accumulation on the
white paper. Tape another piece of white pa-
per to the stick and repeat the operation, this
time over soil with 100% ground cover, and
observe the accumulation of soil on the paper.
Compare the two pieces of paper. This simple
test shows how effective ground cover can be
at preventing soil particles from detaching from
the soil surface.

Figure 6. Simple erosion test.

Drawing from Cropland monitoring guide (27).

2. Use Tools and Techniques to Build Soil

Can a cover crop be worked into your rotation?
How about a high-residue crop or perennial

PAGE 21

sod? Are there economical sources of organic

materials or manure in your area? Are there
ways to reduce tillage and nitrogen fertilizer?
Where feasible, bulky organic amendments may
be added to supply both organic matter and
plant nutrients. It is particularly useful to ac-
count for nutrients when organic fertilizers and
amendments are used. Start with a soil test and
a nutrient analysis of the material you are ap-
plying. Knowing the levels of nutrients needed
by the crop guides the amount of amendments
applied and can lead to significant reductions
in fertilizer cost. The nutrient composition of
organic materials can vary, which is all the more
reason to determine the amount you have with
appropriate testing. In addition to containing
the major plant nutrients, organic fertilizers can
supply many essential micronutrients. Proper
calibration of the spreading equipment is im-
portant to ensure accurate application rates.

Animal Manure

Manure is an excellent soil amendment, provid-
ing both organic matter and nutrients. The
amount of organic matter and nitrogen in ani-
mal manure depends on the feed the animals
consumed, type of bedding used (if any), and
whether the manure is applied as a solid or liq-
uid. Typical rates for dairy manure would be
10 to 30 tons per acre or 4,000 to 11,000 gallons
of liquid for corn. At these rates the crop would
get between 50 and 150 pounds of available ni-
trogen per acre. Additionally, lots of carbon
would be added to the soil, resulting in no loss
of soil organic matter. Residues from crops
grown with this manure application and left on
the soil would also contribute or-

ganic matter.

Since an established fescue pasture needs twice

as much nitrogen as it does phosphorus, a com-
mon fertilizer application would be about 50
pounds of nitrogen and 30 pounds of phospho-
rus per acre. If a ton of poultry litter were ap-
plied to supply the nitrogen needs of the fescue,
an over-application of phosphorus would result,
because the litter has about the same levels of
nitrogen and phosphorus. Several years of lit-
ter application to meet nitrogen needs can build
up soil phosphorus to excessive levels. One easy
answer to this dilemma is to adjust the manure
rate to meet the phosphorus needs of the crop
and to supply the additional nitrogen with fer-
tilizer or a legume cover crop. On some farms
this may mean that more manure is being pro-
duced than can be safely used on the farm. In
this case, farmers may need to find a way to
process and sell (or barter) this excess manure
to get it off the farm.

Compost

Composting farm manure and other organic
materials is an excellent way to stabilize their
nutrient content. Composted manure is also
easier to handle, less bulky, and better smelling
than raw manure. A significant portion of raw-
manure nutrients are in unstable, soluble forms.
Such unstable forms are more likely to run off if
surface-applied, or to leach if tilled into the soil.
Compost is not as good a source of readily avail-
able plant nutrients as raw manure. But com-
post releases its nutrients slowly, thereby mini-
mizing losses. Quality compost contains more
humus than its raw components because pri-
mary decomposition has occurred during the

composting process. How-

ever, it does not contribute as

However, a common problem

with using manure as a nutrient
source is that application rates are
usually based on the nitrogen
needs of the crop. Because some

A common problem with us-

ing manure as a nutrient
source is that application
rates are usually based on the
nitrogen needs of the crop.

much of the sticky gums and

waxes that aggregate soil par-
ticles together as does raw
manure, because these sub-
stances are also released dur-
ing the primary decomposi-

manures have about as much phosphorus as

they do nitrogen, this often leads to a buildup
of soil phosphorus. A classic example is chicken
litter applied to crops that require high nitro-
gen levels, such as pasture grasses and corn.
Broiler litter, for example, contains approxi-
mately 50 pounds of nitrogen and phosphorus
and about 40 pounds of potassium per ton.

PAGE 22

tion phase. Unlike manure, compost can be

used at almost any rate without burning plants.
In fact, some greenhouse potting mixes contain
20 to 30% compost. Compost (like manure)
should be analyzed by a laboratory to determine
the nutrient value of a particular batch and to
ensure that it is being used effectively to pro-
duce healthy crops and soil, and not excessively
so that it contributes to water pollution.

Composting also reduces the bulk of raw or-

ganic materialsóespecially manures, which of-
ten have a high moisture content. However, while less bulky and easier to handle, composts can be expensive to buy. On-farm composting cuts costs dramatically, compared with buying compost. For more comprehensive information on composting at the farm or the municipal level, see the ATTRA publication Farm-Scale Composting Resource List.

Cover Crops and Green Manures

Many types of plants can be grown as cover
crops. Some of the more common ones include
rye, buckwheat, hairy vetch, crimson clover,
subterranean clover, red clover, sweet clover,
cowpeas, millet, and forage sorghums. Each of
these plants has some advantages over the oth-
ers and differs in its area of adaptability. Cover
crops can maintain or increase soil organic mat-
ter if they are allowed to grow long enough to
produce high herbage. All too often, people get
in a hurry and take out a good cover crop just a
week or two before it has reached its full poten-
tial. Hairy vetch or crimson clover can yield up
to 2.5 tons per acre if allowed to go to 25% bloom
stage. A mixture of rye and hairy vetch can
produce even more.

In addition to organic matter benefits, legume
cover crops provide considerable nitrogen for
crops that follow them. Consequently, the ni-
trogen rate can be reduced following a produc-
tive legume cover crop taken out at the correct
time. For example, corn grown following two
tons of hairy vetch should produce high yields
of grain with only half of the normal nitrogen
application.

When small grains such as rye are used as cover
crops and allowed to reach the flowering stage,
additional nitrogen may be required to help off-
set the nitrogen tie-up caused by the high car-
bon addition of the rye residue. The same would
be true of any high-carbon amendment, such
as sawdust or wheat straw. Cover crops also
suppress weeds, help break pest cycles, and
through their pollen and nectar provide food
sources for beneficial insects and honeybees.
They can also cycle other soil nutrients, making
them available to subsequent crops as the green
manure decomposes. For more information on

cover crops, see ATTRAís Overview of Cover

Crops and Green Manures. This publication is
comprehensive and provides many references
to other available information on growing cover
crops.

Humates

Humates and humic acid derivatives are a di-
verse family of products, generally obtained
from various forms of oxidized coal. Coal-de-
rived humus is essentially the same as humus
extracts from soil, but there has been a reluc-
tance in some circles to accept it as a worth-
while soil additive. In part, this stems from a
belief that only humus derived from recently
decayed organic matter is beneficial. It is also
true that the production and recycling of organic
matter in the soil cannot be replaced by coal-
derived humus.

However, while sugars, gums, waxes and simi-
lar materials derived from fresh organic-matter
decay play a vital role in both soil microbiology
and structure, they are not humus. Only a small
portion of the organic matter added to the soil
will ever be converted to humus. Most will re-
turn to the atmosphere as carbon dioxide as it
decays.

Some studies have shown positive effects of
humates, while other studies have shown no
such effects. Generally, the consensus is that
they work well in soils with low organic mat-
ter. In small amounts they do not produce posi-
tive results on soils already high in organic mat-
ter; at high rates they may tie up soil nutrients.

There are many humate products on the mar-
ket. They are not all the same. Humate prod-
ucts should be evaluated in a small test plot for
cost effectiveness before using them on a large
scale. Salespeople sometimes make exaggerated
claims for their products. ATTRA can provide
more information on humates upon request.

Reduced Tillage

While tillage has become common to many pro-
duction systems, its effects on the soil can be
counter-productive. Tillage smoothes the soil
surface and destroys natural soil aggregations
and earthworm channels. Porosity and water

PAGE 23

infiltration decrease following most tillage op-

erations. Plow pans may develop in many situ-
ations, particularly if soils are plowed with heavy equipment or when the soil is wet. Tilled soils have much higher erosion rates than soils left covered with crop residue.

Because of all the problems associated with con-
ventional tillage operations, acreage under re-
duced tillage systems is increasing in America.
Any tillage system that leaves in excess of 30%
surface residue is considered a ìconservation
tillageî system by USDA (32). Conservation till-
age includes no-till, zero-till, ridge-till, zone-till,
and some variations of chisel plowing and
disking. These conservation till strategies and
techniques allow for establishing crops into the
previous cropís residues, which are purposely
left on the soil surface. The principal benefits of
conservation tillage are reduced soil erosion and
improved water retention in the soil, resulting
in more drought resistance. Additional benefits
that many conservation tillage systems provide
include reduced fuel consumption, flexibility in
planting and harvesting, reduced labor require-
ments, and improved soil tilth. Two of the most
common conservation tillage systems are ridge
tillage and no-till.

Ridge tillage is a form of conservation tillage that
uses specialized planters and cultivators to
maintain permanent ridges on which row crops
are grown. After harvest, crop residue is left
until planting time. To plant the next crop, the
planter places the seed in the top of the ridge
after pushing residue out of the way and slic-
ing off the surface of the ridge top. Ridges are
re-formed during the last cultivation of the crop.

Often, a band of herbicide is applied to the ridge
top during planting. With banded herbicide
applications, two cultivations are generally
used: one to loosen the soil and another to cre-
ate the ridge later in the season. No cultivation
may be necessary if the herbicide is applied by
broadcasting rather than banding. Because
ridge tillage relies on cultivation to control weeds
and reform ridges, this system allows farmers
to further reduce their dependence on herbi-
cides, compared with either conventional till or
strict no-till systems.

PAGE 24

Maintenance of the ridges is key to successful

ridge tillage systems. The equipment must ac-
curately reshape the ridge, clean away crop resi-
due, plant in the ridge center, and leave a vi-
able seedbed. Not only does the ridge-tillage
cultivator remove weeds, it also builds up the
ridge. Harvesting in ridged fields may require
tall, narrow dual wheels fitted to the combine.
This modification permits the combine to
straddle several rows, leaving the ridges undis-
turbed. Similarly, grain trucks and wagons can-
not be driven randomly through the field. Main-
tenance of the ridge becomes a consideration
for each process.

Conventional no-till methods have been criti-
cized for a heavy reliance on chemical herbi-
cides for weed control. Additionally, no-till
farming requires careful management and ex-
pensive machinery for some applications. In
many cases, the spring temperature of untilled
soil is lower than that of tilled soil. This lower
temperature can slow germination of early-
planted corn or delay planting dates. Also, in-
creased insect and rodent pest problems have
been reported. On the positive side, no-till meth-
ods offer excellent soil erosion prevention and
decreased trips across the field. On well-drained
soils that warm adequately in the spring, no-till
has provided the same or better yields than con-
ventional till.

A recent equipment introduction into the no-
till arena is the so-called ìno-till cultivator.î These cultivators permit cultivation in heavy residue and provide a non-chemical option to post-emergent herbicide applications. Farmers have the option to band herbicide in the row and use the no-till cultivator to clean the middles as a way to reduce herbicide use. ATTRA can provide a number of resource contacts on cul-
tural methods, equipment, and management for conservation-till cropping systems.

Minimize Synthetic Nitrogen Use

If at all possible, add carbon with nitrogen
sources. Animal manure is a good way to add
both carbon and nitrogen. Growing legumes
as a green manure or rotation crop is another
way. When using nitrogen fertilizer, try to do

it at a time when a heavy crop residue is going
onto the soil, too. For example, a rotation of
corn, beans, and wheat would do well with ni-
trogen added after the corn residue was rolled
down or lightly tilled in. Spring-planted soy-
beans would require no nitrogen. A small
amount of nitrogen could be applied in the fall
for the wheat. Following the wheat crop, a le-
gume winter-annual cover crop could be
planted. In the spring, when the cover crop is
taken out, nitrogen rates for the corn would be
reduced to account for the nitrogen in the le-
gume. Avoid continual hay crops accompanied
by high nitrogen fertilization. The continual
removal of hay accompanied by high nitrogen
speeds the decomposition of soil organic mat-
ter. Heavy fertilization of silage crops, where
all the crop residue is removed (especially when
accompanied by tillage), speeds soil decline and
organic matter depletion.

3. Continue to Monitor for Indicators of
Success or Failure

As you experiment with new practices and
amendments, continue to monitor the soil for
changes using some of the tools discussed above
in Assess Soil Health and Biological Activity.
Several of these monitoring guides have sheets
you can use in the field to record data and use
for future comparison after changes are made

to the farming practices. Review the principles

of sustainable soil management and find ways

to apply them in your operation. If the thought

of pulling everything together seems over-

whelming, start with only one or two new prac-

tices and build on them. Seek additional moti-

vation by reading the next section on people

who have successfully built their soils.

Photo by USDA NRCS

Photo by USDA NRCS

PART III. EXAMPLES OF SUCCESSFUL SOIL BUILDERS (FARMER PROFILES)

Steve Groff

Steve and his family produce vegetables, alfalfa,
and grain crops on 175 acres in Lancaster
County, Pennsylvania. When Steve took over
operation of the family farm 15 years ago, his
number one concern was eliminating soil ero-
sion. Consequently, he began using cover crops
extensively in his fields. In order to transform
his green cover crop into no-till mulch, Steve

uses a 10-foot Buffalo rolling stalk chopper.

Under the hitch-mounted frame, the stalk chop-
per has two sets of rollers running in tandem.
These rollers can be adjusted for light or aggres-
sive action and set for continuous coverage.
Steve says the machine can be run up to eight
miles an hour and does a good job of killing the
cover crop and pushing it right down on the
soil. It can also be used to flatten down other

PAGE 25

crop residues after harvest. Steve improved his

chopper by adding independent linkages and
springs to each roller. This modification makes
each unit more flexible and allows continuous
use over uneven terrain. Other farmers report
similar results using a disk harrow with the
gangs set to run straight or at a slight angle.
Following his cover crop chopping, Steve trans-
plants vegetable seedlings into the killed mulch;
sweet corn and snap beans are direct-seeded.
Since conversion to a cover crop mulch system,
his soils are protected from erosion and have
become much mellower. For more information
on his system, order Steveís videos listed under
Additional Resources, or visit his Web page at
<http://www.cedarmeadowfarm.com/about.html>.
At Steveís Web site you can see photos of his
cover crop roller and no-till transplanter in ac-
tion, as well as test-plot results comparing flail
mowing, rolling, and herbicide killing of cover
crops.

Bob Willett

Bob started no-tilling 20 years ago on his corn
and soybean farm in Pride, Kentucky. He not
only reduced his machinery costs by switching
to no-till but also made gains in conserving top-
soil. His goal is to develop a healthy level of
humus in the top two inches, which keeps the
seed zone loose. He has stopped the sidewall
compaction in the seed slot that still plagues his
neighbors during wet springs. He attributes this
improvement to the increase in humus and or-
ganic matter. His soil surface layer is crumbly
and doesnít smear when the disk openers pass
through. Bob proclaims that earthworms take
the place of tillage by incorporating residue and
converting it to humus. Worms help aerate his
soil and improve internal drainage, which con-
tributes to good rooting for his crops (33).

David Iles

On the Ilesís North Carolina dairy farm the soil
has actually changed from red to a dark, almost
black color since conversion to no-till in 1970.
David first learned about no-till from his col-
lege professor at North Carolina State Univer-
sity in 1964. Before he switched to no-till,
Davidís corn silage yielded between 12 and 15
tons per acre in years with adequate rainfall and
4 to 5 tons in dry yearsóindicating that mois-

PAGE 26

ture was his major limiting factor (34). David

realized that his water runoff losses and soil
erosion were a direct result of tillage. Address-
ing the root cause of the problem, he switched
to no-till and began to spread manure on 1/3
of his land annually. Since these changes, soil
water is no longer limiting. With adequate rain-
fall he makes nearly 20 tons of silage now. David
says his land is vastly more productive, with
increased cation exchange capacity and in-
creased phosphorus levels due to the humus
present in his soil. Though his soil pH ranges in
the 5.6 to 5.8 level, he applies no lime. His fields
are more productive now than when he applied
lime in the ë70s and more productive than those
of his neighbors who currently use lime and fer-
tilizer.

David laments that this country has lost half of
its topsoil in less than 100 years (34). North
Carolina State agronomist Bobby Brock agrees
and says that for the first time in history we have
the opportunity to produce food and build soil
at the same time. David reasons that no-till is
the way to improve the soil structure, increase
tilth, and increase productivity while still prac-
ticing intensive agriculture. He realizes that
organic matter is the engine that drives his sys-
tem and provides food for earthworms and mi-
croorganisms. David built his soil by fallowing
out 20 to 25 acres of his 380-acre farm each year.
On these fallow acres he spreads manure and
then sows crops that are not harvested but
grown just for their organic matter. Even weeds
are not clipped but left for their organic matter.
David loves his earthworms and says they are
the best employees he has. ìThey work all the
time and eat dirt for a livingî (34).

His best field is one he cleared himself in the
ë70s. In spite of traditional native pHs in the
high 4s in his area, he did not lime this new
ground but instead just planted rye on it. He
had a fine rye crop that year, so he applied
manure liberally and planted rye a second time.
His second rye crop was excellent as well and
was followed by corn the third year. That field
yielded the most corn on the entire farm. This
field has been in continuous corn since 1981 and
has never been fertilized with conventional
products or tilled (34). This field has a pH of

6.1 at a 6-inch depth, an exchange capacity of

8, and an 80% base saturation. David believes this fieldís productivity is high because it has never been harmed by tillage.

References

1) Cramer, Craig. 1994. Test your soilsí

healthófirst in a series. The New Farm.

January. p. 17ñ21.

2) Pimentel, D., et al. 1995. Environmental

and economic costs of soil erosion and con-

servation benefits. Science. Vol. 267, No.

24. p. 1117ñ1122.

3) U.S. Department of Agriculture. 1998.

Soil Biodiversity. Soil Quality Information

Sheet, Soil Quality Resource Concerns.

January. 2 p.

4) Edwards, Clive A., and P.J. Bohlen. 1996.

Biology and Ecology of Earthworms.

Chapman and Hall, New York. 426 p.

5) Edwards, Clive A., and Ian Burrows.

1988. The potential of earthworm com-

posts as plant growth media. p. 211-219.

In: Earthworms in Waste and Environmen-

tal Management. C.A. Edwards and E.F.

Neuhauser (eds.). SPB Academic

Publishing, The Hague, The Netherlands.

6) Graff, O. 1971. Stikstoff, phosphor und-

kalium in der regenwormlosung auf der-

wiesenversuchsflche des sollingprojektes.

Annales de Zoologie: Ecologie Animale.

Special Publication 4. p. 503ñ512.

7) Anon. 1997. Product choices help add to

worm counts. Farm Industry News.

February. p. 64

Kladivko, Eileen J. No date. Earthworms

and crop management. Agronomy Guide,

AY-279. Purdue University Extension Ser-

vice, West Lafayette, IN. 5 p.

9) Soil Foodweb. 1228 NE 2^nd Street.

Corvallis, OR.

10) Bollen, Walter B. 1959. Microorganisms

and Soil Fertility. Oregon State College.

Oregon State Monographs, Studies in Bac-

teriology, No. 1. 22 p.

11) Jackson, William R. 1993. Organic Soil

Conditioning. Jackson Research Center,

Evergreen, CO. 957 p.

12) Comis, Don. 1997. Glomalinósoilís

superglue. Agricultural Research. USDAñ

ARS. October. p. 22.

13) Boyle, M., W.T. Frankenberger, Jr.,

and L.H. Stolzy. 1989. The influence of

organic matter on soil aggregation and

water infiltration. Journal of Production

Agriculture. Vol. 2. p. 209ñ299.

14) Pipel, N. 1971. Crumb formation. En-

deavor. Vol. 30. p. 77ñ81.

15) Land Stewardship Project. 1998. The

Monitoring Toolbox. White Bear Lake,

MN. Page number unknown.

16) Allison, F.E. 1968. Soil aggregationósome

facts and fallacies as seen by a microbiolo-

gist. Soil Science. Vol. 106, No. 2. p.

136ñ143.

17) Reicosky, D.C., and M.J. Lindstrom. 1995.

Impact of fall tillage on short-term carbon

dioxide flux. p. 177-187. In: R.Lal, J.

Kimble, E. Levine, and B.A. Stewards

(eds.). Soils and Global Change. Lewis

Publisher, Chelsea, MI.

18) Nation, Allan. 1999. Allanís Observa-

tions. Stockman Grass Farmer. January.

p. 12-14.

19) Sanderson, M.A., et al. 1999. Switchgrass

cultivars and germplasm for biomass feed-

stock production in Texas. Bioresource

Technology. Vol. 67, No 3. p. 209ñ219.

20) Sachs, Paul D. 1999. Edaphos: Dynam-

ics of a Natural Soil System, 2^nd edition.

The Edaphic Press. Newbury, VT. 197 p.

PAGE 27

21) Kinseyís Agricultural Services, 297 County

Highway 357, Charleston, MO 63834

573-683-3880

22) Tisdale, S.L., W.L. Nelson, and J.D. Beaton.

1985. Soil Fertility and Fertilizers, 4th

Edition. Macmillian Publishing Company,

New York. 754 p.

23) Francis, Charles A., Cornelia B. Flora, and

Larry D. King. 1990. Sustainable Agri-

culture in Temperate Zones. John Wiley

and Sons, Inc., New York. 487 p.

24) Parker, M.B., G.J. Gasho, and T.P. Gaines.

1983. Chloride toxicity of soybeans grown

on Atlantic coast flatwoods soils.

Agronomy Journal. Vol. 75. p. 439ñ443.

25) Schertz. 1985. Field evaluation of the ef-

fect of soil erosion on crop productivity.

p. 9ñ17. In: Erosion and Soil Productivity.

Proceedings of the National Symposium

on Erosion and Soil Productivity. Ameri-

can Society of Agricultural Engineers. De-

cember 10ñ11, 1984. New Orleans, LA.

ASAE Publication 8-85.

26) Troeh, F.R., J.A Hobbs, and R.L. Donahue.

1991. Soil and Water Conservation.

Prentice Hall, Englewood Cliffs, NJ.

27) Sullivan, Preston G. 1998. Early Warn-

ing Monitoring Guide for Croplands. Cen-

ter for Holistic Management, Albuquerque,

NM. 22 p.

28) Gantzer, C.J., S.H. Anderson, A.L. Thomp-

son, and J.R. Brown. 1991. Evaluation of

soil loss after 100 years of soil and crop

management. Agronomy Journal. Vol.

83. p. 74ñ77.

29) Shiflet, T.N., and G.M. Darby. 1985. Table

3.4: Effect of row and sod crops on runoff

and erosion [from G.M. Browning, 1973].

p. 26. In: M.E. Heath, R.F. Barnes, and

D.S. Metcalfe (eds.). Forages: The Science

of Grassland Agriculture, 4^th ed. Iowa

State University Press, Ames, IA.

PAGE 28

30) Jackson, Wes. 1980. New Roots for Agri-

culture, 1st edition. Friends of the Earth,

San Francisco, CA. 150 p.

31) Bowman, Greg. 1994. Why soil health

matters. The New Farm. January. p. 10ñ

16.

32) Magdoff, Fred. 1992. Building Soils for

Better Crops, 1st ed. University of Ne-

braska Press, Lincoln, NE. 176 p.

33) Sickman, Tim. 1998. Building soil with

residue farming. Tennessee Farmer.

August. p. 32, 34.

34) Dirnburger, J.M., and John M. Larose.

1997. No-till saves dairy farm by healing

the harm that tillage has done. National

Conservation Tillage Digest. Summer.

p. 5ñ8.

Additional Resources

Videos

No-till Vegetables. By Steve Groff. 1997.

This video leads you from selection of the

proper cover crop mix to plant into, through

how to control cover crops with little or no

herbicide,as shown on Steve Groffís Pennsyl-

vania farm. You will see mechanical cover-

crop-kill and vegetables being planted right

into this mulch using a no-till transplanter.

Youíll also hear comments from leading re-

searchers in the no-till vegetable area. Order

this video for $21.95 + $3.00 shipping from:

Cedar Meadow Farm

679 Hilldale Road

Holtwood, PA 17532

717-284-5152

Books and Periodicals

The Farmerís Earthworm Handbook: Manag-
ing Your Underground Money Makers. 1995.

By David T. Ernst. Lessiter Publications,
Brookfield, WI. 112 p.

To order, send $15.95 + $4.00 shipping and

handling to:

Lessiter Publications

245 Regency Court

Brookfield, WI 53045

262-782-4480

800-645-8455

The Soul of Soil: A Guide to Ecological Soil Management, 4th edition. 1995. By Grace

Gershuny and Joe Smillie. AgAccess, Davis, CA. 158 p.

To order, send $8.50 + $4.00 shipping and

handling to:

Fertile Ground Books

3912 Vale Ave. Oakland, CA 94619

530-297-7879

books@agribooks.com

http://www.agribooks.com/

Neal Kinseyís Hands-On Agronomy. 1993.

By Neil Kinsey. Acres, USA. Metairie, LA. 340 p.

To order, send $24.00 + $3.00 shipping and

handling to:

ACRES USA

P.O. Box 91299

Austin, TX 78709-1299

800-355-5313 (toll-free)

512-892-4400

Building Soils for Better Crops, 2nd edition. 2000. By Fred Magdoff and Harold van Es. University of Nebraska Press, Lincoln, NE.

240 p.

To order, send $19.95 + $3.95 shipping to:

Sustainable Agriculture Publications

Hills Building, Room 10,

University of Vermont

Burlington, VT 05405-0082

802-656-0484;

sanpubs@uvm.edu.

Edaphos: Dynamics of a Natural Soil System, 2nd edition. 1999. By Paul D Sachs. The

Edaphic Press, Newbury, VT. 197 p.

To order, send $14.95 + $1.50 shipping and

handling to:

North Country Organics

P.O. Box 372

Bradford, VT 05033

802-222-4277

Soil Quality Test Kit Guide. 1998. USDA. Soil
Quality Institute. 82 p.

This publication has detailed, step-by-step

instructions with color photographs on how

to assess soil quality, soil respiration, soil

water infiltration, bulk density, electrical

conductivity, soil pH, soil nitrate, soil ag-

gregate stability, slaking, and earthworms.

It also covers soil physical observations and

estimations and water quality tests, and

includes background information on the tests

and appendices. To order this free test kit

publication, paid for by your federal tax dol-

lars, contact:

Dr. Charles Kome, Soil Scientist

Soil Quality National Technology

Development Team

USDA-NRCS ENTSC

200 E. Northwood St., Ste. 410

Greensboro, NC 27401

phone: (336) 370-3363

charles.kome@gnb.usda.gov

Early Warning Monitoring for Croplands.
1998. By Preston G. Sullivan. Center for Holis-
tic Management, Albuquerque, NM. 22 p.

To order this guide, send $13.00 ppd. to:

Savory Center for Holistic Management

1010 Tijeras, N.W.

Albuquerque, NM 87102

PAGE 29

505-842-5252

http://www.holisticmanagement.org/

LaMotte Soil Handbook. 1994. Lamotte Com-
pany. Chestertown, MD. 81 p.

Covers soil basics, nutrients, pH, acidity

and alkalinity, and principles of the LaMotte

soil testing system. Has relative nutrient

and pH requirements for common crops and

plants. To order this handbook ask for ref-

erence # 1504 and send $4.85 to:

LaMotte Company

P.O. Box 329

Chestertown, MD 21620

410-778-3100

800-344-3100 (toll-free)

410-778-6394 FAX

ese@lamotte.com

http://www.lamotte.com/

How to Get Started in Biological Farming. No
date. Gary F. Zimmer. 11 p.