[Homestead] The Overstory--Soil Erosion

Gene GeRue genegerue at ruralize.com
Tue Jul 12 10:24:52 EDT 2005


For you flatlanders, soil erosion is ho-hum. I prefer land that has the 
character of hills and hollers. Such landform is highly vulnerable to 
erosion, indeed, it was created by erosion. So any found dirt is to be 
protected.

When I bought my land there was erosion at the driveway area and the field 
behind the house. I have eliminated nearly all of it and caused ruts to 
fill simply by continually mowing across the slope for many years. Mown 
grass grows thicker than grass that nature nurtures alone. Know that when I 
say grass, I mean the multitude of small plants that nature provides. Any 
resemblance to suburban grass is an inscrutable anomaly.

I looked at that field some years ago and decided it would profit from 
terracing. Just gentle terraces, instructions to the water that it should 
stay close to where it fell. Being the lazy guy I am, I decided to let 
someone else do the terracing. I chose chickens. So, using steel T-posts 
and poultry mesh I built a long run from the Taj Mahen area out across the 
field to give the construction crew a defined workplace. They love it.

I laid it out using the walking land level design that Lee Frier gave us: 
two six-foot one-by-twos and a crosspiece, forming a tall A. If you are a 
hill person you should have one. To the bolt joining the top ends of the 
long sticks tie a strong cord that extends well below the cross piece. Tie 
a stone or other weight to the bottom end of the string. Place the frame on 
uneven ground and hold it so the string swings freely, just barely touching 
the crossbar. Mark the crosspiece where the string settles against it. 
Reverse the contact points of the long pieces' feet precisely and mark the 
new string point. Now make a strong mark or groove in the crosspiece 
exactly in the middle of the two trial marks. That is the level point. To 
use the land level, "walk" the frame across the ground, keeping the string 
to the level mark. Put something on the ground to mark each level foot spot.

Well, I did this to lay out two parallel fence lines about six feet apart 
out into the field. Reminded me of the chicken moat. Pounded in the 
T-posts, strung the wire, cut a doorway in the hen pen and the flock rushed 
out to gobble all the new bugs and greenery. And scratch. That's the main 
terracing work, scratching. Chicken people know that scratching is to 
chickens as swimming is to fish.

The first terrace is not yet finished, but when it is I will lay out 
another just below and continue until the field has been terraced. 
Shouldn't take more than a couple decades and it will be delovely. Most 
importantly, heavy rain will stay on the field instead of rushing down to 
the stream, carrying precious soil with it.

To: "Gene GeRue" <genegerue at ruralize.com> Subject: The Overstory #157--Soil 
Erosion and Water Infiltration
The Overstory #157 - Soil Erosion and Water Infiltration
By Rolf Derpsch
WASWC Vice President for South America

::::::::::::::

The Overstory Book, 2nd Edition, a formatted, indexed and illustrated
compilation of The Overstory ejournal editions 1 - 138 is in stock.
Your purchase helps support publication of The Overstory:
http://www.agroforestry.net/overstory/ovbook.html
ADDRESS CHANGES: Please send any changes in your e-mail address to
overstory at agroforestry.net

::::::::::::::
The Overstory #157 - Soil Erosion and Water Infiltration
By Rolf Derpsch
WASWC Vice President for South America

Contents:
: INTRODUCTION
: THE EROSION PROCESS
: REFERENCES
: ORIGINAL SOURCE
: ABOUT THE AUTHOR
: RELATED EDITIONS OF THE OVERSTORY
: PUBLISHER NOTES
: SUBSCRIPTIONS

::::::::

INTRODUCTION
Soil erosion is caused by rainwater that does not infiltrate into the
soil, but instead runs off the soil surface. It is essential that the
interconnected processes of soil erosion and water infiltration be well
understood by farmers, extension workers, and scientists.
The consequence of conventional cultivation methods can be the gradual
loss of soil and fertility until the land becomes unproductive. Erosion,
as well as intensive weathering under hot, humid conditions, has brought
about widespread, poor, badly eroded, and infertile soils throughout the
tropics and subtropics (Ochse, et al., 1961). The same process has also
taken place in temperate climates (e.g. the United States and Russia).
Eroded, unproductive and abandoned lands, as well as advanced signs of
desertification are a silent testimony to this phenomenon worldwide.
Besides making agricultural soil unproductive, erosion and runoff result
in the deposition of soil particles in unwanted areas (sedimentation of
roads, creeks, rivers, lakes, dams, etc.) with all its negative
consequences for traffic, electric power generation, sources of drinking
water, leisure areas, etc. Correcting these collateral effects costs
huge sums, usually from public sources. Efficient erosion control is
therefore very advantageous from the ecological and social perspectives,
besides being highly significant from an economic point of view. It
helps maintain the productive potential and fertility of soils for
future generations, and is an effective means to ensure continued
economic viability of farmland and therefore gainful employment in rural
areas.
Soil erosion by runoff water is often accepted as an unavoidable
consequence of agriculture on sloping land, but this is not necessarily
so. According to Lal (1982), erosion on cultivated land is a symptom of
land misuse for a particular environment. In other words, it is not
slope or rainfall intensity that are responsible for erosion and its
negative consequences, but rather farming methods--inappropriate farming
practices cause erosion. Through the utilization of site specific and
adapted farming systems and management practices, farmers can
effectively control erosion, reduce runoff, and increase water
infiltration on their land.
FIGURE 1: <http://www.swcc.cn/waswc/articles/f-1.jpg>
<http://www.swcc.cn/waswc/articles/f-1.1.jpg> The impact of raindrops on
a bare soil surface. Pictures showing raindrop impact on a bare soil
surface and information explaining the mechanisms of water infiltration
go back to the 1940s. When it rains, drops up to 6 mm (0.24 inch) in
diameter bombard the soil surface at impact velocities of up to 32 km/hr
(20 mph). The force throws soil particles and water in all directions up
to a distance of 1 m (3.3 feet). (Pictures made by USDA in the 1940s).

THE EROSION PROCESS
Despite scientific and empirical evidence explaining erosive processes,
many people still think that the soil has to be loosened by tillage to
increase water infiltration and reduce runoff.
Runoff and erosion start with the impact of raindrops on bare soil. Soil
splash seen on fence posts or walls next to bare soil is evidence of the
impact of large raindrops (Harrold, 1972). Meyer and Mannering (1967)
reported that raindrops annually deliver impact energy equivalent to 50
tons of TNT to a hectare (20 t/ac) of land. The impact of falling
raindrops breaks (disaggregates) the soil into very fine particles,
which clogs soil pores and creates a surface seal that impedes rapid
water infiltration (Figure 2). The use of tillage systems leaves the
soil bare allowing rain to pulverize it excessively, creating conditions
where it is carried away by heavy rains. Later, the surface sealing
dries, resulting in crusting that may hinder or impede the germination
and emergence of crop seeds.
FIGURE 2: <http://www.swcc.cn/waswc/articles/f-2.jpg>
FIGURE 3: <http://www.swcc.cn/waswc/articles/f-3.jpg>
FIGURE 4: <http://www.swcc.cn/waswc/articles/f-4.jpg>
Due to surface sealing, only a small portion of rainwater can infiltrate
the soil; most of it runs off over the soil surface and causes erosion
damage. Research conducted in Brazil (Roth, 1985) shows that the
percentage of soil covered with plant residues is the most important
factor that influences water infiltration into the soil. While virtually
all water from a simulated rainfall of 60 mm/hour infiltrated when the
soil was 100% covered with plant residues, 75% to 80% of rainwater left
the plots as runoff when the soil was bare (Figure 4). Researchers in
many parts of the world have obtained similar results.
When the soil is covered with living plants or plant residues, the plant
biomass absorbs the energy of falling raindrops. Rainwater flows gently
downward where it infiltrates into soil that is porous and undisturbed.
By protecting the soil surface from impact, soil cover impedes the
clogging of soil pores (Figures 2, 3, 4 and 5). Soils highly
susceptible to crusting do not have this problem once no-tillage and
permanent cover systems are used. Soil crusting only develops under bare
soil conditions.
It is therefore essential to maintain soil cover with plants or plant
residues year-round. Any attempt to control runoff and erosion by
tillage to maintain a loosened and uncovered soil surface or by burying
plant residues will eventually lead to failure. A no-tillage system with
a cover of crop residues or green manure cover crops is the most
efficient method for preventing and controlling erosion, and should be
the "best practice" technology promoted worldwide.
FIGURE 5: <http://www.swcc.cn/waswc/articles/f-5.jpg> Rainfall simulator
demonstration performed at the No-till on the Plains Winter Conference
in Salina, Kansas, in 2001. From left to right: (1) 100% soil cover,
little runoff and no sediments. (2) 30% soil cover, more runoff and some
sediments. (3) Bare soil, no cover, resulting in a huge amount of runoff
and the dark color of water shows also a lot of sediments. (4) Pasture
with 100% soil cover and undisturbed soil, even less runoff than (1).
Not tilling the soil, crop rotations combined with the use of cover
crops, and not burning plant residues ensure permanent, year-round soil
cover. Conservation agriculture, using these no-tillage methods, offers
the most effective strategy and affordable methods available today to
control soil erosion and, in this way, achieve sustainable agriculture.
The long-term gains from widespread conversion to no-tillage could be
greater than from any other innovation in developing countries (Warren,
1981).
While most of the numerous advantages of the no-tillage system come from
the permanent cover of the soil with plant residues, there are several
additional advantages from no-till. Tillage destroys the vertical pore
system created by roots, earthworms and other soil fauna, destroys soil
structure, accelerates organic matter mineralization (depletion) and
reduces aggregate stability. Fields under no-till systems for many years
are expected to further increase water infiltration as the vertical pore
system builds up and organic matter increases. In this way, no-till with
abundant soil cover allows for both the natural rebuilding of soil
structure and porosity, as well as protecting the soil from damaging
raindrop impact.
In addition to increasing water infiltration and controlling erosion,
soil cover has a major impact in reducing soil temperature, reducing
evaporation, increasing available water for plants, enhancing the life
and biological activity of the soil, contributing to the reduction of
soil compaction and soil crusting. These all have positive effects on
the chemical, physical and biological properties of the soil and leads
to higher productivity and long-term agricultural sustainability.

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REFERENCES
Derpsch, R., Roth, C.H., Sidiras, N. and Köpke, U. 1991. Controle da
erosão no Paraná, Brasil: Sistemas de cobertura do solo, plantio direto
e preparo conservacionista do solo. Sonderpublikation der GTZ, No. 245
Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH,
Eschborn, TZ-Verlagsgesellschaft mbH, Rossdorf, 272 pp.
Harrold, L.L. 1972. Soil erosion by water as affected by reduced tillage
systems. Proceedings No-tillage Systems Symp. Feb. 21-22, 1972, Ohio
State University, 21-29.
Lal, R. 1982. Management of clay soils for erosion control. Tropical
Agric., 59(2), 133-138.
Merrill, S.D., Krupinsky, J.M. and Tanaka, D.L. 2002. Soil coverage by
residue in diverse crop sequences under no-till. USDA-ARS. Poster
presented at the 2002 Annual Meeting of ASA-CSSA-SSSA, November 10-14,
Indianapolis, IN.
Meyer L.L. and Mannering, J.V. 1967. Tillage and land modification for
water erosion control. Amer. Soc. Agric. Eng. Tillage for Greater Crop
Production Conference. Proc. Dec. 11-12, 1967, 58-62.
Ochse, J.J., Soule Jr., M.J, Dijkman, M.J. and Wehlburg, N.C. 1961.
Tropical and Subtropical Agriculture, Vol. 1. The Macmillan Company, New
York, London, 760 pp.
Roth, C.H. 1985. Infiltrabilität von Latossolo-Roxo-Böden in Nordparaná,
Brasilien, in Feldversuchen zur Erosionskontrolle mit verschiedenen
Bodenbearbeitungs-systemen und Rotationen. Göttinger Bodenkundliche
Berichte, 83, 1-104.
Warren, C.F. 1981. Technology Transfer in No-tillage Crop Production in
Third World Agriculture. Proc. Symp. August 6-7, 1981, Monrovia,
Liberia. West African and International Weed Science Societies.
International Plant Protection Center, Oregon State University,
Corvallis, OR 97331 USA. IPCC Document 46-B-83. 25-31.

::::::::::::::
ORIGINAL SOURCE
This article was adapted with the gracious permission of the author
from:
Derpsch, R. nd. "Understanding the Process of Soil Erosion and Water
Infiltration." url:
<http://www.swcc.cn/waswc/articles/Rolf's%20article%202%20DS%20040614.htm>
The author thankfully acknowledges the revision, inputs and improvement
of the original manuscript by Matt Hagny, Board of Directors, No-till on
the Plains, Salina, Kansas, USA, as well as the revision by Melissa
McDonald, Asuncion, Paraguay.

::::::::::::::
ABOUT THE AUTHOR
Rolf Derpsch studied agronomy at the Universidad de Chile in Santiago
and the Instituto Superior de Agricultura Adolfo Matthei in Osorno,
Chile, and obtained a M.Sc. degree from the University of Reading, UK.
He worked for the German Agency for Technical Cooperation (GTZ) as Team
Leader for the Soil Conservation Project at the Research Institute of
Paraná, IAPAR, in Londrina, Brazil and Senior Advisor to the MAG - GTZ
Soil Conservation Project. Since September 2001 he has worked as a
freelance consultant in no-tillage and conservation tillage, development
and diffusion of sustainable agricultural production systems with
permanent soil cover, green manure cover crops and crop rotations, and
development of production systems for small farmers. He has worked in
Paraguay, Brazil, Argentina, Bolivia, Chile, Honduras, Colombia, Cuba,
Somalia and Germany. He was among the first to research no-tillage
technology in Brazil and Latin America beginning in 1971. Rolf can be
reached at Rolf Derpsch, No-tillage Consultant, CC 13223, Shopping del
Sol, Asunción, Paraguay; Tel/Fax: 00 595 ­ 21 - 609717; E-mail:
<rderpsch at quanta.com.py>; Web: <http://www.rolf-derpsch.com/>.

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WEB LINKS
The World Association of Soil and Water Conservation (WASWC) is an
international non-government organization of professionals and informed
laypersons dedicated to promoting the sustained use of the earth's soil
and water resources. There quarterly newsletter is now published in
English, Spanish, French, Chinese and Portuguese: <http://www.waswc.org>
and Photo Websites: <http://community.webshots.com/user/waswc> and
<http://community.webshots.com/user/waswc1>
The US Department of Agriculture's Natural Resources Conservation
Service provides helps people conserve, maintain, and improve natural
resources and the environment: <http://www.nrcs.usda.gov/>
The Soil and Water Conservation Society fosters the science and the art
of soil, water and related natural resource management to achieve
sustainability: <http://www.swcs.org/>
CONTOUR is a newsletter dedicated to the exchange of information on soil
and water conservation in South East Asia:
<http://www.asocon.org/main.htm>
International Soil Reference and Information Centre provides soils
information and promotes sustainable use of the land:
<http://lime.isric.nl/>
Cornell University Worldwide Portal to Information on Soil Health
has an excellent list of links:
<http://mulch.mannlib.cornell.edu/newslett.html>
Management of Organic Inputs in Soils of the Tropics (MOIST)
covers green manures and cover crop research and exchange. This
site also maintains the high quality Mulch-L discussion forum on
green manures/cover crops:
<http://ppathw3.cals.cornell.edu/mba_project/moist/home2.html>
Centro Internacional de Información Sobre Cultivos de Cobertura
(CIDICCO) has green manure/cover crop information for small
farmers: <http://www.cidicco.hn/>
UC SAREP Cover Crop Resource Page has data on thousands of
species used for organic matter production and erosion control:
<http://www.sarep.ucdavis.edu/ccrop/>

::::::::::::::
RELATED EDITIONS OF THE OVERSTORY
The Overstory #111 - Land Husbandry
The Overstory #104 - Soil and Water Conservation
The Overstory #103 - Land Management
The Overstory #96--Sheet Mulch
<http://www.agroforestry.net/overstory/overstory96.html>
The Overstory #81--Soil Foodweb
<http://www.agroforestry.net/overstory/overstory81.html>
The Overstory #80--Forests and Water
<http://www.agroforestry.net/overstory/overstory80.html>
The Overstory #73--Buffers
<http://www.agroforestry.net/overstory/overstory73.html>
The Overstory #70--Rhizosphere
<http://www.agroforestry.net/overstory/overstory70.html>
The Overstory #66--Carbon Sequestration: Storing Carbon in Soils and
Vegetation
<http://www.agroforestry.net/overstory/overstory66.html>
The Overstory #29--Tropical Green Manures/Cover Crops
<http://www.agroforestry.net/overstory/overstory29.html>
The Overstory #18--Designing Resource Systems
<http://www.agroforestry.net/overstory/overstory18.html>
The Overstory #17--Microcatchment
<http://www.agroforestry.net/overstory/overstory17.html>


::::::::::::::
PUBLISHER NOTES

The Overstory Book, 2nd Edition, a formatted, indexed and illustrated
compilation of The Overstory ejournal editions 1 - 138 is in stock.
Your purchase helps support publication of The Overstory:
http://www.agroforestry.net/overstory/ovbook.html
ADDRESS CHANGES: Please send any changes in your e-mail address to
overstory at agroforestry.net

::::::::::::::


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required, the services of a professional should be sought.

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