Overstory Online #4 Nitrogen Fixing Trees

Thu Jan 6 20:30:37 PST 2000

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The Overstory 
#4 

Nitrogen Fixing Trees--A Brief Introduction 

The Overstory # 4 

Authors:
Craig Elevitch and Kim Wilkinson

Contents:
* Nitrogen Fixing Trees -- A Brief Introduction
* Some useful books on nitrogen fixing trees
* Organization Highlight: FACT Net (Farm, Community, and Tree Network)
* Seed Source
* How to contact us

Nitrogen Fixing Trees -- A Brief Introduction
Nature has many ways of creating abundance under adverse conditions. Imagine
plants that accumulate their own fertilizer, grow extremely quickly, tolerate
harsh climatic conditions, and are prolific. Many nitrogen fixing plants fit
this description, and have numerous uses in gardening, farming and forestry.

Although many nitrogen fixing plants lend themselves to agroforestry, nitrogen
fixing trees (NFTs) have perhaps the most use in sustainable systems. The uses
for NFTs include windbreak, shade, fodder, organic matter production, mulch,
fuel, timber and food. Chances are that if you live in the tropics, there are
several NFTs already growing as pioneers in your area. 

Nature has devised a unique path of nutrient cycling used by these trees. Air
consists of approximately 80% nitrogen gas, which is normally unavailable to
plants. NFTs utilize this atmospheric nitrogen. Through an association with
Rhizobium, a bacteria which is hosted in the root system of NFTs, these plants
biologically accumulate nitrogen, pulling this essential nutrient out of the
air for their own use, and, if managed, making it available to other crops as
well. 

In addition to their ability to make use of atmospheric nitrogen, NFTs are
often also deep rooted, which allows them to seek out nutrients in deep soil
layers. This allows NFTs to fulfill many of their own needs in infertile,
harsh
conditions, and therefore have the ability to quickly "pioneer" bare or
degraded lands. Pioneer plants are nature's first endeavor to establish
vegetation wherever it is lacking. In addition, many NFT species can be pruned
back frequently, and the nutrient-rich leaves used as a high-fertility mulch,
or for animal fodder. In this way, NFTs support many other life forms on the
farm. 

The long list of useful characteristics of NFTs includes their ability to:
* establish readily
* grow rapidly
* tolerate poor soils
* tolerate drought
* thrive in full sun
* enhance overall fertility
* regrow easily from pruning

Selecting an NFT for a certain function can be tricky. As a start, a survey of
your area will be helpful in determining the habit and vigor of some NFTs. You
may notice some exemplary specimens which could be useful in a windbreak or
for
shade. Information may be available at the your local agricultural extension
service, or you may contact one of many international organizations that have
agroforestry programs (see FACT Net highlight below). 

If possible, use only NFTs which are already established in your area, or that
have a history of not becoming weeds. For example, if an Albizia species is
already naturalized on the site, it may be useful as a source of organic
matter, fodder, shade and even a light weight timber. 

There are also many NFTs which are not considered weedy and are extremely
useful. The common pigeon pea, a perennial edible "pea tree," has demonstrated
little potential for becoming a weed in Hawaii, and makes excellent fodder,
quick windbreak, green manure, as well as many other uses. 

For more detailed information on NFTs and how to design them in a farm system,
please see our article
"<http://www.agroforester.com/articles/NFTs.html>Nitrogen
Fixing Trees: Multipurpose Pioneers" at
<http://www.agroforester.com/articles/NFTs.html>

Some useful books on nitrogen fixing trees
FAO, 1984. Legume Inoculants and Their Use, FAO of the United Nations, Rome.
Excellent practical handbook for inoculation.

MacDicken, Kenneth G. 1994. Selection and Management of Nitrogen-Fixing Trees.
Winrock International Institute for Agricultural Development, Morrilton,
Arkansas, USA. Comprehensive treatment of NFTs and their uses.

National Academy of Sciences. 1979. Tropical Legumes: Resources for the
Future,
National Academy Press, Washington, D.C.. A very useful reference at a
reasonable cost. 

Nitrogen Fixing Tree Association. 1989-1994. NFT Highlights. Nitrogen Fixing
Tree Association, Morrilton, Arkansas, USA. Each highlight covers an NFT
species in detail. (Available from FACT Net, listed below.)

Organization Highlight: FACT Net (Farm, Community, and Tree Network)
For information on nitrogen fixing trees, you may wish to contact Farm,
Community and Tree Network (FACT Net, formerly the Nitrogen Fixing Tree
Association) which is an international organization dedicated to stimulate the
use of multipurpose trees. Among the many publications FACT Net offers at a
reasonable cost, you will find comprehensive fact sheets on many important
NFTs
as well as research reports, and agroforestry information. Address:
<http://www.winrock.org/forestry/factnet.htm>FACT Net, Winrock International,
Rt. 3, Box 376, Morrilton, Arkansas 72110, Internet:
<http://www.winrock.org/forestry/factnet.htm> Email:
<mailto:forestry at msmail.winrock.org>forestry at msmail.winrock.org.

Seed Source
AgroForester Tropical Seeds can fill your requirements for a wide range of
high
quality nitrogen fixing tree seed, as well as pure rhizobia inoculants. For
further information contact us at
"<http://www.agroforester.com/agfor/agroforester.html>AgroForester" (contact
information below), or link to
<http://www.agroforester.com/agfor/agroforester.html>

The Overstory is brought to you by the people at
<http://www.agroforester.com>agrof<http://www.agroforester.com>o<http://www
.agroforester.com>rester.com <http://www.agroforester.com> your resource for
sustainable forestry and agroforestry in the tropics.

AgroForester
PO Box 428
Holualoa, HI 96725 USA
Tel: 808-324-4427
Fax: 808-324-4129
<mailto:email at agroforester.com>email at agroforester.com
http://www.agroforester.com 

We welcome your comments, suggestions, and input sent to
<mailto:overstory at agroforester.com>overstory at agroforester.com. Inquiries with
wide appeal will be featured in a Overstory edition. We regret that we are
unable to answer all inquiries individually.

Copyright 1998 by Craig Elevitch and Kim Wilkinson. Reproduction only by
written permission. For permission please contact overstory at agroforester.com.

To make corrections or add another name or address to our list, send an email
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P.O. Box 428
Holualoa, Hawaii 96725 USA
Tel: 808-324-4427
Fax: 808-324-4129
To contact The Overstory:
<mailto:overstory at agroforester.com>overstory at agroforester.com

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