Achieving sustainability in the use of green manures
- Achieving sustainability in the use of green manures
By Roland Bunch
Teaching farmers that green manure and cover crops have valuable uses
besides maintaining soil fertility can help sustain the widespread
use and adoption of green manuring practices.
Today, well over 125,000 farmers are using green manure and cover
crops in Santa Catarina, Brazil. Green manure and cover crops are
equally popular in neighbouring Parana and Rio Grande do Sul. In
Central America and Mexico, an estimated 200,000 farmers are using 20
traditional systems involving some 14 different species of green
manure and cover crops and organisations from Central Mexico to
Nicaragua are promoting their use in at least 25 additional systems.
Across the ocean in West Africa more than 50,000 farmers have adopted
Mucuna spp. or Dolichos lablab as green manures in the last eight
The present widespread use and rapid adoption of green manure and
cover crops has taken many people by surprise. To some extent this is
because little attention has been given to the extent to which green
manures and cover crops have always been used in traditional systems.
Gene Wilken, for example, in his otherwise excellent book, Good
farmers: traditional agricultural resource management in Mexico and
Central America stated that "cover cropping is not widespread in
traditional Middle America," (Wilken 1987). Many scientists believed
the technology inappropriate for village farmers. As late as 1989,
Anthony Young in the classic Agroforestry for soil conservation
dismissed green manuring as "a form of non-productive improved fallow
which has rarely found favour with farmers" (Young 1989).
For more than a decade it has been accepted that green manures and
cover crops would only be accepted by small farmers if they could be
grown on land that had no opportunity cost, could be intercropped
with other produce, grown under tree crops or on fallow land and be
cultivated in periods of expected drought or extreme cold. They would
also be favoured if they involved no extra labour and out of pocket
cash expense (Bunch 1995).
Whilst these assumptions have proved correct, recent experience has
shown that the sustainability of green manure and cover crops is more
likely to guaranteed when they provide farmers with some other
benefit besides fertile soil. This condition is consistent with the
observation that village farmers generally prefer multiple use
Experience from many parts of the world confirms the value
attribute to green manures and cover crops that have multiple uses.
In most known, traditional systems legumes are appreciated not only
because they maintain soil fertility, but because the seeds or pods
can also be eaten. Examples include the Vigna spp. which is
intercropped in Southern Honduras, El Salvador and South-east Mexico
and the high-altitude scarlet runner bean (Phaseolus coccineus),
which is widely used from upstate New York (Seneca bean) to Mexico
(ayocote) and from Guatemala (piloy) to Honduras (chinapopo) and
The velvet bean (Mucuna spp) is easily the most popular of all the
green manures/cover crops used today and was initially used and
spread by farmers along the southern border of the Himalayas in
Nagaland partly because it was such a valued source of food (Young
1989). In Central Honduras, where World Neighbours and COSECHA have
taught farmers to intercrop velvet bean with maize, there has been a
disappointing failure (35%+) to continue this technology except in
those villages where it is consumed as a major component of coffee,
hot chocolate, bread and tortillas. In fact, their value of green
manures and cover crops as human food seems to be the strongest
factor motivating in their sustained adoption.
Perhaps the second most common use of green manures and cover crops
is in weed control. In South-east Asia, a perennial species of the
velvet bean is use to improve fallow and to control weeds. More
modern practices include using jack bean (Canavalia ensiformis,
tropical kudzu (Pueraria phaseoloides) and perennial peanuts (Arachis
pintoi) under a variety of plantation crops, including coffee,
citrus, and African oil palm. The velvet bean is also used to control
imperata grass (Imperata spp.) and this practice is spreading rapidly
throughout Benin, Togo, and Columbia. Velvet bean and jack bean are
used to control paja blanca (Saccharum spp.) in Panama and to combat
nutgrass in several other countries.
A third practice, which is now more widespread but which is still
under-appreciated, is the use of green manures and cover crops to
stabilise swidden agriculture. Since decreased fertility and weed
infestation are the two most important reasons why farmers abandon
their fields today, and since green manures and cover crops can, to
some extent, often solve both these problems they have proved to be
an effective way of stabilising shifting cultivation in many
One dramatic example can be drawn from the work of the Centro Maya in
Guatemala's northern Peten region. In this humid forest area, farmers
could only grow maize for one or two years and then the ground had to
be left to regenerate. Now hundreds of farmers are growing velvet
bean intercropped with maize on the same fields year after year.
Those who initially adopted this system have been growing maize on
the same land for eleven consecutive years and productivity has
improved over time. Another interesting example is that of Central
Ghana, where village farmers are inventing their own ways of
stabilising their agriculture, including one system in which 30,000
leucaena trees (Leucaena spp.) are intercropped with maize and burned
very lightly each year. This practice has allowed maize to be planted
on the same land for 20 years in succession.
A fourth potential benefit that will probably acquire more
insignificance as experience increases, is the use of green manures
as animal feed. Most green manures and cover crop species, with the
major exception of Melilotus albus cannot be grazed well, but many
can be used for cutting and carrying even after months of drought,
the most notable examples of this type being Lathyrus nigrivalvis and
lablab bean (Dolichos lablab). Seeds also provide fodder, one good
example being the seeds of the velvet bean which in Campeche, Mexico
are cooked for half-hour, mixed with an equivalent amount of maize
and then ground into pig feed. The University of Yucatan calculated
that this velvet bean feed cost less than commercial feeds per unit
of weight gained.
Green manure and cover crops can be used in other ways as well. Two
years after Alter-Vida stopped working in El Naranjito, Paraguay,
farmers abandoned using velvet beans as a green manure, but continued
to used to use them when they wanted to prepare their land for
tobacco. In Southern Brazil, hundreds of thousands of farmers
regularly use some 25 different species of green manure and cover
crops for soil improvement partly because this allows them to
increase the amount of organic matter in their soil to the point
where tilling is no longer necessary. The financial as well as
ecological advantages of zero-till systems are tremendously
A number of conclusions can be drawn from the examples given above.
First, the variety of sustainable green manure and crop cover systems
already established in traditional as well as more recently
introduced agricultural system is remarkably diverse. Green manures
and cover crops have been adopted on a wide scale despite the
seemingly prohibitive conditions mentioned earlier in this article.
The fact that virtually every system we have refered to has some
elements of these conditions confirms their predictive value. Thus,
programmes to introduce new green manure and cover crop systems
should teach farmers not only how these species can be used to
improve their soil but that they have other uses as well.
Tremendous potential still exists for the development of new green
manure and cover crop systems. Scores of potential systems for using
green manure and cover crops still need to be investigated, most
notably the major possibilities of using them for animal feed; the
potential latent in new as yet untried species, including trees and
non-legumes, and the value to be derived from using combinations of
green manures and cover crops rather than individual species.
Experience leads us to believe that, with the possible exception of
very intensive farming systems such as irrigated vegetable and rice,
green manure and cover crops systems can probably be introduced into
many, if not most of the world's, small-scale farming systems.
Roland Bunch, COSECHA, Apartado 3586, Tegucigalpa, Honduras
- Larry, I was taking a look at the website. I checked the Links pages, and
was rather surprised. I was expecting to find many links - so many have been
posted on this group, so many wonderful links to wonderful things. But on
the website I found only a shor list of things, only directly relating to
Fukuoka. The were links for seedballs, links for seeds, and links for
Fukuoka's books. That is all great, but don't you think that it could be a
little broader? Personally, when I find a really good website, I am glad.
Let's say I find a site which is really on my wavelength. Then I will
apreciate links that are directly connected, but also links which that
person (/persons) is also interested in. The chances are that I will also be
interested in at least some of them. Like on Amazon, you find a book, and
you click on "those who bought this also bought..." or those who bought this
recommend.." I know some people feel that Fukuoka should not be mixed wth
other things. Well, I disagree. At least in a way. I mean, even he mixes. He
gets a lot from Buddhism, and also a lot from Daoism, for example. That is
great. How about some Permaculture links. And links to Agroforestry. Perhaps
to the various projects in Thailand, Sri Lanka and so on. How about to CAT
(centre for alternative technology) which is also about living in a
sustainable way. How about to the Schumacher college, founded on principles
of holism, us being a part of nature, and bringing that into eduation. It is
wonderfull that we can help open peoples' eyes to Fukuoka, and I feel that
it can only help to also provide some links to other such good ideas. If you
ask me, I almost feel that we are a part of the bottom-up drive system
powering the paradigm shift that is all so important in these times, and
networking and working together is so important for this.
Well, that's an idea!
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- At Wednesday, 06 November 2002, Justin wrote:
>Larry, I was taking a look at the website.It's good to know that someone is... :)
> I checked the Links pages, andhave been
>was rather surprised. I was expecting to find many links - so many
>posted on this group, so many wonderful links to wonderful things.But on
>the website I found only a shor list of things, only directly relatingto
>Fukuoka. The were links for seedballs, links for seeds, and links forcould be a
>Fukuoka's books. That is all great, but don't you think that it
>little broader?I've gone back through the entire archive and extracted all of those
links. You are right that there are a lot of good ones there. I've
also added a bunch of possible others gathered from my surfing/searching.
I haven't added them to the website yet because I was waiting to
see how the people here want to see the site develop. One option
is to keep it as closely focused on Fukuoka as possible since there
are no other sites that do this or provide comprehensive or extensive
info about him and his methods. It's easy to find info about other
methods of sustainable agriculture -- any Google search turns up
thousands of links to such sites. It's not easy to find hardcore
detailed info on Fukuoka and his method.
The other possibility is what you suggest. Add a bunch of links to
other sustainable ag sites (I also have a HUGE collection of those).
I don't mind doing that, but I'm concerned that it might dilute
what the Fukuoka site is all about. That's where I need input from
other list participants.
Even though I built and maintain the site I don't think of it as
"mine". I don't feel I have the right or freedom to do just anything
I want to with it. Changes and direction should come from concensus
amongst participants of this list. Maybe your questions and suggestions
will stir some dialog about this. I would definitely welcome that.
>I know some people feel that Fukuoka should not be mixed wthhe mixes.
>other things. Well, I disagree. At least in a way. I mean, even
The more I come to understand what he is saying and doing, the more
I come to realize just how unique his message is. All of the other
methods (I've spent more hours than I care to think about researching
them) are human-centered and human-dominated. They all come at it
with the attitude of dominating and overcoming natural processes
even while they talk of working "with" nature. Holmgren, one of the
co-creators of the Permaculture concept, alluded to this in that
article Robert Monie told us about.
Having said that, I also have to add that I agree about mixing other
methods into the process if its needed. There are parts of Permaculture,
agroforestry and biointensive gardening that I think can be used
very effectively in certain circumstances.
>He gets a lot from Buddhism, and also a lot from Daoism, for example.I know that he weaves a lot of Buddhist philosophy through his books,
but in that interview with Plowboy he made the point that its all
about farming, not religion. I get the feeling that all of the mystique
surrounding him often obscures the fact that he was, first and foremost,
a commercial farmer. Raising food for sale was his primary occupation
and all the rest was wrapped around and focused on that.
>Well, that's an idea!Excellent comments. It will be interesting to see what others have
to say about all of this.