Low fertility of soils, erosion, and rampant weed problems on small farms in developing countries give low yields leading to decreasing productivity, increased poverty, and migratory farming practices.

Basic Recommendations

An agricultural revolution, allowing the small farmer to compete with mechanized production has occurred through the increased use of selected legumes as green manure. This green manure maximizes organic matter production thereby increasing the fertility of the soil over time, keeps the soil covered, needs little or no tillage, significantly reduces weed growth, maintains biological diversity, and feeds plants through the mulch.

Definitions of Main Concepts

Green Manure - (also cover crops) originated from practices of using primarily leguminous plants and plowing them under to fertilize soils. However, under different climatic and terrain conditions, the practice has changed in the tropics to refer to a series of plants, mostly leguminous, which are used by farmers for a whole range of purposes, one of which is the fertilization and improvement of the soil by applying the vegetation to the soil surface.

Detailed Solutions or Recommendations

Use of green manure principally in the form of the velvet bean (mucuna pruriens).

Using the Velvet bean (Mucuna pruriens, a legume) as well as other selected legumes (see below) as green manure, has produced an agricultural revolution by dramatically increasing yields, increasing soil fertility for sustainable agriculture, provided ground cover and extensive weed control, reduced tillage of the soil to zero, and reduced to completely eliminated the use of fertilizers and pesticides. Farmers can produce five to six times the maize they used to, the agriculture is much more diversified than in the past, and incomes are probably anywhere from ten to twenty times what they were fifteen years ago. The method allows small farmers to compete with mechanised farmers, without the capital outlay. [Pettifer, Julian Correspondent, BBC Video Report - The Magic Bean, June 2001]

Explanation

Green manure, for a capital outlay of a handful of seed, dramatically improves the yield and the fertility of the soil year after year by adding organic matter and nitrogen while reducing the need for fertilizers and herbicides, weed control, burning, and tilling of the soil.

- adds up to 50 tons per hectare(green weight) of organic matter to the soil improving its water holding capacity, nutrient content, nutrient balance, friability and pH.

- Nitrogen added to the soil reported to be about 150kg per hectare otherwise costing at least US $75/Ha in chemical fertilizer.

- improves soil conservation by providing crop cover and productivity. Study of mono cropped maize on 35% slopes with a 2000+ mm rainfall in northern Honduras, increased soil productivity year by year with soil covered by velvet bean ten months each year.

- ending migratory ("slash and burn" or "swidden") agriculture and agriculture burning by improving soil fertility and controlling weeds.

- can provide food for people and fodder for animals although this reduces value to soil.
[Bunch29 1995]

For discussion and listing of types of green manure producing plants, see typescovercrops

Bunch has stated that "Experience leads us to believe that, with the possible exception of very intensive farming systems such as irrigated vegetables 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." [Bunch2]

Problems within Solution

If green manure is used for food and fodder, its value to the soil is reduced. With no weeding and no tilling, non mechanized farms can compete with the mechanized in a world where trade barriers are falling.

In spite of the advantages named above, many farmers will not plant green manures where they can plant either subsistence or cash crops. Soil improvement and improvement in productivity is not usually visible until the second cropping cycle or second year. Green manures must either continue to grow or form a mulch during the dry season, and grazing animals, agricultural burning, termites, and a host of other problems may prevent their lasting very long during this period. Extreme drought, extreme infertility, extremes in pH, severe drainage problems will affect green manures almost as much as traditional crops, thereby reducing their impact.
[Bunch29 1995]

Limitations of Solution

It is generally believed that green manures and cover crops would only be accepted by small farmers if they could be grown on land that has 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 no out of pocket cash expense.
[Bunch29 1995]
Whilst these assumptions have proved correct, recent experience has shown that the sustainability of green manure and cover crops is more likely to be 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 technologies.
[Bunch3 1997]

Preparations Needed: None

Results

Some 45,000 farm-families in Honduras and Guatemala have benefited from the adoption of sustainable agriculture, increasing crop yields from 400-600 kg/ha to 2000-2500 kg/ha. Farmers use green manures, cover crops, contour grass strips, in-row tillage, rock bunds, and animal manures, which are finely-tuned through experimentation to local conditions. These programmes have regenerated local economies. Land prices and labour rates are higher inside the project areas, and families have moved back from capital cities. There are also benefits to the forests. Farmers say they no longer need to cut the forests, as they have the technologies to farm permanently the same piece of land. Throughout Central America, various NGOs have promoted the use of grain legumes, especially velvet bean (Mucuna pruriens) to be used as green manure, an inexpensive source of organic fertilizer to build up organic matter. Taking advantage of well established farmer-to-farmer networks, e.g. campesino a campesino movement in Nicaragua and elsewhere, the spread of this simple technology has occurred rapidly.
[Pretty 2001]

Personal Experiences Related to Solutions Five key principles in agriculture for sustainability, based on the natural processes of fertility found in humid tropical forest ecosystems:
1) Maximize organic matter production
2) Keep the soil covered
3) Use zero tillage
4) Maintain biological diversity
5) Feed plants through the mulch

For a discussion of these principles, see Crop Principles

Past Experience and Outcomes

Experience from many parts of the world confirms the value farmers' 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 Northern Chile. 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 as green manures and cover crops as human food seems to be the strongest factor motivating 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 countries. 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 significance 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 a 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 costs 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 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 attractive.
[Bunch2]

Authorities and Contacts

Roland Bunch, Director of COSECHA email: rolando@cosecha.sdnhon.org.hn

Professor Jules Pretty, Director of the Centre for Environment and Society at Essex University

Other Organizations, Groups dealing with problem

COSECHA (the Association of Consultants for a Sustainable, Ecological and People-Centred Agriculture) Apartado 3586, Tegucigalpa, Honduras

Management of Organic Inputs in Soils of the Tropics (MOIST) covers green manures and cover crop research and exchange. Site includes CIEPCA Newsletter (Eng & Fr), TropSCORE, the consortium for Tropical Soil Cover and Organic Resource Exchange, Learning modules for agroforestry and organic resources, Symposium on Fallow Management in the Tropics, CIAT-Uganda Extension Guides, and Mucuna News. http://ppathw3.cals.cornell.edu/mba_project/moist/home2.html

University of California, Sustainable Agriculture Research and Education Program: UC SAREP Cover Crop Database includes over 5,000 items concerning the management and effects of more than 32 species of plants usable as cover crops and more than 400 different cover crop images. Reports on research related to cover cropping http://www.sarep.ucdavis.edu/ccrop/

Other Relevant Sites, Contacts

International Institute for Environment and Development (IIED) "IIED is an independent, non-profit organization promoting sustainable patterns of world development through collaborative research, policy studies, networking and knowledge dissemination. We work to address global issues such as mining, the paper industry and food systems."
See in particular:
Sustainable Agriculture and Rural Livelihoods
Current Research Projects: Themes
Information

Centre for Research and Information on Low External Input and Sustainable Agriculture Independent organization with the mandate to contribute to poverty alleviation through the promotion of agro-ecological approaches. http://www.ileia.org/

References

[Bunch20 1985] Bunch, Roland The Overstory #20 Five Fertility Principles Discovering Principles of Agriculture for the Humid Tropics from original at http://www.echonet.org/edn58t.htm http://www.agroforester.com/overstory/overstory20.html

[Bunch29 1995] Bunch, Roland, The Overstory #29--Tropical Green Manures/Cover Crops http://www.agroforester.com/overstory/overstory29.html
The text is a summary with excerpts from an original article by Roland Bunch of COSECHA, Honduras: The Use of Green Manures by Villager Farmers: What We Have Learned to Date, Technical Report No. 3, 1995, CIDICCO, Apdo. Postal 4443, Tegucigalpa MDC, Honduras C.A., e-mail cidicco@gbm.hn

The Overstory is published by Permanent Agriculture Resources, P.O. Box 428, Holualoa, HI 96725 USA; Tel: 808-324-4427; Fax: 808-324-4129 email: email@agroforester.com; site: http://www.agroforester.com/

Bunch, Roland and ECHO Staff, GREEN MANURE CROPS, 1985 http://www.echonet.org/tropicalag/technote.html

John Thompson and Fiona Hinchcliffe [2000], Sustaining the harvest
"A recent global analysis of 109 sustainable programmes and projects in 26 countries has shown that resource conserving methods and farmer-centred approaches can produce startling increases in food production and contribute to the regeneration of rural economies" Authors from the International Institute of Environment and Development (IIED)

[Pye-Smith 98] Pye-Smith, Charlie, Mimicking Nature to Grow More, People & the Planet http://www.peopleandplanet.net/doc.php?id=391
Also see Feeding a world of 8 billion [2003] http://www.peopleandplanet.net/doc.php?id=341§ion=3

Bunch, Roland 2000 Centre for Environment and Society SAFE-World Research 47 Portraits of Sustainable Agriculture Projects and Initiatives (from Pretty and Hine, 2001) 47 Portraits of Sustainable Agriculture Projects and Initiatives

FAO's Digital Resoource Centre Search for 'sustanaible agriculture' or for specific topics desired in Spanish French English.

Pettifer, Julian (BBC Correspondent), The Magic Bean, BBC Video The Magic Bean, BBC Video