Re: VITA Tehnology Broadcast

Brij Mathur (mailto:query@VITA.ORG)
Fri, 15 Sep 1995 18:16:54 GMT

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Message-ID:  <199509151816.SAA21275@lan.vita.org>
Date:         Fri, 15 Sep 1995 18:16:54 GMT
From: Brij Mathur <mailto:query@VITA.ORG>
Subject:      Re: VITA Tehnology Broadcast
To: Multiple recipients of list DEVEL-L <mailto:DEVEL-L@AMERICAN.EDU>

NOTE: This electronic version of the enclosed paper does not show photos, figures, etc. that are included in the paper version which is available for sale from VITA.

TECHNICAL PAPER # 57

UNDERSTANDING AGROFORESTRY TECHNIQUES

By Fred Weber and Carol Stoney

Illustrated By Frederick J. Holman

Published By VOLUNTEERS IN TECHNICAL ASSISTANCE 1600 Wilson Boulevard, Suite 500, Arlington, Virginia 22209 USA Telephone: (703) 276-1800, Fax: (703) 243-1865 Telex: 440192 VITAUI, Cable: VITAINC Internet: mailto:vita@gmuvax.gmu.edu, Bitnet: vita@gmuvax

Understanding Agroforestry Techniques ISBN: 0-86619-276-X [C] 1989, Volunteers in Technical Assistance

PREFACE

This paper is one of a series published by Volunteers in Techni- cal Assistance to provide an introduction to specific state-of-the-art technologies of inter- est to people in developing countries. The papers are intended to be used as guidelines to help people choose thechnologies that are suitable to their situations. They are not intended to provide construction or implementation details. People are urged to contact VITA or similar organiza- tions for further information and technical assistance if they find that a particular technology seems to meet their needs.

The papers in the series were written, reviewed, and illustrated almost entirely by VITA Volunteer technical experts on a purely voluntary basis. Some 500 volun- teers were involved in the production of the first 100 titles issued, contributing approxi- mately 5,000 hours of their time. VITA Staff included Suzanne Brooks handling typesetting and layout and Margaret Crouch as editor and project manager.

Co-author Fred Weber, a pioneer in the community forestry con- cepts presented here, has advised projects for over 20 years. He wrote the original edition of the VITA publication Reforestation in Arid Lands based on a training manual he prepared for Peace Corps volunteers in Niger. Carol Stoney collaborated with Mr. Weber on the revisions for the new edition of Reforestation, which is the basis for the techniques in this technical paper. Frederick J. Holman, a landscape architect, provided the illustrations in this paper, which are taken from Reforestation.

VITA is a private, nonprofit organization that supports people working on technical problems in developing countries. VITA offers information and assistance aimed at helping individuals and groups to select and implement technologies appropriate to their situations. VITA maintains an international Inquiry Service, a specialized documentation center, and a computerized roster of volunteer technical consultants; manages long-term field pro- jects; and publishes a variety of technical manuals and papers.

UNDERSTANDING AGROFORESTRY TECHNIQUES by VITA Volunteers Fred Weber and Carol Stoney

I. INTRODUCTION

Agroforestry refers to the integration of trees and shrubs as essential elements of agricultural and other land use systems, with the idea of improving the fertility and productivity of the soil. In this concept, trees and shrubs can be deliberately managed (that is, established, tended, protected, harvested, etc.) and considered as one of the resource elements used by people or their livestock, even though the trees may appear to be randomly dispersed in the landscape. Trees and shrubs, then, need not be forests, woodlots, orchards, or other discrete stands especially set aside for a single purpose or product. Rather, they can be planted wherev- er people have not allocated the space to some other use. In many situations this makes much more sense than setting aside specific areas of usable farm land for woodlots--where the most acute problem is lack of food, for example, not lack of wood. Certain tree species may provide food (fruit, leaves, edible seeds, etc.) not only for people but also for livestock, particularly during seasons when food supplies from other sources are low.

In addition to producing wood for fuel, construction, implements, tools, and art objects, other important and locally appreciated by-products of agroforestry include fiber for mats, baskets, and rope, or plant materials for medicines, dyes, tannin, cosme- tics, and glue. These raw materials were easily obtainable a few generations ago when extensive woodlands still existed throughout dry regions. Today they are scarce because much of the "useless brush" has been converted to farm fields or plantations of rapid growth species, the use of which is usually limited to only a single product.

Agroforestry or soil conservation techniques, often combined, can help to stabilize cultivation on a given piece of land. Certain of these methods help prevent or reverse environmental damage in areas where fallow cropping is no longer practical. Adding trees and shrubs as permanent features in the landscape in the form of field trees, border and alignment plantings, windbreaks, and live fencing can protect the soil against erosion and improve nutrient cycling. Proper maintenance of trees in agroforestry or soil conservation systems may allow permanent cultivation of farm fields that previously could only be fallow cropped.

Many of the techniques described in this paper are based on farming systems that have evolved to allow long-term sustainable production systems to take the place of shifting cultivation. Most can be used by anyone who wishes to make better use of trees and shrubs to restore or improve their land. The techniques have been drawn largely from VITA's publication Reforestation in Arid Lands by Fred Weber and Carol Stoney.

II. AGROFORESTRY TECHNIQUES

A wide assortment of different agroforestry techniques is being used today. Many are based on traditional practices that have been carried on for genera- tions. Others are relatively new, "invented" by technicians working with local farmers or pastoral- ists and still being adapted to varying site conditions. The methods described here provide a practical guide for use in the field, rather than extensive coverage of background information, theory, and reference sources. As a practical measure they have been divided into two catego- ries: on-farm, which includes those most directly related to agricultural operations, and off-farm, which includes non-agriculture techniques.

ON-FARM TECHNIQUES

Trees can be integrated with crops in a number of ways. They may be dispersed randomly across a field, planted in careful rows between rows of other plants, or planted as separate stands for orchards or woodlots. Trees may also be used to mark borders or as live fencing.

Dispersed Trees

Intensive interaction between crops and trees occurs when they are grown together. The classic farm/park landscape that covers large parts of the Sahel is a perfect example of a traditional agroforestry arrangement where trees dispersed in farm fields form an integral part of a cropping system. Different species are found in these dispersed, park-li- ke stands, depending on site conditions. The best known are Acacia albida, Butyrospermum parkii, Parkia biglobosa, and Borassus aethiopum.

In traditional systems these trees regenerate naturally, and so they are more or less homogeneously distributed across fields in random patterns. Where they have been regenerated through human efforts they are planted in lines (normally 10m x 10m). Regular spacing is particularly important if mechanized cultivation, such as animal traction, is practiced. The main feature of this approach is that the trees are more or less uniformly dispersed either in a natural, irregular pattern or more systematically in a grid pattern.

Some problems do arise. The seedlings are difficult to protect from grazing when they are young (up to five years). Brush fences or woven baskets can be placed around individual trees, but this is expensive. Birds are also attracted to the trees, especially when they are established near rivers and lakes. The birds can cause problems for farmers if they eat crops and seed.

Efforts to introduce Acacia albida in farm fields in the Sahel have been particularly successful, however, because this species drops its leaves during the rainy season and does not leaf out again until well into the dry season. Cereal crops can be grown under the leafless trees during the rainy season. The crowns of almost all other tree species compete with light-demanding crops for space, thus the areas shaded by the trees cannot be used for crop production. Even small trees can create enough shade during the rainy season to take a significant part of a farmer's land-holding out of production.

Alley Cropping

Small trees or shrubs, pruned frequently to prevent them from producing too much shade, are grown in relatively compact rows (between 2 and 4m, never more than 6m apart). Crops are grown in the space--the "alley"--between the rows of trees. This method was developed in more humid areas of the tropics, and it is being tried in drier regions of Africa, Asia, and Latin America. The International Institute of Tropical Agriculture (IITA) has been experimenting with alley cropping in Nigeria for a number of years, as has the Centro Agronomico Tropical de Investigation y Ensenanza (CATIE) in Turrialba, Costa Rica, in Central America. Most research is focused on obtaining the right species combination, but the question as to which crops respond best to which tree species also varies according to site condi- tions.

Leguminous trees, such as Calliandria calothrysus, Leucaena leucocephala, Mimosa species, Prosopis cineraria, and Acacias, are often used in alley cropping schemes because their nitrogen-fixing ability enriches the soil. Such diverse crops as corn, millet, cowpeas, yams, and manioc can be grown in the alleys. The trees/shrubs are pruned as often as five times per year. The clippings are laid down as a mulch around both trees and crops, gradually decomposing and becoming incorporated into the soil as organic matter. The shade and mulch from the tree rows also reduce weed growth. Yields of some crops are higher between the mulched rows than in comparable fields that are not being alley cropped. The IITA found that yields from maize were three times greater after four years of mulching with Leucaena leucocephala clippings (IITA, 1986).

Farmers may want to use the pruned branches for poles or fire- wood. The clippings can also be used as fodder for livestock. If the leaves and branches are not used to mulch the crops, alley cropping may not have the effect of increasing crop yields, but it will still be an effective technique for controlling soil erosion, increasing the availabil- ity of tree products, and maintaining agricultural sustainability.

In addition to the increased complexity of matching compatible crop and tree species to specific site conditions, several other problems may limit the widespread adoption of alley cropping. A major consideration of farmers who are considering various intercropping schemes is the amount of arable land that the trees will take up. Farmers tend to favor methods that will take as little land out of crop production as possible. Alley cropping requires fairly close placement of tree rows, which can substantially reduce the amount of land left for the crop rows. Where land scarcity is a problem, therefore, alley cropping is probably not the best method to use.

Alley cropping also requires fairly strict adherence to planting and pruning schedules in order for the technique to give good results. If the trees are not cut back at regular intervals, they will create too much shade for the intercropped plants. For light sensitive crops like corn, too much shade over a period of just a few days can interrupt flower- ing and fruiting processes. Other crops simply do not thrive in excess shade. Trained extension personnel are needed to work closely with farmers on crop and tree species selection and on setting up planting and pruning schedules.

Line Plantations

Another alternating row arrangement involves planting larger trees at a wider spacing (7 to 10m) with crops planted between the rows. In this system, species that provide fuelwood, and timber, Grevillea robusta, or fruit trees like avocado and citrus, are often used. As much as 60 percent of the species composition of the line plantations may be shrubs. Other possibilities such as Markhamia platycalyx, Inga vera, Trema orientalis, and Maesopsis eminii are being studied on trial sites, where they serve as shade trees for coffee planta- tions. Several species of Acacia or Cacao and Gmelina arborea can also contribute to honey produc- tion. The species mix should include trees that provide different products as well as nitrogen fixing plants.

Borderline Trees

Borderlines consist of trees, shrubs, and grasses established to delineate individual farm fields. They serve as property markers while they provide wood and other products for various purposes. They do not occupy too much space, nor do they shade large areas of the fields. Because the tree rows are not actually in the fields, they do not interfere with regular farming operations. As in line plantations, wood and other products can be harvested from the trees.

The promotion of additional species for borderline plantation has potential, if species selection takes into consideration local preferences. Protection of young trees is necessary unless the species being used are unpalatable to livestock. Issues of land and tree tenure should be carefully researched and discussed with a community before this technique is tried. If the trees are planted on a borderline between two farmers' property, to whom do the trees and the harvesting rights belong? There may be several alternative approaches to resolve this question, but all parties involved should agree in advance as to how the situation will be handled.

Live Fencing

Live fencing consists of dense hedges or thickets usually planted around a garden or farm field to protect it from free ranging livestock. They are also planted around family compounds and other buildings. This technique differs from borderline planta- tions in that shrubbier species are used, the shrubs or trees are tightly spaced (0.5-1m), and they are intensively pruned to maintain a compact, dense barrier. This is a very important alternative to traditional fences that are constructed and annually repaired using interwoven thorny branches.

A number of species have shown that they adapt well to use as live fences. Members of the Euphorbia family are especially good because animals will not eat them (people too must be careful--when Euphorbias are cut, the milky sap can cause severe irritation if it touches the skin). A number of Acacia and Prosopis species as well as Leucaena, Gliricidia sepium, and Cajanus cajun, are also useful for this purpose.

Frequently, the main function of a hedge is to keep animals out. If this is the case, plants must be spaced tightly and kept well pruned. Select species that are:

* Thorny * Easily coppiced (sprout back) * Relatively unpalatable * Fast growing

No one species will meet all these requirements. Trade-offs are inevitable although a mixture of species may provide the most protection. Final choice depends much on specific site conditions. If protection from animals is not a primary concern, the spacing between plants can be wider. Hedges can have many other advantages and functions besides keeping out animals:

* Demarcation of property boundaries * Protection against wind * Addition of organic matter from leaf litter * Fruit and forage, when combined with borderline trees * Privacy

As garden fences, or wherever irrigation is possible, trees for a live fence can be started by direct seeding. The seeds should be planted in furrows or in small pockets placed at intervals along the fence row.

Live fences can also be established from cuttings, especially from some species such as Gliricidia sepium, members of the Euphorbia and Commiphora genera, and some perennial legumes. Freshly cut branches from these species are likely to make root and sprout if they are planted at the beginning of the rains. These species are therefore, particular- ly useful for establishing live fences. Normally, one would not wait until the beginning of the rainy season to build fences, but this might be done when using post materials that may take root. Care should be taken not to damage the bark or wood when attaching wire for the fence.

OFF-FARM TECHNIQUES

In most rural areas as well as in towns and urban areas, there are unused spaces along roads and water courses, and around houses and public buildings. While they may traverse agricultural land, these open spaces are not used for agricultural production. Trees planted in these spaces can enhance the environment by providing erosion control and shelter from the sun and wind for both people and animals.

Road and Trail Alignment

A long-standing tradition in many tropical areas is to line roads with trees, mainly for shade, but also for wood and other tree products. This practice can be extended to include foot paths and trails. Certain species such as Albizia lebbek and Syzygium cumini are common street trees in India, Sesbania grandiflora is often found in the Philippines, and Prosopis alba in South America.

A frequently made mistake has been to plant trees too close to the road. On major roadways, enough room must be left for two vehicles to pass with additional space on the roadside for vehicles to pull over in an emergency. A space of less than seven meters between tree rows creates traffic hazards. Additional width is needed around curves, because the trees reduce the distance ahead that drivers can see.

Trees are also established along livestock and bicycle trails and footpaths, sometimes in combination with live fencing or rock walls to control access to adjacent fields. Shade and fruit trees are favored for footpaths.

Water Course Alignment

The banks of streams are frequently cleared for cultivation of cereal crops or irrigated gardens. They are extremely susceptible to erosion once the natural vegetation has been removed. These areas can be protected by restoring tree and shrub cover along the stream banks. Water course alignments also create good habitats for wildlife.

Trees and shrubs can be established around water sources in much the same way as alignment plantings along roads. Rivers, ponds, or drainage canals in irrigation schemes provide excellent growing conditions for trees. Fruit trees (mangos, citrus) should be given special consideration because of their value as food sources. Dry river beds (wadis) provide a suitable site for species such as Tamarix, Anogeissus leiocarpus, Prosopis spp., or other more drought-resistant varieties

Shade Trees

Shade trees planted in public places around government buildings, schools, market places, churches, and mosques serve an important function. These are areas where people congregate during the day, and shade is an essential part of the environment. These are also places where trees can be established and maintained quite easily by local people themselves with minimal assistance from outside.

Most of the street and road trees mentioned above are excellent shade trees. Others are Pithecellobium dulce, Azadirachta indica (neem), and Grevilla robusta.

Trees planted in public places usually need individual tree fences to protect them until their branches are out of reach of free-ranging animals. Even after they are no longer threatened by livestock, good local cooperation is needed to keep people from over-harvesting the trees. For example, the twigs of the neem tree are very popular in Africa for toothpicks. A seemingly harmless practice like breaking off an occasional twig can, however, stunt the growth of young neems if the stems are continuously stripped by passers-by.

Although farmers generally try to restrict the amount of shade in areas where crops are grown, shade trees are used to protect livestock from intense heat during the day. Shade trees are particularly necessary wherever animals are corraled or fenced in, and around watering spots.

REFERENCES

Bognettau-Verlinded, E. 1989. Study, on the Impact of Windbreaks in Majjia Valley, Niger. Niamey/Wageningen, Holland: CARE/Agricultural University, Wageningen, Holland.

Buck, L.E. (ed.). 1983. Proceedings of the Kenya National Seminar on Agroforestry, Nov. 1980. Nairobi: ICRAF and the University of Nairobi.

Delehanty, J., J. Thomson, and M. Hoskins. 1985 Majjia Valley Evaluation Study: Sociology Report. Niamey: CARE International Report.

FAO. 1977. Guidelines for Watershed Management. Rome: FAO Conservation Guide Series No. 1., 298 pp.

FAO. 1977. Conservation in Arid and Semi-Arid Zones. Rome: FAO Conservation Guide Series No. 3.

FAO. 1977. Special Readings in Conservation Techniques. Rome: FAO Conservation Guide Series No. 4.

FAO. 1983. Management of Upland Watersheds; Participation of the Mountain Communities. Rome: FAO Conservation Guide Series No. 8.

FAO. 1985. Sand Dune Stabilization: Shelterbelts and Afforesta- tion in Dry Zones. Rome: FAO Conservation Guide Series No. 10.

FAO. 1985. FAO Watershed Management Field Manual: Vegetative and Soil Treatmentt Methods. Rome: FAO Conservation Guide Series No. 13.

Felker, P. 1978. State of the Art: Acacia albida as a Comple- mentary Permanent Intercrop with Annual Crops. Riverside, California: University of California, 133 pp.

Flannery, R.D. 1981. Gully Control and Reclamation. Arlington, Virginia; Volunteers in Technical Assistance (VITA), 26 pp.

Gulick, F.A. 1984. Increasing Agricultural Food Production Through Selected Tree Planting Techniques: A Summary Memorandum with Selected References. Washington, D.C.: USAID/Bureau for Africa, 149 pp.

Hagedorn, H. et al. 1977. Dune Stabilisation: A Survey of Literature on Dune Formation and Dune Stabilization. Eschborn, W. Germany: GTZ, 193 pp.

Hoekstra, D.A. and F. M. Kuguru (eds.) Agroforestry Systerm for Small-Scale Farmers: Proceedings of an ICRAF Workshop. Nairobi: ICRAF, 283 pp.

IITA. 1986. Alley Cropping. Ibaden: IITA Research Report.

ILCA. Pastoral Systems Research in Sub-Saharan Africa: Proceed- ings of the IDRC/ILCA Workshop Held at ILCA, Addis Ababa, Ethiopia. Addis Ababa: ILCA, 480 pp.

Kunkle, S.H. 1978. Forestry Support for Agriculture Through Watershed Management, Windbreaks and Other Conservation Actions. Position Paper, Eighth World Forestry Congress. Jakarta, Indonesia, 28 pp.

Le Houerou, H.N. (ed.) 1980. Browse in africa: The Current State of Knowledge. Addis Ababa: ILCA, 491 pp.

McGahuey, M. 1986. Impact of Forestry Initiatives in the Sahel on Production of Food, Fodder, and Wood. Washington, D.C.: Chemonics Interna- tional, 25 pp.

Nair, P.K.F. 1980. Agroforestry Species: A Crop Sheets Manual. Nairobi: ECRAF, 83 pp.

Niar, P.K.F. 1982. Soil Productivity Aspects of Agroforestry. Nairobi: ICRAF, 336 pp.

National Academy of Sciences. 1983. Agroforestry in the, West African Sahel. Washington, D. C.: NAS/Advisory Committee on the Sahel, 86 pp.

USDA/SCA. 1962. Soil Conservation Manual. Paris: USAID/Centre Regional d'Editions Techniques, 359 pp. (Also available in French).

Vergera, N.T. (ed.) 1982. New Directions for Agroforestry: The Potential of Tropical Legume Trees. Honolulu Environment and Policy Institute, East-West Center.

Weber, F. and M.W. Hoskins. 1983. Soil Conservation Technical Sheets (Fiches Techniques de Conservation du Solss). Moscow, Idaho: University of Idaho for USDA (OICD), 112 pp.

Weber, F. and M.W. Hoskins. 1983. Agroforestry in the Sahel. Blacksburg, Virginia: Virginia Polytechnic Institute, Department of Sociology.

INFORMATION SOURCES

The following organizations work in arid forestry, range manage- ment, or agriculture, and can be contacted for information on specific problems:

Research Organizations

Centro Agronomico Tropical de Investigacion y Ensenanza (CATIE) Department de Recurses Naturale Turrialba, Costa Rica

Centre Technique Forestier Tropical (CTFT) 45 Bis Avenue de la Belle Gabrielle 94 Nogent Sur Marne France

Consultative Group on International Agricultural Research (CGIAR) 1818 H Street Washington, DC 20433 USA

Environment and Policy Institute East-West Center 1777 East-West Road Honolulu, HI 96848 USA

International Crops Research Insitute for the Semi-Arid Tropics Patancheru P.O. Andhra Pradesh 502 324 India

National Academy of Sciences Board on Science and Technology for International Development (BOSTID) 2101 Consitution Avenue, NW Washington, DC 20418

Nitrogen Fixation by Tropical Agricultural Legumes (NifTal) Project P.O. Box 0 Paia, Hawaii 96779 USA

Overseas Development Natural Resources Institute (ODNRI) 56/62 Gray's Inn Road London WC1 X8LU United Kingdom

TECHNICAL PAPER #72

UNDERSTANDING SOIL EROSION AND ITS CONTROL

By Jim Chamberlain

Technical Reviewers Robert S. Jonas Fred R. Weber

Illustrated By Frederick J. Holman

Published By

VITA 1600 Wilson Boulevard, Suite 500 Arlington, Virginia 22209 USA Tel: 703/276-1800 * Fax: 703/243-1865 Internet: mailto:pr-info@vita.org

Understanding Soil Erosion and Its Control ISBN: 0-86619-315-4 [C] 1990, Volunteers in Technical Assistance

PREFACE

This paper is one of a series published by Volunteers in Technical Assistance to provide an introduction to specific state-of-the-art technologies of interest to people in developing countries. The papers are intended to be used as guidelines to help people choose technologies that are suitable to their situations. They are not intended to provide construction or implementation details. People are urged to contact VITA or a similar organization for further information and technical assistance if they find that a particular technology seems to meet their needs.

The papers in the series were written, reviewed, and illustrated almost entirely by VITA Volunteer technical experts on a purely voluntary basis. Some 500 volunteers were involved in the production of the first 100 titles issued, contribution approximately 5,000 hours of their time. VITA staff included Patrice Matthews and Suzanne Brooks handling typesetting and layout, and Margaret Crouch as senior editor and project manager. VITA Volunteer Dr. R.R. Ronkin, retired from the National Science Foundation, lent his invaluable perspective to the compilation of technical reviews, conversations with contributing writers, editing, and in a variety of other ways.

Jim Chamberlain, the author of this paper, is a program officer for the Nitrogen Fixing Tree Association in Hawaii. A specialist in tropical forestry, he has experience in the Philippines and elsewhere in East Asia. Technical reviewer Robert S. Jonas is a soil scientist retired from over 30 years with the U.S. Department of Agriculture's Soil Conservation Service. Fred Weber, the other technical reviewer, is the author of Reforestation in Arid Lands (VITA, 1986) and a community forestry expert with extensive experience in Africa. All three are active VITA Volunteers.

VITA is a private, nonprofit organization that supports people working on technical problems in developing countries. VITA offers information and assistance aimed at helping individuals and groups to select and implement technologies appropriate to their situations. VITA maintains an international Inquiry Service, a specialized documentation center, and a computerized roster of volunteer technical consultants; manages long-term field projects; and publishes a variety of technical manuals and papers.

UNDERSTANDING SOIL EROSION AND ITS CONTROL

by VITA Volunteer Jim Chamberlain

1. EROSION AND SOIL LOSS

Geological erosion is a natural, continuous process that occurs almost anywhere that water flows on the land. It can also result from the action of wind, changes in temperature, and the activities of living things. Wind dislodges and moves soil particles. Rapid temperature variation between day and night, not a major problem in most tropical climates, affects soil surface structure. Biological agents are lichens, mosses, and animals, including livestock that compact soils and overgraze vegetation cover. Erosion by water receives the most attention in this paper.

Erosion forms many kinds of soil from rock and is controlled by such factors as rock properties, topography, vegetation, and climate. Some forms of erosion result in topsoil removal, rock failures, landslides, slumps, and riverbank cutting.

Erosion is usually accelerated by such human activities as forest destruction, traditional agriculture, grazing, construction, and mining. Whenever vegetation is removed, as when forests are cleared for agriculture, and the ground is exposed to rainfall, soil erosion by water and wind may increase. On sloping land it far exceeds the rate under natural conditions. Accelerated erosion, widespread throughout the tropics, is one of the most serious environmental and socioeconomic problems affecting rural people.

Soil loss is affected by soil composition, type of cover, soil management practices, and microclimate conditions. With highly fertile soils erosion has little adverse effect on productivity but increases production costs. In soils with medium rooting depth and surface thickness, the effects of erosion can be hidden by the use of technologies that work these potentially fragile soils. Erosion of marginal soils with shallow rooting depth, found throughout poor countries, results in continued decline of crop yields. Mismanagement of marginal soils can lead to permanent loss of soil fertility.

Loss of a few centimeters of topsoil can reduce the productivity of good soils by 40 percent and poor soils by 60 percent. In the United States, wind erosion over 30 years caused a loss of 30 cm of topsoil, resulting in a 70 percent decline in wheat yield.

Land-use planning should aim for an acceptable income and a minimal soil loss. Planning for erosion control must consider these factors: soil type, extent of erosion, topography, location of waterways and drainage, runoff diversions, size and arrangements of fields, cropping system, and tillage methods. Vegetation is an especially important tool for erosion control.

2. TYPES OF WATER EROSION

It is important to recognize the kinds of erosion, because each type may require a different approach to its control.

The flow of water over sloping land may be the most erosive factor affecting soils. Soil particles are dislodged or break from the soil mass, disrupting the physical and chemical bonding of soils. Soil erosion by water includes detachment, transport and deposition of soil by raindrops and runoff. Suspended soil particles dislodge other lighter particles through abrasion.

The extent of erosion depends on the amount, velocity, and turbulence of the runoff. The type of abrasive material being transported also affects the extent, which also depends on the energy of flowing water and amount of suspended material. Velocity increases as depth of flow and slope increase. Turbulence increases in proportion to the intensity of rainfall.

The major forms of erosion affecting agricultural lands are sheet, rill, and gully. Sheet erosion is caused by the even flow of water over sloped lands. It removes lighter soil particles, organic matter, and soluble nutrients. Its effects are less apparent than those of other forms, but they can seriously affect soil fertility and farm productivity.

Rill erosion occurs on sloped land dissected by small parallel channels running downhill. If these do not interfere with normal tillage practices they are called rills. Soils that are easily worked are more apt to form rills, and rills typically flow together and form gullies.

Two types of gully erosion create problems on agricultural lands. They are named for their distinctive cross-sections: V-gullies are identified by downward cutting centers, whereas the flat bottoms of U-gullies are parallel to the slope of the field. Control measures for the two types are different, as described at the end of Section 3.

3. AGRONOMIC CONTROL OF WATER EROSION

Tillage Practices

Intense cultivation and harrowing break down heavier textured soils into easily transportable particles. Changing the physical structure of soils through tillage thus can make them more susceptible to erosion. Conservation tillage, the practice of leaving crop residue on the soil surface, can reduce sheet and rill erosion as much as 90 percent.

One type of conservation tillage, called no-till, zero-till, or low-till, eliminates all plowing, disking, and cultivating. The new crop is seeded directly into the crop residue of the previous season. The system conserves soil moisture, decreases runoff, reduces soil loss and helps maintain organic matter. In a research study in Nigeria, zero-till prevented 96 percent of runoff and 99.5 percent of soil loss on 10 percent slopes. Unfortunately, this strict variety of conservation tillage requires special equipment (for instance, to loosen the soil under the crop residue without turning it over) and expensive herbicides.

Contour Cultivation

In India, contour cultivation on 2 percent slopes reduced soil loss by 28 percent and runoff by 61 percent, compared to traditional, up-and-down plowing. It is most effective on 3 percent to 8 percent slopes. On steeper slopes, runoff may concentrate in the furrows and if it breaks through may cause serious erosion. Contour cultivation on steep slopes must be supplemented by other methods.

Vegetation Cover

Well planned and managed vegetation cover can effectively control soil movement. Vegetation protects soil against erosion by reducing water movement and building soil structure. It also affects the soil surface, where running water does the most damage. Vegetation protects soils against erosion in a number of ways. First, it decreases the amount of rain reaching the soil by intercepting rainfall; the decrease was about 12 percent under forest canopy in a project in Indonesia. The decrease, of course, varies with the types of trees and management practices. Second, leaves break the initial erosive power of rain. (However, they may also increase the erosive power if drops concentrate and fall from greater heights.) Third, vegetation prevents the direct impact of rain on the soil, which reduces soil compaction and clogging of soil pores. Fourth, the increased formation of humus by vegetation improves soil permeability and structure, improving its capacity to retain moisture.

During natural fallow periods erosion rates tend to drop due to the formation of a layer of plant litter, invasion of weeds, and buildup of humus and organic matter. In planted fallow areas, on the other hand, erosion rates may increase. For example, in densely planted tree fallows, litter decomposes rapidly, natural ground covers will not grow due to excessive shade, and water flows freely over the land.

Removing the litter layer from under trees may increase erosion from 10 percent to 100 percent. But removal of the canopy without disturbing the litter layer affects the erosion rate by only about 0.3 percent.

A complete soil cover protects against erosion except on the steepest slopes. The most effective vegetation cover to control erosion is a multi-layered canopy of trees, shrubs, and ground cover. Multiple layers slow the impact of raindrops, increase rain flow over the stems, and increase the litter buildup. Where field crops are grown, cover cropping and intercropping help to control erosion.

Mulching

Mulching covers the soil with materials that reduce soil moisture evaporation and inhibit weed growth. Mulching slows rainfall infiltration and protects the soil from direct impact from rain. Mulches applied before the beginning of the rainy season can reduce soil erosion and runoff. Further, they build soil structure and protect soil from extremes of temperature.

A study in Nigeria showed 50 percent more soil lost from land with no mulch than from land with a mulch layer of 2 t/ha. A 5-cm layer of straw mulch almost eliminated erosion of bare soil. In any location, mulching is likely to control erosion and bring other benefits.

The best mulching materials have a high humus content, along with good infiltration rates and water storage capacity. The properties to look for in selecting mulches are listed below:

o Withstand the forces of runoff; stay in place o Last for several seasons; slowly decomposing o Allow water to percolate into the soil o Ease of application o Inexpensive; require low maintenance

Crop residues are an excellent local source for mulches, particularly if they are not required for other purposes, such as animal feed, fuel, and roofing materials. If limited supply and high costs are not a problem, crop residues should be tried. In addition to their ability to aid in erosion control, they add humus to the soil.

Cropping Patterns

Changes in the cropping pattern that will help reduce soil movement include intercropping, alley farming, use of grass strips, and pasture improvement. For example, conversion of cultivated land to grassland can reduce erosion by at least 10 percent. Producing feed crops for livestock presents an opportunity to integrate animal husbandry and erosion control. Producing sufficient fodder grasses reduces the need to graze animals; cutting and carrying feed may reduce the space needed by the animals and allow for more crop land. Alternating strips of protected plants (vegetables) with protective plants (fodder grasses) will trap suspended particles and reduce soil movement. It must be noted that the use of protective grass strips is effective only if grazing is avoided.

Crop rotation helps to preserve soil fertility. A rotation of one year of grain millet, wheat, etc.) followed by three to four years of legume pasture may be an excellent alternative to shifting cultivation. But introducing crop rotation often requires a change from traditional methods. The new system may require new markets, for example, as existing markets may change if grain crops are lost for a period of years. Farmers may be reluctant to adopt new cropping patterns without market incentives.

4. PHYSICAL CONTROL OF WATER EROSION

Effective control of erosion requires either a reduction of slope steepness (as in terracing) or of slope length. Both physical and biological interventions are effective, depending on soil character, slope, crop cover, and land-use practice. Frequently, a combination of interventions gives better results than applying just one measure.

Vegetation Strips

Vegetation strips are contour plantings of suitably spaced strips of perennial grasses or shrubs on sloping lands. The objectives are to reduce soil and water loss, reduce slope length, hold soils on the land, and eventually convert the barriers into benches. Dense vegetation strips will stop or slow runoff and will trap moving soil particles. It is important to give particular attention to the layers of vegetation; dense ground covers are more effective than vegetation with a high canopy of trees.

Research in Taiwan showed that vegetation strips work best on slopes of less than 45 percent. Spacing of strips is governed by the distance between crop rows and is normally not more than 8 meters. If strips are used with contour ditches, the distance between then can be increased.

Slope is the most important factor affecting the design of vegetation strips. Table 1 gives approximate dimensions. For grass barriers use fresh cuttings; plant two or three cuttings on each hill; plant 2 close rows to form one grass barrier. The second row should be planted to cover the gaps in the first row so that the plants in the two rows form a triangular pattern.

Table 1 Estimated Spacing Between Grass Strips

In areas where the annual rainfall is 60 to 100 cm, strip width and distance between strips should be increased 20 percent and 10 percent, respectively. With more than one meter of rainfall, increase Width by 50 percent and Distance by 20 percent.

Slope, Width Distance between percent of strips, m strips, m 10 5 43 20 8 38 40 13 28 60 20 20 Source: Weber & Stoney, 1986

Horizontal Hedgerows

Horizontal hedgerows may be the simplest physical structure for controlling erosion on steep slopes. To form a hedgerow, plant single or double rows of perennial grasses or fast-growing trees along the contours to block runoff and catch rolling or suspended soil particles. First, mark the contours and set stakes every three to seven meters. Plow the soil along each marked contour into a furrow and remove the weeds before planting seeds, seedlings, or fresh grass cuttings.

The spacing of hedgerows depends on the slope of the field. The average difference in elevation between hedges should not exceed 1.5 m, or about the distance between your eyes and your feet. As the slope increases this distance decreases. Plant seedlings and cuttings no further apart than 15 cm. Wide spacing between trees or grass on a contour will concentrate erosion in the gaps, forming rills and perhaps washing away the young plants.

Only after the seedlings are well established should they be thinned. Remove the weak or small seedlings leaving not more than 6 to 10 cm separating the plants. When trees reach a height of 2 m, prune them back to about 0.5 m (knee height). Trees are pruned to reduce shading of crops, encourage coppicing (regrowth), and produce products needed by the household.

After two to seven years, terraces will develop as twigs, stones, and weeds are trapped on the uphill side of each hedgerow.

Sloping Agricultural Land Technology (SALT)

SALT, developed in the Philippines, has become well accepted by farmers to conserve soil and water. The technology includes a system of diversion ditches, canals, waterways, and check dams or soil traps on steep lands for erosion control. Figure 1 illustrates the layout and design of an erosion control system using diversion ditches, contour canals, and drainage waterways.

Diversion ditches, the first line of defense for controlling runoff, are designed to prevent runoff from entering the field. The depth and size of a diversion ditch depends on the slope and depth of soil. In general diversion ditches are one meter wide and one meter deep. The soil from within the ditch is placed just below the ditch where possible and planted with trees.

Contour canals control runoff within crop fields. They are constructed in parallel lines across the slope of the land. A slight gradient encourages surplus water to flow to collection points. On deep soils with adequate percolation, canals are constructed flat to hold water in the canals and increase soil-moisture retention. Contour canals are typically one-half meter wide and one-half meter deep. Wider canals can be lined with grasses. Soil removed in construction of canals is placed on the downslope side just outside the canal and planted with trees or fodder grasses.

Drainage waterways are catchments for water collected in the drainage ditch and contour canals. They concentrate runoff from the fields into constructed and managed channels. The major objective is to provide safe outlets for runoff and prevent soil erosion. The recommended dimensions of a drainage waterway are one-half meter wide and one meter deep. Side walls should slope outward to reduce erosion. Waterways are lined with grass or stone to slow water movement and soil loss. The distance between waterways depends on the slope of the land and the amount of water expected, but is usually less than 100 meters, measured along the diversion ditch. When possible use natural drainage areas; water naturally moves to these places and it will reduce construction costs.

Soil traps, constructed within waterways to capture suspended soil particles, are 1 m by 1 m pits placed every 35 meters within the waterway. The trapped sediment is a source of nutrient-rich soil to put on crop fields. If soil conditions prohibit construction of soil traps, check dams can be built that slow water movement and catch suspended soil particles. Check dams can be constructed from field stones, fresh branch cuttings from local trees, sticks, or crop residue. Branch cuttings from some trees will sprout and form live barriers serving several purposes by holding subsoil with their roots, producing needed products such as fuelwood, and catching suspended soil particles. Sticks and crop residues used as the main part of check dams will decay and provide only short-term solutions to trapping suspended soil particles.

The steps in laying out a SALT system are as follows: first, mark the location of the diversion ditch. Then locate and mark the contours, about 1.5 m downslope. Remove the soil from the diversion ditch, placing it just below the ditch and planting it with fast growing trees or grasses. Build the contour canals in the same manner, with a slope of 0.5 percent to 1 percent. Build the drainage waterways, planting them with grasses or lining them with stones. Finally, dig soil traps or build check dams.

Stone Walls

Where stones are available, stone walls can be built to reduce soil and water loss and gradually produce terraces. Walls minimize the length of slopes and removing the stones from the field facilitates soil cultivation. Figure 2 shows the cross-section of a stone wall. The outside walls lean into the hillside, while inside walls are almost vertical. The top of the wall should be about 30 cm across and the bottom about one meter. The distance between stone walls is determined the same way as contour canals. To construct a stone wall, first determine and mark the contours with an A-frame level. Excavate the soil to a depth of 30 cm, forming a flat base. Select the largest rocks to form the foundation and outside face. If the wall is built after a terrace has been formed by erosion, limit its height to 30 cm.

Terraces

Terraces are nearly-level strips built along contours. Their main purpose is to intercept runoff and control erosion. Terraces control erosion in many ways. They segment fields into small separate drainage areas and reduce the length of the slope. Runoff and its damage are reduced. Water is conserved on the field or moved off in a controlled manner. Terraces reclaim eroded lands and provide continuous protection of the reclaimed lands. In general, terraces are suitable on slopes up to about 50 percent. Level terraces are best on narrow slopes; outward sloped terraces are designed for steep land.

Unless labor is plentiful, the main constraint of constructing terraces is their very high labor cost. Despite this, terraces are the best means of soil conservation on cultivated lands.

The amount of topsoil is a factor when designing terraces. To ensure that the terrace can be filled, the amount of topsoil should be not less than half the height of the riser. The riser should lean into the slope a little and the length should not exceed 100 meters. Terrace width varies from 2 to 5 meters, depending on several factors: slope, depth of soil, crop spacing, and farm operations.

To determine the Vertical Interval use the formula:

D x S VI = Vertical Interval (m) VI = ----- D = Width of Terrace (m) 100 S = Slope of Field ( percent)

Slope is calculated by:

|r
|i
rise |s S = ---- x 100 ---------------|e run run

Sample results are illustrated in Table 2. The spacing in this table may be adjusted for the type of crop and the farming practices. In the case of pasture grasses, with permanent cover, ditches can be spread further apart.

To construct terraces, first survey the area and develop a management plan. Starting with sites that have uniform slopes, determine and mark the contour lines: place the first row of stakes at the top of the slope; walk downhill to the next contour line; set stakes about 3 to 7 meters apart. Clear the land of weeds, shrubs and trees and other obstacles. Finally, cut and fill starting at the bottom contour line; be sure to compact each filled area.

Table 2 Spacing of Flat-Based Terraces at Various slopes

Slope, Spacing Between Ditches (m) percent Vertical Interval Horizontal Spacing

5 1.1 22 10 1.6 16 20 2.6 13 40 4.6 11.5 55 6.1 11.4

Source: Liau & Wu, 1987

Figure 3 illustrates three different types of terraces. The formula above can be used to calculate the vertical distance between terraces for each of the three types.

The most important type of terrace for semi-arid regions is the flat channel terrace, sometimes known as the Zingg conservation bench. In Figure 4. the vertical interval (VI), in meters, between Zingg terraces is calculated by:

VI = 0.25 x S + 0.30 VI = Vertical Interval (m) S = slope ( percent)

An A-frame level is a simple, inexpensively built tool to use for mapping contours (Figure 5). To build one, use rope or vines to securely fasten three poles or bamboo pieces to form a rigid letter "A" 2 m high and 1 m wide at the bottom. Tie string or twine to the joint of two <FIGURE> long sticks and tie a rock or weight to the lower end so that it hangs below the cross-piece of the A.

To calibrate the A-frame level (this needs to be done only once), stand it on level ground and place a stake at the base of each leg. Mark the crosspiece where the string passes it. Then reverse the leg positions of the A-frame and put another mark where the string passes the crosspiece. Now put a permanent mark on the crosspiece exactly midway between the other two marks. In mapping a contour, the string should always pass over this control mark.

To use the A-frame to plot a contour canal below a diversion ditch, walk downhill from the ditch until you can look at the base of the ditch without raising or lowering your head. This is the location of the first contour line. Place the A-Frame on the contour line; set a stake at the base of each leg. Pivot the A-Frame on one leg until the string passes over the center mark. Set a stake at the base of the new leg position (Figure 7).

Continue to pivot, or "wall", the A-Frame across the slope setting stakes at the base of each leg as the string passes the center mark. If the string does not pass the center mark the A-Frame is not on the contour: adjust the placement of the forward leg until the string is in the table right place.

Below the first contour line mark the location for the next contour; measure the vertical distance the same way as described above. Continue this process until the entire field has been marked.

Control of Gully Erosion

Gullies are surface channels that have eroded to the point where the land cannot be smoothed by normal tillage practices. They form when large amounts of water accumulate and concentrate erosion in rills that deepen and form V-gullies or U-gullies, named for the shapes of their cross-sections (Figure 7).

Check dams, made of locally available materials such as rocks, stones, stakes, freshly cut branches, sacks of soil, can be built to shorten gully length and reduce runoff velocity. Areas above check dams fill with sediment and form terraces. The base of each dam should be level with the top of the next downhill check dam. The top of each dam should be concave to allow excess water to flow over its center and should extend past the sidewalls of the gully. Branches cut from some trees will sprout and form live barriers serving several purposes by holding subsoil with their roots, producing needed products such as fuelwood, and catching suspended soil particles. Impermeable check dams prevent water and sediment from moving downslope.

V-Gullies. V-shaped gullies form with downward cutting of the center of the channel. The gradient of the channel center is greater than the slope of the field. Typically, V-gullies deepen downslope and grow in length upslope. Water flows through V-gullies in small amounts but with high velocities.

V-gullies should be eliminated. If shallow, they can be filled with new soil. Immediate control measures are needed to assure that they do not re-appear. Other methods to control V-gully erosion include contour cultivation and strip cropping. A diversion ditch should be constructed around the top of the gully. Protect the outlets of diversion ditches from erosion. Construct permeable check dams within V-gullies to slow down the flow of water and catch sediment (Figure 8). The distance between check dams depends on slope and amount of runoff; make dams closer together on steep slopes.

U-Gullies. The flat bottoms of U-shaped gullies have slopes parallel to the slope of the land. Water flow is greater, but the velocity is much less than in V-gullies. Control starts at the points where they grow, the head (length) and sides (width). First, raise the bottom of the channel by constructing a series of permanent, impermeable check dams (Figure 9). Eventually, the area uphill of each check dam fills with sediment, raising the bottom of the U-gully. Reshape gully walls so that for every meter of rise one meter of horizontal distance is covered. Finally, stabilize the channel by planting grasses, vines, or shrubs.

5. CONTROL OF WIND EROSION

Strong wind detaches soil particles from the surface, transports them, and deposits them downwind. Two danger signs of possibly harmful wind erosion are sand buildup on the downwind sides of obstacles and sediment ripples in fields. Even in a short time, wind can blow away enough soil to greatly reduce soil fertility and crop yields. Wind may expose recently planted seed and prevent germination. The abrasive power of soil particles suspended in the wind can permanently damage small plants.

Loose, dry, and finely granulated soil particles are blown away more easily than heavier textured soils. Wind erosion is favored by sandy soils, smooth surfaces, sparse vegetation, open expanses of land, and strong or turbulent winds. Accordingly, control measures include increasing soil stability and surface roughness. Tillage can compress soils and smooth the surface, and should be limited to the adequate preparation of seed beds and the control of weeds. Conservation cultivation, particularly minimum tillage, is a practical method to stabilize soils.

Physical barriers should be perpendicular to the wind direction. A windbreak is a dense barrier of perennial tree crops and shrubs specifically designed to reduce wind speed for the benefit of annual crops (Figure 10). Well planted and well grown windbreaks can reduce wind velocity by as much as 70 percent to 80 percent near the barrier. Moreover, a windbreak can modify air temperature within the protected areas and conserve soil moisture by reducing evapotransporation. The relative humidity within the canopy on the downwind side increases. Another important side effect, especially if already-limited cropland must be taken out of production to plant the windbreak, is the fruit, fuel, nuts, or other produce of the trees.

The effect of a windbreak is proportional to its height. In general the reduction of wind velocity past the windbreak weakens and becomes negligible at a distance of 30 to 40 times the its height. The density of windbreaks also affects the decrease in wind velocity (Fig 11). A dense windbreak reduces velocity sharply and quickly. A windbreak that is too dense causes the wind velocity to recover in a shorter distance, thus reducing the length of the protected area. The most effective density is between 35 percent and 50 percent.

The distance between windbreaks (Figure 12) is critical, but varies with crops and soil stability. The best distance between barriers shielding forage crops is 10 to 14 times the height. In areas with highly erodible soils, strong winds, or sensitive crops (fruit or vegetables) the distance between windbreaks should be 5 to 10 times the height of the barrier. For moderately responsive crops (wheat, rye, oats, etc.) the distance is extended to 15 to 25 times the height of barriers.

Windbreaks should extend the total length of the field and run perpendicular to the wind direction. Gaps or breaks will accelerate wind through them and increase erosion; allowance for necessary pathways or stock crossings should be made on the diagonal (Figure 13). Windbreaks not perpendicular to wind direction will channel wind along the barriers. The best shape for windbreaks is created by multiple rows of trees, but this takes more land out of crop production. Local tree species that send deep tap roots and develop narrow crowns are best.

To keep windbreaks viable it is essential to maintain the vigor and growth of the trees by thinning and cutting when necessary.

6. PLANNING FOR EROSION CONTROL

Individually, the control measures discussed above reduce runoff and slow erosion under specific conditions. However, maximal control of erosion is achieved through planned activities that use a variety of control measures. Effective planning involves selecting and developing the best course of action to reduce or halt the movement of soil from crop fields while maintaining farm productivity.

It is essential first to collect all available data about the land. Critical information for land use planning includes soil depth, soil type, drainage characteristics, and slope of the land. A field survey should assess the target area for the severity of erosion; consider the extent of sheet erosion, the space between rills, and the type and spacing of gullies; and determine the texture class of the soil. The field survey also should consider the abundance of stones; the consistency, structure, and stability of the surface; and soil reaction, salinity, and drainage. Frequency, duration, and intensity of rain and wind should also be noted.

In addition, the survey should look at tillage and animal husbandry practices in use, and the resources farmers have available to make necessary changes. In this regard, it is important to engage the farmers' interest and participation by assuring that they are intimately involved in the survey and planning process.

The practices selected to control erosion should be based on a combination of principles. First, the practices should maintain soil infiltration rates at high levels to reduce runoff to negligible amounts. Examples are mulching and vegetation cover. Second, they should safely dispose of runoff from the field. Such physical structures as hedgerows, contour canals, stone walls, and terraces are used for this. Finally, practices must be within the means of farmers to implement and maintain, or they will not be continued more than a season or two.

SOURCES OF INFORMATION (FURTHER READINGS)

Addresses are in the United States unless otherwise stated.

El-Swaify, S.A., Moldenhauer, W.C. and Lo, A. (eds). Soil Erosion and Conservation. Proceedings of an international conference held in Honolulu, Hawaii, January 16-22, 1983. Ankeny, Iowa: Soil Conservation Society of America, 1985.

United Nations. Food and Agriculture Organization. Guidelines for Watershed Management. FAO Conservation Guide No. 1. Rome (Italy): FAO, 1977.

Finkel, H.J., Finkel, M., and Naveh, Z. (eds.) Semi-arid Soil & Water Conservation. Boca Raton, Florida: CRC Press, 1986.

Follet, R.F. and Stewarts, B.A. (eds.) Soil Erosion and Productivity. Madison, Wisconsin: American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 1985.

Greenland, D.J. and Lal, R. Soil Conservation and Management in the Humid Tropics. New York: Wiley, 1977.

International Institute of Rural Reconstruction. Agroforestry Technology Information Kit, the output of a workshop (texts and illustrations) November 4-13, 1989. New York: IIRR (Room 1270, 475 Riverside Drive, New York, New York 10115), 1990.

Joint commission on Rural Reconstruction. Soil Conservation Handbook, rev. ed. Taipei (Taiwan): Food and Fertilizer Technology Center, 1987.

Liao, Mein-Chun, and Wu, Huei-Long. Soil Conservation on Steep Land in Taiwan. Taipei, (Taiwan): The Chinese Soil and Water Conservation Society, 1987.

MacDicken, K.G. and Vergara, N.T. Agroforestry: Classification and Management. New York: Wiley, 1989.

Moldenhauer, W.C. and Hudson, N.W. (eds). Conservation Farming on Steep Lands. Proceedings of an international workshop, San Juan, Puerto Rico, 22-27 March 1987. Ankey, Iowa: Soil and Water Conservation Society, 1988.

O'Loughlin, C.L. and Pearce, A.J. Symposium on Effects of Forest Land Use on Erosion and Slope Stability. Proceedings of a symposium held in Honolulu, Hawaii, May 1984. Honolulu: East-West Center, 1984.

Pearce, A.J. and Hamilton, L.S. Water and Soil Conservation Guidelines for Land Use Planning. Report of a seminar. Honolulu, Hawaii: East-West Center, 1986.

Schiechtl, H.M., and Michaelson, T. FAO Watershed Management Field Manual; Vegetative and Soil Treatment Measures. FAO Conservation Guide 13/1. Rome (Italy): Food and Agriculture organization of the United Nations, 1985.

Weber, F.R. with Stoney, C. Reforestation in Arid Lands. Arlington, Virginia: Volunteers in Technical Assistance, 1986.

TECHNICAL PAPER #12

UNDERSTANDING POULTRY MEAT AND EGG PRODUCTION

By Dr. H.R. Bird

Technical Reviewers Leonard Z. Eggleton Ralph Ernst Herman Pinkston

VITA 1600 Wilson Boulevard, Suite 500 Arlington, Virginia 22209 USA Tel: 703/276-1800 . Fax: 703/243-1865 Internet: mailto:pr-info@vita.org

Understanding Poultry Meat and Egg Production ISBN: 0-86619-212-3 Volunteers in Technical Assistance

PREFACE

This paper is one of a series published by Volunteers in Techni- cal Assistance to provide an introduction to specific state-of-the-- art technologies of interest to people in developing countries. The papers are intended to be used as guidelines to help people choose technologies that are suitable to their situations. They are not intended to provide construction or implementation details. People are urged to contact VITA or a similar organiza- tion for further information and technical assistance if they find that a particular technology seems to meet their needs.

Dr. H.R. Bird, the author of this paper, is a professor emeritus and former chairman of the Department of Poultry Science at the University of Wisconsin. He has taught poultry nutrition, feeding, management, and general animal nutrition at the Universities of Wisconsin and Maryland. He has also consulted on these topics in Brazil, Indonesia, Belize, and Nepal. Leonard Z. Eggleton is the Chairman of Agricultural Projects with the Iowa-Yucatan Peninsula Partners project at Iowa State University. He has consulted on poultry in Uruguay and Mexico. Ralph Ernst is a Poultry Specialist with the cooperative extension program of the Department of Avian Sciences, University of California at Davis. He has worked with game bird, duck, and turkey producers. Herman Pinkston is a returned Peace Corps Volunteer who worked in animal husbandry in the Philippines, which included developing a vaccine program for poultry, engaging in incubation of eggs, and raising swine.

UNDERSTANDING POULTRY MEAT AND EGG PRODUCTION

By VITA Volunteer Dr. H.R. Bird

I. INTRODUCTION

Since ancient times, chickens, ducks, and geese have served farming communities by gleaning the fields of grain that other- wise would be lost; picking up grain that is dropped by the wayside in threshing, drying, and transportation; making produc- tive use of the scraps from the family table; and, supplementing those feed items by foraging for grass, weed seeds, and insects. With such a diet these animals are able to produce eggs and meat, which provide protein of high quality plus several essential vitamins and mineral elements. Eggs and meat are ideal supple- ments for the cereal grains, tubers, and roots that provide much of the energy in many human diets.

Besides being recoverers of waste grain and users of scraps and by-products, poultry can function to provide a food reserve. Any farming community that can do so would like to produce more grain than the people need. Maybe the excess can be sold; but, if not, it can be fed to poultry. Then if there is decreased production of grain in a certain year, the poultry flock can be decreased instead of decreasing the grain that is supplied to the people.

Small flocks of poultry--from a few birds to a few hundred--were the rule all around the world, until the 20th Century. In the early 1900s, flocks numbering in the thousands began to appear in North America and Europe. In the 1920s and 1930s, geneticists, nutritionists, physiologists, and disease specialists developed improved breeds and strains of chicken and improved methods of feeding and managing them and protecting them against disease. The rapid introduction of new technologies so increased the efficiency of producing eggs and poultry meat that costs to consumers went down at a time when prices for most other consumer goods were climbing.

This paper addresses the following important questions to help you decide whether poultry raising is for you:

* How can poultry flock owners in developing countries take advantage of modern technology?

* Is it better to use native birds or import improved modern strains?

* Is it possible with local feedstuffs to approximate the composition and the efficiency of feeds based on corn (maize) and soybean meal?

* Can vaccines, coccidiostats, antibiotics, vitamins, and mineral supplements be imported economically? Can any of them be made locally?

* Is it possible to make feeding and watering equipment, cages, and nests locally?

II. POULTRY PRODUCTION: VARIATIONS AND ALTERNATIVES

FREE-RANGING POULTRY VERSUS CONFINED POULTRY

When one thinks of free-ranging poultry that find their own food, require no care, and provide food for the family table, one sees obvious advantages. However, there are disadvantages too. Most communities that take a serious interest in their poultry, practice some degree of confinement.

Letting poultry range freely is an economical way to provide them with feed. On the other hand, it exposes them to predators. Moreover, they cannot be guaranteed a balanced diet from just foraging. To achieve a well-balanced diet, they must be periodi- cally supplemented with hand-fed food.

Free-ranging poultry are not crowded and therefore may be less susceptible to disease, but Newcastle disease--a virus that often plagues poultry--can exterminate even a free-ranging population and the protozoa that cause coccidiosis live everywhere that chickens live. Regardless of whether they are confined or free-ranging, chickens must be vaccinated or medicated against these diseases as well as many others. It is much easier to vaccinate and treat confined flocks. Free-ranging poultry do require less labor than confined poultry, but in finding waste feed and pools of water they are more likely also to find parasites, bacteria, and molds.

Free-ranging poultry incubate their own eggs and thus reproduce themselves, but they may lay eggs in unexpected places so that some are lost. Furthermore, the process of becoming broody and incubating eggs decreases the rate of egg production. Genetical- ly improved laying strains are non-broody and often will not incubate their own eggs.

Confining poultry and providing sanitary feeders and waterers have a number of advantages:

* better control of diseases;

* protection from predators;

* more efficient collection of eggs; and

* easier access to poultry.

The disadvantage of confinement is that poultry can neither glean nor forage. In the Orient, to overcome this problem, poultry attendants drive their flocks of ducks to the rice fields and then return them to their living quarters. Similarly, a flock of chickens can be confined in a house and yard next to a threshing floor, for example, and let out when there is grain to recover. Particularly when birds are confined, poultry production can be a successful enterprise. There are three distinct production systems to consider, and each has gone through dramatic changes. These systems are designed to produce chicken eggs, chicken meat, and duck meat. There have not been parallel developments in goose production. Most geese are still kept in small flocks and depend on grazing and gleaning for much of their feed.

The changes in the system involve changes in the birds them- selves, in their feed, in disease control (vaccines, medicines, sanitary practices) and in equipment and management.

THE BIRDS

What kinds of birds are best for the enterprise? This is the first question the small producer (200 birds or less) will have to answer. In many parts of the world there are varieties of local birds that have been selected, to some degree, for better production of eggs and meat. There are also available, in most areas, chicks of egg strains and meat strains that have been developed by selection and strain crossing in North America, Europe, Japan, and Australia. Imported strain crosses are always more productive and more uniform than improved local breeds. But they are also more expensive and cannot reproduce themselves. Flock owners must continue to buy chicks, for as long as they use this kind of stock.

Unfortunately, there appears to be no published information on the levels of productivity available with local breeds of chick- ens, given the advantages of modern feeds, sanitation and management. Such birds are kept in small confined flocks for egg production, and both floor pens and battery cages are used for this purpose. It is important to cull such flocks to eliminate the poor egg producers. The comb and wattles of a good layer are large, soft, warm, and red. The vent is enlarged and moist and the pubic bones are spread apart. They can be felt, to the right and left of the vent. A poor layer or non-layer will have shrunken, pale, dry comb and wattles, a small dry vent and closely spaced pubic bones.

Commercial production of eggs and broilers, with flocks numbering in the thousands, is now widespread and depends entirely on strain crosses rather than local varieties. Reports from India and Pakistan emphasize the importance of imported strain crosses in the development of their commercial production in those countries.

The establishment of a small flock of ducks is not likely to involve the same choices as in the case of chickens. In most situations one would have to depend on locally available stock of a local strain.

FEED

Poultry feeds usually consist of combinations of energy and protein sources, which make up 90 percent or more of the total feed. The remainder of the feed consists of calcium and phos- phate supplements and salt, which make up two to eight percent; and trace mineral, vitamin, and amino acid supplements, which make up one or two percent, or sometimes more. In the United States, for example, a feed would consist of corn (maize), which is an excellent energy source and supplies some protein; soybean meal, which is a very good protein source and supplies some energy; limestone (for calcium); dicalcium phosphate (for phosphorus and calcium); salt; methionine (an amino acid not abundantly provided by soybean meal); and trace mineral and vitamin supplements. Trace mineral and vitamin supplements are shipped all over the world, and are priced so low that they usually are not major cost items. Cereal grains and legumes, unlike mineral and vitamin supple- ments, are costly to produce and often in short supply in many developing countries. Due to their scarcity and to the competi- tion with human food supplies, their use for poultry feed in the Third World is usually kept to a minimum.

We noted above that poultry served early farming communities by utilizing scraps and otherwise wasted food materials. Modern poultry can also utilize by-products of food processing. There is a prevalent notion that modern high-producing strains of poultry must have modern high-protein, high-energy diets. The modern chicken still functions well on by-product diets even though it is descended from many generations of ancestors that were fed high energy, high protein corn-soy diets. To illustrate, strain- -cross layers in an experiment at the Univeristy of Wisconsin maintained 67 percent of egg production on the following diet:

Rice bran 90.0 percent Fish meal 1.0 percent Alfalfa meal 1.0 percent Ground limestone 5.4 percent Iodized salt 0.5 percent Dicalcium phosphate 1.0 percent Methionine hydroxy analogue 0.1 percent Vitamin trace - mineral 1.0 percent supplement Free choice limestone grit ---

The vitamin-mineral supplement provided, per kilogram (kg) of diet: 6000 International Units (I.U.) of vitamin A, 900 Interna- tional Chick Units (I.C.U.) of vitamin D3, 22 I.U. of vitamin E, 10 milligrams (mg) of riboflavin, 0.7 mg of folic acid, and 200 mg of zinc carbonate.

Costa (1981) observed good performance with a broiler starter feed of the following composition:

Rice bran and polishings 32.5 percent Grain sorghum 30.0 percent Soybean meal, solvent process 17.0 percent Meat and bone meal 15.0 percent Molasses 4.0 percent Salt 0.5 percent Vitamin-trace mineral supplement 1.0 percent

The vitamin trace mineral supplement provided, per kilogram of diet: 8000 I.U. of vitamin A, 1000 I.C.U. of vitamin D3, 5 I.U. of vitamin E, 6 mg of menadione sodium bisulfite, 4 mg of ribo- flavin, 30 mg of niacin, 12 mg of d-pantothenic acid, 301 mg of choline chloride, 20 micrograms of vitamin B12, 100 mg of BHT, 70 mg of zinc (as zinc oxide), 50 mg of manganese (as manganous oxide), 0.25 mg of iodine (as ethylene diamine dihydroiodide), 50 mg of iron (as iron sulfate), and .10 mg of selenium (as sodium selenite).

The two formulas given above are examples of poultry rations that would be economically feasible in some areas. It is beyond the scope of this report to provide formulas for a wide range of circumstances or to present a treatise on feed formulation. Table 1 gives the requirements of different classes of poultry for energy, protein, calcium, and phosphorus; and Tables 2 and 3, respectively, give the levels of these nutrients in various feed ingredients and mineral supplements. Using this information, one could calculate formulas to supply these four nutrients. One almost always has to add 0.5 percent of salt (NaCl); since most ingredients do not supply it. One must also use a vitamin-trace mineral supplement similar to the one used for adult birds or for young growing birds in the two diets presented earlier.

Table 1. Nutrient Requirements of Broilers, Laying Hens, Growing Ducks, and Growing Geese

Metabolizable Type of Energy Protein Calcium Phosphorus Poultry (kcal(*)/kg) (Percent) (Percent) (Percent)

Starting broilers 3200 23.0 0.9 0.7

Laying hens 2850 15.0 3.25 0.5

Growing ducks 2900 16.0 0.6 0.6

Growing geese 2900 15.0 0.6 0.4

----------------------

(*) Kilocalorie: a unit of heat energy equal to 1,000 calories.

Table 2. Composition of Feed Ingredients (as fed)

Metabolizable Crude Type of Feed Energy Protein Calcium Phosphorus Ingredient (kcal/kg) (Percent) (Percent) (Percent)

Dehydrated alfalfa 1370 17.5 1.44 0.22 (lucerne) Barley 2640 11.6 0.03 0.36 Beans, field 2300 23.0 0.13 0.6 Brewers' grains 2080 25.3 0.29 0.52 Cane molasses 1960 7.8 1.10 0.12 Cassava meal ---- 2.6 ---- 0.03 Coconut (copra) meal 1773 20.7 0.21 0.62 Corn (maize) 3430 8.8 0.02 0.28 Cottonseed meal, solvent process 2400 41.4 0.15 0.97 Crab meal 1819 31.4 15.0 1.57 Distillers' grains with solubles 2480 27.2 0.17 0.72 Fish meal 2820 60.5 5.11 2.88 Meat and bone meal 1960 50.4 10.1 4.96 Millet ---- 12.2 0.05 0.28 Mustard seed meal ---- 31.9 ---- ---- Palm nut meal ---- 18.2 ---- 0.68 Peanut (groundnut) meal, solvent process 2200 50.7 0.20 0.63 Poultry by-product meal 2670 58.0 3.0 1.7 Rapeseed meal, expeller process 2040 35.0 0.72 1.09 Rice bran 1630 12.9 0.07 1.50 Sesame meal, expeller process 2210 43.8 1.99 1.37 Sorghum grain 3370 8.9 0.03 0.28 Soybean meal, solvent process 2230 44.0 0.29 0.65 Sunflower seed meal, solvent process dehulled 2320 45.4 0.37 1.0 Sweet potato meal ---- 4.9 0.15 0.15 Wheat, soft 3120 10.2 0.06 0.31 Wheat bran 1300 15.7 0.14 1.15 Wheat middlings 1800 16.0 0.12 0.90

Table 3. Composition of Mineral Supplements

Type of Feed Calcium Phospho- rus Ingredient (Percent) (Per- cent)

Bone meal 29 12.6

Defluorinated phosphate 32 18

Dicalcium phosphate 21 8.5

Limestone 38 0

Oyster shell 38 0

By-product feeds vary greatly depending on the method of process- ing. Processing methods are well standardized in developed countries, but may be highly variable in developing countries. The resulting products may also be highly variable and quite differ- ent from those listed in Table 2.

Some feed ingredients have special disadvantages that must be noted. Cottonseed meal contains gossypol, which discolors egg yolks and inhibits growth of young birds. Cooking the meal during processing decreases the free gossypol and results in a product that is usually satisfactory for growing birds but may still discolor yolks. Mustard seed meal contains a growth inhibitor and should not represent more than five percent of the diet. Rapeseed meal contains a goitrogenic compound that interferes with thyroid function, and also should not represent more than five percent of the diet, unless improved strains of the plant are used.

Soybeans contain an inhibitor of one of the important amino acids, trypsin, which, interferes with digestion but can be destroyed by cooking. The processing of soybean meal is now so well standardized that this inhibitor is seldom a problem.

To know whether soybean meal is cooked thoroughly enough, follow this simple procedure:

* Place 10 teaspoons (about 30 grams) of the meal in a small jar with a tight lid.

* Add 1 teaspoon (about 4 grams) of fertilizer grade or feed grade urea and 5 teaspoons of water.

* Stir the contents and cover the jar with the lid.

* Wait 20 minutes. Sniff for the odor of ammonia.

* If ammonia is present, the soybean meal contains the enzyme urease and has not been heated enough.

Field beans (navy, pinto, kidney, etc.), like soybeans, contain a growth-inhibiting material which can be destroyed by cooking.

The information provided here is intended to help in evaluating the feasibility of starting a poultry production enterprise as an important source of food and income. Now you must ask yourself: What feeds are available locally, at what volume, and at what price? Are they, or substitutes, available year round? Can they be combined to make a suitable formula, or will other ingredients have to be shipped in from other areas? If you are considering a medium-sized or large-scale operation, you should get local feed ingredients analyzed. The final test of the quality of the ingredients and the formulation is how well the poultry perform.

DISEASE CONTROL

No poultry business can succeed very long unless measures are taken to control diseases. With this in mind, here are some general guidelines that will help in maintaining a healthy flock:

* Feeding poultry a well-balanced diet will prevent them from developing deficiency diseases. To illustrate how important this is, note that a marked deficiency in the ration may retard growth, decrease the rate of egg production, and lower resistance to infections.

* Whether your poultry flock is large or small, it is a good idea to keep it separated as much as possible from other poultry. Do not encourage visitors. Do not "change help" with neighbors who have poultry. Do not buy adult or half-grown birds and add them to your flock. If a flock is purchased, birds should be isolated for a period of 5 to 15 days for observation. Raise young birds separately from mature stock.

* When selling birds, empty the poultry house completely. Clean it thoroughly, wash with a disinfectant (e.g., lye), and let it stand empty for four weeks before putting in new birds.

* Provide your poultry with clean, sanitary waterers and feeders, and well-ventilated houses.

* For birds housed in floor pens, provide litter such as wood shavings, straw, sawdust, rice hulls, or similar materials. Provide sufficient ventilation to keep the litter dry enough so the birds can scratch in it. It should not be wet or sticky.

* If your birds are housed in cages, the cages should be constructed with a slatted bottom to allow manure to fall through to the floor. For small numbers of birds, the manure can be collected in pans, which must be scraped and cleaned once or twice each week. The manure can be composted and used to fertilize your crops or sold as fertilizer. The sale of recycled manure can be an important source of income. For large flocks, the cages are arranged so that the manure falls on the ground or floor where it can be allowed to accumulate for several months or possibly even one year. Longer periods of accumulation are possible in dry rather than humid climates. If manure becomes wet, fly breeding may occur. This is usually best controlled by weekly removal and processing (drying, composting, etc.) of manure. It may also be necessary to add an insecticide to the manure under the cages to prevent development of flies. Local authorties should be consulted to learn which pesticides are permitted.

Table 4 presents a general vaccination and medication schedule for chickens. It is not necessary to follow the entire schedule at all times in all locations. In tropical areas, it is safe to assume that Newcastle virus is present and to vaccinate against it. Furthermore, the strains of the virus that occur in the tropics are commonly more virulent and more damaging than those in temperate areas. Therefore it is sometimes recommended that poultry farmers use a Newcastle vaccine produced locally rather than an imported product.

Fowl cholera and fowl pox are two common diseases found all over the world, but this does not necessarily mean that they are prevalent in your areas. So, inquire first before starting a vaccination or inoculation program. Fowl pox is caused by a virus; fowl cholera is caused by a bacterium.

As shown in Table 4, vaccines are available against infectious bronchitis and Marek's disease. Both of these are caused by viruses, but are less likely to cause trouble than Newcastle disease, fowl cholera, or fowl pox.

The microscopic protozoan organisms that cause coccidiosis are present wherever there are chickens. Young chickens encounter these organisms early in life and may show bloody diarrhea, weight loss, sluggishness, and ruffled feathers. The number of deaths may be few or it may be many. Most survivors will recover and carry some degree of resistance to the organism thereafter. Drugs known as coccidiostats protect against this disease and are widely available. Maintenance of dry conditions in pens will minimize this disease.

Chickens kept on the ground or in floor pens are always exposed to intestinal worms (ascarids). Chickens may carry considerable numbers of the parasites without showing disease symptoms, but a heavy infestation decreases egg production.

Ducks are affected by fewer diseases than chickens. They may harbor roundworms and tapeworms without showing symptoms. Such infestations may cause problems if ducks have access to stagnant water or muddy, poorly drained soil.

If disease is suspected, it is desirable to seek expert advice, including diagnosis and possible post-mortem examination.

EQUIPMENT AND MANAGEMENT

During its first week of life, a baby chick should have access to a brooding area at a temperature of 32 to 35[degrees]C. After the first week, the temperature can be decreased 2 to 3[degrees] each week. The typical small square poultry house is about six or seven meters on a side. It will house 400 broilers or 100 layers. Early attempts to increase the size of poultry farms were achieved by increasing the number of houses, but it was obviously more labor-efficient to increase the size of the house. However, even in temperate climates with moderate rainfall it is difficult to ventilate a house that is more than 13 meters wide. For the humid tropics, 10 meters is probably the limit. The length is limited only by the topography of the land or the poultry owner's bank account. In the tropics, the house may well be open on one or both sides except for wire netting or woven wire. A house open on both sides should be equipped with a canvas that can be pulled up or let down on the windward side in order to prevent drafts at night and during storms. The house should be closed at both ends, and it should have a floor and a gable roof, which should provide at least 0.8 meter of overhang on each side. A covered opening at the peak of the roof can be used to provide ventilation.

Roosts are not required but are often preferred to make upkeep easier. A laying house that has a solid wall on one side may have a row of roosts arranged against the wall. The front, or lower, row should be about 0.8 meters above the floor. Two or more additional rows of roosts go between it and the wall, with each roost slightly higher than the one in front. The area under the roosts may be closed with wire netting to prevent access by the chick- ens. It then serves to collect most of the droppings without giving the chickens access to them.

If both front and back of the house are open, movable roosts may be provided along the center line of the house, or to the front or back. If the house is more than about 20 meters long, nests can be installed not only along the ends but also along parti- tions.

Nests should be about 30 centimeters (cm) square and 30 cm high. They are usually arranged in rows two to three tiers high. There should be a perch below the entrance of each nest, and the lowest row of nests should be about 0.5 meter above the floor. There should be about one nest for every four layers.

Nests for ducks should be on the floor, one nest for each four or five birds. Partitions between nests are 30 cm by 35 cm. They are fastened at 28-cm intervals to a 15-cm board at the back along the house walls and have a 5-cm board along the bottom front. This leaves the top and front open.

Feeding troughs can be made of bamboo, wooden boards, pottery, or metal. Mechanical feeders are available for large flocks. Water- ers can be made from bamboo or from recycled glass or metal containers, or automatic watering devices may be purchased. Allow 3 cm of feeder space per chicken in the first three weeks of life, then 5 cm until they are eight weeks old, and 9 to 10 cm after that. A feeder 100 cm long provides 200 cm of feeder space.

In temperate and subtropical zones, it is customary to provide artificial light for layers. A 14-hour day is optimal for egg production. This may not be necessary in equatorial regions. In Java, for example, strains imported from the United States achieve the same annual egg production without lights as they do in the United States with lights. Day length varies by only a few minutes throughout the year in Java. However, at the latitude of Delhi, India, day length varies annually (from 10 hours 20 minutes to 13 hours 57 minutes) and artifical lighting is beneficial.

LABOR REQUIREMENTS

In every poultry house, cleaning and refilling waterers and feeders should be the first maintenance task in the morning. Clean waterers every day, whether they are automatic or handfill- ed. If they are hand-filled, they must be filled often enough so that water is always available. Feeders should never be empty, but they should not be overly full either. Adding feed frequently encourages the birds to eat and prevents waste.

In a laying house, eggs should be collected at least four times a day: morning, noon, afternoon and late afternoon. Making a second collection in the morning would be even better.

The following additional daily chores are recommended:

* Dispose of dead birds.

* Observe nest boxes. Clean when necessary. Add litter.

* Remove wet litter around waterers.

* Observe height of feed hoppers. Edge of trough should be at level of birds' backs. Adjust when neces- sary.

* Add limestone or oyster shell to hoppers when needed.

* Sweep down wire netting.

* Watch for evidence of rodents, and eliminate them.

* Add disinfectant to foot bath or pad at entrance to house.

* Watch for sick birds.

* Observe condition of litter. Stir when necessary, perhaps weekly.

* Observe light bulbs. Clean when necessary.

* If electric fans are used for ventilation, clean blades and oil motor.

The following are recurring specialized jobs that require extra help:

* Distribute day-old birds in the house. * Move pullets from growing house to laying house. * Catch broilers (or old hens) and send them to market. * Vaccinate against poultry diseases.

Thirty years ago in the United States, two hours per year of labor were required for each laying hen kept, and one hour of labor for each pullet raised. Now it is customary to calculate about seven minutes per year of labor for each laying hen and four or five minutes for each pullet raised. This dramatic change resulted from mechanization, larger flocks, the change from floor pens to laying cages, and some miscellaneous improve- ments in the organization of the operation. In many parts of the world, existing economic and social structures favor labor-inten- sive rather than capital-intensive operations. In those situations, the labor requirement will lie somewhere between the extremes indicated.

CARE OF EGGS AND MEAT

Gather eggs several times each day (see section on "Labor Re- quirements"). Clean eggs with a clean, damp cloth or in an egg washer. If an egg washer is used, the water should be slightly warmer than the temperature of the eggs and should contain a detergent-sanitizer. Eggs should be as fresh as possible when consumed or sold. For whatever time they are held before use, they should be placed small end down in a cool place, preferably a refrigerator.

Kill chickens the same day the meat is to be used unless a refrigerator is available to keep the meat from spoiling. To kill chickens, hang them by their feet and cut across the veins in the throat with a sharp knife. Let all of the blood drain into a container. The blood can be cooked, dried, and added to feed for other chickens.

To remove feathers, place the bird (after it has been bled) in water at 60[degrees]C. That temperature is well below boiling, but too hot to put your hand in. As soon as the feathers are well soaked with hot water, pluck them as quickly as possible.

De-feathering ducks is more difficult than de-feathering chick- ens. Slightly higher scalding temperatures are used for ducks. The temperature of the water should not be above 65[degrees]C and the length of scald varies from one and a half to three minutes.

In hand-scalding, grasp the bill with one hand and the legs with the other hand and submerge the rest of the body, breast down- ward, in the water. The bird is then pulled repeatedly through the water against the feathers.

OPERATING COSTS

Because costs vary so much from area to area, it is impossible to make accurate generalizations. The operating cost breakdowns for egg production and broiler production in the United States and India are shown in Tables 5 and 6. In all cases, the major cost item is feed. A large part of the increase in efficiency of poultry meat and egg production is the result of more efficient conver- sion of feed to product. About 2 kg of feed are now required to produce 1 kg of broiler; 50 years ago, 4.5 kg of feed were required. And while about 1.7 kg of feed are required now to produce one dozen eggs, 50 years ago, 2.3 kg of fed were needed.

Table 5. Egg Production Costs

India United States (Percent of Total) (Percent of Total)

Pullet cost 21.6 20.4 Feed 51.9 58.2 Depreciation of buildings and equipment 6.9 9.2 Labor 2.6 4.9 Miscellaneous 17.0 7.3

Table 6. Broiler Production Costs

India United States (Percent of Total) (Per- cent of Total)

Chick 26.4 19.4 Feed 44.4 73.6 Contract grower -- 1.7 Labor 2.9

--
Depreciation                               5.5
--
Miscellaneous                             20.8
5.3

The cost of baby chicks has gone up with inflation, but genetic
improvement has increased productivity so that chick cost per
unit of product has remained nearly the same.

It is difficult to compare labor costs for broilers. In the
United States, the contract grower furnishes some labor, and some
is provided by special crews under "miscellaneous." The feed is
delivered into an automatic feeding system, so some labor cost is
included in the feed cost. High interest rates contribute to the
high miscellaneous costs in India. In the United States, broiler
costs may allow for depreciation under "Miscellaneous" and/or
"Contract grower," but the allowance appears to be inadequate.

III. DESIGNING THE RIGHT SYSTEM FOR YOU

Table 7 summarizes the poultry requirements for small-, medium-,
and large-scale poultry operations. Note, however, that all
poultry farms, regardless of size, should try to use modern
disease control methods. Modern vaccines and medications are
widely distributed in many parts of the world.

                 Table 7. Requirements for Egg or Meat Production
                          According to Flock Size

                     Less than             200-1000          More
than
                     200 Birds             Birds             1000
Birds


Stock                Local or imported     Imported
Imported
                     strain-cross          strain-cross
strain-cross

Feed                 Crop residues,        Formulated
Formulated
                     table scraps, local   feed              feed
                     by-products or        emphasizing
emphasizing
                     formulated feed       local
local
                                           by-products
by-products

Disease              Isolation,            Isolation,
Isolation,
Control              sanitation,           sanitation,
sanitation,
                     vaccination,          vaccination,
vaccination,
                     medication            medication
medication

Buildings            Homemade              Homemade
Homemade or
and
commercial
Equipment

Labor                Family                Family or
Hired or
                                           hired
mechanized


Even the smallest poultry farm can practice isolation and sanita-
tion.
Small operations may choose between local and imported
stock and between formulated feed and a feeding program based on
what is available from day to day. Large operations will surely
use imported stock and formulated feed.

Small units will use homemade buildings and equipment and family
labor. Large units may choose either homemade or commercial
equipment and either hired labor or a combination of mechaniza-
tion
and labor. In some tropical countries laying flocks numbering
in the thousands are housed in homemade, two-level, stair-step
laying cages of bamboo and wood slats. Such cages do not
last long in the tropics, but they can be replaced at relatively
low cost.

Table 8 summarizes the requirements for different classes of
poultry.

              Table 8. Requirements for Different Masses of
Poultry

                                 Chickens
Ducks
                         Eggs               Meat

Stock              Local or imported    Local or imported   Local
                   strain-cross         strain-cross

Feed               Crop residues,       Crop residues,      Crop
residues
                   table scraps,        table scraps,
recovered by
                   local by-            local by-
herding in
                   products, or         products, or
fields, table
                   formulated feed      formulated feed
scraps, local

by-products,

formulated feed

Disease            Isolation,           Isolation,
Isolation,
Control            sanitation,          sanitation
sanitation
                   vaccination,         vaccination,
                   medication           medication

Buildings          Homemade or          Homemade or
Homemade or
and                commercial           commercial
commercial
Equipment

Labor              Family, hired,       Family, hired,
Family, hired,
                   or mechanized        or mechanized       or
mechanized


                           BIBLIOGRAPHY

Costa, M.A. "The Evaluation of Indigenous Feedstuffs for the
     Nutrition of Swine and Poultry in Belize, Central America."
     M.S. Thesis, Michigan State University, 1981.

Gupta, S. P., ed. Indian Poultry Industry Yearbook, 1975-1976.

Khan, A.S.; Chaudhry, A. M.; and Aslam, M. Economics of Modern
     Poultry Production in West Pakistan. Lyallpur, Pakistan:
     West Pakistan Agricultural University, 1969.

Maurer, A.J., and Maurer, E.A. Raising Chickens in Eastern
Nicaragua.
     Wisconsin-Nicaragua Partners and Centro para el
     Desarrollo Regional.

National Academy of Sciences. Atlas of Nutritional Data on United
     States and Canadian Feeds. Washington, D.C.: National
Academy
     Press, 1972.

National Academy of Sciences. Nutrient Requirement of Poultry.
     Washington, D.C.: National Academy Press, 1977.

North,  M. O. Commercial Chicken Production Manual. Second
edition.
     Westport, Connecticut: AVI Publishing Co., Inc., 1978.

Orr,  H.L. Duck and Goose Raising. Publication 532. Ontario,
     Canada: Ministry of Agriculture and Food.

Piliang, W.G.; Bird, H.R.; Sunde, M.L.; and Pringle, D.J. "Rice
     Bran as the Major Energy Source for Laying Hens." Poultry
     Science 61 (1982): 357.


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