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Technical Paper 3: Agroforestry Systems - Concepts and Classification

M. Avila


3.0 Performance objectives
3.1 Introduction
3.2 Basic elements of a system
3.3 Application to agriculture and agroforestry
3.4 Systems analysis
3.5 Systems and interdisciplinary research
3.6 Classification of agroforestry systems
3.7 Summary
3.8 Feedback exercises (Find out the answers from the text)
3.9 Suggested reading
3.10 References


3.0 Performance objectives

Technical paper 3 is intended to enable you to:

1. Explain the systems concept.
2. Describe 6 basic elements of a system.
3. Discuss the use of systems terminology in agriculture and agroforestry.
4. Describe analytical steps in systems analysis.
5. Explain interdisciplinary nature of systems research approach.
6. Identify criteria to classify agroforestry systems.
7. Classify agroforestry systems.

3.1 Introduction

The word system is used very often in the agricultural research and development literature. Yet use of the system concept is rather a recent development and consequently lacks uniformity in its conceptual definition and methods of approach. In a broad sense, a system is defined as a group of associated elements forming a unified whole and working together for a common goal. For example, the sociological household is a system composed of elements of persons, resources, customs, etc. A farm is an agricultural system composed of crops, livestock, trees, etc.

An important characteristic of a system is that since different elements of the system are interrelated, a change in one element causes change in one or more of the other elements. Further, an element of a system can itself be considered as a system. The crop production activities of a farm constitute its cropping systems. An animal is also an example of a living system, an element of the animal production system. Every system can be thought of as one component of another larger system.

Many different systems approaches are used by scientists to unravel complexities. Humankind is ever busy trying to understand the real world. To make sense of reality, scientists use their imagination to define systems that simplify real phenomena. Systems can be of any size or complexity varying from a molecule to a solar system. Where systems are highly complex, they are studied in terms of subsystems. Models, which are extensions of the known to understand the unknown, are often used to visualize systems. A model is appropriate if it incorporates all relevant elements and their relationships. Reality, however, is too complex to be represented completely by a model.

Although scientists are always keen on the descriptive and/or analytical value of their systems, other professionals and practitioners are also interested in systems, perhaps for different reasons. For example, the systems approach can be effective for management (e.g., for monitoring key factors that can improve operations and performance), predictions (knowing what will happen if key factors change in the future), or for training (e.g., for auto mechanics, electronics, agricultural production).

A systems approach helps to focus attention on what is important, effective, and practical.

3.2 Basic elements of a system

A system may have many elements. The six basic elements of any system are:

· boundary
· structure
· function
· state
· hierarchy
· type

A system has a boundary. This clearly defines what remains inside (endogenous) and what remains outside (exogenous). Understanding a system means knowing how the endogenous pans relate to each other and how they independently and holistically relate to the exogenous environment. Boundaries can be real or imaginary.

A system has structure. This refers to how the pans relate to each other in terms of space and time. In other words, structure signifies spatial and temporal arrangements.

A system has function. This refers to input-output relationships. A function is a process in which inputs are introduced, managed, and convened into outputs within a time spectrum, in order to achieve desired objectives or goals.

A system also has state. For example, a steady state system is one that does not experience any change in structure or function within a given period. This would not be the case in a system that is just being developed, or a system experiencing a declining state of resources or productivity. Both endogenous and exogenous factors can cause changes in the state of the system.

There is a hierarchy of interrelated and interdependent systems. For example, a human being system is pan of a household system, which is pan of community system, which is part of a regional system, which is pan of a nation, which in turn is part of a community of nations. This means that the analysis of any system in this hierarchy must take cognizance of the influence of higher and lower-order systems. For example, one cannot fully understand an individual person's behavior without understanding the household and community of which he or she is part.

Furthermore, there is the question of how generally or specifically a system is defined. One could describe and analyze a human being system, for example, at a general level such that it applies to all human beings on earth, or at a very detailed level such that each person is, in fact, a different system. Thus the choice of the precise level in this hierarchy is critical for systems definition and analysis.

Basically, there are two types of systems: mechanistic and purposeful. In the former, behavior is predictable as the system does not determine its own goals, rather it reacts to predetermined stimuli (e.g., a computer or an airplane). A purposeful system determines its own goals and the ways to achieve them (e.g., an animal, household or nation).

3.3 Application to agriculture and agroforestry


3.3.1 Farming Systems
3.3.2 Other Systems


There are many uses of systems terminology in agriculture, such as ecozone system, land use system, farming system, cropping system, livestock system, agroforestry system. Let us develop one of which is in common use today, the farming system, and refer to it to explain others.

3.3.1 Farming Systems

Most experts agree to a definition of a farming system as a combination of crops, livestock, and trees, managed in diverse spatial and temporal arrangements, subject to biophysical and socioeconomic conditions, to satisfy the household's objectives and priorities. Such a system can be described, first, in terms of structure (Figure 1). Literally, structure is what one sees on a farm and where each component is located in relation to the others: boundary, buildings, crops, animals, etc. Often the structure of a farming system is subject to seasonal variations within or across years particularly with respect to the temporal arrangement of annual crops.

A farming system can also be described functionally, as in Figure 2. This is a qualitative representation, indicating the endogenous interactions among production systems and the household, and also the exogenous interactions with the environment. It is imperative to quantify these interactions in order to understand how well this system is managed and how well it is meeting the household's objectives as well as to Identify its constraints.

Figure 1. The structure of a sample small-farming system. This is an example of structural description in system analysis.

Figure 2. Production systems in relation to household goals and exogenous factors. This is an example of functional description in system analysis.

3.3.2 Other Systems

Cropping and Livestock Systems: A structural description of the crop component alone, that is to say the cropping system of a farming system, is presented in Figure 3. The figure shows how different cropping patterns are managed with respect to spatial and temporal arrangements. A functional description of the livestock component is presented in Table 1. It identifies the specific contributions of various livestock species to the household and to other components of a farming system.

Agroforestry systems: The presence of trees on external and internal boundaries, cropland, homestead plots or on any other available niche of farmland, defines the agroforestry systems structurally (see Figure 1). There are several agroforestry systems on this farming system, and each can be described functional, i.e., in terms of inputs used and outputs generated. Table 3 contains a full list of structural and functional considerations which can be used to define and analyze agroforestry systems. However, it is essential to remember that any agroforestry system can be subdivided into other systems and is a part of larger systems.

Figure 3. Structure of cropping sub-system of a small-scale farming system.

Land-use systems: What is a land-use system? Each system identified thus far can be described and analyzed with emphasis on how land as an essential resource is being used and managed by. the household in the farming system or in any production system.

The land-use systems analysis could comprise:

· household priorities and objectives,
· land-use intensity, namely, units of inputs or labor per hectare,
· levels of management,
· productivity levels and potentials, and
· disposal and use of outputs.

Similarly, one could analyze systems defined on the basis of other crucial factors such as labor, household information, or market participation. It is all a question of the desired focus or emphasis for understanding a given farming system or its parts.

Ecozone System: One usually wants to study farming systems within a larger system, e.g., an ecozone system. The latter could be defined on the basis of homogeneous characteristics such as altitude, climate, topography, soil type, or vegetation; or, alternatively, on the basis of specific farming and/or production systems which reflect to a large extent what is feasible in terms of the above agroecological determinants. The analysis at this level can be conducted as follows: If one studies many farming systems in a particular ecozone, one notices common patterns with respect to structural and/or functional characteristics which provide a logical basis for classifying farming systems. A general definition criteria (e.g., systems with maize and cattle), will encompass a greater number of farms, while a more specific definition criteria (e.g., systems with specific management and yield levels of maize), will contain a lesser number of farms.

3.4 Systems analysis


3.4.1 System Assessment Criteria
3.4.2 Analytical Steps


Systems analysis aims at comparing one system with others or assessing the comparative performance of the same system over different periods of time. The performance of a system depends to a large extent how its components interact, both structurally and functionally. To analyze a system one should use assessment criteria based on the relationship between structural and functional components of the system. Farming systems in tropical environments are typically characterized by multiple combinations of structural and functional interactions and therefore it is important to identify such interactions and to quantify their positive and negative effects.

Table 1. Qualitative assessment of livestock roles in a farming system

Role

Cattle

Goats

Sheep

Donkeys

Pigs

Poultry

Wildlife

Food








Meat

X

XXX

X



XXX

XX

Milk

XX

X






Egg






XXX


Traction








Land prep

XXX



XXX




Cultivation

X







Transport

XX



XXX




Manure/Fert.

XXX

X

X



X


Storage








Food Supply


XXX

X


X

XXX


Capitalization

XXX

XX

X





Seasonal feed excesses

XXX

XXX

X


X

XX


Weed and Bush Control

X

X





XX

Cultural Needs








Contract agreement

XXX

XX






Rituals

XXX

XXX




X


Ornamentation

X

X





XX

Sports/Recreation

X

X





X

X = Weak XX = Moderate XXX = Strong

3.4.1 System Assessment Criteria

Three useful indicators of performance for a system are:

· Management intensity, which is measured as an input/input ratio. For example, amount of fertilizer/ha, or labor input/ha.

· Productivity, which is measured as an output/input ratio, For example, yield/ha, or yield/livestock unit.

· Profitability, which is measured as output value/input. For example, net benefit invested or net benefit/ha.

Other indicators include those related to the physical resource status, such as soil fertility and structure, or vegetation cover.

The criteria are calculated for a given time period, usually a season or year. If one studies how and why these indicators vary over the medium term (2 - 5 years) or the long term (5 - 15 years), then one can assess whether the system in question is stable and sustainable. Thus, sustainability of a system can be ascertained by studying long-term trends in the indicators of physical resource status, management intensity, productivity, and profitability.

3.4.2 Analytical Steps

In a general sense, systems analysis means an explicit consideration of system objectives, interplay of endogenous components and factors, and interaction/linkages with exogenous systems; the analysis Uses the time factor as an important variable. On the basis of the preceding sections, the systems analysis process can be broken into a series of steps, each answering one of the following key questions:

Present Performance of the System

· What is the structure of the system(s)? The structural components refer to basic resources such as edaphic, biotic, abiotic, or economic resources. Structural assessment involves a specification of boundary and spatial, as well as temporal arrangements of physical components; this is Usually done on a qualitative and/or quantitative basis.

· What is the function of the system(s)? The functional components refer to management resources, viz, input levels used, technological and economic input, and output levels achieved, both in physical and/or economic terms. Functional assessment involves a description of inputs (use of labor, cash inputs, information), outputs (food, feed, materials) and their disposal (home consumption, sale), and the timing of when these events occur. Management and performance analysis is needed here, including quantitative analysis. Biophysical as well as socioeconomic criteria should be used for functional assessment over a given period such as 1, 2, or 5 years.

· What is the state of the system? Answering this requires analysis of trends with respect to changes in the basic structure and/or functions of the system. Stability and sustainability are important considerations in this step.

In all these investigations, the influence of risk and uncertainty factors (e.g., climate price structure, human emergencies) should not be underestimated, especially in agriculture-based systems.

Future Improvements

The above questions seek information on the present performance of the systems. If the task is to improve the system, then one must ask a set of additional questions:

· What are the objectives of the system manager(s) (e.g., farmer and household). And how do those objectives match up with present system performance? It should be noted that, although the manager's objectives and priorities for the system may not acceptable to all, they can be ascertained and recorded accurately.

· What are the positive and negative effects on the system of the present component structures and/or functions? How could they be modified or replaced to achieve higher levels of performance? Any proposed interventions must to be appropriate and acceptable to the manager(s).

· What are the positive and negative effects on the system of exogenous factors, and what should be done about these factors to move the system in the desired direction?

· If endogenous and/or exogenous changes should be carried out, what adjustments of structure and/or function are required by the system manager to successfully implement the proposed changes? Are they feasible technically, managerially, and economically?

The primary focus analysis of system performance is the identification of constraints and key opportunities for improvement. This leads to a better understanding of the type of changes to structure and function that would be required to make the system perform as expected by its manger(s) - whether fine-tuning, incremental changes, or major changes.

3.5 Systems and interdisciplinary research

Research with a systems approach is used in almost all biophysical disciplines, such as ecology, genetics, soil science, husbandry, pathology, and engineering, as well as in social science disciplines including economics, sociology, anthropology, and political science. However, there is a major difference in the conceptual framework and analytical methods used by natural scientists, as compared to social scientists. For the former, research typically deals with plants, organisms, and animals under "controlled" conditions, while for the latter, research deals with people in their "natural" habitat where "controls" can be exercised only through analytical methods. In this respect, each discipline in the natural and social sciences has different tools for studying and improving land-use production systems.

An interdisciplinary, systems approach is often used in research on land-use systems, whether homogenous or mixed systems (Table 2). Research to improve any of the land-use systems shown in Table 2 would require interaction among scientists from the different disciplines. Particularly in the case of mixed systems, interdisciplinary research can be quite complex and challenging. To be effective, team interaction should be based on a consensus on the systems analysis process and on the specific contribution to be made by each discipline to the overall research strategy. Productive interdisciplinary research requires a leader or leaders possessing expertise in systems analysis, orientation to client farmer needs, technical know-how, and team management skills.

3.6 Classification of agroforestry systems

Agroforestry systems can be classified in different ways using structural and functional considerations (Table 3). One common classification of agroforestry includes agrosilvopastoral, silvopastoral or agrosilviculture systems, which can be further sub-divided depending on specific arrangements and/or functions.

Table 2. Types of land-use systems.

Type of System

Examples of Components

Homogenous Systems



Monocropping systems,

Maize, wheat, rice.


Mono-animal systems

Cattle, sheep, poultry.


Mono-tree systems

Timber plantations, woodlots.

Mixed Systems



Crop-crop

Maize/cassava, maize/beans.


Animal-animal

Cattle/goat, cattle/poultry.


Crop-animal

Maize/cattle, cereals/poultry/household waste.


Crop-tree

Alley farming, mixed intercropping, boundary tree planting.


Animal-tree

Alley grazing, fodder tree banks.


Crop-animal-tree

Homegardens, alley farming with Livestock.

Another classification divides agroforestry systems into "mainly agrosilvicultural" (i.e., trees with crops), "mainly or partly silvopastoral" (i.e., trees with pasture and livestock) "tree-component predominant", and "other components present". This scheme recognizes further subdivision according to structural or functional considerations (Table 4). This particular classification is probably best suited for analysis of the potentials of agroforestry.

More recently, with a view to reviewing and synthesizing the state-of-the-art in agroforestry research and development for an annual ICRAF three-week course, the author and a lecturing team adopted the classification shown in Table 5.

Table 3. Structural and functional criteria for defining and classifying agroforestry systems.

* Each can derive from: leaves, flowers, fruits, wood, bark and root effects.

Table 4. An example of the classification of agroforestry systems. (After Young, 1987).

1. Mainly Agrosilvicultural (trees with crops)

Rotational:

. Planted tree fallow
. Taungya

Spatial mixed

. Trees on cropland
. Plantation crop combination

- with upper-storey trees
- with lower-storey
- tree/shrubs crops
- with herbaceous crops

. Tree gardens:

- multistorey tree gardens
- home gardens

Spatial zoned;

Alley farming
Boundary planting
Trees for soil conservation:

- barrier hedges
- on grass barrier steps
- on bunds, etc.
- on terraces

. Windbreaks and shelterbelts
. Biomass transfer

2. Mainly or partly Silvopastoral (trees with pastures and livestock)

Spatial mixed:

. Trees on rangeland or pastures
. Plantation crops with pastures

Spatial zoned:

. Live fences

- mainly barrier function
- multipurpose

. Fodder banks

3. Trees Component Predominant

. Woodlots with multipurpose management
. Reclamation forestry leading to production:

- on eroded land
- on salinized land
- on moving sands

4. Other Components Present and Special Aspects

. Apiculture with forestry
. Aquaforestry (trees with fisheries)
. Trees in water management
. Irrigated agroforestry

Table 5. A second example of the classification of agroforestry systems (Torquebiau, 1989).

1. Alley Farming (hedgerow intercropping)
2. Crops under tree cover
3. Pastures and animals under tree cover
4. Agroforests (live fencing, boundary planting, windbreaks, shelterbelts)
5. Sequential technologies (shifting cultivation, taungya, improved fallow)
6. Other technologies (aquaculture and apiculture with trees)

Structural criteria are readily applicable in classifying agroforestry systems. In contrast, the use of functional criteria to classify agroforestry systems is uncommon. The science of agroforestry is not yet sufficiently advanced in the analysis of technology management and performance to define useful functional criteria for system classification. The occasional exceptions include, for example, speaking of alley farming for soil fertility improvement or for fodder production, or indicating how a farming system's output is to be disposed of (e.g., for home consumption, cash generation, or both).

The key task at present is to determine the most appropriate criteria to apply in classifying agroforestry systems. The choice of classification depends on its intended use of the classification. For purposes of technology development, the chosen classification should provide a useful framework for guiding research and assessing research progress.

3.7 Summary

This paper presented six basic elements of a system namely, boundary, structure, function, state, hierarchy, and type. These were applied to define and describe farming systems, agroforestry systems, and land use systems. Subsequently, systems analysis was explained in terms of the types of interactions, assessment criteria, and analytical steps researchers should follow as they seek to answer specific questions related to understanding and improving systems. The implications of the systems approach for interdisciplinary research and for classification of agroforestry systems were reviewed.

3.8 Feedback exercises (Find out the answers from the text)

1. Fill in blank spaces in the following sentences.

a.) A system may be defined as a group of ___________ forming a ___________ and sharing a common ___________.

b.) Where systems are highly complex, they are studied in terms of ___________.

c.) Models are often used to visualize a system. However a model is appropriate only when all___________ and their ___________ are incorporated in the model.

2. Identify the correct statements.

a.) A system has a state, which refers to input-output relationship.
b.) All systems can be grouped into two categories, namely, mechanistic and purposeful.
c.) A system's structure refers to spatial and temporal arrangement of its parts.
d.) Systems are governed by the theory of hierarchy. This means every system is composed of sub-systems, which in turn are composed of further sub-systems.

3 a) Give four examples of the use of system's terminology in agriculture.

1) ________________________
2) ________________________
3) ________________________
4) ________________________

b) Prepare a rough sketch of a farming system in terms of its functions.

c) When describing an agroforestry system as a part of a farming system,
what two functional criteria can be used?

1) ________________________
2) ________________________

d) Name four indicators of system performance

1) Management intensity
2) ________________________
3) ________________________
4) ________________________

4 a) Write 3 questions that should be asked to learn about the present performance of a system.

1. _________________________________________________
2. _________________________________________________
3. _________________________________________________

b) What additional 4 questions should be asked to address improvement of the system?

1. _________________________________________________
2. _________________________________________________
3. _________________________________________________
4. _________________________________________________

5. An interdisciplinary team is to work on constraints' analysis of some mixed production systems. Can you name 6 possible types of mixed systems for such a study?

1) Crop-crop system
2) ________________________
3) ________________________
4) ________________________
5) ________________________
6) ________________________

6 a) What are the two main types of criteria used to classify agroforestry systems?

1) ________________________
2) ________________________

b) List 6 classes of agroforestry systems as per a recent ICRAF classification scheme (Torquebiau, 1989).

1) Alley Farming
2) ________________________
3) ________________________
4) ________________________
5) ________________________
6) ________________________

c) Would this classification be useful for your research work? Why or why not?

_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________
_________________________________________________

3.9 Suggested reading

Bertalanffy, L. von. 1973. General Systems Theory. Fourth Edition. Brazillier. New York, U.S.A.

Huxley, P.A., Robinson P.J., and Wood. P.J., 1985. Glossary of Terms for Agroforestry Research (Section 6C of Methodology for Exploration and Assessment of Multipurpose Trees). Nairobi, Kenya: ICRAF.

Nair, P.K.R. 1985. Classification of Agroforestry Systems. Agroforestry Systems 3:97 -128.

Ruthenberg, H. 1980. Farming Systems in the Tropics. Third Edition. Oxford, U.K.: Oxford University Press.

3.10 References

Torquebiau, E. 1990. Introduction to the Concepts of Agroforestry. ICRAF working paper 59, 122 pp.

Young, A. 1987. The Potential of Agroforestry for Soil Conversation and Sustainable Land Use. ICRAF Reprint No. 39. Nairobi, Kenya: ICRAF.


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