|Environment, Biodiversity and Agricultural Change in West Africa (UNU, 1997, 141 pages)|
|4: Criteria for designing sustainable farming systems in tropical Africa|
Farming systems of tropical Africa and their sustainability under changing conditions
Ingredients of sustainable farming systems and issues to be considered in the design of these systems
Sectorial interface requirements
Conclusions and recommendations
Bede N. Okigbo
The World Commission on Environment and Development (WCED 1987) defined sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Although I do not feel like adding to the unending list of definitions of sustainable development, there is need to consider definitions that make it easier to better conceptualize the nature and processes involved in sustainable development rather than the usual listing of characteristics of the term(s). Here, I attempt to present an operationally practical definition of sustainable development as the current global development paradigm consisting of policies, plans, programmes and activities of conserving, managing and utilizing resources to at least satisfy basic needs and improve human welfare by employing such strategies, technologies, processes and systems of production that do not degrade the resource base, cause losses or changes in the environment that are ecologically, economically and culturally undesirable. According to the WCED (1987) definition, the changes that are ecologically, economically and culturally undesirable are those that damage the environment to the extent that future generations will find it more difficult to find ways or generate technologies for rehabilitating the degraded environment and/or reversing the adverse changes in order to utilize environmental resources to meet their needs and ensure human welfare than we are finding it easy today to achieve the same objective. In other words, sustainable development consists of practices and techniques of managing and utilizing resources to fulfil human needs without damaging the environment so badly as to make it more difficult for future generations to manage and utilize environmental resources to satisfy their own needs.
Sustainable agriculture has been variously defined as follows:
- the successful management of resources for agriculture to satisfy changing human needs, while maintaining or enhancing the natural resource base and avoiding environmental degradation;
- the ability of an agricultural system to maintain production over time in the face of social and economic pressures;
- one that should conserve and protect natural resources and allow for longterm economic growth by managing all exploited resources for sustainable yield (BIFAD 1988).
According to Dover and Talbot (1987), although sustainability means different things to different people, on the basis of ecological principles sus tainable agricultural systems are those whose productivity can continue indefinitely without undue degradation of other ecosystems.
- the economic viability of agricultural production;
- the natural resource base; and
- other ecosystems which are influenced by agricultural activities.
- more thorough incorporation of natural processes such as nutrient cycles, nitrogen fixation, and pest-predator relationships into the agricultural production process;
- reduction in the use of off-farm inputs with the greatest potential to harm the environment or the health of farmers and consumers;
- greater productive use of the biological and genetic potential of plant and animal species;
- improvement of the match between cropping patterns and the productive potential and physical limitations of agricultural lands to ensure long-term sustainability of current production levels; and
- profitable and efficient production with emphasis on improved farm management and conservation of soil, water, energy and biological resources (BOA/NRC 1989).
These agricultural systems employ a broad spectrum of practices that include:
- crop rotations that mitigate weed, disease, insect and other pest problems; increase available soil nitrogen and reduce the need for purchased fertilizers; and, in conjunction with conservation tillage practices, reduce soil erosion;
- integrated pest management (IPM), which reduces the need for pesticides by crop rotations, scouting, weather monitoring, use of resistant cultivars, timing of planting and biological pest controls;
- management systems to control weeds and improve plant health and the abilities of crops to resist insect pests and diseases;
- soil- and water-conservation tillage;
- animal production systems that emphasize disease prevention through health maintenance, thereby reducing the need for antibiotics;
- genetic improvement of crops to resist insect pests and diseases and to use nutrients more effectively (BOA/NRC 1989).
In this paper, for a discussion on criteria for designing sustainable agricultural systems, I hope you will bear with me for introducing yet another definition. Sustainable agriculture is the science, art and business enterprise in which the farmer manipulates environmental resources and orchestrates several inputs in amounts, quality, sequences and timing in order to bring about or "create" environmental conditions that favour the production of plant and/ or animal products needed for food, fibre and other products without causing environmental degradation and decline in yields. Sustainable agriculture in any given location can only be achieved where there is appropriate scope of research linked with extension and the farmer to ensure that there is knowledge, skill, understanding and technology for manipulating and dealing with:
In a sustainable farming system, despite the vicissitudes of the weather, climate, political and socio-economic conditions causing perturbations in the yield curve, the overall trend does not show a decline in the long term. This paper is devoted to a review of the main characteristics of the farming systems of tropical Africa, extent of their sustainability, changes they are undergoing under impacts of different human activities and a host of other factors, reasons why they are becoming unsustainable and what needs to be done to render them more sustainable now and in the future. Finally, based on an understanding of the causes of unsustainability of the existing farming systems, the ingredients that must be wrought into farming systems during the design stage are considered.
Farming systems in tropical Africa consist of an amalgam of crops and animals managed in various production systems with their component cultural practices and technologies made up of varying mixes of traditional and introduced elements adapted to the requirements of different ecological zones and peoples of diverse cultures. As in other parts of the world, these systems are culminations of several millennia of experimentation which gave rise to extensive production systems such as shifting cultivation and nomadic herding - sustainable systems that were economically viable, ecologically sound and culturally acceptable under the then prevailing low population densities. With increasing population pressure these gave rise to more intensive fallow systems. The various characteristics of these farming systems are listed below:
The various farming systems consist broadly of traditional (e.g. bush fallow and compound farms) systems, transitional systems (e.g. smallholder cocoa and coffee plantations) and modern farming systems and their local adaptations, such as large-scale plantations, ranches, poultry farming and market gardening. The details of these typologies need not concern us here. What is of concern is that the farming systems are not static. They are changing as a result of changes in the environment, both natural and socio-economic. Some of these changes have rendered the traditional farming systems unsustainable and somewhat outmoded. A few examples of the changes and their effects on sustainability are presented hereunder:
|Change||Effect on Sustainability|
|Introduction of Asian and American crops||Positive and negative|
|Commercialization of agriculture||Largely negative for low resource farmers|
|Mechanization||Largely negative, sometimes positive|
|Agricultural chemicals||Largely negative unless strictly controlled|
|Fertilizer use||Negative and positive|
|European settlement||Negative and positive|
The manner in which changes affect sustainability can be illustrated with two or more of these examples. For instance, the introduction of Asian and American crops can be regarded as contributing to the increase of biodiversity and therefore contributing to increasing stability of production and biodiversity. But it is also true that the production of the introduced crops has often been promoted at the expense of the indigenous food crops, some of which are so neglected that they are not much being grown and a considerable degree of biodiversity has been lost. Population explosion has considerably increased pressures on land, resulting in intensification of farming associated with a drastic shortening of the period of fallowing from about 10 years or more to only 2 years or less. Use of agricultural chemicals has different impacts on the environment. Where reasonable amounts of chemicals are appropriately used, the effects are largely beneficial. Where, for example, no fertilizers are used and farming is intensified, the nutrients are depleted and yields drop as soils become degraded. But where excess amounts of farm chemicals are applied the environment may become polluted and unsustainability is the result.
Causes of Unsustainability in Agriculture of Developing Countries in Africa
The intensification of agricultural production as a result of increasing population pressure, intensification of farming, overgrazing and conversion of land to several uses that were not tested in the evolution of farming systems in Africa, have resulted in several undesirable changes in the environment with adverse effects on agricultural production. Figure 4.1 shows that with intensification of farming due to population and other pressures the following changes occur:
Table 4.1 Inputs of Technologies Used in Traditional and "Modern" Conventional Farming Systems
|Traditional agriculture||Modern agriculture|
|Land||Small (<1-5 ha)||Large (10-100 ha or more)|
|Tools||Simple: fire, axe, hoe, digging sticks, machete||Complex: tractors and imple meets, threshers, combine harvesters, etc.|
|Crops||Many species (5-80), land races, no genetic improvement, wide genetic base||Few species (1-3), improved narrow genetic base|
|Animals||Several species (2-5)||Usually 1 or 2 species|
|Labour||Manual, human energy, or animal power||Mechanical, petroleum fuels, electrical energy|
|Soil fertility maintenance||Fallows, ash, organic manures||Inorganic fertilizers, sometimes manures, soil amendments, e.g. lime and gypsum|
|Weed control||Manual, cultural||Mechanical, chemicals (herbicides and petroleum-based products)|
|Pest and disease management||Physical/cultural||Mainly mechanical, chemicals, insecticides, fungicides, bactericides, nematocides, rodenticides|
|Crop management||Manual||Growth regulators for defoliation, control of flowering, fruit drop, etc.|
|Harvesting||Manual or with simple tools||Mechanical, tractors plus implements: pickers, balers, threshers, combine harvesters|
|Post-harvest handling and drying||Simple sun-drying and over fires||Mechanical forced-air artificial drying using petroleum fuels, sometimes refrigeration|
Source: Okigbo (1988).
The changes that take place under intensive agriculture are the same as those that occur under shifting cultivation except that the inputs used vary.
Table 4.1 shows the differences in practices and inputs used in traditional agri culture as compared to those used in "modern" intensive agriculture. Note that while simple hand tools used in traditional agriculture do not cause compaction, heavy machinery used in intensive agriculture does and this, in turn, causes structural deterioration, poor drainage and waterlogging.
Case-study of Changes Causing Environmental Degradation and Reduced Productivity in Southern Nigeria
Lal and Okigbo (1990) conducted an assessment of soil degradation in the southern states of Nigeria and identified factors that cause environmental degradation in the humid tropics of southern Nigeria and in the humid tropical African environment.
The main change in traditional farming systems is that of intensification of farming and the shortening of the periods of fallow. It was found that changes that occur in the soil are physical, chemical and biological, and there were changes of a socio-economic character also. If these changes are identified, it is possible for us to incorporate into the production system practices, technologies, etc., which will prevent adverse changes that threaten sustainability.
The main causes of soil degradation encountered were:
The most serious soil degradation occurred in areas where fallow periods are minimal or non-existent. But the effects of long periods of cultivation often result from various practices ranging from clearing and cultivation to subsequent cropping. Symptoms of soil degradation observed were:
Commodities and Production System Changes
Sustainable Farming Systems
The assessment of soil degradation in southern Nigeria also resulted in identification of the following as the main sustainable farming systems currently practiced or emerging:
It is obvious from the above that many of the traditional and arable crop farms, especially those that are highly commercialized and on which most of our fertilizers are used, are not sustainable. It is on the basis of the above considerations that the elements of sustainable farming systems to be considered in designing sustainable farming systems will be based in addition to issues discussed in SCA (1991) and Lal and Okigbo (1990).
The overall objective of agricultural or farming system design and management is the creation of environmental conditions that remain favourable for crop and animal production or even increase their productivity in perpetuity while at the same time minimizing adverse impacts on the resource base or, where possible, enhancing it. Consequently, it is necessary in any effort at designing sustainable farming systems to begin with:
In addition to the various causes of unsustainability indicated in figure 4.1, or the characteristics of resources and inputs which may, in association with certain practices cause unsustainability for which remedies are given (table 4.2), there are overall general issues that need to be taken into account in designing sustainable agricultural systems. These include:
Table 4.2 Selected Sustainable Agriculture Resource Input Features and Practices, Effects and Remedies
|Resource characteristic||Practice or factor contributing to unsustainability||Ameliorating or restoration technology or practice|
|1. Land tenure||Lack of security of tenure||Secure land permanently or for period that commodity is in field|
|2. Land use||Absence of plan or agreement on plan||Start as early as possible to get authorities thinking of and evolving plan|
|Land in dispute||Early settlement before use, especially for perennial crops|
|3. Vegetation management||Use of heavy mechanical equipment||Selective mechanization, e.g. use of shear blade and partially mechanized clearing; avoid very heavy equipment|
|Avoid burning large amount of dry biomass for long periods at high temperatures|
|Overgrazing||Relate stocking rate to pasture condition; use rotational grazing and fence partitioning|
|Relate all land use to the capability|
|(a) Structural damage or decline||Fire pasture||Early burning of limited dry biomass|
|Excessive or mechanical cultivation||Develop appropriate fire management for specific land use requirement|
|Fallowing and bare soil; overgrazing and loss of cover; machinery and animal traffic||Ensure adequate cover by vegetation or mulch|
|Rotational grazing and cover management|
|Relate tillage and stocking rate to pasture condition and soil type|
|(b) Acidification nutrient loss||No lime used on acid soil; use of acidifying fertilizers||Lime application if possible and|
|Use most appropriate recommendations|
|Use of resistant or acid tolerant varieties|
|(c) Erosion||Removal of vegetation cover and exposure of soil||Retention of vegetation cover by stocking adjustment, good pasture and/or wildlife management, stubble mulch - rough surface retention|
|Degradation resulting from poor cultivation technique||Use of reduced or minimal tillage, deep ripping, pasture rotation and measures to rejuvenate fragile soil|
|Use of wind-breaks and alley cropping|
|Adoption of land use that is not compatible or does not match capability of land||Improvement of capability assessment and better matching of use to it|
|5. Fire management||Uncontrolled use of fire in clearing, hunting, pasture management, etc.||Controlled use of fire; early burning in pasture management and to maintain desired species composition|
|6. Water quality||Inadequate drainage, waste and effluent water disposal||Improved engineering works to carry drainage water and effluent from animal housing; provision of sanitary inspection to enforce laws|
|Contamination of surface and groundwater by fertilizer and pesticides||This is not of common occurrence and is limited to a few large-scale "modern" farms|
|Care in use of pesticides near open water|
|Measures to minimize access of chemicals to groundwater|
|Use suitable fertilizer type and method of application to increase uptake|
|Apply fertilizer in amounts needed by crops as determined by analysis|
|Sediment and salt run-off into surface water||Better management to minimize soil erosion and salinity|
|7. Soil salinity, water- logging (irrigated agriculture)||Inefficient/excessive water use by flooding, too frequent irrigation, low infiltration||Improved water scheduling|
|Conjunctive reuse of groundwater|
|Drainage and gypsum to improve infiltration|
|Inadequate/deteriorating infrastructure||Improved water distribution networks|
|Poor site selection for irrigation areas||Soil selection should be consistent with soil and land capability|
|8. Soil salinity (dryland)||Excessive clearing of deep-rooted perennials causing rise in groundwater levels||Identification and revegetation of recharge areas|
|Strategic tree and shrub planting/management|
|Use of deep rooted perennials wherever possible|
|9. Use of monoculture crops||Reliance on a single crop without rotation or use of row crops||Better to use tested and row rotations|
|Use mixed crop sequences rather than just row sole crops|
|10. Pesticide residues resistance||Overreliance and persistent use of pesticides||Use of integrated pest and management|
|Overreliance on chemical control of crop weeds||Biological control of pests|
|Selection of genetically resistant species|
|Low pesticide use farming|
|Use of biodegradable pesticides|
|Use of rotations to reduce pest, weed or pathogen infestation|
Sources: Adapted from SCA (1991) and Lal and Okigbo (1990).
Table 4.3 Yield in Gram Equivalents and Percentage of Crop Land for Various Levels of Production Inputs in the World
|Farming system or technology input level||Yield t/ha||Crop land (%)||Average area of arable land needed (ha/caput)|
Source: FAO (1991b).
However appropriate and realistic the design of a sustainable farming system may be, it is necessary to ensure that threats to it from other sectors are eliminated or significantly minimized. For example, poor road construction could result in flooding, eutrophication and erosion, all of which can seriously damage farm land and even fish-ponds or stream fisheries. A related example is a policy issue such as structural adjustment aimed at increasing export earnings or at reducing debt burdens. This may result in a lot of forest areas being cleared for the commercial row-growing crops, which will expose the soil to erosion. Similarly, removal of subsidies may result in farmers not using fertilizers which, in turn, will result in environmental degradation. Therefore, designing sustainable agricultural or farming systems and adhering to the design alone will not ensure sustainability unless policies, strategies, technologies, systems and components of resource management, and input/technology use in other sectors such as forestry, fisheries, animal production, manufacturing industries, tourism and management of nature reserves and trade are designed to ensure sustainability in development devoid of adverse impacts on the other sectors. A few examples of sectoral activities in one sector which affect other sectors are presented below:
Uncontrolled expansion of agricultural land reduces land available for reserves, forestry and other multiple land use requirements.
All these call for not only integrated land use planning but also adoption of a holistic approach in development planning, in policy formulation and in selecting strategies and the execution of development programmes. The earlier we pay attention to these, the better.
In designing sustainable agricultural production systems, it is necessary to give due consideration to the characteristics of various resources used in production, the ways they are managed or manipulated in the production process and the technologies and practices which render the resultant production system unsustainable. Unsustainability results when impacts of practices and technologies used are economically not feasible and sometimes also culturally unacceptable. In addition to the selection of methods for manipulation of resources and use of practices and technologies which ensure sustainability, there is a need to ensure that other sectoral activities do not render the farming systems unsustainable. At the same time measures must be taken to ensure that various accelerators of agricultural development and factors which ensure enabling the environment for agricultural production for a majority of farmers are present. These include:
The effectiveness of these are accelerated by:
Recommendations on Principles for Designing Sustainable Farming Systems in Tropical Africa
In designing sustainable farming systems there are five principles or objectives that should be aimed at, namely:
Guidelines for Designing Sustainable Systems
The main guidelines to follow in designing sustainable agricultural systems are to:
Table 4.4 Different Operations Performed during Different Stages of Crop Production and Utilization and Extent of Likely Erosion Hazard Involved
|Operations at different stages of crop production and utilization||Extent of possible erosion hazardsa|
|Tillage and pre-planting cultivations||High|
|Subsequent soil management||Low|
|Weeds, pest and disease management||Negligible-high|
|Primary processing (e.g., shelling, winnowing)||Negligible|
Source: Okigbo (1985,1993).
a. Extent of erosion hazard depends on interaction of operations with environment and other factors.
The above principles and guidelines are by no means exhaustive but they are illustrative of the principles and procedures involved in determining: the management schedules; the manipulations of resources; and the input orches tration in amounts, sequences and timing in order to satisfy objectives in pro ducing desirable levels of food, fibre, and other products or otherwise satisfy ing the farmers' objectives. The design can only operate with success where there is an appropriate policy umbrella in the presence of all the accelerators of agricultural development and compatibility among all sectors.
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