Ingredients of sustainable farming systems and issues to be considered in the design of these systems

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:

• reviewing the characteristics of environmental resources and ways of managing and manipulating them to achieve specific results;
• selection characteristics of inputs, practices and technologies that in tropical Africa can be used to render outmoded and new farming systems sustainable. Table 4.2 lists resource characteristics, practices that render them unsustainable and restorative measures for dealing with the undesirable changes.

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:

• The need for low resource farmers in developing countries to minimize use of external inputs such as fertilizers and herbicides by increasing reliance on internal inputs, because of lack of credit and foreign exchange. In this regard, we can also regard the buying of stakes from neighbours or the local market as purchase of an external input which can be internalized by using agroforestry systems such as alley cropping, which supplies stakes and even fuelwood that is home grown.
• Increase reliance on biological processes such as biological nitrogen fixation, nutrient cycling mechanisms and mycorrhizal phosphate nutrition for minimizing the amount and cost of fertilizer use.
• The fact that the use of fertilizers (organic or synthetic) in tropical agriculture is imperative and that the only options we have are how to optimize the use and increase the efficiency of fertilizer use.
• In some situations we may resort to the growing of crops (e.g. cassava) that are adapted to soil acidity wherever possible rather than always resorting to liming in dealing with soil acidity.
• Use of integrated approaches in agriculture systems, e.g. integrated watershed development;
  • integrated pest, disease and weed management (IPM);
  • integrated field crop and shrub/tree (ligneous species) production systems agroforestry;
  • integrated crops, trees, pastures/animal systems (agrosilvopasture);
  • mixed cropping systems and rotational sequences rather than monoculture;
  • integrated land use planning; - integration of traditional, "modern" and emerging technologies;
  • minimal and strategic use of pesticides and chemicals associated with a spectrum of compatible physical, cultural and biological methods;
  • combination of manual and appropriate mechanization systems;
  • need for intensification of production and use of appropriate technologies under increasing population pressures, since shifting cultivation and related fallow systems cannot meet the demands of higher carrying capacity (table 4.3);
  • elimination of gender bias in technology development and extension;
  • need for adequate level of human resources development and institutional capacities in research and development to keep up with changing needs of farmers and changing circumstances;
  • research of sufficient scope on research stations and on the farm level with increasing farmer participation;
  • balance between production research and post-harvest-phase research and development necessary for successful agribusiness growth;
  • need for policy umbrella in support of sustainable agriculture and one which ensures compatibility among agriculture, forestry, fisheries, etc., in order to render practices more environmentally friendly;
  • need for suitable infrastructure in support of sustainable agriculture, including roads from farms to markets and effective pricing and market structure.

Table 4.2 Selected Sustainable Agriculture Resource Input Features and Practices, Effects and Remedies

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

Source: FAO (1991b).