Africa is rich in both natural and human resources, yet nearly 200 million of its people are undernourished because of inadequate food supplies. Comprehensive strategies are needed across the continent to harness the power of science and technology (S&T) in ways that boost agricultural productivity, profitability, and sustainability -- ultimately ensuring that all Africans have access to enough safe and nutritious food to meet their dietary needs. This report addresses the question of how science and technology can be mobilized to make that promise a reality.
A production ecological approach disentangles growth- and yield-defining factors (genetic potential and solar radiation), growth - and yield - limiting factors (water and nutrients), and growth - and yield - reducing factors (weeds, pests, and diseases) in agricultural-production systems. This approach allows for more comprehensive identification and prioritizing of agro-ecological constraints while helping to recognize technological opportunities for improvement.
The production ecological approach is a method for systematically studying the integration of basic physical, chemical, physiological, and ecological processes (Ittersum and Rabbinge, 1997). To understand, for instance, the growth performance of crops or animals, it is important to study not just the growth (i.e., biomass accumulation) itself but the processes that generate growth - such as the absorption of radiation, the photosynthetic production of carbohydrates, and the conversion of carbohydrates into proteins, fats, lignin and other components.
Systematic analysis of these underlying eco-physiological processes has improved the understanding of the dynamics of plant and animal behaviour to the point that the relative importance of growth and yield factors and inputs to productivity may be identified. This in turn presents opportunities for improving productivity and evaluating the effectiveness of new technologies and input measures. The approach has thus facilitated communication among various disciplines in agricultural science, thereby allowing comprehensive analyses of agricultural systems. This ability is illustrated in Box 3.3. A systematic categorization using production ecological analysis distinguishes four production levels (Figure 3.4):
The potential yield can be influenced by manipulation of radiation, temperature and carbon dioxide levels only under controlled conditions, such as in greenhouses and stables. Growth- and yield-limiting and growth- and yield-reducing factors can be influenced by agronomic practices under field conditions. Measures range from fertilization and irrigation to protection with biocides against pests, weeds and diseases. Genetic improvement can affect crop performance under all production conditions. The yield potential of cereal crops has, for instance, been increased through improving allocation to desired parts (i.e., the grains, resulting in increased harvest index). Genetic adjustments can also aim to enhance use efficiencies of nutrients and water, improve ability to take up water and nutrients and increase resistance or tolerance to drought, certain diseases or pests.
Applying the production ecological approach, estimates can be made of yields that can be obtained under various ecological conditions. Also, the impact of management practices, such as fertilizer application or irrigation on yield can be assessed, revealing trade-offs and synergies of input use. Whether or not required inputs will be actually applied by farmers depends on socio-economic conditions, in particular market access and input-output price ratios. Yield assessments using the production ecological approach facilitate yield gap analysis, which has been elaborated in Box 3.4.
The strength of the production ecological approach is its ability to differentiate among the individual and combined effects of the various production factors on yields. Understanding these synergies is of fundamental importance to the development of management and cultivation strategies to enhance productivity. This aspect is elaborated in Box 3.5.
The need to develop the production ecological approach has emerged from the urge to explain the behaviour of living or biological systems. Statistical analyses will reveal differences observed in experimental fields, but these ex post analyses lack the ability to explain those differences. For that, it is necessary to understand 'underlying processes' that govern the observed factors. For instance, to understand growth, the processes of photosynthesis and maintenance must be described. The insight gained of the impact of these basic processes on systems behaviour allows us to better influence the course of living processes, such as crop growth and yield. Crop growth models that explain growth and yield therefore include a large number of basic physiological processes. Over time, soil processes and the influence of pests, diseases and weeds have been incorporated. The complexity of the models increases as more processes and factors are considered. In principle, yield decreases with an increasing number of factors affecting growth, as has been elaborated in Figure 3.4.
The production ecological approach therefore demands an integrated approach from a wide range of biophysical disciplines. It has increased the need for improved communication and exchange of information among disciplinary scientists, including socio-economists. Obviously, this approach requires new skills and changes the mind set of scientists who need specific training to effectively implement the production ecological approach. Not surprisingly, the approach has significantly affected the research and education agenda at various advanced research centres around the world, in particular Europe, North America, Australia and Asia (Penning de Vries et al., 1993; Bouma et al., 1994; Teng et al., 1997). The power of the approach is illustrated in the report, Method in our Madness, by the International Service for National Agricultural Research (ISNAR) in which three African case studies are described. In these studies, African national agricultural research institutes (NARIs) in Kenya and Tanzania have been actively involved (ISNAR, 2004).
The production ecological approach has been implemented in a number of areas. Various decision support systems at operational, tactical and strategic levels are operational. Instigated by the concern for the environment, the search for more efficient use of natural resources at the field level has been intensified, leading to a fine tuning of crop demand and supply in time and space for supporting operational measures (e.g., Ten Berge et al., 1997). Minimizing the application of chemicals in pest, disease and weed control have reduced the use of agrochemicals. Tactical decision information has been derived from analyses that search for optimal planting dates to maximize production or to escape drought or diseases. At increasing aggregation levels, farming and land use systems analyses can be used to optimize resource use. The systems approach is increasingly being used to design entire farming systems that comply to economic, as well as to ecological and social desires. Analyses for policy support on regional land use planning or on global food production seeks to optimize seemingly conflicting desires, such as on nature conservation and food production through multiple goal linear programming techniques (WRR, 1995; Ittersum et al., 1998). This concise overview illustrates that the production ecological approach provides fundamental support to systems analyses at various aggregation levels.