CHANGES IN PARADIGMS FOR SOIL FERTILITY MANAGEMENT IN SUB-SAHARAN AFRICA
Since the 1960s, the paradigms underlying soil fertility management research and development efforts have undergone substantial changes because of experiences gained with specific approaches and changes in the overall social, economic, and political environment faced by various stakeholders. During the 1960s and 1970s, an external input paradigm characterized by increased use of improved germplasm and fertilizer significantly led to a rapid increase in food production, commonly referred to as the “Green Revolution,” especially in Asia and Latin America. This paradigm put little if any significance on the set of organic resources as sources of nutrients for soil health.
The impacts of the Green Revolution strategy resulted only in minor achievements in SSA. The environmental degradation resulting from massive and injudicious applications of fertilizers and pesticides observed in Asia and Latin America between the mid-1980s and early 1990s (Theng 1991) and the abolition of the fertilizer subsidies in SSA (Smaling 1993), imposed by structural adjustment programs, led to a renewed interest in organic resources in the early 1980s. The balance shifted from mineral inputs to low input sustainable agriculture (LISA) where organic resources were believed to enable sustainable agricultural production (Vanlauwe 2004). The adoption of LISA technologies, such as alley cropping or live mulch systems, was constrained by both technical (e.g., lack of sufficient organic resources) and socioeconomic factors (e.g., labor-intensive technologies) (Vanlauwe 2004). This led to the second paradigm, integrated nutrient management (INM), which emphasized the need for the judicious use of both mineral and organic inputs to sustain crop production (Vanlauwe 2004).
A further shift in paradigm in the mid-1980s to the mid-1990s advanced the combined use of organic and mineral inputs accompanied by a shift in approaches toward involvement of the various stakeholders in the research and development process, mainly driven by the “participatory” movement. One of the important lessons learned was that the farmers’ decision-making process was not merely driven by soil and climate but by a whole set of factors cutting across the biophysical, socioeconomic, and political domain. The integrated natural resource management (INRM) research approach was thus formulated, aimed at developing interventions that take all the above aspects into account (Izac 2000).
Past paradigms of soil fertility management focused on fertilizer or “low-input” methods, but rarely on both, and ignored the essential scientific fact that fertilizers are most effective and efficient in the presence of soil organic matter (SOM) and well-conserved soil structure. This dichotomy is resolved by the integrated soil fertility management (ISFM) framework. The framework entails applying locally adapted soil fertility management practices to optimize the agronomic efficiency of fertilizer and organic inputs in crop production. Large-scale adoption of ISFM will promote soil fertility management practices, which include the use of mineral fertilizers, organic inputs, improved germplasm, and knowledge of their local adaptation. Such practices would maximize agronomic use efficiency of applied nutrients and improve crop productivity (Figure 4.4). Widespread adoption of ISFM is crucial in harnessing healthy soils, given that inorganic fertilizer provides most of the nutrients and organic fertilizer increases SOM status, soil structure, and buffering capacity of the soil in general. Moreover, use of both inorganic and organic fertilizers has proven to result in synergy, improving efficiency of both nutrient and water use.
In addition, the ISFM concept also takes into account other socioeconomic factors such as land tenure, input-output markets, access to credit, and institutional support, among others, in a value chain approach. ISFM, therefore, seeks to develop competitive commodity chains by strengthening the technical and managerial competencies of the various actors involved, particularly the farmers and local entrepreneurs (including inputs dealers, processors, stockists, and traders) at the grassroots level. Past paradigms had ignored such a holistic approach to agricultural development.
FIGURE 4.4 The ISFM paradigm. (Source: Vanlauwe, B. et al., Outlook Agr., 39, 17-24, 2010.)