2011年-世界发展银行全球_Maize_revolutions_in_Sub-Saharan_Africa_34页_958kb

Summary of "Maize Revolutions in Sub-Saharan Africa"

Core Content

This paper examines the historical and ongoing development of the maize sector in Sub-Saharan Africa (SSA), focusing on the challenges and opportunities for increasing maize productivity. It highlights the role of technical change, policy environments, and market dynamics in shaping the adoption of improved seed and fertilizer practices, and explores the implications for food security and rural development.

Main Points

• Adoption of Improved Seed: Improved maize varieties, including open-pollinated varieties (OPVs) and hybrids, have been adopted across SSA, with 44% of maize area in Eastern and Southern Africa (excluding South Africa) and 60% in West and Central Africa using improved seed by 2006-07 and 2005 respectively. Adoption has increased significantly in recent decades, particularly in West Africa.

• Yield Growth: Overall yield growth in SSA has been around 1% per year over the past 50 years, but this figure masks significant regional and temporal variability. In Southern Africa, yields have stagnated at just over 1 ton per hectare, while in West Africa, they have been higher, reaching up to 1.7 tons per hectare.

• Fertilizer Use and Management Practices: Fertilizer use remains low and inefficient in SSA, with an average of 17 kg per hectare, far below the 100 kg per hectare in developing countries and 270 kg per hectare in industrialized nations. The lack of widespread adoption of restorative crop management practices is a major constraint to productivity.

• Policy Influence: The authors emphasize that conducive policies are as important, if not more so, than technological development for improving maize productivity. Voucher-based subsidies, while popular, may "crowd out" private sector participation and be fiscally unsustainable.

• Regional Variations:

  • Eastern and Southern Africa: Early successes in maize breeding, such as in Kenya, Zambia, and Zimbabwe, were driven by state support and market policies. However, recent years have seen a decline in public investment and a shift toward market-based approaches.
  • West and Central Africa: The adoption of improved varieties has been more recent but shows promising growth. The introduction of open-pollinated varieties like TZB and TZPB in the 1970s by IITA was instrumental in the Nigerian maize revolution and has since spread across the region.

• Technical Challenges:

  • Maize is a cross-pollinating crop, making it difficult to maintain genetic purity without frequent seed replacement.
  • Environmental heterogeneity and the need for location-specific germplasm pose challenges for transferring breeding advancements from temperate to tropical regions.
  • Preferences for white maize among Sub-Saharan Africans have limited the adoption of certain hybrid varieties.

• Urbanization and Trade:

  • Urban populations in SSA are growing rapidly (over 4% per year), increasing the demand for staple food imports, especially wheat and rice.
  • Maize imports are relatively small (around 1.5 million tons), but they play a crucial role in Eastern and Southern Africa. Regional trade, both formal and informal, is important but often constrained by erratic trade policies.

• R&D Systems:

  • National and international research programs have played a key role in improving maize productivity. However, public investment in R&D has declined since the 1990s, and many countries have lost key breeders.
  • The International Maize and Wheat Improvement Center (CIMMYT) and the International Institute of Tropical Agriculture (IITA) have been central to these efforts.
  • Private sector involvement in plant breeding and seed production is growing, with over 60% of new varieties being private hybrids.

• Conclusion:

  • Continued investment in maize R&D and improved crop management practices is essential for sustaining agricultural growth and food security in SSA.
  • A combination of public and private strategies, tailored to local conditions, is needed to address the diverse agricultural environments and support the adoption of improved technologies.

Key Information

• Maize Production: Covers 25 million hectares in SSA, with 38 million tons produced in 2005-8, primarily for food.
• Maize Consumption: Accounts for 22-25% of starchy staple consumption in Africa, with the highest levels in Southern Africa (85 kg per capita per year).
• Yield Gaps: Sub-Saharan Africa's maize yields are significantly lower than those in other tropical regions, such as Brazil, Mexico, and Thailand.
• Fertilizer Use: Only 40% of fertilizer is applied to maize in SSA, with an average dose of 17 kg per hectare.
• Adoption Trends:
  • In Kenya, adoption of improved maize reached 70-75% of the area.
  • In Zimbabwe, adoption reached 96% as early as 1990.
• Research Impact: Studies show high returns to research in SSA, with rates of return exceeding 40% in West Africa from 1971 to 2005.

Recommendations

• Support for diverse and region-specific maize varieties is critical.
• Investment in research and extension services should continue to ensure the diffusion of improved practices.
• Policies should encourage sustainable market development and avoid fiscal unsustainability through voucher-based subsidies.
• Regional cooperation and integration of public and private R&D efforts are essential for long-term productivity gains.