The enormous success of the Green Revolution in enhancing food supplies and food security in the developing world is well known. The development and promotion of modern, high-yielding varieties was the most important factor contributing to this success. While new tools, technologies, and products will come from rapid advances in molecular biology and genetic engineering, the science that made the Green Revolution possible remains important today and will continue to play a crucial role in the future. Modern biotechnology tools will complement conventional breeding approaches rather than substituting for them. Crop improvement requires more than genetic manipulation using conventional breeding or molecular techniques; genetic-resource management, agronomy, and crop-management research will continue to play a crucial role in enhancing and sustaining crop productivity.
Productivity gains achievable from conventional technologies have not been fully exploited. The yield gap between what is possible and what is actually achieved on farmers’ fields is quite large, especially in the more marginal environments. The best farmers in high-potential environments achieve yields that are at par with experiment-station yields, but the majority lag far behind—by as much as 2 to 3 metric tons per hectare for the major cereal crops. Farmers in the high-potential environments have excellent access to modern farming inputs but often lack the agronomic and crop-management technologies and knowledge that are crucial for bridging the yield gap. For example, the yield achieved on farmers’ fields depends not only on the amount of fertilizer applied but also on when and how it is applied. Research on and promotion of improved crop-management technologies lags behind that on improved varieties. Even where such information is available, farmer adoption has been limited, because knowledge about crop husbandry tends to be highly location-specific and requires a significant amount of farmer time for experimentation and decisionmaking.
In the less-favorable production environments, the yield gap is substantially larger, often more than 4 metric tons per hectare. Here access to inputs is indeed a problem, but so are knowledge and adoption of improved crop- and resource-management technologies. General knowledge about growth in sustainable crop productivity in the marginal environments rarely translates to farmer practice at the local level. Substantial opportunities exist for applying what is already known to increase and stabilize food supplies in the marginal environments.
In addition to the persistent yield gap, the geographic areas in which the Green Revolution occurred are showing signs of a slowdown in the rate of growth in cereal yields on farmers’ fields—despite a steady growth in yield potential on experiment stations. Declining productivity trends are a direct consequence of the environmental and ecological stress imposed by intensive cereal-crop systems on the agricultural resource base. The stress manifests itself in several ways, including buildup of salinity and waterlogging, declining soil-nutrient status, increased soil toxicities, and increased pest buildup. More judicious use of inputs can go a long way toward sustaining crop productivity. Improved crop- and resource-management technologies that are already on the shelf and a policy environment that creates incentives for their adoption could help reverse the degradation trends.
The conventional research pipeline continues to provide a steady stream of significant products for enhancing cereal-crop productivity. Products continue to emerge in the areas of seed, crop-management, and resource-management technologies.
Yield potential for the major cereals has continued to grow at a steady rate since the initial jump that kick-started the Green Revolution. For example, yield potential in irrigated wheat has been rising at the rate of 1 percent per year over the past three decades, an increase of around 100 kilograms per hectare per year. For both rice and wheat, a more dramatic shift in yield potential is anticipated over the next decade with the development of super-high-yielding varieties that are already in the research pipeline at the International Rice Research Institute and the International Maize and Wheat Improvement Center. These varieties are the result of a deliberate change in plant architecture introduced to increase the ratio of grain-to-plant biomass and are expected to increase yields by 15–20 percent. These super-high-yielding varieties have been developed using only conventional breeding techniques.
Starting in the early 1980s, the more marginal production environments began to experience the benefits of the Green Revolution, especially for wheat, rice, and maize. In the case of wheat, the rate of growth in yield potential in drought-prone environments was around 2.5 percent per year during the 1980s and 1990s (see figure). Interestingly, the source of this growth in yield potential has changed through time. Initially the growth in yield potential for the marginal environments came from technological spillovers as varieties bred for the high-potential environments were adapted to the marginal environments. During the 1990s, however, further gains in yield potential came from breeding efforts targeted specifically at the marginal environments. In both environments, the dramatic shifts in yield potential have come from conventional breeding methods.
In addition to their work on shifting the yield frontier of cereal crops, plant breeders continue to have successes in the less glamorous areas of maintenance research. These include plants with durable resistance to a wide spectrum of insects and diseases, plants that are better able to tolerate a variety of physical stresses, crops that require significantly lower number of days of cultivation, and cereal grain with enhanced taste and nutritional qualities.
In addition to plant breeding, research on crop and resource management plays an important role in sustaining improvement of crop productivity. The best varieties often fail to express their potential on farmers’ fields because of inadequate investment in the development and dissemination of complementary crop management technologies. Moreover, as discussed earlier, improved land and crop management practices can reduce environmental stress caused by intensive farming. With the current and anticipated future decline in cereal-crop prices, crop management innovations—given their ability to save on input use and thereby reduce unit production costs—will be increasingly crucial for sustaining the competitiveness of cereal-crop production. Farmers will eagerly seek technologies that improve the efficiency of input use in the quest to sustain farm profits in a world with increasingly integrated food markets. The rapid spread of zero-tillage in the rice-wheat zone of South Asia is a case in point. Farmers there achieve cost savings from reducing power, water, and labor use and at the same time help reduce environmental stress.
Biotechnology knowledge and tools are extremely complementary to those of conventional plant breeders, and a marriage of the two would have significant social benefits. Indeed, breeders and molecular biologists have been working together for some time now, especially in the areas of genetic fingerprinting, molecular marker-aided selection techniques, and tissue culture. Genetic engineering and genomics are areas in which future collaboration can be anticipated.
Molecular marker-aided selection methods have resulted in significant improvements in breeding efficiency by reducing the trial-and-error aspect of the breeding process and by allowing for time and sometimes cost savings. Genetic fingerprinting has made it easier for breeders to identify economically useful traits in genetic resource collections and to bring them into the breeding pools. Genes from wild species of rice, wheat, and maize have been brought into the breeding pools with the help of tissue culture. Genetic engineering could widely extend the breeder’s impact by bringing genes from other species into the breeding pools for cereal crops.
While exciting new developments in biotechnology are grabbing many of the headlines, the conventional research pipeline has not run dry. Conventional research methods will continue to be an important source of technology supply for crop improvement and management. Advances in biotechnology can play an important complementary role by strengthening the breeder’s toolkit and extending the reach of conventional methods. At the same time, increased understanding and acceptance of research tools that draw on farmers’ participation could help target research outputs to particular environmental and socioeconomic niches. Agricultural scientists have at their disposal a wide spectrum of complementary tools, from molecular biology to social sciences. Choosing not be inclusive and integrative can be counterproductive to the goal of sustainable food security for the poor in the developing world.
For further information see P. L. Pingali, M. Hossain, and R. V. Gerpacio, Asian Rice Bowls: The Returning Crisis? (Wallingford, U.K.: CAB International, 1997); P. L. Pingali and P. W. Heisey, “Cereal-Crop Productivity in Developing Countries: Past Trends and Future Prospects,” in J. M. Alston, P. G. Pardey, and M. Taylor, eds., Agricultural Science Policy (Baltimore, Md.: Johns Hopkins University Press for IFPRI, 2001).
Prabhu L. Pingali (p.pingali@cgiar.org) is director of the Economics Program at the International Maize and Wheat Improvement Center, Mexico City, Mexico