Sustainability of rice in the global food system

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SUSTAINABILITY OF RICE IN THE GLOBAL FOOD SYSTEM

A joint publication of IRRI and the Pacific Basin Study Center

Edited by N.G. Dowling, S.M. Greenfield, and K.S. Fishcer

Sustaining food security in Asia: economic, social, and political aspects

Mahabub Hossain

Will Asia be able to sustain favorable food balances and further improve food security for low income households? This paper addresses these issues by assessing the impact of recent socioeconomic developments on the organization of the production of rice, the dominant staple food in Asia. It also analyzes the forces that influence the trends in demand and supply of rice and examines the political factors that could affect the trade-off between pursuing self-sufficiency in domestic production and achieving self-reliance through trade to sustain food security. The paper argues that the rapid increase in rural wages associated with growing economic prosperity, and changes in the tenancy market from sharecropping to fixed-rent tenancy and ownership cultivation, will put an upward pressure on the cost of rice cultivation in middle- and high-income countries and regions that have achieved a high level of productivity. The comparative advantage in rice cultivation will shift from irrigated to rainfed environments. The uncertainty in achieving food security through international trade because of the thin and volatile rice market would encourage middle- and high-income Asian countries to maintain a safe capacity of producing this staple grain through market interventions, although such action is not economically efficient.

A stable landscape? Social and cultural sustainability in Asian rice systems

Francesca Bray

Agriculture is a human system and agricultural sustainability, however defined, is a goal that has to take into account the social as well as the environmental and technical aspects of farming systems. Social sustainability, environmental sustainability, and sustainable increases in food production are not necessarily compatible. The concept of "landscape" is used in this paper to explore the links and contradictions between these dimensions, and the complex interests that are at stake when transformation in the name of sustainability is proposed. Three examples of wet-rice farming systems in East and Southeast Asia are considered: the Lower Yangzi provinces of China in late imperial times as an example of the long-term social, economic, and environmental equilibrium that progressive intensification and diversification of wet-rice farming can underpin; the contemporary Vietnamese province of Thai Binh as an example of rice monoculture pushed to what appears to be the natural limits of productivity; and the rice-farming sector of Japan, whose acknowledged inefficiencies have not prevented a fierce resistance to reform that unites the nation.

Sustainability, food systems, and rice: exploring the interactions

Kenneth A. Dahlberg

This paper seeks to explore the main elements involved in pursuing more sustainable rice systems and cultures and how they fit into and interact with the progressively larger frameworks and structures of regenerative food systems and sustainable development. A number of different analytic, scale, and time horizon issues are involved. These are reviewed in the first section via contextual analysis. Next, a range of existing and emerging social paradigms are reviewed to clarify their fundamentally different assumptions about the nature of society and how these affect policy prescriptions. Several recent food policy studies are reviewed in this light. The third section discusses a number of structural, institutional, and value questions that existing paradigms have not asked or have left unanswered. The fourth section outlines the nature and structure of regenerative food and fiber systems and reviews how they are based on new evaluative criteria involving the health and regenerative capacities of their biological and social systems. This framework is then applied to historical and current rice cultures to outline how rice fits into efforts to create more sustainable food systems in Asia, and how such systems are in turn a central component in pursuing sustainable development internationally. The final section sketches the implications for research of employing a food systems approach within the larger framework of sustainability.

Genetic enhancement of rice yields

S. Peng and D. Senadhira

The yield potential of irrigated rice in the tropics has stagnated at 10 t ha-1 since 1966, when the first semidwarf indica variety, IR8, was released. During the past 30 yr, rice improvement efforts have been directed toward incorporating disease and insect resistance, shortening growth duration, and improving grain quality. Because 75% of all rice is produced on irrigated land, breaking the yield ceiling of irrigated rice through genetic improvement has become the top priority in rice research. The yield of current semidwarf varieties is limited largely by dry matter production. It can be improved by modifying the present high-yielding plant type. High DM accumulation coupled with selection of large panicles will lead to an increased sink size (defined as spikelet number per unit ground area). Grain filling has to be improved to convert an increased sink into additional grain yield. Lodging also limits yield, especially at high yield levels. Studies on chemical composition and physical structure governing stem strength are needed. Breeding for the new plant type using tropical japonica germplasm has resulted in a phytotype with increased sink size because of large panicles and fewer unproductive tillers.

The yield potential of this new plant type is limited by poor grain filling. Exploitation of hybrid vigor or heterosis through hybrid rice breeding provides a good opportunity for increasing the yield potential of rice in the tropics. Intersubspecific hybridization between indica and japonica varieties has shown higher heterosis for yield than indica/indica hybrids. Hybrids between elite indica varieties and the new plant type tropical japonicas are being developed. Rainfed rice constitutes about 45% of the total rice-growing area in Asia. The present average yield of 2 t ha-1 should be increased to about 4 t ha-1 during the next 30 yr. This increase is also essential to release the pressure on irrigated rice. Water- and soil-related stresses are the constraints to increases in rainfed rice production. Tolerance for these abiotic stresses is available in the germplasm. Various combinations of these tolerance traits that can match the many different subecosystems are needed to increase and stabilize yields.

The success so far in developing improved varieties tolerant of abiotic stresses has been limited mainly because understanding of the physiological mechanisms and the inheritance of these traits is inadequate, and rapid and reliable techniques for screening genotypes, especially for multiple stresses, are lacking. Some progress has been made in developing tolerance of flooding and salinity. But for drought and other soil stresses, progress has been slight. We urgently need to intensify research on the genetics and physiological mechanisms of tolerance for abiotic stresses. This research is also essential for exploring new genetic engineering opportunities such as marker-aided selection techniques that seem to offer solutions for breeding rainfed rice.

Intensification of rice production systems: opportunities and limits

W. Reichardt, A. Dobermann, and T. George

Intensification of rice systems implies the disturbance of existing equilibria in soil by extensive submergence and elevated levels of agrochemicals in nutrient and pest management. In keeping pace with the deployment of ever higher yielding rice varieties, nutrient management risks adversely affecting the agronomic and environmental sustainability of rice lands. The first signs of declining productivity reported from on-station field experiments have been linked to reduced soil N supplying capacity. Furthermore, neglect of non-N mineral fertilizers has frequently led to depletion in K, P, S, and Zn. In regions with rapidly progressing intensification, inputs of organic carbon as residue or as manure have been discontinued. On the other hand, the organic matter pool of rice-cropping systems can be seen as a mechanistic key to nutrient supply. With microbial biomass as its most rapidly recycled segment, the organic phase serves as a source of biocatalysts governing nutrient supply and as a nutrient pool by itself. The dynamics of the organic matter phase in flooded soils are fundamentally different from those in aerated soils. Green manure derived from N-fixing organisms has its merits in less intensified systems where it can provide sufficient N at N rates below 100 kg ha-1. Options for sustaining the most intensified resource bases would have to include a demand-driven integrated inorganic/organic nutrient management and rotation cropping, the latter mainly in response to periodic annual shortages of irrigation water. As a prerequisite for the rotation of rice with upland crops, however, an efficient, fine-tuned nutrient and pest management would have to be established. In tropical wetlands, intensive rice cropping is dealing with a greater diversity of habitats and biological and biogeochemical functions over space and time than other agroecosystems. In accordance with ecological theory, this is likely to confer maximum stability and sustainability on agricultural wetlands.

Importance of rice pests and challenges to their management

M.B. Cohen, S. Savary, N. Huang, O. Azzam, and S.K. Datta

New technologies and a greater understanding of the rice ecosystem are contributing to more effective and sustainable pest management in farmers' fields. Prioritizing research on rice pests (insects, plant diseases, and weeds) has been made difficult by a lack of systematic survey data on pest losses in different ecosystems and under different production conditions. To bridge this knowledge gap, work in progress is quantifying risk probability and risk magnitude of pest injuries. Surveys in farmers' fields have been conducted at hundreds of sites in several countries to quantify the risk probability for various pests. Experiments at IRRI have manipulated pest levels under varying production situations to quantify the magnitude of yield loss across these conditions. Researchers are applying biotechnology to produce rice varieties with improved resistance to insects and diseases. Marker-aided selection can improve the efficiency of rice breeding, and be used to "pyramid" multiple genes for resistance to a given pest. Plant transformation enables us to introduce novel resistance genes from any organism into rice. Varietal resistance to pests has many desirable features, such as environmental safety and convenience for farmers, but has suffered from a lack of durability as pest populations adapt to new resistant varieties. Researchers are using DNA fingerprinting to enhance understanding of pest population genetics and behavioral studies of insects to develop resistance management strategies for the sustainable use of resistant cultivars in farmers' fields.

Weeds: a looming problem in modern rice production

M. Olofsdotter, A. Watson, and C. Piggin

Weeds are a constant problem in all rice-growing areas. The reduced availability of water and labor is the driving force that changes cultural practices in rice production. The shift from transplanted to direct seeding of rice aggravates the problem because weeds and the crop emerge together and it is more difficult to use early flooding for weed control. Herbicide use is increasing in Asia because herbicides are cheaper than hand labor and easy to apply. Herbicides have negative effects, however, such as changes in weed flora that result in the increase of hard-to-control weed species, environmental contamination, and selection for herbicide-tolerant weed biotypes. Thus, it is becoming increasingly important to develop integrated weed management systems in which several control measures are combined and herbicide use is minimized. More tools are therefore required to complement good agronomic practices. IRRI research has shown that allelopathy and biological control have the potential to increase weed control. Some rice cultivars can suppress weed growth by more than 50% under field conditions. Research on biological control shows promising results for controlling some of the major weeds in rice.

Management of water as a scarce resource: issues and options in rice culture

S.I. Bhuiyan, T.P. Tuong, and L.J. Wade

Rice culture is known for its crucial dependence on an adequate supply of water. But how much water is really needed for producing the crop? How can water management and rice production systems be improved to obtain more rice per unit of water supplied? How can the agrochemicals associated with rice production be managed for minimal impact on the quality of water resources that are vital for sustainable agriculture? These and other related questions must be adequately addressed to achieve the needed rice production growth in Asia, where water for agriculture is becoming increasingly scarce. This paper addresses these issues in a holistic perspective that elucidates options from the farm to the irrigation system and basin level. Prospective technological innovations in areas such as crop management and varietal development, which should improve water use efficiency in rice culture, are also discussed.

Securing the future of intensive rice systems: a knowledge-intensive resource management and technology approach

L.M.L. Price and V. Balasubramanian

Scientific achievements in increasing yields have been fast and profound in Asia's intensive rice systems, but farmers' knowledge and corresponding practices have not kept pace, particularly in disease, pest, nutrient, and water management. Knowledge-intensive resource management and technology can be used to fine-tune farmer management to enhance profitability and environmental protection in high-productivity systems. This paper identifies, defines, and discusses two strategies: (1) KIT-P, knowledge physically embedded in machines and instruments that provide field-level information to farmers, and (2) KIT-H, knowledge embedded in the farmers themselves and composed of information directly linked to cognition and acquired through a process of learning and experimentation. Making more knowledge and information available to farmers is one way of addressing the problems of resource depletion in both quantity and quality, of degradation of the environment, and of increased health risks caused by lack of appropriate knowledge in managing changes in cropping systems. Knowledge-intensive approaches are expected to serve farmers in decision making and in enhancing precision as they come to terms with the Green Revolution of the past and face future challenges.

Rice and the global environment

R. Wassmann, T.B. Moya, and R.S. Lantin

The productivity and sustainability of natural resources ultimately depend on favorable climatic conditions that are currently being altered by human activities. The key process for changing the atmospheric environment is the combustion of fossil fuels, but agricultural activities are also associated with the release of trace gases that affect the radiation balance of the Earth. The ambivalent role of agriculture, one of the most important sectors affected by global change as well as one of the contributors to a changing environment, has prompted IRRI to investigate the interaction of rice cultivation and changing climate. Irrigated rice production at ambient growth temperature (25 oC) will benefit from increased atmospheric CO2. Increased rates of CO2 assimilation and decreased rates of maintenance (dark) respiration at elevated CO2 result in increased plant biomass accumulation. Grain yield also increases with rising atmospheric CO2 concentration. Concomitant temperature increases, however, could entail substantial losses in future yield because rice yields are extremely sensitive to temperature increases during the grain-filling stage, which can lead to abundant spikelet sterility. The coupling of crop models to future climate scenarios for the main rice-growing areas has given diverging results, from an 11% increase to a 12% decrease, depending on the model and scenario. The most significant contribution by rice fields to global change stems from the emission of the greenhouse gas methane. Methane formation in wetland rice fields is an important component of carbon cycling in the predominantly anaerobic soils. The quantity of methane emitted to the atmosphere is regulated by inherent soil and climate properties as well as agricultural practices. The shift from organic manure to mineral fertilizers substantially reduces methane emission. Likewise, the flux is reduced by intermittent drying of soils. New, high-yielding cultivars also reduce methane emission compared with traditional varieties. These findings help identify promising strategies to mitigate methane emission without yield losses, but they still have to be corroborated and improved by field experiments.

New Frontier Projects: beyond the pipeline

J. Bennett, J.K. Ladha, V. Schmit, and J. Sheehy

Because of the advent of biotechnology tools over the past 15 years, rice breeding in the 21st century will be able to use many of the discoveries in the basic biosciences to solve problems that have proved intractable using traditional breeding methods. Breeders will also be able to contemplate the introduction of traits that were previously not considered feasible for rice, although they were well known in other crops, such as N2 fixation, apomixis, and perenniality. This chapter describes the rationale for introducing these traits into rice and potential or actual research approaches for achieving these ambitious goals. The chapter concludes with an overview of the challenge of achieving higher yields in rice from the perspective of systems analysis and mathematical modeling. Based on this perspective, New Frontier Projects at IRRI combine the high risk of failure with a high impact if successful. Each project is being evaluated by IRRI and collaborating institutes. These projects extend beyond the pipeline that carries completed research from the laboratory or the breeding plot into farmers' fields.

Rice genetics resources

M.R. Bellon, D.S. Brar, B.R. Lu, and J.L. Pham

The use and conservation of biodiversity are increasingly important concerns for society. In this paper, we focus on the genetic diversity aspects of biodiversity as they pertain to the rice gene pool and its contribution to agriculture and our food supply. We review what is known about the rice gene pool and the need to conserve it. We investigate the threats and challenges that conservation of rice genetic diversity faces from changing socioeconomic and cultural conditions, as well as from the development and widespread adoption of modern varieties. We analyze the different conservation strategies that have been developed, emphasizing their strengths and weaknesses. We also examine the use of rice genetic diversity, from the perspectives of both farmers and breeders. Finally, we deal with current policy issues associated with the conservation and use of the rice gene pool, such as intellectual property rights and the Convention on Biological Diversity, and discuss the challenges ahead.

Biological diversity of rice landscapes

K. Schoenly, T.W. Mew, and W. Reichardt

A tropical rice field offers a biologically diverse and dynamic environment for microbial, floral, invertebrate, and vertebrate populations to flourish shortly after fields are flooded and well after canopy closure. A significant challenge is how to inventory, characterize, and assess such biodiversity in an agroecosystem of staggering taxonomic richness, interconnectedness, and spatiotemporal flux. For invertebrate biodiversity, research indicates that most insect pests are controlled by the activity of not just a few natural enemies, but a whole array, through a complex and rich food web of generalist and specialist predators and parasites that live above, below, and at the water surface as well as in flooded and aerated soil habitats. Microbial communities in the soil and on the rice plant, functioning as biocatalytic and antagonistic agents, may also have sufficient similarity in functions to maintain ecosystem-level processes within narrow limits. The roles that such functionally diverse organisms play as stabilizing and buffering agents in rice production systems remain to be discovered through future laboratory and field research.

The economic value of genetic improvement in rice

R.E. Evenson

Rice productivity increased dramatically during the Green Revolution of the late 1960s. A number of factors contributed to this increase, such as expansions in multiple cropping, irrigation, and input use. Genetic improvement in the form of modern, high-yielding rice varieties contributed productivity gains as well. These genetic improvements often enabled and complemented other productivity-enhancing activities. This paper reviews data on varietal releases from approximately 100 rice breeding programs from 1965 to 1990. The data showed that IRRI aided genetic improvement both directly by making crosses leading to released varieties and indirectly through parental, grandparental, and other ancestral contributions to the genealogies of released rice varieties. The International Network for Genetic Evaluation of Rice-INGER-facilitates the international exchange of genetic resources.

Food, energy, and the environment: implications for Asia's rice agriculture

Vaclav Smil Rice

is now the world's largest cereal crop, but its share of typical Asian diets has been decreasing because the grain is being displaced by greater consumption of wheat and animal foodstuffs. Nevertheless, total harvests will have to increase to satisfy Asia's growing population. Because of continuing losses of rice fields to urbanization and industrialization-the process that also leads to the loss of valuable ecosystem services-this will have to be done largely through higher yields. Two inevitable consequences of the necessary increased use of fertilizer will be higher inputs of reactive nitrogen into the environment and an increased generation of greenhouse gases.

Rice production constraints in China

Justin Yifu Lin

This paper reports the results of two surveys, one on agronomists at the agricultural bureaus in China's rice-producing prefectures and the other on scientists at China's various rice research institutions. In the study, two yield gaps are identified. Yield gap I refers to the difference between the highest experimental yield and potential farm yield under favorable conditions. This gap reflects the differences between the characteristics of experimental varieties and existing farm varieties and between the environment of the experimental plot and farm fields. Yield gap II refers to the difference between potential farm yield under favorable conditions and actual farm yield, taking the existing farm varieties as given. This gap reflects the constraints arising from weather, soil, pests, diseases, and so on. The study finds that the highest experimental yield is about 16 t ha-1, which is about three times the average farm yield in 1990. More than 70% of the gap between the highest experimental yield and the average farm yield belongs to yield gap I. Both yield gaps I and II can be attributed to a small number of factors. For yield gap I, important variety-related factors are canopy architecture, photosynthetic rate, and growth duration, and important environment-related factors are duration of sunshine, accumulated heat unit, and soil condition. For yield gap II, the main constraints arise from low soil fertility; cold, waterlogged, and acid soil; drought, submergence, heat, and cold at the seedling, vegetative, and anthesis periods; lodging; weeds; sheath blight; and stem borer. Most of the above constraints for yield gap I and II cannot be easily overcome by conventional breeding methods. Therefore, they are the potential areas where biotechnological research may have the highest returns.

Priorities and opportunities of rice production and consumption in India for self-sufficiency

R.S. Paroda

From 1965 through 1995, India surged forward in its national rice production from a situation of food deficit to one of sustainable surplus. This achievement was made possible primarily because of the adoption of high-yielding varieties, the extension of irrigation, and expansion of the area under rice cultivation. The highest growth rate in rice productivity occurred between 1985 and 1995 because of the joining of the eastern region of the country with the rapidly advancing western region and the steadily growing southern region. To sustain this self-sufficiency and meet the food requirements of millions of people, India needs at least a 3% yr-1 productivity growth rate to achieve rice production targets of 95 and 125 million tons by the years 2000 and 2020, respectively. This growth rate can be achieved by (1) using available technology while reducing the constraints to rice production, (2) increasing genetic yield and stabilizing productivity through hybrid technology, and (3) exploiting abundant untapped opportunities in potential rice-growing environments.

Because inventory management is essential from the natural resource base to the distribution system, information systems must support national and state decision making on the food supply. National decision making currently emphasizes international markets, buffer stocks, and operational food policies, while state decision making stresses local prices, market regulations, seasonal weather aberrations, production trends, and infrastructure for distribution. Sustainable food security in general, and rice production in particular, require the mobilization of political support to reform existing policies and encourage cooperation and coordination between the central government and different states. Food security also depends on the management and conservation of the natural resource base in a manner that will ensure the continued supply of rice for future generations. In this context, sustainable determinants and nonsustainable indicators have been identified for different agroecological zones.

To bridge technology transfer gaps, different methods are suggested for achieving sustainability. Current constraints to rice production and consumption may be ameliorated by research and development in an international context. Decentralization of research and technology development based on the comparative advantages and needs of different countries may contribute to synergy and further progress for all. Planning for sustainable food security should emphasize information availability, resource use efficiency and management, input policies, policy research, and technology development. The greatest challenge will be to reform policy processes themselves, which will have to focus more on participation and social mediation to counter the complexities and uncertainties in achieving sustainability of rice production.

Sustaining food security in Asia: economic, social, and political aspects

A stable landscape? Social and cultural sustainaiblity in Asian rice systems

Sustainability, food systems, and rice: exploring the interactions

Genetic enhancement of rice yields

Intensification of rice production systems: opportunities and limits

Importance of rice pests and challenges to their management

Weeds: a looming problem in modern rice production

Management of water as a scarce resource: issues and options in rice culture

Securing the future of intensive rice systems: a knowledge-intensive approach

Rice and the global environment

New frontier projects: beyond the pipeline

Rice genetics resources