Vietnam and IRRI: A Partnership in Research Proceedings of a Conference held in Hanoi , 4-7 May 1994

Editors G.L. Denning and Vo-Tong Xuan

Vietnam and IRRI: A Partnership in Rice Research Proceedings of a Conference held in Hanoi Vietnam, 4-7 May 1994

Editors G.L. Denning and Vo-Tong Xuan

1995

Contents

Foreword ix

Message from His Excellency Prime Minister Vo Van Kiet xi

Preface xiii

KEYNOTE ADDRESSES

Policy renewal in agriculture and rice production in Vietnam 3 His Excellency Minister Nguyen Cong Tan

Rice research for the 21st century 9 Klaus Lampe

INVITED PAPERS

History of Vietnam-IRRI cooperation 21 Vo-Tong Xuan

World rice market and Vietnam’s agriculture beyond 2000 31 Mahabub Hossain

National program for Vietnam on food crops research and development 41 Vu Tuyen Hoang

Agriculture and environment: toward a sustainable agriculture in Vietnam 45 Le Quy An

Research organization and management: a strategy and a weapon 47 Byron Mook

RESEARCH PAPERS

Varietal improvement

Vietnam-IRRI collaboration in rice varietal improvement 55 G.S. Khush, Vo-Tong Xuan, Nguyen Van Luat, Bui Chi Buu, Dao The Tuan, and Vu Tuyen Hoang

Sustaining rice productivity in Vietnam through collaborative utilization of genetic diversity in rice 61 Nguyen Huu Nghia, R.C. Chaudhary, and S.W. Ahn Current status and future outlook on hybrid rice in Vietnam 73 Nguyen Van Luat, Nguyen Van Suan, and S.S. Virmani

Classification of traditional rice germplasm from Vietnam based on isozyme pattern 81 Luu Ngoc Trinh, Dao The Tuan, D.S. Brar, B.G. de los Reyes, and G.S. Khush

INSA-IRRIcollaboration on wild rice collection in Vietnam 85 Dao The Tuan, Nguyen Dang Khoi, Luu Ngoc Trinh, Nguyen Phung Ha, Nguyen Vu Trong, D.A. Vaughan, and M.T. Jackson

Ecophysiology of rice-crop establishment in wet direct seeding in Vietnam with emphasis on anaerobic seedling growth 89 Minoru Yamauchi, Pham Van Chuong, and Nguyen Minh Chau

Water and nutrient management Leaching of acid sulfate soils and its environmental hazard in the 99 Le Quang Minh, To Phuc Tuong, and Vo-Tong Xuan

Dry seeding rice for increased cropping intensity in Long An Province, Vietnam 111 Tran Van My, To Phuc Tuong, Vo-Tong Xuan, and Nguyen Thanh Nghiep

Effect of phosphorus and growing season on rice growth and nutrient accumulation on acid sulfate soils 123 Phan Thi Cong, Cong Doan Sat, E.G. Castillo, and U. Singh

Improving nitrogen-use efficiency of direct-seeded rice on alluvial soils of the Mekong River Delta 137 Ngo Ngoc Hung, U. Singh, Vo-Tong Xuan, R.J. Buresh, J.L. Padilla, Tran Thanh Lap, and Truong Thi Nga

Nitrogen-use efficiency in direct-seeded rice in the Mekong River Delta: varietal and phosphorus response 151 Vo Thi Guong, Tran Thanh Lap, Nguyen My Hoa, E.G. Castillo, J.L. Padilla, and U. Singh

Management of urea on degraded soils of the Red River Delta: effect of growing season and cultural practice 161 Tran Thuc Son, U. Singh, J.L. Padilla, and R.J. Buresh

Less-favorable ecosystems

Deepwater rice research in the Mekong River Delta 179 Vo-Tong Xuan, Le Thanh Duong, Nguyen Ngoc De, Bul Chi Buu, Pham Thi Phan, and D.W. Puckridge

Opportunities for upland rice research in Vietnam 191 MA. Arraudeau and Vo-Tong Xuan

vi Pest management

Relationships between rice intensification, plant nutrition, and diseases in the Red River Delta 201 Ha Minh Trung, Ngo Vinh Vien, Dinh Thi Thanh, Nguyen Thanh Thuy, Ha Minh Thanh, K.G. Cassman, T.W. Mew, P.S. Teng, and R.M. Cu

Relationships between rice intensification, rice plant nutrition, and leaf-yellowing disease in the Mekong River Delta 211 Pham Van Kim, R.M. Cu, P.S. Teng, K.G. Cassman, T.W. Mew, Truong Thi Nga, Nguyen Bao Ve, and Pham Van Bien

Reducing early-season insecticide applications through farmers’ experiments in Vietnam 217 K.L. Heong, Nguyen Thi Thu Cuc, Nguyen Binh, S Fujisaka, and D.G. Bottrell

Characterization of pests, pest losses, and production patterns in rainfed lowland rice of the Mekong River Delta 223 H.O. Pinnschmidt, Nguyen Dang Long, Tran Tan Viet, Le Dinh Don, and P.S. Teng

Surveys of pesticide use in three provinces of the Red River Delta 243 Ha Minh Trung, Ngo Vinh Vien, Dinh Thi Thanh, Nguyen Thanh Thuy, Mai Thi Lien, Ha Minh Thanh, P.S. Teng, T.W. Mew, and K.G. Cassman

Nematode parasites of deepwater and irrigated rice in the Mekong River Delta 251 Nguyen Thi Thu Cuc and J.-C. Prot

Social sciences

Change from deepwater to irrigated rice ecosystem in the Mekong River Delta. impact on productivity and on farmers’ income 263 Mahabub Hossain, Duong Ngoc Thanh, and F. B. Gascon

Supply responses of rice and three food crops in Vietnam 275 Nguyen Tri Khiem and P.L. Pingali

Gender roles in rice farming systems in the Mekong River Delta: an exploratory study 291 Truong Thi Ngoc Chi, Nguyen Thi Khoa, Bui Thi Thanh Tam, and T.R. Paris

Institution building

Strengthening the Cuu Long Delta Rice Research Institute 303 Nguyen Van Luat, Pham Sy Tan, and D.W. Puckridge

Costs and benefits of the Cuu Long Delta Rice Research Institute project in the Mekong River Delta 309 A.M. Mandac, Dang The Truyen, and Hoang Thi Mai Huong

vii Strengthening social science research capacity in Vietnam 323 Nguyen Tri Khiem and P.L. Pingali

Vietnam-IRRI collaboration in training: progress and priorities in human resource development 327 E.L. Matheny, R.T. Raab, and Vo-Tong Xuan

Vietnam-IRRIcollaborative activities on agricultural engineering 333 Pham Van Lang and G.R. Quick

WORKSHOP OUTPUT

Workshop output 337

Appendices

Participants 349

Acronyms and abbreviations 351

viii Foreword

Rice research seeks to generate knowledge and technologies that bring improvement in the welfare of rice-dependent households. In pursuit of this goal, individuals and institutions seek partnerships with expectations of increased effectiveness and efficiency. This volume documents the achievements of a quarter century of partnership between Vietnam and the International Rice Research Institute (IRRI) in rice research and identifies some of the remaining challenges and opportunities. IRRI has long recognized the value of collaborative research, as have the scientists of Vietnam. An early result of this partnership was the planting of seeds of IR8 (known as Than Nong 8 in the south and Agriculture 8 in the north) by Vietnamese farmers in 1968. Rapid acceptance of this and many other IRRI-derived lines followed. The exchange of varieties and information continued during the early 1970s, and direct collaboration resumed shortly after reunification when scientists of the Socialist Republic of Vietnam participated in the International Rice Research Conference in April 1976. Suffering the effects of war and economic isolation, Vietnam progressed slowly toward rice self-sufficiency during the late 1970s and most of the 1980s. However, to accelerate economic growth, the Government Introduced important policy reforms in 1988 that laid the foundation for a transition to a market-oriented economy. Vietnam's rice farmers responded quickly and, by 1989, Vietnam emerged as the world's third largest rice exporter — a position it retains today. Both IRRI and the Government of Vietnam take this opportunity to express their deep appreciation to the Government of Australia for its financial contribution to rice research in Vietnam. This support, which began at a time when few donors were willing to make such a public commitment, has been a source of great encouragement to researchers concerned with increasing rice production. More recently, the United Nations Development Programme and the International Development Research Centre of Canada have also provided valuable support to rice research in Vietnam. As Vietnam and IRRI prepare for the 21st century, we can look back with satisfaction on the results of this long and productive partnership in rice research. However, new problems are emerging and new directions are needed. The Vietnam-IRRI Rice Conference was an important milestone in documenting progress and charting new paths to sustainable agricultural growth. With the release of this volume, we hope that researchers, students, and policymakers — indeed all those concerned with rice — will be challenged and encouraged to redouble efforts toward a brighter future for rice producers and consumers in Vietnam.

Klaus Lampe Vu Tuyen Hoang Director General National Coordinator International Rice Research Institute Vietnam-IRRI Cooperation Los Baños, Philippines Ministry of Agriculture and Food Industry Hanoi, Vietnam

Message from His Excellency Prime Minister Vo Van Kiet

The Government of Vietnam is well aware that the economy of the country is based mainly on agricultural production, of which rice production ranks in first place. Therefore, promoting its production has an important role not only in food self-sufficiency for the population but also in exports, which contribute to foreign-exchange earnings. The progress in rice production assures food security for the country as well as stability for the farmers’ life. It makes way for major changes in agriculture and for development of industry. Therefore, the Government of Vietnam pays great attention to agriculture in general and rice production in particular. For many years, the International Rice Research Institute has given Vietnam valuable assistance and has provided a great variety of germplasm. Varieties coming from IRRI or those developed from IRRI germplasm are planted widely throughout the country and occupy 73% of the total area under rice in Vietnam. This has brought a major increase in agricultural production. IRRI has trained many Vietnamese scientists who are now using their knowledge to help farmers in applying new technologies in rice production. The Government of Vietnam greatly appreciates the assistance of IRRI and considers its contribution as one of the most important factors in the achievement of the increased rice production of recent years. On behalf of the Government and people of Vietnam, I would like to express our sincere thanks to IRRI and its scientists for the effective assistance given to our country in the field of agriculture. On this occasion, I would also like to thank the Vietnamese scientists for their contribution to the increase in rice production in our country during recent years. It is hoped that the fruitful, cooperative relationship between IRRI and Vietnam will develop further in the future. I hope that the scientists of IRRI and Vietnam attending this conference will work out an effective program of cooperative research that will contribute further to the development of sustainable agriculture in Vietnam, to the improvement of rice quality, and to the narrowing of the gap between our country and other rice producers all over the world. I wish all the best to all participants and success to the conference.

Preface

Since the introduction of crucial agricultural policy reforms in 1988, Vietnam’s rice production has grown annually by more than 5%, resulting in surpluses for export. From a state of food deficits and poor incentives for farmers, the rice economy of Vietnam was transformed to one of great dynamism. Adoption of modern varieties rose sharply, fertilizer use increased, and double cropping of rice became common — especially in the Mekong River Delta. Farmers sought new technologies, invested in their land and water resources, and forged commercial links to ensure access to input and output markets. Vietnam’s success story has taken many observers by surprise. Initially, some analysts predicted that the surpluses would be short-lived and that the clearing of stocks and population growth would soon reduce the country’s export share. Yet by 1994, exports continued to exceed 1.5 million tonnes annually, with no apparent decline in sight. It is widely recognized that the availability of modern rice technologies — especially high-yielding, early-maturing varieties — contributed greatly to Vietnam’s rapid growth in rice production. The policy reforms of 1988 and the existence of modern rice technologies provided the conditions for farmers to exploit the potential of their land, water, and labor resources. Researchers from Vietnam and IRRI have worked in partnership since 1968 to provide the scientific base for this transformation of the rice economy. Since the introduction of IR8, a total of 63 breeding lines from IRRI have been released in Vietnam. Adoption of these varieties now extends to 70% of the rice-growing area. Supporting the introduction, testing, and evaluation of modern rice varieties and related technologies was a strong network of national research institutions from the Ministry of Agriculture and Food Industry and agricultural universities under the Ministry of Education and Training. Since 1964, 362 Vietnamese scientists have been trained at IRRI in degree and nondegree programs (90% of them since 1981). During the latter half of 1993, discussions were initiated to establish the direction of Vietnan-IRRI collaboration for the remainder of the 1990s and into the 21st century. It was clear that much of the collaboration between Vietnamese and lRRI scientists had not been adequately documented; and without a systematic compilation of research progress, it would be difficult to establish priorities for future work. As a result of these deliberations, a Vietnam-IRRI Rice Conference was held in Hanoi, Vietnam, in May 1994. The theme of the conference was “Partnerships for rice research and development in Vietnam: toward increased sustainability and productivity by the year 2000.” One hundred and five scientists attended the conference: 82 Vietnamese (representing 17 institutions), 22 from IRRI, and one from the International Service for National Agricultural Research. The objectives of the conference were twofold: • To review past collaboration between Vietnam and IRRI; and • To identify strategic research and development priorities for Vietnam’s rice sector for 1994-2000. This volume includes 36 papers that were presented at the conference. Keynote addresses were presented by His Excellency Nguyen Cong Tan, Vietnam’s Minister of Agriculture and Food Industry, and Dr. Klaus Lampe, Director General of IRRl. Both addresses emphasized the need to balance concerns for productivity and equity while sustaining the resource base and protecting the environment. Minister Tan outlined the key policy changes that have promoted agricultural growth and the complementary role of modern rice-farming technologies. Dr. Lampe presented a vision of rice research for the 21st century, identifying several important areas of future collaboration. Five individuals were invited to share their insights on a range of topics of broad interest to Vietnam’s rice sector. Their papers were • History of Vietnam–IRRI cooperation; • World rice market and Vietnam’s agriculture beyond 2000; • National program for Vietnam on food crops research and development; • Agriculture and environment: toward a sustainable agriculture in Vietnam; and • Research organization and management: a strategy and a weapon. The remaining 29 papers are the products of Vietnatn–IRRI collaboration; each coauthored by Vietnamese and IRRl scientists. Papers are grouped into the following themes: varietal improvement; water and nutrient management; less-favorable environments: pest management; social sciences; and institution building. In a final session, participants were asked to identify priorities for future Vietnam–IRRI collaboration. Based on an assessment of past progress in rice research, the emerging problems and opportunities, and Vietnam’s agricultural policy priorities, it was decided to focus the discussions on three major ecological conditions: • Intensive systems (Red River and Mekong River deltas); • Uplands; and • Flood-prone and problem-soil areas.

In addition, the cross-cutting theme of “Genetic conservation and varietal improvement” was identified as an area of collaboration of high priority to both Vietnam and IRRI. Small working groups comprising Vietnamese and IRRI scientists identified key constraints, research priorities, and potential collaborative projects. The outputs of these four working groups appears as the final section of this volume. The conference and this publication would not have been possible without the support of many committed people in Vietnam and at IRRI. In Vietnam, responsibility for local planning and preparation for the conference was accepted by a Local Organizing Committee comprising Professor Dr. Vu Tuyen Hoang (Chairperson), Dr. Nguyen Ngoc Kinh. and Dr. Vo-Tong Xuan. Numerous scientific colleagues and support staff helped ensure excellent organizational and administrative arrangements. We gratefully acknowledge the excellent logistic support provided by staff of the Department of Agricultural Science and Technology in Hanoi. At IRRI and in Vietnam, Mr. Abraham Mandac of IRRI’s International Programs Management Office provided invaluable managerial support. Editorial services for these proceedings were provided by Mr Gil Croome. Finally, we gratefully acknowledge the valuable contribution of the Australian International Development Assistance Bureau in supporting costs associated with the conference and the publication of this volume.

G. L. Denning Vo-Tong Xuan Head Vice Rector, University of Cantho, and International Programs Management Office Director, Mekong Delta Farming Systems International Rice Research Institute Research and Development Centre Los Baños, Philippines Cantho, Vietnam

xiv Denning and Xuan Keynote addresses

Policy renewal in agriculture and rice production in Vietnam

His Excellency Minister Nguyen Cong Tan 1

The Vietnam—IRRI Rice Conference, organized by the Ministry of Agriculture and Food Industry (MAFI) in collaboration with the International Rice Research Institute, symbolizes the cooperation between Vietnam and IRRI, and is an encouragement for Vietnamese scientists and farmers. IRRI's assistance to Vietnam over the past years, especially the transfer of good rice varieties and the training of scientific staff for Vietnam, has been significant — the area planted with IRRI rice varieties, or varieties with gene sources from the IRRI germplasm bank, now totals 4.7 million ha. A great number of IRRI rice varieties with high yield, broad adaptability, and resistance to pests, and diseases have been sown in different regions since the mid-l970s, and created a revolution in rice production in Vietnam. Many Vietnamese scientific staff trained at IRRI have played an active role in the research and transfer of advanced technologies on rice production to farmers. The assistance of IRRI has been appreciated by the State of Vietnam and has been one of the major factors in the advances in rice production of Vietnam over recent years. The Friendship Award presented to IRRI by the State of Vietnam is an affirmation of the Government and the people of Vietnam's appreciation of IRRI's assistance and is also a symbol of their wish to further develop the cooperation between Vietnam and IRRI in the future. Vietnam is predominantly an agricultural country with abundant agricultural resources and over 70 million inhabitants, of whom 50 million are in agricultural households. The population is growing and is expected to reach 80 million by the end of this century and 100 million in the early years of the next. Stretching from 8°N to 23°N with a variable topography, including many high mountains, Vietnam has several specific climatic areas: the typically tropical area, warm-humid all year round and ample sunshine, for example, the area of the southern delta; the tropical monsoon area with cold winters, like the northern delta and midland; the tropical plateaux, which are cool all year round with a long dry season, like the Central Highland; the subtropical areas with cool summers and bitterly cold winters, like the northern mountainous areas; and also those areas with a mixture of northern and southern climates, like the central coast of the country. These and other characteristics create agroecological diversity so that the agriculture of Vietnam includes tropical and subtropical fauna and flora. Vietnam has 33 million ha of land, of which 7 million ha are agricultural land that has been developed over many generations. There is a possible expansion of 1–2 million ha of various types of soil: in the fertile alluvial soils of the Red River and Mekong River deltas, in the red basaltic soils in the Central Highland, and in other soils that, if improved, could become fertile and an additional potential land resource for high-yielding crop development. Abundant water resources (a long rainy season, 6–7 mo of rain/yr, with an annual rainfall of 1,800 mm and water from large rivers, especially the Mekong and Red rivers, together with underground water) make it possible to irrigate almost all the cultivated area. With 3,200 km of coastline, Vietnam has a great potential for fishing and aquaculture in both salt and brackish water. One of the most important resources for agriculture in Vietnam is the farmers — they are over 90% literate, diligent, dynamic, and creative, with a 1,000-yr- long agricultural tradition, and the capacity to learn quickly and adopt new scientific advances and technologies.

1 Ministry of Agriculture and Food Industry, Ngoc Ha, Bach Thao, Hanoi, Vietnam After reunification in 1975, Vietnam entered a period of reconstruction after several years of war. During the past years, the State of Vietnam has put great efforts into developing agriculture with the aim of improving the people’s, especially farmers’, living conditions, foremost by focusing on food production in general and rice production in particular. However, during the 1976-88 period, food production, especially rice production, developed slowly and erratically — rice paddy production rose from 11.8 million t to 17.0 million t, while the population increased rapidly by over 1 million/yr. Thus the increase in rice paddy production per capita was slight, from 240 kg/person per year up to 266 kg/person per year. With the subsidy policies, this caused serious food shortages during a 14-yr period and the country even had to import as much food as the equivalent of 800,000 t in 1 yr. Still, much of the population subsisted in conditions of hunger and poverty. Being a poor country, heavily damaged by war and faced with a complicated international environment, Vietnam had only the choice of a self-reliance approach, using its potential capacity and all available resources — particularly the Vietnamese farmers and other agricultural resources — at the same time seeking international assistance to create a new situation for agriculture in the country. The decisive policy of all-round agricultural renewal was initiated in early 1988. Since then, the State of Vietnam has integrated and renewed its policies and the institutional system to provide momentum to stimulate the 10 million farm households to harness the potential of the land and other resources and so boost production.

New policies

The new policies directly related to agriculture, along with a series of other macro policies, have helped the agricultural production of Vietnam, especially rice production, to develop encouragingly. The average rice yield grew from 2.02 t/ha during 1976-80 to 2.66 t/ha in 1981-88 and up to 3.25 t/ha during 1989-93; total annual rice paddy production grew from 19.0 million t in 1989 to 22.3 million t in 1993. Thus, Vietnam has moved from a chronic food deficit to become a country with enough food for its population, enhanced food security, and a food surplus that allows rice exports of 1.5-2.0 million t/yr. Since 1989, although the population has increased by 6 million in the same period, this growth in rice production has contributed to a stabilized society and has facilitated the process of restructuring agriculture. These are important preconditions for Vietnam to enter a period of industrialization and modernization of the country’s economy. The most important policies related to agriculture are outlined in the following sections.

On farm-household economy and agriculture Previously, in the centrally planned economic system, the agricultural economy of Vietnam was based mainly on the State and collective economic sectors, and the role of the farm-household economic sector was not properly recognized. Since 1988, the State has considered every farm household to be an independent, self-directed economic unit that has the right to plan and perform its own production and business and to enjoy its results. The State has also reformed management of State enterprises and agricultural cooperatives, encouraged development of the private economy in agriculture, and created a favorable environment for development of all economic sectors.

On land Since 1988, especially after the New Land Law was approved by the National Assembly of Vietnam, land has been allocated to farmers on a long-term, stable basis. Farmers have the right to control their lands and are encouraged to reclaim additional fallow or virgin lands, Vietnamese farmers view land as a sacred property, and the potential capacity of tens of millions of farmers can only be fully

4 Nguyen Cong Tan mobilized for producing more wealth for themselves and society when they become the real owners of their land.

On agricultural land-utilization tax During and after the war, national income through the agricultural tax was an important source for the national budget of Vietnam. To help farmers accumulate more resources to develop their production and to improve their living conditions, the State enacted a new law of agricultural land-utilization tax. With this new law, the rate of tax paid to the State by farmers is now just over 60% of what it was and is stable on a long-term basis. That means that the total national income through the agricultural tax in the past, which was equivalent to about 1.2–1.3 million t of paddy/yr, is now about 0.8 million t of paddy/year, a reduction of 0.4–0.5 million t.

On credit for farm households Farmers have land and a labor force, but are still poor and short of capital. The State has adopted a policy on rural credit for farm households. In 1993, 4,000 billion dong (US$360 million) were available for over 3 million farm households to borrow. This helped farmers gain additional investment capital and reduce their borrowing from the noninstitutional, high-interest-rate system in rural areas.

On science, technology, and agricultural extension The State has enacted policies on development of science and technology and increased investment levels for agricultural science and agricultural extension in which transfer of technical advances to farm households is the main activity. Many new technical advances, particularly on rice production, have been popularized among farmers, thus helping them to increase the yields of crops and animals and the efficiency of production and business, and thus improve their income and living condition.

On circulation of agroproducts and agricultural input materials During the process of developing commercial commodities in the market-economy system, the State has adopted a new mechanism of agroproduct distribution that allows free circulation for selling products and buying input materials at the best price — “price is agreed by both seller and buyer” — and has eliminated the mechanism of “commodity checks and barriers” that applied during the years of the centrally planned economy. Simultaneously, in the market-economy practice. the State has also implemented policies to stabilize agroproduct prices and input material prices with a balance acceptable to both producers and consumers. In implementing these policies, the State has been forming and using a national reserve fund as an instrument to regulate demand–supply relations in the market and a pricing stabilization fund to subsidize some essential agroproducts and input materials in favor of the farmers.

On hunger eradication, poverty alleviation, employment, and rural development Since the implementation of a market economy, the rich–poor polarization has increased in some place. With that background, the State has carried out a policy of hunger eradication and poverty alleviation, and wealth formation by everyone. The State considers the broad policy of hunger eradication and poverty alleviation as one of the most important at the national level. Based on that policy, a number of decisive policies, solutions, and activities have been implemented for poor regions and for poor farm households to reduce their problems and poverty. The policy is based on the community’s participation in helping the poor gain access to land, capital, and training for better production performance. The State has also budgeted for a considerable investment to help the poor regions and the poor people — especially those in the mountainous and remote regions, including the minority peoples. The State also has an employment-generating fund to create more jobs for farmers

Policy renewal in agriculture 5 in their native villages and to move people to new settlement areas for agricultural production on new lands. The policies toward rural development will aim, for some years to come, at creating more favorable conditions for rural people to develop and improve their houses, and to supply clean drinking water, education, health care, transport, and cultural activities. In many rural areas, electric power systems, roads, schools, clinics, and health-care dispensaries have been improved, giving rural Vietnam a new face.

Agriculture

Vietnam is an agricultural country, and agriculture is the primary economic activity. In the last decade of this century, as the country starts a process of industrialization and modernization of its economy, agricultural development in the broad sense continues to be the foremost task. In future, even though its contribution to the gross domestic product (GDP) will get smaller and the agricultural labor force will become a smaller part of the national labor force, agriculture and new rural development will remain in their long-term strategic positions in the overall social and economic development of Vietnam. The major direction for agricultural development in Vietnam is to raise agriculture from poverty and remove its image of small-scale, subsistence production, to create a commercial agriculture that is gradually modernizing with high productivity, quality, efficiency, and a diversified structure that combines development of food production for food security with that for industrial crops, where animals, forestry, and fishery development are balanced, and agriculture and the agroprocessing industry are coordinated. Thus, a modernized agriculture will be built that is based on ecologically and economically sustainable development, along with an agriculture–industry–service structure in new rural developments so that farmers have enough employment and an increasing income. In this way, they will become a richer people with hunger and poverty eliminated to create a rural society of equity and civilization that integrates agriculture and industry, and rural and urban areas, through industrialization and modernization of the country. In the agriculture of Vietnam, rice production was, is, and will continue to be a most important sector. The Vietnamese are rice eaters and consider rice as their staple food. Rice is a suitable crop for the soils and climatic conditions of the country and is the most important crop in the farming systems of most areas. Rice production is also a traditional occupation of Vietnamese farmers. In Vietnam, therefore, priority continues to be given to rice production with incentives to rice farmers. In the past years, the rice-production sector has made many scientific and technical advances, of which the most outstanding was the popularization of high-yielding, widely adaptable, and pest- and disease-resistant varieties in most of the cultivated area. Of these, over 70% are IRRI varieties or varieties with gene Sources from the IRRI germplasm bank. In recent years, rice production has continued to make scientific and technical advances of which the following are five examples. Soils and farming systems. An integrated approach has been applied to improve the acid sulfate soils in the southern area of rice production. During 1989-93, 160,000 ha of reclaimed land in Dong Thap Muoi (Plain of Reeds) and T u Giac Long Xuyen (Long Xuyen Triangle) within the Mekong River Delta were put into rice production. The advances that were applied were irrigation development for leaching the acid sulfate soils, replacement of a single autumn rice crop by winter-spring and summer-autumn crops, development of more tolerant and resistant varieties, an increase in potassium fertilizer application, and limiting the constraint of phosphorus deficiency. These advances have increased rice production in the Mekong River Delta from 8.8 million t in 1988 to 10.7 million t in 1993: a decisive contribution to the growth of rice production for the whole country.

6 Nguyen Cong Tan Pest- and disease-resistant varieties. From experience in the loss of 600,000 t of rice to brown planthopper in the 1992/93 winter-spring crop, it is clear that we must use high-yielding and pest- and disease-resistant varieties in the southern part of the country. For the 1993/94 winter-spring crop, pest- and disease-resistant varieties were sown and integrated pest management (IPM) practiced. As a result, this crop had no serious pests and yield increased 700,000 t over the previous one. Cropping pattern. Changes of cropping pattern structure, such as the development of summer-autumn rice crops to be harvested by August in central Vietnam, avoid damage from typhoons and floods. Equally, development of early autumn crops in northern Vietnam can increase rice yield and expand the area for winter crops in the plains and midlands. Hybrid rice. The area under experimental production of hybrid rice, using hybrid combinations imported from China in the northern provinces, increased from 11,000 ha in 1992 to 40,000 ha in 1993 and over 50,000 ha in the 1993/94 winter-spring crop season. The average yield was 6-8 t/ha per crop with an outstanding yield of 13-15 t/ha per crop in some areas. Experimental multiplication of cytoplasmic male sterile (CMS) lines and hybrid rice-seed production based on hybrid combinations and germplasm materials from China were also carried out. Some hybrid combinations now have high yield, wide adaptability, and strong tolerance and resistance. In addition, some hybrid rice combinations have good cooking quality to meet the needs of consumers and export. Special rice varieties. It is also necessary to mention the improvement and increase in area of special rice varieties and development of tolerant varieties, especially -tolerant varieties to be used in rainfed areas so as to ensure and stabilize rice production in the mountainous provinces of Vietnam.

The future

In the coming years, Vietnam’s rice production must focus not only on productivity but also on quality and economic efficiency. The total land area for rice production in Vietnam is now 4.2 million ha. This area might be reduced by converting areas of low or unstable yield to greater economic efficiency with other crops, or reducing areas of upland rice to protect the environment. Also, reduction might be caused by converting a part of the rice-growing area to nonfarm purposes during industrialization and urbanization. However, the area that can be reclaimed for rice growing is very limited and will require heavy investments. Therefore, Vietnam must carefully preserve land and concentrate intensification on the irrigated rice-growing areas that have high economic efficiency. It must also increase rice yield from the present 3.4 t/ha per crop to 4.0-4.5 t/ha per crop by the end of this century. For the essential rice-growing areas such as the Mekong River and Red River deltas, rice yield must be increased to over 5.0 t/ha per crop, and the area of high-quality rice must be expanded. In addition, greater effort must be expended on research and applying new advances in technology to reduce production costs, especially to reduce the costs of water management, fertilizer, and pesticides, and to increase income for rice farmers. In addition, Vietnam must direct efforts to widely apply organic-farming technology to production — this will reduce chemical residues in rice to a minimal level and protect the environment. Along with the process of modernization of the country’s economy, Vietnam’s rice-production sector must be progressively modernized, gradually increasing rice-production holdings at the farm- household level and mechanizing to improve productivity. Situated in a diversified ecological region, that has thousands of years experience in rice growing, Vietnam has a broad rice-gene base. The country must focus on the importance of preserving this gene resource and consider it as a valuable national asset. Vietnam has an encouraging record in rice production. This is an achievement both of Vietnam and also of the programs of international cooperation of which IRRI’s is an example in its cooperation

Policy renewal in agriculture 7 with and assistance to Vietnam. In the process of further developing rice production, Vietnam hopes to continue to cooperate with and receive assistance from IRRI. Food production in general and rice production in particular are still primary concerns for our planet, especially in the countries of Asia. The world is about to enter the 21st century with enthusiastic economic development, but also with the threat of food shortages due to the global population explosion. Hundreds of millions of people suffer from famine, and other millions are hungry — their situation must spur our efforts.

8 Nguyen Cong Tan Rice research for the 21st century

Klaus Lampe 1

To introduce the topic of rice research for the 21st century, some important statistics about rice need to be highlighted. • Each year, the world’s population increases by almost 100 million people and population growth is not expected to level off until the middle of the 21st century at the earliest. Feeding these 100 million more people every year is the biggest challenge of the next decades. • Rice is the basic staple food for half the world. • More than 90% of the world’s rice is grown and consumed in Asia, home to more than 50% of the world’s poor and more than 90% of the world’s rice farmers. • Only 4% of rice production is traded on the world market.

When the International Rice Research Institute was founded in 1960, only a few people had the vision, the determination, and the will to oppose the predicted famine in Asia. This opposition resulted in the so-called Green Revolution — an unprecedented leap in annual rice supplies, enough to feed at least 600 million more people. Like every breakthrough in development, however, this achievement had another side — unforeseen social and environmental costs. Nongovernmental organizations (NGOs) and others initially alerted the world to the adverse effects of reduced genetic diversity in the being planted and to pesticide misuse. Although many of these issues are being addressed today, work on them must be accelerated to eliminate or reduce the environmental costs. The focus of agricultural research in many parts of the world, particularly in the world of donors, has been shifting from food production to greatly increased concern for natural resource conservation and environmental protection. This concern of donors, as well as the need for food security, has been considered in formulating IRRI’s strategic plan for the year 2000 and beyond. We have sought to balance IRRI’s concern for adequate food production with an equally strong concern for sustainable use of resources, for environmental health, and for increased attention to less-favorable rice ecosystems. This strategy is the product of a careful consultation with partners from rice-growing countries and from “high tech” institutions dealing with strategic and basic research. This approach has led to a strategic document that actually goes beyond IRRI’s mandate but reflects research needs related to rice research in general. The common goal that IRRI shares with all partners in the rice-consuming world is to improve the well-being of present and future generations of rice farmers and consumers, particularly those with low incomes. Its objectives are to generate and disseminate rice-related knowledge and technology of short- and long-term environmental, social, and economic benefit and to help enhance national rice research systems. Its strategy is to increase efficiency and sustainability of rice production in all rice- growing environments through interdisciplinary research, and to ensure the relevance of IRRI research and the complementarity of international and national research efforts through close collaboration with national programs.

1 Director General, International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. The challenges ahead

The future presents even more challenging, ambitious tasks than the rice-yield increases of the 1960s and 1970s and the more stable production achieved in the 1980s. The yield ceiling of irrigated rice must be lifted yet again and rice-production systems are needed that can make the best use of shrinking resources in a sustainable manner. By 2020, the world must produce 350 million t of rice more than it produced in 1992 to meet the demand created by increasing populations and rising incomes, This production increase must be achieved on less land, with less labor, less water, and less pesticides. It must be sustainable. Simultaneously, rice production must be made profitable to farmers. Otherwise, today’s and tomorrow’s farmers will leave the land and join the rapidly expanding, highly explosive communities of the urban poor. Thus, in rice research, we should emphasize four key challenges: • Addressing social equity; • Achieving sustainability of the resource base; • Increasing productivity and resource-use efficiency; and • Protecting the environment.

Meeting the challenges

Rice research should focus on meeting these key challenges by making significant progress toward resolving researchable questions.

Addressing social equity In less than 30 yr from now, the world must feed more than 3 billion rice consumers — 50% more than it feeds today. Many of them are among the world’s poorest people. It must be made possible for farmers to grow enough rice to feed the rice consumers of the future, using input-efficient technologies that allow the grain to be sold at prices profitable to the farmers and affordable to consumers. At the same time, those who work in the rice fields — including the women and children of low-income rice-farming families, particularly in the less-favorable ecosystems — must be helped to improve their working conditions, their economic status, their health, and their general well-being. In the less-favorable rice-growing environments, unemployment, malnutrition, illiteracy, and widespread poverty are major social issues. Agriculture and related rural industries and activities are under pressure to absorb excess labor. That increases rural poverty and induces depletion of resources and degradation of the environment. It puts special pressure on women and children. If we are not successful in improving the life of rice-farming families, we might, in the foreseeable future, not have enough farming families in Asia. Remarkable progress has been made over the last 30 yr in increasing rice yields and achieving food security in large parts of Asia where irrigated rice production predominates. In many of these productive rice systems, the gap between experimental yields and farm yields is closing. In the less- favorable rice-growing environments, however, modern rice technology has yet to make a definitive impact. The priority target for intensively cropped irrigated systems is to raise the experimental yield ceiling to 15 t/ha. In less-favorable rainfed lowland areas, where farmers’ yields vary widely, the target should be to increase and stabilize yields at 2.5-3 t/ha on about 26 million ha. Raising the yield ceiling for irrigated rice is best pursued in two ways:

10 K. Lampe • Developing hybrid rice for the tropics and • Redesigning the rice plant to improve its yield potential. Tropical hybrids based on heterosis among indica rice lines yield up to 20% more than the best conventional cultivars. Combinations of japonica and indica rices could increase yields by 25–30%. The primary factor that limits widespread adoption of hybrid rice in the tropics and subtropics is the complexity of hybrid-seed production systems that are based on cytoplasmic male sterility (CMS). Scientists are working with a temperature-sensitive genetic male sterility (TGMS) system to develop a simpler approach. They are also exploring using apomixis — a natural mechanism for asexual seed production — to enable farmers to grow hybrid rice from their own seed rather than having to buy seed for each crop. This would help increase the profitability of hybrid-rice farming and ensure that hybrid vigor is available even to resource-poor farmers. In many rainfed lowland areas, one rice crop a year is the norm, even though available moisture would support a second crop. Short-duration rice cultivars make it possible to increase cropping intensity and to use water more effectively. We should develop new technologies that enable timely crop establishment, a rice and grain-legume or forage-legume rotation, and on-farm water harvesting.

Achieving sustainability of the resource base The permanence of the food-production base on which we all rely, today and for generations to come, depends on care and use of the genetic diversity of rice and on husbandry of the natural resource base of soil-water-biological activity. Preserving and using genetic resources. Conserving genetic resources in perpetuity is an important foundation for permanence in agriculture. Despite widespread conservation efforts over the last three decades, the challenge continues. Efforts will be accelerated to collect and characterize vanishing land races and wild species from areas not yet fully explored, such as the highlands of Asia, and worldwide assessment of rice germplasm potential in different rice environments will be intensified. Effective use of the rice germplasm collection relies on knowledge of the genetic diversity it contains. Using new biotechnology and modeling tools will enable more precise documentation and deployment. Sustaining the resource base of intensive rice systems. Long-term soil-fertility trials have been conducted in intensively cropped rice areas. There are signs in intensively cultivated rice areas in China, , the Philippines, and Vietnam of a decline in the capacity of the resource base to maintain yields at the same level of inputs. The extent of this phenomenon in farmers’ fields must be quantified and we must seek ways to reverse trends of declining productivity in intensively cultivated rice areas. The rice-wheat system accounts for more than 11 million ha of intensive food production in South Asia: about 30% of irrigated rice production and 50% of irrigated wheat production. The Centro Internacional de Mejoramiento de Maiz y Trigo (International Center for Maize and Wheat Improvement, CIMMYT) and IRRI, together with the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), will continue an international collaboration for research on the productivity and sustainability of rice-wheat based cropping systems. Sustaining the resources of the rainfed lowlands. Although rice production in the favorable rainfed lowlands is expected to increase, yields in the fragile and heterogeneous, less-favorable subecosystems vary widely. Unpredictable drought and flooding can occur within the same growing season, and nutrient losses, particularly of nitrogen (N), are severe. The key to improving productivity is risk-management strategies that are appropriate for the resources of relatively poor farm families. However, little is known about the factors that these farmers consider in making their crop- management decisions. Farmers’ responses to risk and uncertainty caused by abiotic stresses will be

Rice research 11 studied in the variable rainfed lowlands as will the relationships the farmers have through labor, tenancy, and credit markets, and the effects of these relationships on distribution of assets and income. The biophysical and socioeconomic resources of the principal rainfed lowland environments must be characterized — this can be done using geographic information systems (GIS). Stabilizing the uplands. Developing permanent and sustainable land-use systems is critical if degradation is to be arrested in the 19 million ha worldwide where upland rice is grown. The consequence of slash-and-burn land management at ever-shorter intervals is erosion and, ultimately, abandonment. This causes losses, not only in the uplands but also in the lowlands that are vulnerable to destruction of the watershed. Although not always the major component of upland farming systems, rice is the dominant and preferred subsistence crop and the focal point of Asian farmers’ resource-allocation decisions. Improving rice productivity provides an entry point into alleviating poverty and enhancing sustainability. Two important factors minimize soil degradation in the uplands: maintenance of permanent ground cover and minimal disturbance of the soil surface. Obviously, growing an annual crop such as rice is not congruent with these objectives. The use of hedgerows made up of other species to provide a permanent barrier to soil movement is being studied. Development of a perennial rice plant that could provide both food and ground cover to minimize soil erosion could be a good solution and deserves serious attention and support. IRRI has developed a research program for such a new plant type and we are confident that such a plant can be developed.

Increasing productivity and resource-use efficiency Nearly 75% of the increase in rice production since 1966 came from the increase in land productivity made possible by widespread adoption of modern varieties and associated farming practices. Short- duration varieties that followed IR8 (such as IR36 and IR64) were able to produce similar yields in much less time and using less pesticide, thus allowing for cropping intensification and further increases in land productivity. In addition to the urgency to break the yield frontier again, to increase land productivity further, the productivity of other resources also must increase. With current irrigated rice technology, only about 30-50% of the N fertilizer applied is actually used by the rice plant. In irrigated systems, more than 5,000 liters of water are used to produce 1 kg of rice. Clearly, a 50% increase in irrigated rice yields is not a realistic target without increasing the input-output efficiency of the major inputs of N, water, and labor. Research in all ecosystem-focused programs should seek to improve the long-term productivity of land, water, nutrients, and labor. Basically, this involves matching improved genotypes with improved resource management. Nitrogen and water use under irrigated conditions. At current levels of N efficiency, a 30-50% increase in yield would require almost doubling the amount of N applied. The priority target is to increase the uptake by rice plants of available N by better synchronizing the supply of N from the soil and applied fertilizer with the crop’s demand for N. The ability to predict soil N supply and the seasonal pattern of crop N demand through simulation models could lead to fertilization strategies that would double the efficiency of the N that farmers apply. Simultaneously, research in breeding for increased nutrient uptake efficiency has been accelerated. Strategic research at IRRI on Azolla and blue-green algae has been completed, and its results now support the application of this technology in countries where it might have potential. New opportunities must be explored to enhance the symbiotic relationship between rice and indigenous dizotrophs (bacteria that fix N in the rhizosphere, the soil-root interface zone). This can account for 40-80 kg N/ha taken up by a rice crop, It is important to develop molecular markers to aid selection

12 K. Lampe of rice cultivars with this trait. Furthermore, the opportunity for symbiosis and N fixation within the rice plant itself will be examined. Of the more than 5,000 liters of water used to grow 1 kg of irrigated rice, less than 50% is needed for transpiration by the crop. Most of the water is used for soil preparation and traditional nonchemical weed control — flooding the field to reduce weed emergence and transplanting to reduce weed competition. Competition for water and labor are stimulating our work to develop new methods and machines for tillage and planting, and environment-friendly practices for weed management. Productivity in the variable rainfed ecosystem. The rainfed rice ecosystems (rainfed lowlands, uplands, and flood-prone areas) share one major characteristic: uncertain moisture supply. Fields may have too much water, too little water, or both within the same cropping season. This uncertainty is the basis of resource-poor farmers’ decisions on investment of resources and the degree of risk they are willing to take. Research on these ecosystems should minimize farmers’ exposure to risk by making available cultivars that have more-stable resistance, tolerance, and yields and by increasing the productivity of resources. Work to enhance productivity should focus on understanding processes and mechanisms, to establish a basis for developing site-specific applications. A systems approach should be developed to quantify performance of rice systems and to design quantitative models. Such a tool will help focus research and be useful in extrapolation of technology. Rainfed lowlands. Priority targets for the rainfed lowlands are fivefold: • Capture more of the moisture in the soil profile through improved soil management and by developing cultivars with root systems that can explore more of the soil profile; • Select for cultivars that are more N and phosphorus (P) efficient; Continue to identify germplasm with tolerance to deficiencies of P and zinc, and for tolerance to excess salinity, aluminum, and iron. Improve screening methods using genetic markers for tolerance to excess minerals; Expand knowledge on nutrient dynamics under different moisture regimes, as the key to managing plant residues for maximum capture of N in the system; and • Select germplasm lines that are tolerant of excess water. Uplands. In the uplands, priority targets are threefold: • Increase the capture zone of nutrients and water, particularly where an acidic subsoil impedes root exploration of the profile, and determine the most economical management of P; Identify the P-use efficiency of different rice cultivars; and • Explore mechanisms for improved water capture by roots, for tolerance to periods of moisture stress, and for increased water-use efficiency. Protecting the environment We are all concerned about the environment at all levels — globally, in the watershed, and in the farming community. Efforts to produce more rice are already putting pressure on fragile environments. We share the world’s rising concerns about such issues as land degradation, soil erosion, water shortages, and pollution. For rice research, this translates into the challenge of developing production system that protect the environment and human health. Reducing the use of pesticides. Pesticides are significant inputs to rice production. Research not only at IRRI showed, however, that misuse, unnecessary use, and overuse of pesticides had a negative effect on the ricefield communities of the natural enemies of rice pests. Misuse also affects human health. We have been developing environment-friendly pest-management components to apply in implementing integrated pest management (IPM) concepts in collaboration with the Food and Agriculture Organization of the United Nations (FAO). Biodiversity for sustainable pest management should be exploited. This requires better understanding of ecosystems and the interactions of biodiversity at different trophic levels

Rice research 13 — vegetative (including rice), pests, and natural enemies. Pest-ecology studies and the use of modern tools of biotechnology and computer modeling in this project will be useful. Host-plant resistance is the cornerstone of effective pest management. Combining resistance with biological controls and improved cultural practices is an ideal pest-control strategy for resource-poor farmers. Of all the pest-resistant rices planted worldwide, nearly half have direct IR-line parentage. Reducing the need for pesticides by introducing more-durable resistance would have a significant effect on the world's rice crop. Research is beginning on the coevolution of multiple pests and rice, and on predicting the longevity of resistance genes in rice in relation to population pressures of pests in different agricultural environments. Concern for the environment and human health will expand with a collaborative project on vectors of human diseases in rice ecosystems. Managing weeds with less herbicide dependence. Farmers worldwide spend about US$900 million each year on herbicides to control weeds in rice. As the costs of labor for hand weeding increase, herbicide use can also be expected to increase. Studies on the water–tillage–weed interaction should continue, with the aim of reducing water use and reducing herbicide dependency. Plant characteristics that increase the competitiveness of rice against weeds, particularly during the early stages of crop establishment, are being incorporated into improved breeding lines. Exploring the use of natural pathogens for biological weed control will continue, along with exploring the use of allelopathy in rice cultivars to minimize herbicide use in weed management. Global and rice. No one yet has a definitive answer to questions related to the cause and effect of the thinning ozone layer and the possible trend toward global warming. Yet the world cannot afford to be unprepared. The rate of global climate change and its effect on food and sustainability are debatable. The best estimates are that rice cropping contributes some 10–20% of total emissions; there are no estimates for nitrous oxide (N 2 O). Two aspects of global climate change should be examined: effects of flooded rice cropping on global-warming gases and effects of climate change on the rice plant. It is possible that the ricefields of Asia, particularly the flooded paddies, are the modern world's carbon and N sinks. Research on this possibility should quantify emissions of carbon gases (particularly methane) and seek cultural and genetic mechanisms that can mitigate harmful effects while ensuring maximum capture of N by the cropping system. The interactive effects of changes in carbon dioxide (CO 2 ) concentration and temperature on the productivity of rice and on pest ecology and the effects of an increase in ultraviolet (UV-B) radiation should be measured. This research, coupled with a process-based simulation model and GIS, will enable prediction of likely changes in rice supplies and losses with different global climate scenarios.

Strengthening partnerships and sharing leadership

The four key challenges — meeting the food needs of the future, achieving social equity, conserving natural resources, and protecting the environment — are complex issues that must be addressed simultaneously. The central issue is how to balance the need for even greater food production, at prices affordable by consumers and profitable to farmers, against the very real concerns about protecting natural resources and the environment for the generations to come. This issue is complex: no single institution has all the necessary expertise and resources to address this challenge. IRRI must collaborate with national agricultural research systems (NARS), other international agricultural research centers (IARCs), advanced research institutes and universities, nongovernmental organizations (NGOs), and the private sector. Collaboration has many advantages:

14 K. Lampe • Problems can be resolved more easily and in relatively less time; • New rice information, technologies, and research methods can be disseminated faster; • Feed-forward and feedback to researchers is better; • Expertise and other scarce resources can be shared; and • Scientific cooperation across political borders and economic barriers is facilitated. Collaboration requires partnership based on common interests and objectives. We use several mechanisms for collaboration, choosing different modes to improve the participation, competence, and commitment of partners. The form of collaboration depends on the knowledge sought, the capacity and commitment of the research partner, and the resources available. Parallel with collaboration and interdependence is the principle of sharing regional leadership responsibilities with national programs. Some countries with strong research capacity are in a unique position to take on regional leadership in rice research and training. For example, ’s program for flood-prone rice leads in selecting, testing, evaluating, and distributing breeding materials to South and Southeast Asian countries that need them. Thailand also is taking responsibility for the short-term training course on rice-production research. Indonesia and Malaysia have indicated interest in offering a regional course on IPM, and the Philippines is offering a regional course on rice-based farming systems. In 1991, IRRI helped initiate the Rainfed Lowland Rice Research Consortium and the Upland Rice Research Consortium and is now working as a research partner in each, as well as coordinating both. Consortia activities involving both strategic and applied research are carried out at key sites where a consortium member has the institutional capacity to conduct the research needed on specific ecosystem problems. Collaboration with the private sector and NGOs is also being intensified in the areas of technology evaluation and dissemination, manufacture of improved farm tools and equipment, socioeconomic assessments, and studies on impact of technologies.

Vietnam-IRRI collaboration

Vietnam and IRRI have enjoyed a long, fruitful history of collaboration, starting with the release of IR8 in both the northern and southern delta rice-growing areas during the late 1960s. Soon after 1975, scientists from the Socialist Republic of Vietnam reestablished contact with IRRI. In April-May 1978, an IRRI team headed by then Director General N.C. Brady visited Vietnam at the invitation of the Minister of Agriculture, Vo Chi Cong. A memorandum of agreement between the ministry and IRRI laid the foundation for work during the next decade. In September 1984, a new agreement for collaborative research and training was signed during the visit by IRRI’s Director General M.S. Swaminathan to Ho Chi Minh City and Hanoi. In 1988, the Australian government funded research and nondegree training of Vietnamese scientists at IRRI over a 3-yr period with a donation of US$290,000. The Australian International Development Assistance Bureau (AIDAB) extended the project in 1991 with an additional US$600,000 grant. This led to the establishment of formal ties among IRRI, the Ministry of Agriculture and Food Industries (MAFI), and the Ministry of Education and Training (MET) a year later. At a planning meeting held in Hanoi in June 1992, a new agreement with MAFI and MET further expanded Vietnam-IRRI collaboration, The same year, IRRI and the Cuu Long Delta Rice Research Institute (CLRRI) began implementing a project to strengthen CLRRI’s research and training capabilities. The 3-yr project is supported by US$857,000 from the United Nations Development Programme (UNDP).

Rice research 15 In September 1993, we were highly honored at IRRI to receive a visit from Deputy Prime Minister Tran Duc Luong. During his visit, the Deputy Prime Minister expressed the Vietnamese government’s desire to expand its collaboration with IRRI and to place greater emphasis on the upland ecosystem.

Highlights of collaboration Improvement of rice varieties. Since the release of IR8, a total of 63 breeding lines from IRRI have been released in Vietnam. IRRI varieties now cover 70% of the irrigated rice-growing area in the Mekong River Delta. Since 1983, CLRRI and IRRI have been collaborating to develop hybrid rice technology for farmers in the Mekong River Delta provinces. Vietnam also participates in the International Network for the Genetic Evaluation of Rice (INGER) that coordinates the exchange and evaluation of promising breeding lines among rice-growing countries. Germplasm conservation. Vietnam’s participation in IRRI’s germplasm conservation program has resulted in 1,895 registered accessions and 10 samples of three wild rice species from Vietnam being conserved in the International Rice Germplasm Center. Local varieties Tetep and Moc Tuyen are parents for hybridization work at IRRI and have been of value in breeding programs in many other countries. Sustainable rice-farming systems. Recent research in IPM, integrated nutrient management, improved water management, and rice-based farming systems has added new dimensions to developing sustainable intensive agriculture in Vietnam. Sustaining adequate rice production will continue to be a major challenge with an annual population growth of 2.1% and practically all arable land already being farmed. Strengthening economics research. IRRI, with its strong history of microeconomics research, familiarity with Asian economies, and network of Asian agricultural economists, has been strengthening agricultural economics research capabilities in Vietnam with financial support from the International Development Research Centre of Canada (IDRC) since 1991. Among the early accomplishments of the project are the collection of data on farm characteristics, rice-production practices, farmers’ response to recent changes in policy and institutional arrangements through farm surveys in the Mekong and Red River deltas, and a study on the effect of recent reforms on rice productivity and Vietnam’s sustainability as a rice exporter. IRRl also helped organize the Vietnam Society of Agriculture and Forestry Economics in December 1991. Publications. Six publications have been translated into Vietnamese and distributed widely to researchers, extension workers, and farmers. Training. Since 1964, 362 Vietnamese scientists have been trained at IRRI in degree and nondegree programs (90% of them since 1981). Twenty-seven have obtained master’s of science degrees; another nine earned doctoral degrees. A further 12 Vietnamese scholars are now at IRRI working toward master’s and doctoral degrees.

Toward new research opportunities and a stronger partnership

It is time to reflect on more than 25 yr of partnership and progress toward a better life for rice producers and consumers. Through progressive agricultural policies and dissemination of modern rice technology, Vietnam has emerged as the world’s third largest rice exporter. In addition, achieving food security has been a fundamental step toward broader economic development. In preparing for the 21st century, we see five important areas where Vietnamese and IRRI scientists can collaborate.

16 K. Lampe Understanding and ensuring sustainability of intensive farming environments — the Red River and Mekong River deltas. We see opportunities to Integrate work on nutrient, water, and pest management to understand the constraints and consequences of crop intensification and diversification. IRRI is now planning a multicountry research consortium that will focus initially on long-term productivity and IPM under irrigated conditions. Improvement of yield potential. With limited land and water resources and the need for crop diversification, there will be increasing pressure to raise rice yields in irrigated areas. The new plant type with a yield potentia1 of 12-15 t/ha may be appropriate for the Red River and Mekong River deltas. Improved grain quality. With the achievement of rice self-sufficiency and surpluses for export, we are aware of increasing interest in the improvement of grain quality. IRRI will work with Vietnamese scientists and institutions to identify means of enhancing grain quality through varietal and postharvest management improvements. Upland farming systems development. We are aware of the concern about environmental degradation in the northern and central highlands of Vietnam. Slash-and-burn farming is widespread throughout and few alternatives exist at present. We believe that solutions to this problem must involve an “integrated livelihood” approach to research and development. Linkages among the crop, livestock, and forestry enterprises need to be better understood — this will require multi-disciplinary, multi-institutional approaches. Germplasm conservation. In a recent meeting at IRRI, the ”Indochina” region was given top priority for rice germplasm collection. Much of the region’s rice production, particularly in the uplands, is based on locally adapted land races. Vietnam’s was one of three national programs elected to the Steering Committee of the rice biodiversity project, funded by Swiss Development Cooperation (SDC), that will be coordinated by IRRI. Vietnam has always given rice the highest priority in agricultural research, The various institutes and agricultural universities supporting the national rice program of MAFI all have strong linkages with IRRI. For example, Dr. Vu Tuyen Hoang, Director of the Food Crops Research Institute and on the staff of MAFI, coordinates the Vietnam-IRRI Rice Research and Training Project. Professor Vo-Tong Xuan, Vice Rector and Director of the Farming Systems Research and Development Center of the University of Cantho, has served as an IRRI Trustee since 1990. Dr. Mai Van Quyen, Vice Director of the Institute of Agricultural Sciences of South Vietnam, was an IRRI visiting scientist in 1989 Dr. TO Phuc Tuong, who chaired the Department of Water Management at the University of Agriculture and Forestry in Ho Chi Minh City, joined IRRI as a staff member in 1991. These partnerships are the key to success, In closing, I return to the four key challenges affecting rice production today and in the future: • Addressing social equity; • Achieving sustainability of the resource base; • Increasing productivity and resource-use efficiency; and • Protecting the environment. At IRRl, we see these challenges also as opportunities to serve both present and future generations of people who depend on rice. With over 6 million ha of rice, rapidly growing human- resource capacity, and supportive political leadership, Vietnam is emerging as a key partner in the global rice research community.

Rice research 17

Invited papers

History of Vietnam-IRRI cooperation

Vo-Tong Xuan 1

In 1989, Vietnam emerged from a state of near famine to become the world’s third largest rice exporter after Thailand and the United States. The export of 1.67 million t of rice was a surprise not only to the international community but also to the Vietnamese. Rice exports rose in 1990 to 1.76 million t, but then decreased to about 1.20 million t for 1991 because of crop damage in several regions. The income from rice exports may not add enough of the foreign currency needed for various economic reconstruction programs for Vietnam, but a net surplus of food grains certainly maintains the social stability of the country. Although other factors — improved technology, better irrigation systems, and increased availability of inputs — contributed to the big gain in Vietnamese rice exports, the underlying factor was the rapid change in government policy, known as doi moi or renovation. The changes included the “privatization” of agriculture, opening of foreign trade, and setting a competitive exchange rate for the ‘Vietnamese dong. For many years before the policy of renovation was introduced, technical support for rice production had been offered by all levels of government throughout Vietnam, but especially in the central and southern parts. This support included encouraging farmers to use new rice varieties - in the Mekong River Delta (MRD), IRRI varieties had been grown since 1968 and now occupy 90% of the irrigated areas. Most of the surplus rice comes from this region. Together with the new varieties, appropriate cultural practices for each variety in each type of soil and water conditions were encouraged among farmers in the MRD through agricultural extension programs on radio and television. For the Vietnamese, increased rice production resulted from the availability of the new Than Nong (TN) varieties. (Than Nong is the God of Agriculture.) The TN varieties are IRRI rice. Thus, the Vietnamese farmers and most government officials know IRRI through the new rice varieties.

Period before 1975

According to the Bureau of National Statistics in Saigon for the period 1960-74, the introduction of high-yielding rice began in the 1968/69 crop year with IR8 and R5 (locally known as TN8 and TN5) introduced under a cooperative program of the United States Agency for International Development (USAID) and the Government of the former South Vietnam. From the first crop on 23,373 ha (Table l), only 80% was harvested because most of the IR8 and IR5 crops planted in An Gang Province (a region of floating rice) were totally submerged by flood water. With the first encouraging results, more than 200,000 ha were planted in the following crop year, 1969/70. The use of TN rice kept expanding until, in 1973/74, the total rice area under high-yielding varieties in South Vietnam was 0.89 million ha out of a total of 2.83 million ha planted with all rices. The MRD alone, which had at that time a total of 2.04 million ha of rice, contained 0.55 million ha of IR8 and IR5 and some other IRRI lines. There are several versions of the introduction of IR8 and IR5 into North Vietnam. Some people said that because IR8 made such a big difference in rice production in the South, the revolutionary forces took seeds to the North for testing. This could have happened only in 1969, after the first crop

1Director, Farming Systems Research and Development Center, and Vice Rector, University of Cantho, Cantho, Vietnam. Table 1. Area of TN or IRRl rice varieties in South Vietnam, 1968/69 to 1973/74.

Year Area (ha)

1968/69 23,373 1969/70 204,000 1970/71 452,100 1971/72 674,740 1972/73 835,000 1973/74 890,400

Source: National Bureau of Statistics, Saigon, 1974. in the South. However, in The Agricultural History of Vietnam (Dat 1994), the author states that IR8 and IR5 were introduced into North Vietnam in 1967 and that tests proved them to be very well adapted to the winter-spring crop in North Vietnam, after the main season crop. In North Vietnam, the variety IR8 was renamed Nong Nghiep 8 (NNS), meaning Agriculture Number 8. NN8 was widely propagated during 1969, and soon covered about 50% of the rice area in North Vietnam. It occupied 65% of the rice area of the winter–spring crop alone, and 35% of the area of the main season crop. Although IR8 and IR5 produced good yields, their long growth period was not adapted to areas where the potential of the land could allow two crops, such as in Cantho and An Giang provinces. These were mainly traditional deepwater rice areas. When irrigation became available, farmers stopped growing long-period deepwater rice and switched to two crops of high-yielding rice before and after the annual flood. To do so, they needed shorter duration rice varieties. In June 1971, I returned from IRRI after working there for 2.5 yr and joined the University of Cantho. Immediately after that, the University started a program of rice research across the MRD involving our agriculture students. We started to screen and select from the many lines that we obtained from IRRI for varieties that had a short enough growth period to escape submergence by the August flood, and also to economize on pumping irrigation water in the dry season. In September 1971, USAID signed a contract with IRRI (AID/730-3452) that had the major goal of assisting Vietnam to conduct adaptive trials for high-yielding varieties, to develop improved cultural practices and recommendations for rice production (including the use of fertilizers, pesticides, and insecticides), and to train the agricultural research personnel in conducting production-oriented research on their own (USAID/Vietnam 1974). In November 1971, the first two IRRI personnel, Mr. Orlando G. Santos and Mr. Rodolfo C. Aquino, came to Long Dinh Station in My Tho Province (now Tien Giang Province) to construct experimental fields. In early 1972, Dr. Perry Bosshart (IRRI project leader) and Dr. Dwight W. Kanter (IRRI plant breeder) arrived. In February 1974, Dr. Richard L. Tinsley joined the team as a cropping systems specialist, The IRRI team started working with the agronomists and other scientists of the Institute of Agricultural Research of South Vietnam and brought in thousands of breeding lines to test under Vietnamese conditions. The IRRI team employed additional staff and purchased the equipment and supplies necessary to carry out the research at Long Dinh Station. IRRI work was coordinated by Dr. G.S. Khush during that period. In April 1973, IRRI organized a team composed of Drs. Chau Van Hanh, Nguyen Huu Quyen, S.H. Ou, B.R. Jackson, and me to survey all the rice research stations of South Vietnam. Our report to IRRI, Rice Research, Production, Problems and Progress in Vietnam, was submitted to the Vietnamese government (Xuan et al 1973). We emphasized that it would be appropriate to construct a deepwater rice station at Long Xuyen in An Giang Province while continuing work at the Long Dinh Station in My Tho for irrigated rice. During that survey, we also visited five other stations:

22 Vo-Tong Xuan • Nha Ho Station (Ninh Thuan Province in central Vietnam) designated for upland crop seed production and cotton; • Eak Mat Station (Buonmathuot, Dac Lac Province) designated especially for upland rice, food legumes, maize, and coffee; • Bao Loc Station (Lam Dong Province) specializing in horticultural crops, trees, and fruits, and particularly silk-worm production; • Hung Loc Station (in Long Khanh, near Saigon) specializing in upland crops and seed increase for upland crops, such as peanuts and tuber crops. and drought-tolerant crops; and • Phu Yen Station (in Phu Yen Province, central Vietnam) where the highest-yielding rice varieties were selected for the plain of the central coastal area of Vietnam. It was not until 1973/74 that results of our efforts in rice research began to appear (MDSP 1974). The two rice varieties TN73-1 and TN73-2 (formerly IR1529-6-80 and IRl561-22-8) were released in October 1973. The IRRI team also worked on other experiments such as applications of nitrogen (N), phosphorus (P), and potassium (K), and testing herbicides and insecticides on transplanted rice. Dr. Kanter started to test deepwater rice in An Gang Province at Binh Duc Station, near Long Xuyen town. During that time, our rice research program at the University of Cantho continued in collaboration with IRRI. In fact, the participation of the University of Cantho rice program in the MRD started as early as 1971. At the University, we were also helping the Rice Service and Agricultural Extension Service of the Ministry of Agriculture. Our research in the Delta was focused mainly on the varieties resistant to brown planthopper (BPH), although we also worked to shorten the growth period of high-yielding varieties. Cultural techniques such as planting density, fertilizer management, the effect of P and of several insecticides, herbicides, and fungicides on high-yielding rice were also studied. Results of the pre-1975 period of rice research with assistance from IRRI can be summarized as follows: • Although IR8 and IR5 were released early in the program, they were affected by BPH hopper burn in 1972 and were therefore replaced with TN73-1 and TN73-2, which were selected through the IRRI program. • The University of Cantho also selected IR26 and IR30, which were very resistant to the BPH biotype 1, and had grain quality similar to that of TN73-2. During the release of IR26, the University of Cantho collaborated with the daily radio program “Uncle Tam’s Family” that was broadcast to farmers every morning from 0500 to 0530 hours, As a result of this radio program, we were able to disseminate IR26 seeds throughout the southern part of Vietnam in less than 1 wk. Later, we also distributed IR30. With these new varieties, damage by BPH biotype 1 was stopped immediately. • Because of the effects of war, Vietnam ceased to be a rice exporter in 1968. Part of the food needs were supplied by rice imports from the USA. However, with the introduction of new rice varieties from IRRI, rice production was improved rapidly, particularly in areas where fighting was minimal. In April 1975, when the war ended, annual rice production in South Vietnam had reached nearly 8 million t.

From 1975 to the present

As for most governments after a destructive war, food security was the main concern of the Vietnamese government immediately after fighting stopped. Every Vietnamese farmer was encouraged to grow high-yielding rice. As a result of this policy campaign, farmers hastily prepared the land, chopped weeds and incorporated them into the fields, harrowed, and then immediately sowed the seeds

Vietnam–IRRI cooperation 23 to take advantage of the May–June rain. The most popular varieties, such as IR26, IR30, TN73-1, and TN73-2, were all used in all types of rice fields. One month after seeding, rice planted in most of the fields started to turn yellow. The farmers reacted by applying urea fertilizer, but unfortunately the result was opposite to that expected — the more urea they applied, the faster the rice died. Everywhere rice fields were becoming yellow. The agricultural officer in Cantho Province asked me to go with him to determine whether we could do something about the yellowing problem. We found that this was a classic problem that occurs when rice is planted immediately after incorporating weeds into the soil. As the organic matter is decomposed by microorganisms in the soil, organic acids and hydrogen sulfide are produced. When urea is applied, the microorganisms multiply faster, produce more organic acids, and therefore the rice plants are killed faster. I recommended to the farmers that they stop spreading urea and try to flush the fields with fresh water to remove the organic acids from the soil solution. When they could see new roots coming from the plants, they could apply urea fertilizer as usual. They followed the recommendations, the rice crop improved, and they had a good harvest. Another problem appeared the next year, 1976. Several University of Cantho graduate students who worked with the agricultural offices in An Giang and My Tho provinces came to the University to report that the high-yielding rice varieties such as IR26, IR30, and even TN73-2 were starting to suffer from hopper burn. Mr. Nguyen Van Huynh, the University entomologist, found that the new population of BPH was a new biotype, possibly biotype 2. I passed this information on to Dr. Khush at IRRI. Soon afterwards, he sent me four envelopes, each containing 5 g of a new rice variety, IR32 to IR38. We immediately tested these new varieties against the new BPH and found that IR36 was the most resistant. We started multiplying this line using a one-seedling-per-hill technique to multiply it as fast as possible. That was in mid-1977. Simultaneously, at the Long Dinh Agricultural High School — the site of the IRRI program in My Tho before 1975 — one staff member who remained after the war, Mr. Pham Ngoc Lieu, was screening promising lines left by IRRI. He selected the varieties Long Dinh 1 and Long Dinh 2, which had some resistance to BPH biotype 2. As we were screening and multiplying the new lines in early 1978, the BPH was burning off almost all the high-yielding rice fields in the MRD. It was estimated that in 1978 nearly 700,000 ha of high-yielding rice varieties in the Delta were damaged by hopper burn and ragged stunt disease. By this point, at the University of Cantho, we had increased the 5 g of IR36 to nearly 2,000 kg. We discussed the problem and finally the University leadership agreed to close the school for 2 mo. The students at the University of Cantho, no matter what discipline they were studying. all joined the agriculture students. We gave them a crash training program in only three topics: how to prepare a good seedling nursery, how to prepare a field for transplanting, and how to transplant rice using the one-seedling-per-hill method. All students then went out, each carrying 1 kg of IR36, to plant 1,000 m2 of rice field. During their first contact with the farmers and local administrators in areas where BPH damage was severe, the students were not welcomed by the local people. They came with only 1 kg of seed and no insecticide, in areas where people thought they needed more insecticide. Everyone said that “if you want to solve the problem, you’d better bring more insecticide.” Many of the political administrators at that time attributed the problem to the fact that southern Vietnamese farmers were not yet in cooperatives and that they grew rice any time they liked and created favorable conditions for the BPH. The students and instructors did not argue but tried to prove that it is the genetic makeup of rice lines that would provide the answer to the problem. After 2 mo, the students had set up their production plots of 1,000 m 2 and the IR36 rice grew normally. They turned the plots over to the farmers and returned to the University.

24 Vo-Tong Xuan This 2,000 kg of IR36 in 1978 provided enough seed for farmers in the whole Delta in the next two cropping seasons. Starting with the winter–spring crop of 1978/79, the spread of the BPH biotype 2 was stopped, and farmers in irrigated rice areas began having good production again. In the meantime, we also selected medium-term rice varieties for the rainfed, semi-deepwater in the saline-affected region. Soon we identified a suitable variety, IR42, which was accepted widely by the farmers in the saline area and virtually replaced the traditional medium-term rices — IR42 really produced the Green Revolution in the semi-deepwater rice area in Soc Trang, Bac Lieu, and Ca Mau provinces. At one time, it was grown on more than 400,000 ha in the southern part of Vietnam. No other rice variety covered as large an area. As time went by, varieties resistant to BPH biotype 2 were used widely in both central and southern Vietnam, but a new biotype of BPH soon developed. Some varieties such as NN7A, that is MTL 30, and IR42 started to show signs of loss of resistance. Collections of the new BPH confirmed that it was another new biotype. In 1990, Dr. Khush sent more than 300 promising lines from crosses with BPH-resistance genes, including crosses with the wild rice Oryza officinalis. At Cantho, we multiplied the seed immediately and, in the following crop season, sent these lines into the BPH- affected centers in Tien Giang and An Giang provinces. Very soon we, together with the local agricultural officers and scientists, were able to identify several promising new lines, such as MTL 98, MTL 103, MTL 105, MTL 114, and MTL 119, with good grain quality and, most important of all, good resistance to the new BPH. To help farmers to control the new BPH, we released these lines for farmers’ production in 1992 (see Khush et al, this volume, page 55). Although the new lines have not been released by the Ministry of Agriculture (MOA), they have been accepted by farmers and allowed by the different provincial governments to multiply and enter into the export market in their own provinces.

Formal collaboration after 1975

At the invitation of the MOA, the first IRRI delegation to Vietnam after the war, comprising Director General Dr. N.C. Brady, Dr. G.S. Khush, and Dr. E.A. Heinrichs, came in May 1978, and made a survey from the south to the north. They contacted different officials and research organizations throughout Vietnam and signed a Memorandum of Understanding (MOU) of collaboration between IRRI and Vietnam through the MOA. Unfortunately, no donor was willing to contribute to IRRI’s Vietnam program, so IRRI had to use its core funds to send materials for the International Rice Testing Program (IRTP, now the International Network for Genetic Evaluation of Rice, INGER) to Vietnam and to provide training to Vietnamese scientists at IRRI. With the IRTP seeds contained in different nurseries, several agricultural research stations and universities in Vietnam were able to continue screering for rice varieties with better grain quality and greater resistance to BPH, and also better adaptability to different soil and water conditions. (The results of the release of these varieties are described by Khush et al, in this volume, page 55.) In 1984, IRRI Director General Dr. M.S. Swaminathan visited Vietnam. He soon recognized the problems in coordination of the rice program between different organizations in Vietnam and IRRI. As a result, a general MOU was signed with the MOA as an umbrella agreement. Separate sub-MOUs were signed with different institutions to assure their efficient participation in collaborative rice research. In 1985, the Australian International Development Assistance Bureau (AIDAB) became a donor to support the IRRI program in Vietnam. This program has been providing funds for collaboration in all fields of rice research and training, except for upland rice, which remains unsupported to date.

Vietnam-IRRI cooperation 25 AIDAB continued to support the second phase of our Vietnam-IRRI collaborative program soon after the signing in 1988 of another MOU between IRRI (represented by the Deputy Director General Dr. F.A. Bernardo and Dr. Glenn Denning) and representatives of the Ministry of Education and Training (MET) and the Ministry of Agriculture and Food Industry (MAFI). Relations between Vietnam and IRRI took a new turn when IRRI was reorganized under the direction of Dr. Klaus Lampe. Starting in 1989, the number of Vietnamese trainees was almost doubled and collaboration among IRRI scientists and the agricultural research institutes and universities throughout Vietnam was increased. The most significant result of Vietnan-IRRI collaboration can be seen in the rapid spread of new improved varieties of rice throughout Vietnam. The collaboration is also addressing many other scientific areas. During the last 2 yr, IRRI research staff accepted a contract with the United Nations Development Programme (UNDP) to help upgrade the capability of the Cuu Long Delta Rice Research Institute (CLRRI) in Omon, Cantho Province (see Luat et al, this volume, page 303). Vietnam's contributions to IRRI in return have been the close collaboration of Vietnamese scientists with the IRRI scientists in various experiments carried out in the different ecosystem programs of IRRI. Vietnam also contributed to IRRI one member of the Board of Trustees and one staff member.

Advantages and shortcomings

Advantages In Vietnam, there are many scientists working on rice in different research institutions and universities. In collaborative projects, the IRRI scientist can usually find an experienced Vietnamese scientist counterpart. Therefore, IRRI scientists can feel confident that a research project will be carried out with high scientific standards. This could be why, at present, there are no IRRI scientists resident in Vietnam. Second, IRRI programs in Vietnam have generally received a warm welcome from administrators of both the central and provincial governments — IRRI scientists are welcome everywhere. Third, Vietnamese farmers are eager to seek improvements. At the beginning of every cropping season, they always approach research scientists to ask for new seed to try. Therefore, in terms of agricultural extension, it is easy to approach or to work with the advanced farmers, particularly those who are providing extension or demonstration sites for the new technologies generated from IRRI through the research institutions in Vietnam.

Problems I think the most significant problem may be the loose coordination at the national level of the different collaborative programs involving IRRI in Vietnam. We know that in Vietnam there are many research institutions and each is involved in one or more rice experiments. All of these institutions want to collaborate with IRRI. Before 1975, activities in rice research involving IRRI in South Vietnam were conducted by the MOA'S Rice Service, Extension Service, and Regional Research Stations throughout the country, and the Bio-Agronomy Department of University of Cantho. To rationalize this cooperation, the IRRI group planned, before 1975, with the MOA to organize an Institute of Agricultural Research, hoping that it would serve as the national coordinating body to deal with rice research at different institutions in South Vietnam. At the end of the war, the plan had still not been put into effect and the institutions were still working separately. After the

26 Vo-Tong Xuan country was unified in 1975, the number of rice-related institutions grew further: the National Agricultural Sciences Institute (INSA), the Food Crops Research Institute (FCRI), the Soil and Fertilizer Institute, the Plant Protection Institute, the Agricultural Mechanization institute (AGMI), the University of Agriculture No 1 in Gia Lam, the University of Agriculture No 2 in Hue, the University of Agriculture No 3 in Bac Thai, the University of Agriculture and Forestry at Ho Chi Minh City (UAF), the Institute of Agriculture Sciences of South Vietnam in Ho Chi Minh City (IAS), and CLRRI. In addition, several provincial agricultural research stations carry out research on rice. In an attempt to coordinate agricultural research activities of these institutions, the ministry of Science, Technology and Environment (MOSTE) has organized several national research programs, among which is the national research program on foods and feeds, so that efforts would not be duplicated and scarce resources not wasted. However, this attempt was unsuccessful because each of the ministries controlling those institutions have their own budget, and they allocate money to their own institution, even if MOSTE does not. In the middle of this internal competition, IRRI has not known where to direct its efforts. That is why, from the time of Director General Dr. M.S. Swaminathan, IRRI has had to sign separate MOUs with individual institutions in Vietnam to ensure that the institution could cooperate with IRRI scientists. In particular, the MOU that IRRI signed in 1988 with two ministries (MAFI and MET) assured not only that the agricultural research institutes but also that the agricultural universities in the country could participate in the rice program with IRRI.

Reasons for IRRl’s success in Vietnam

Many of the rice selections made in Vietnam were either from segregating populations or from the different nurseries of the IRTP program sent to different organizations in Vietnam. Virtually every Vietnamese agricultural scientist does something with rice, and sooner or later he or she will make a break-through — in this case, selected varieties that are adapted to one province or district. The effect of this work on a Vietnamese leader at the district. province, or national level has been very pronounced. When Vietnamese leaders — most of whom are politicians — talk about development, they talk about rice. When they talk about rice, they talk about new varieties from IRRI. This top-down approach by the Vietnamese government to agricultural development has accelerated the use of new varieties from IRRI throughout Vietnam. Even now, if we do not have new lines to release each year, scientists are criticized first by the farmers and then by national and provincial leaders. Consequently, every Vietnamese agricultural scientist is trying to develop new rice varieties adapted to each local situation. In addition, the Vietnamese farmer, especially the southern Vietnamese farmer, is very market oriented, always wanting something new. Most Vietnamese farmers want to replace the variety they have been growing for two or three crop seasons to keep up with the evolution of the insects, pests, and diseases in the field. Every year, farmers go to the research station or university and ask for new releases of rice, That demand is increasing, especially now that they cannot sell much of the rice because of its low quality. Therefore, farmers are now demanding varieties of higher yield, with higher insect resistance, especially to BPH, and with better grain quality for export. Thus, the Vietnamese rice scientists cannot stand still. They are pressed to move forward to meet the demands of farmers, provincial leaders, and administrators at all levels in the country. Perhaps one of the reasons for the success of Vietnam–IRRI cooperation has been the strong program in technology transfer, especially in rice production. For nearly 20 yr, many Vietnamese scientists, particularly at the University of Cantho, have practiced the participatory rural appraisal approach to determine constraints in farmers’ fields. From this basis, they have tried to solve the

Vietnam-IRRI cooperation 27 farmers’ problems by cooperating with the local administrators and with other scientists in the country. Generally, the constraints causing low rice production were analyzed systematically on the basis of soils, insect populations, disease occurrence, and varietal improvement. Once the constraints have been categorized into issues that can be tackled, the issues are assigned to different students as a research topic for graduation. These students put into practice the knowledge that they have gained in the first 3 yr in school in trying to solve the problem, They learn both from the issue assigned to them and by going to the districts or villages where the problem occurs, which is also where they carry out their research. Thus, their research plot also serves as a demonstration field for the local farmers and administrators, who can see the solutions that can be applied to their local condition. We started this integration of research–instruction–extension into our education and training of the students in Cantho in 1973. Thanks to this approach, appropriate technology — particularly new rice varieties — can be spread quickly among the farmers by themselves, especially originating from the cooperating farmers. These are the major reasons why IRRI rice varieties have covered most of the rice-growing area in Vietnam. Wherever there is irrigation, the farmers switch to new varieties from IRRI. Also, of course, we must emphasize the importance of the food-security policy of the government through which much of the national budget has been allocated to development of the irrigation systems.

Future collaboration

Looking back, it is clear that we — meaning IRRI and the Vietnamese scientists — have been doing a lot to help famers to improve their production. Thanks to new technology and new policies of the government, Vietnamese farmers are able to produce much more rice than they need, in both the irrigated and rainfed areas, so that some rice is available for export. However, the income of most Vietnamese farmers is still very low and this must now be addressed directly. Of course, the international market could be blamed for the low price of Vietnamese rice, but I believe that the cost of production per kilogram of rice in Vietnam is still too high. Vietnam–IRRI collaboration has addressed the full range of problems in rice production from germplasm improvement to postharvest activities, but coordination among the scientists in Vietnam is not good enough to tackle each of the constraints in different agroecosystems to the degree needed. What we have has come about sporadically, piece by piece, while farmers have to face the whole range of problems in their farms. In other words, we scientists are trying to find the pieces and leave it to the farmer to put them together. The farmers cannot do this because they find it very confusing when a soil scientist tells them to do one thing, an agronomist to do another, and an entomologist or a pathologist to do a third — sometimes in the same locality three or four different groups are working without coordination. I think this kind of uncoordinated practice would be eliminated if the scientists worked within a unified program, where each looked at one aspect of a total picture and considered how he or she would affect that picture. The farming systems approach seems logical to me. While we continue to work on better rice varieties for the irrigated, rainfed, flood-prone, and deepwater ecosystems, the following four aspects of rice production should also be emphasized. Fertilizers. Research is needed on the economics of fertilizer use on each kind of soil: what kinds of fertilizer to use and how to use it. Results from this research would allow the farmers, with the same amount of fertilizer to achieve greater yields and thus lower production costs. Pest management. The integrated pest management (IPM) program has operated for several years in cooperation with IRRI and the Food and Agriculture Organization of the United Nations (FAO), but the concept has yet to take root with farmers. We need a balanced approach for the farmer, so that he or she can use pesticides correctly in smaller quantities, thus saving money and lowering the cost of production.

28 Vo-Tong Xuan Postharvest losses. Although we have done some work on postharvest losses, we have not done enough and this area must be strengthened. Upland rice. One area that we have totally ignored is upland rice, where the total area is too small to get attention. Although the area in each year is small, after 3 yr the farmers slash-and-burn another area to grow the same amount of rice, leaving fallow the land that has now lost its forest. If you visit the highland areas of Vietnam now, you will see very few forests. Slash-and-burn cultivation by the highland people in Vietnam will continue as long as they need food, and their food is mainly rice. In the future, the Vietnam-IRRI program should put strong emphasis on the less-privileged areas of Vietnam. If the well-to-do farmers sponsor research in the favorable areas, our meager research and extension budgets can be used to help farmers in the less favorable areas. I believe strongly that Vietnam-IRRI collaboration will continue to grow ever stronger and to address more significant programs of the lowland farmer and the upland farmer. Let us see if, in the next 10 yr, Vietnam-IRRI collaboration will address the farming community in its entirety so that Vietnam can be assured of rice security, the income of farming families will increase, and the environment will be protected.

References cited

Dat D H, ed. (1994) Lich su nong nghiep Viet Nam [The agricultural history of Vietnam]. Agricultural Publishing House, Hanoi. Vietnam. (In press). MDSP — Mekong Delta Soils Project (1974) Annual report for 1973-1974. Faculty of Agriculture, University of Cantho, Cantho, Vietnam. USAID — United States Agency for International Development/Vietnam (1974) Program review of research and development and the International Rice Research Institute Cooperative Vietnam Rice Research Project. Saigon, Vietnam. Xuan V-T,. Hanh C V. Quyen N H, Ou S H, Jackson B R (1973) Rice research, production, problems and progress in Vietnam: a report to the International Rice Research Institute, Los Baños, Laguna, Philippines.

Vietnam-IRRI cooperation 29

World rice market and Vietnam’s agriculture beyond 2000

Mahabub Hossain 1

Vietnam is a country with pragmatic leadership and intelligent and hardworking people committed to economic progress with sustainable human development. The country is not as well-endowed with natural resources as its Southeast Asian neighbors, and has had very little access to external resources and technology, particularly since the former Soviet bloc has been in turmoil. Yet its economic performance is comparable to that of its neighbors in the fast-growing region of Asia. Since 1981, when the political leadership decided to make a transition from central planning to a market-oriented economy, the agricultural sector has grown at 4.1% per year, a performance similar to China’s and superior to the 3.4% growth achieved in Asia as a whole. Only Malaysia and Indonesia have outperformed Vietnam in this respect (Fig. 1). The main factor behind this impressive agricultural growth has been a vibrant rice sector. Rice production grew at more than 4.7% per year, the highest in Asia and more than double the average during this period. Over the last 7 yr, the Vietnamese economy has expanded by more than 6.5% per year, a record to be envied by most developing countries of the world, and a sharp contrast to the disastrous performance of similar transitional economies in the former Soviet bloc. The achievement is attributable to pragmatic macroeconomic policies and structural reforms adopted in phases — the decollectivization of agriculture and a return to family-based farming, decontrol of most input and output prices, liberalization of external trade and the foreign-exchange regime, active encouragement of foreign investment, and above all an emphasis on training of the people in the operation of the market-oriented economy, so they can respond to economic incentives.

1. Growth in rice and agricultural production for Vietnam compared with selected Asian countries, 1980-93. Source: FAO Statistical Bulletin, February 1994.

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. The recent normalization of external relations will lead to a sharp increase in external resources, and access to foreign investment and improved technologies, which will definitely further invigorate the economy. With a backdrop of these developments, the Vietnamese leadership is rightly concerned with the potentially unfavorable effect of structural reforms and incentive-driven economic growth on the welfare of the disadvantaged sections of the population and on the regional balance in the development of the economy. Despite recent economic progress, living conditions in rural areas are still appalling. Recent surveys indicate widening income disparities associated with the reforms and estimate that 25-30% of the population is still living in poverty. There are marked regional disparities, poverty being most prevalent in mountains and hilly areas, among minority groups, and in rural areas of central Vietnam and in the mountain regions in the north. A well-thought-out strategy that can integrate the disadvantaged people and backward regions in the development process is needed to achieve society’s goal of rapid economic progress with socioeconomic equity. Such a strategy must be based on an understanding of the interdependence among regions, sectors, and economic agents, and how it is going to be affected by economic progress and growing external economic relations through the operation of market forces.

Global rice economy: recent progress and emerging trends

The global rice economy has changed dramatically since the mid-1960s with the introduction of the Green Revolution technologies. Rice yields increased as farmers gradually replaced traditional varieties with modern cultivars developed by international and national rice scientists working in partnership. Over the last quarter century, rice production has grown at 2.8% per year, while population has increased by 2.1%. Many large rice-importing countries, such as Bangladesh, India, Indonesia, and the Philippines have achieved self-sufficiency in rice production, and Asia has been able to reduce its share of global rice imports from 60 to 20%. The rapid increase in rice productivity has helped crop diversification in favorable rice-production environments particularly in East Asia, and checked expansion of rice production on marginal lands in unfavorable environments. Per-capita rice consumption has increased by about 18%, and the technical efficiency in the use of inputs in modern cultivars has led to a decline in unit cost of rice production by 20%. The combined effect of these forces is reflected in the long-term downward trend in real rice prices. The availability of rice at affordable prices has benefited the rural landless, food-deficit farmers, and the urban poor, and contributed to partial alleviation of poverty in many low-income Asian countries. There are emerging signs, however, that indicate that this favorable trend may not continue in future. We may see some decrease in the growth of demand for rice for two reasons. First, per- capita food-grain consumption has almost reached satisfaction levels in major rice-consuming countries and, second, with economic progress, consumers in middle- and high-income countries have started replacing rice with high-cost quality food, such as vegetables and fruits, oil and fats, and fish and meat. However, population growth is still a major force behind the increase in demand, as it is expected to stabilize only after the middle of the next century. The Asian population is projected to increase by 55% over the period from 1990 to 2025, and may double within the next 40 yr in the low-income countries of South Asia and in the Philippines and Vietnam. Recent projections show that the demand for rice may increase at about 2.0% per year during the present decade, and by 1.4% per year over the first quarter of the 21st century, mostly because a larger population must be fed. However, the growth in rice supplies may decrease faster than demand, unless there are major scientific breakthroughs to shift the yield frontier and in the development of varieties suitable for unfavorable rice-growing environments subjected to , submergence, typhoons, and poor drainage. As the economy grows, prime rice land is being lost to accommodate industrialization and urbanization. Irrigated areas, which contribute 75% of the world’s rice supplies, are already planted

32 M. Hossain 2. Changes in growth of rice production. World, 1965-93. Source: Estimated from IRRI. World Rice Statistics, 1991, and FAO Agrostat Database.

with modem cultivars and farmers’ yields are approaching the potential that scientists are able to attain with today’s knowledge in that particular environment. In rainfed areas, yields are still low, although they could be increased through intensive use of agrochemicals. However, this will require development of suitable varieties that can stabilize the yield and reduce risks in rice cultivation. The growing concern for environmental protection may, however, discourage further use of agrochemicals, thereby slowing down the growth in rice yields. The most recent trend indeed shows a rapid slowing in the growth of rice production (Fig. 2). The annual increase in world production has been 1.2% per year since 1985, compared with 2.8% during 1975–85, and 3.5% the decade earlier. Since 1985, major rice-growing countries, except Vietnam and Bangladesh, have had a substantial deceleration in growth in rice production, which has been overtaken by the increase in population.

World rice market and Vietnam

Rice is basically a subsistence commodity. Over 92% of the global production is in Asia, where average farm size varies from 0.5 to 2.0 ha. Most farmers produce rice for family consumption leaving little for the market. The amount of marketed surplus and rice prices fluctuate greatly from year to year depending on weather conditions. Because rice is the single major staple food, its price is often a political issue. Most governments would like to maintain self-sufficiency in rice production to stabilize its price and keep the politically conscious, and vocal, urban population happy. Of the major rice- consuming countries, only Malaysia and Sri Lanka are important importers: only during times of natural calamities must the other Asian countries go to the world market. Only about 4% of the global rice production is traded in the world market, which is characterized by large numbers of small-volume importing countries and a small number of large-volume exporting countries. The market is volatile because a small fluctuation in production in a few major rice-consuming countries has a large effect on the supply-demand situation in the world market. Vietnam has recently emerged as a major exporter of rice in the world market because of rapid growth in domestic production (Fig. 3) and the government’s efforts to earn foreign exchange in the face of the limited access to external borrowing. Over the period 1989–93, Vietnam exported an average of 1.5 million t of milled rice per year, amounting to 11% of the world trade. Over 70% of Vietnam’s rice goes to the low-income countries of sub-Saharan Africa and South and Southeast Asia,

Vietnam’s agriculture 33 3. Trends in population and production, area, and yield of rice, Vietnam, 1961-92. Source: Estimated from IRRI World Rice Statistics 1991, and FAO Agrostat Database.

Table 1. Geographic distribution of Vietnam’s rice exports compared with the global market, 1989-92.

Region % of market or exports

World Vietnam

South and East Asia 27.4 36.3

Africa 25.1 35.6

Central and South America 10.5 14.4

Middle East 11.8 7.3

Former USSR 4.1 5.2

Other developing countries 21.1 1.2

Source: FAO

and the trade is mostly in low-price, lower quality rice. Almost 33% of the world rice market is in Europe, North America, and the Middle East (Table 1); Vietnam’s share of this market was less than 9%. The main constraint to Vietnam’s entry into this high-income market is the quality of rice available for export.

34 M. Hossain Table 2. Growth (% per year) in rice consumption and imports, 1960-92.

Region Production Consumption Imports

Africa 3.4 3.6 5.3 South and East Asia 2.7 2.6 -4.6 Middle East 2.0 3.6 3.8 Central and South America 1.8 3.1 10.6 Europe 2.3 1.5 2.1 North America 1.4 3.6 6.3

Source: FAO, Agrostat Database.

4. Changes in terms of international trade in agricultural commodities, Vietnam, 1981-93. Source: FAO Statistical Bulletin, February 1994.

From the demand side, Vietnam's prospects for maintaining or even expanding its exports in rice are bright. In Africa, per-capita rice consumption is expected to grow with urbanization and increasing per-capita incomes. Over the last three decades, rice consumption in Africa has grown 3.6% per year and rice imports 5.3% (Table 2). The demand for imports may also increase in the low- and middle-income countries of South and Central America, where rice consumption has grown 3.1% and rice imports 10.6% per year. As the consumers are poor, these countries look for exporters who can offer low-priced rice. The Asian market is, however, expected to contract and will remain unstable. The domestic production in low-income South Asian countries is expected to grow, and per-capita rice consumption in middle-income countries will gradually decline with further increases in production. The import demand will increase in the high-income rice economies of Japan, South Korea, and Taiwan due to the agreements on the liberalization of agricultural trade under the General Agreement on Tariffs and Trade (GATT). However, the market will be in superior quality japonica rice and, therefore, may remain beyond the reach of Vietnam.

Vietnam's agriculture 35 5. Per-capita consumption of rice and cereals in Vietnam compared with selected Asian countries, 1988-90. Source: FAO Agrostat Database.

It should, however, be noted that the terms of trade in the world rice market have not been very favorable to Vietnam (Fig. 4). During 1980–92, the volume of agricultural exports increased by 29% per year, but export earnings increased by only 19% because of a rapid decline in the unit value of exports. The import price index almost doubled while the export price index declined by over 50% over the last decade. Vietnam could offer its exports at low prices because of cheap labor and the low opportunity cost of land (as perceived by farmers because land sales and rental markets are nonexistent). The agricultural wage rate is only US$ l.00/d in Vietnam compared with US$4.00 in Thailand. Farmers in many Asian countries pay 30–50% of the gross produce as rent to land owners: in Vietnam, the land tax paid by farmers is less than 5% of the gross produce. According to recent estimates by the Food and Agriculture Organization of the United Nations (FAO), the cost of production per tonne of paddy is US$200 in USA and US$120–140 in Thailand, but only US$l00 in Vietnam as a whole and US$75 in the fertile Mekong River Delta. However, the low prices for exportables has kept farmers and agricultural laborers poor, while importers of cheap Vietnamese products reaped the benefits. With increased access to external borrowings and inflow of private foreign investment, Vietnam should review its strategy of promoting rice exports at low prices.

Internal demand for food grains

An important factor that should be considered in reviewing the export strategy is Vietnam’s capacity to meet the future internal demand for food grains. Although Vietnam exports rice, there is still an unmet demand for food grains in the country and the energy intake of the average Vietnamese is low compared with many Asian countries. The consumption of cereals during 1980–90 in Vietnam was 154 kg/person per year, about 20% lower than in , a rice-exporting country at a similar level of development, and 12% lower than in Indonesia, which has recently become self-sufficient in rice production (Fig. 5). The daily energy

36 M. Hossain 6. Per-capita caloric intake in Vietnam compared with selected Asian countries. 1990. Source: FAO Agrostat Database.

7. Projected population of Vietnam, 1950-2025. Source: World Bank Projections of Population.

intake per capita in Vietnam is estimated by FAO at 2,215 kcal, compared with 2,631 in Indonesia and 2,531 for Asia as a whole (Fig. 6). Yet Vietnam has already exploited its natural resources much more intensively than many Asian countries. The per-capita arable land of Vietnam is only 50% of that for Asia, about 25% of Thailand and 30% of Myanmar. The area cropped with food grains is over 121% for Vietnam (over 100% because of multiple cropping), compared with 52% in Myanmar, 58% in Thailand, 62% in Indonesia, and 90% in the Philippines. Obviously, the availability of natural resources to meet the future food needs of the people is much more limited in Vietnam than in its neigbors.

Vietnam's agriculture 37 Table 3. Rice yield and per capita production of food grains in different regions of Vietnam.

Region Food grain Rice yield production (t/ha) (kg of paddy/ person per year)

Mekong River Delta 676 3.69 Red River Delta 295 3.42 Central Coast of South 284 3.36 Northeast of South 133 2.63 Midlands 244 2.51 Central Coast of North 226 2.47 Central Highland 229 2.46 North Mountains 216 2.10

Whole country 324 3.35

Source: Statistical Publishing House of Vietnam.

A further major factor that is going to increase the internal demand for food grains is the growth of population. The Vietnamese population has increased by 73% over the 1960-90 period, and is projected to increase by another 62% over the next three decades. By 2025, the population is expected to reach 116 million and will continue to grow at 1.1% per year (Fig. 7). If we assume that, with economic prosperity, the per-capita consumption of cereals in Vietnam will reach the level of Indonesia, then the demand for food grains is expected to grow by 80% over the next 30 yr. Vietnam will need to produce 33.6 million t of food grains in rice equivalents to meet this internal demand. If the rice area remains fixed at the current 6.4 million ha, the rice yield will have to increase to 5.25 t/ha from the present level of 3.35 t/ha to meet this internal demand. It is possible to increase rice yields to this level through intensive use of modern agricultural inputs in the Mekong and Red River deltas and on the central coast of the south, but it will be hard to increase productivity in other regions, which have unfavorable rice-growing environments. Nearly 30% of the rice land in Vietnam is in the unfavorable regions where rice yield is lower than 2.5 t/ha (Table 3) and has hardly increased in the past. Thus, to meet the needs of future generations, Vietnam should move to exploit the potential of increasing rice production in the favorable areas.

Agricultural diversification

With rapid growth of incomes, the demand for noncereal foods is expected to grow faster than that for food grains. If Vietnam sustains a growth of per-capita income of 4.0% per year, it will reach the present income levels of Indonesia by 2020, and of the Philippines by 2025. At today’s consumption levels in the Philippines, the demand for most major noncereals foods in Vietnam is projected to increase by over 100% by the year 2025 (Table 4). Meeting those needs will place large demands on scarce land and capital resources. Some rice lands may have to be diverted to produce nonrice foods. If the growth in supplies does not keep pace with the projected demand, relative food prices will change and demand will be adjusted to the limited supply. Not only will this alter the income distribution among producers of different types of food, but also it will change the relative profitability and the allocation of land and other resources among different agricultural activities.

38 M. Hossain Table 4. Projected increase in demand for noncereal foods in Vietnam, 1990-2025.

Foodstuff % increase

Vegetables 120 Fruits 148 Fish and seafood 360 Livestock 82

The agricultural planners will need to work out the comparative advantage of different regions for producing various agricultural products, and plan the development of infrastructure, marketing facilities, and support services to facilitate the exchange of products among different regions. The specialization of production and the exchange of surplus among regions and farmers will expand trade, transport, and service activities and will generate employment for the poor in the rural nonfarm sector. As shown by the development experience of other countries, the rural nonfarm sector can be expected to play an important part in absorbing surplus labor and in moderating income inequalities in farming activities during periods of rapid economic growth.

Vietnam's agriculture 39

National program for Vietnam on food crops research and development

Vu Tuyen Hoang 1

Although Vietnam lies within the tropics (8°-23°N, lat 15°E), the climate is not typically tropical. From the Hai Van mountain pass (16°20'N) to the south, the climate is typically tropical, warm all year round (except in the Central Highlands, which have a mountainous tropical climate). From the Hai Van mountain pass to the north, warm weather only occurs during the rainy season. During the dry season, the temperature drops so that the climate is subtropical. The agricultural area consists of 7 million ha out of a total 33 million ha. The country is divided into seven ecological zones for agricultural production: North Mountainous and Hilly, Red River Delta, Central North, Central Coastal, Central Highland, Southeast, and Mekong River Delta. The Vietnamese people have a long tradition of rice culture with transplanting and, like other Southeast Asian countries, the traditional local rice varieties are tall, have diverse grains, and require low fertilizer inputs, but the yield is low. Rice seed selection started in Vietnam in 1920 but concentrated on the collection and selection of good local varieties for rice export. From 1945 to 1954, some short-maturity Chinese varieties (100-110 d) were imported into Vietnam. From 1956, several thousand local rice varieties were collected by the Agroforestry Academy — this continued in the south until 1975. During 1960-68, several new rice varieties were selected from the imported varieties (including Agriculture 1, Variety 127, and Winter-Spring4) or from local ones (for example, Varieties 813 and 828, and Winter-Spring 2). These new varieties have led to great changes in the rice seed market in northern Vietnam as well as higher yields than the local varieties. The highest yielding variety can produce 5 t/ha. In 1968, the Green Revolution in Vietnam started with the import of IRRI rice varieties that were shorter, highly responsive to fertilization, and high yielding — for example, IR8 (known as Than Nong 8 in the south and Agriculture 8 in the north) produced an average yield of 4-6 t/ha with the highest yield reaching 10 t/ha. The imported IRRI varieties created great changes in rice farming in Vietnam. The agricultural research institutions of Vietnam have used these intensive IRRI lines and varieties with local and imported rice varieties as the initial breeding materials to cross and select new varieties. • The adoption of the new rice varieties took place in two stages: First, in the 1960s and into the 1970s, the new IRRI varieties were introduced with improvement in technology directed to intensive culture, use of fertilizers, improvement of irrigation infrastructure, strengthening of plant protection, and improvement of cropping patterns • Second, from the 1970s to the present, the use of the IRRI rice varieties continued with, at the same time, the use of new locally created rice varieties. In addition, at the end of the 1970s. scientific and technical programs for rice, maize, and other cereals, and tuber crops were developed for the whole country.

Research policy Scientific and technical progress, especially in seeds, has changed a number of cultivation techniques to create a good basis for organizing research programs for various crops, especially food crops.

1 Ministry of Agriculture and Food Industry. Ngoc Ha, Bach Thao. Hanoi, Vietnam, and Director, Food Crops Research Institute. Tu Loc, Hai Hung, Vietnam. During the 5-yr plan of 1981–85, the national scientific and technological programs for rice, other food crops, soils, fertilizers, plant protection, and agricultural mechanization and equipment were put into operation. In the next two 5-yr plans, 1986–90 and 1991–95, these programs were incorporated into the national scientific and technological program on food crops. This national program on food crops has the responsibility to carry out research and to transfer new technology for the production of rice, maize, various kinds of beans, and vegetables, and to study soils and fertilizers, plant protection, farming systems, agricultural mechanization, agricultural processing and storage, and the agricultural economy of food crops. The program includes 43 research institutions and universities throughout the country, which belong to the Ministry of Agriculture and Food Industry (MAFI), Ministry of Education and Training (MET), ministry of Water Conservancy, and Ministry of Light Industry, as well as some of the testing centers and research stations of various provinces and cities. The program has collaborated closely with such international agencies as IRRI, Centro Internacional de Mejoramiento de Maiz y Trigo (International Center for Maize and Wheat Improvement, CIMMYT), International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Centro International de la Papa (International Potato Center, CIP), Food and Agriculture Organization of the United Nations (FAO), and United Nations Development Programme (UNDP). The objective of this national program is to assure continuing improvement in yield, production, and quality of those crops so as to guarantee the food requirements of the people. At present, there are 19 major topics for the benefit of the farmers on the selection of rice, on vegetables, and on farming systems as well as all phases of the production process from cultivation to processing and storage. Since 1989, Vietnam has attained food self-sufficiency and has had a surplus for export. Rice is the major food of Vietnam and makes up 90% of the total food production: about 10% consists of maize and tuber crops, that is, sweet potato, cassava, and white potato. Rice also has a leading role in the national program on food crops. Vietnam’s achievements in food production have resulted from the Green Revolution in rice and other food crops and the new state policies regarding farmers, agriculture, science, and technology.

Rice seed selection

We appreciate greatly IRRI’s contribution to rice development in Vietnam. The Vietnam-IRRT cooperation program has played an important role in the national program on food crops. In selecting rice seed for intensive culture and for the difficult areas, Vietnamese breeders have used IRRI lines and varieties as the initial material for crossing with local Vietnamese or imported varieties or for use in mutation work. In addition, some new IRRI varieties have been put into production directly. During the past 10 yr, an additional 22 new IRRI varieties have been used directly together with 37 new local breeding varieties that have been recognized as state grade seeds. These varieties, with different growing times and tolerance to brown planthopper (BPH), rice blast, and other diseases, have been widely distributed in southern, central, and northern Vietnam. Most IRRI rice lines and varieties can be easily adapted to typical climatic areas. However, in northern Vietnam where the temperatures are low during the winter-spring crop season, fewer IRRI lines and varieties (within the Rice Testing Program) are suitable than in the south. Many IRRI varieties have been widely used in Vietnam for some time, for example, IR8, IR36, IR42, IR8423-6-2-2 (also known as CR203), and CN2. Equally, many locally selected rice seeds, such as VN10, Variety 424, Spring 2, U17, and V14, have long been widely used in mass production. Through the national program on food crops, local research institutions have created new rice varieties through crossing as well as through mutation. These include lines that are used for intensive farming, are tolerant to drought or deep water, or are adapted to acid sulfate soil. The intensive rice

42 Vu Tuyen Hoang varieties that resulted from artificial mutation are DT10 and Spring 5. Varieties that are tolerant to drought belong to the CH category and can be transplanted in rainfed areas using only about half of the water needed for other varieties. They produce an average yield of 3.54 t/ha. Other varieties that are tolerant to drought, such as LC and the imported IR category, can be suitable for upland rice production. Such deepwater (40–60 cm) tolerant varieties as U17, U14, and C10 can yield 4–5 t/ha or more and can tolerate flooding for 7–10 d. The yield potential of the intensive rice varieties can be 10–12 t/ha. However, only 40–50% of the potential is obtained when they are mass produced because of varied ecological conditions. The national program on food crops is now directed toward breeding new intensive varieties with yields of 14–16 t/ha that will have a different form from the present varieties. Researching and using hybrid rice in mass production is another approach of the Vietnamese rice breeders. There is a need to strengthen the selection of rice varieties that are tolerant to acid sulfate soils and saline soils of the Mekong River Delta and the coastal areas. Rice-farming techniques for the intensive rice areas have been developed and applied to production but research and application of such techniques for the difficult areas must be strengthened and developed.

Soils and fertilizers The national program on food crops will use and further develop the progress made since the 1960s on soils and fertilizers; in particular, the use of organic manure with chemical fertilizers. In the Mekong River Delta, if an appropriate balance of organic manure and mineral fertilizers is adopted, the rice yield can increase from 0.7 to 2.0 t/ha compared with chemical fertilizer alone. The use of organic manure in this Delta is twice as efficient as in the Red River Delta. Leguminous green manure can replace 30-60 kg/ha of nitrogenous (N) fertilizer. As well as N and phosphorus (P) fertilizers, potassium (K) has become a necessary input in some rice-farming areas where it was considered unnecessary in the past. For example, on the alluvial soils of the Red River Delta, K efficiency was very low in the past but now, to achieve winter–spring rice yields of 7 t/ha and summer–autumn crops of 4.5–5 t/ha, K must be applied at 30 kg/ha in an NPK ratio of 1:0.5:0.3. For hybrid rice, K need not be applied at the rate proposed by the Chinese, but only at 60 kg K/ha. Using foliar sprays of both local and imported products that contain a plant stimulator, plant regulator, and microelements can increase rice yield by 4-20%.

Plant protection Within the national program on food crops, rice varieties have been evaluated and selected from the IRRI, Vietnamese, and Chinese lines for tolerance to pests and diseases such as BPH, blast, bacterial blight, and tungro. At present, tungro virus has widely affected rice in the Mekong River Delta and caused 40% yield loss. In central Vietnam, it has been found in two forms: the micro and spherical forms, Some transplanted rice varieties used in the north were tolerant to blast but are now affected. During recent years. BPH has been widespread in the south, especially in the Mekong River Delta where the situation has become very complicated. In the north, however, it is still only biotype 2 of BPH that is found. Integrated pest management (IPM) has become widespread in some provinces and includes the use of bioprotection.

Summary

Rice farming is an integrated process where one must consider land fertility, irrigation, seed varieties, fertilizers, plant protection, crop systems, agricultural mechanization, rice storage and processing, environmental and product protection, and economic efficiency. All of these topics have been studied

National program on food crops 43 within the national program on food crops for rice as well as for such other crops as maize, sweet potato, cassava, white potato, and beans. The Vietnam-IRRI cooperation program has brought effectiveness to the national program on food crops, which is greatly appreciated, and we wish to cooperate even more closely with IRRI, on both traditional and advanced techniques including rice biotechnology. At present, national policy for agricultural production is aimed at diversifying agricultural products for food security and environmental protection. However, rice will continue to play a major role in food production in Vietnam. In 1993, the total paddy production of Vietnam reached 22.3 million t with an average yield of 3.4 t/ha, which is not very high. Rice yield must, and can, be increased to meet the unceasing growth in Vietnam’s population, which it is estimated will reach 100 million in the year 2015. To achieve the objective of increasing yield, quality, and production of rice, we must strengthen research in all the scientific and technological fields.

44 Vu Tuyen Hoang Agriculture and environment: toward a sustainable agriculture in Vietnam

Le Quy An 1

Humanity is facing severe challenges and stands at a defining moment in history. For example, in 1985 more than 730 million people lacked the physical and mental stamina to lead productive working lives because they were disabled by malnutrition: most of them were in developing countries. By the year 2025, 83% of the expected global population of 8.5 billion will be living in developing countries. Therefore, the need to feed this growing population is acute. The relationship between human activity and the earth’s resource base is at a critical point. Thus, the Earth Summit in 1992 stressed the need to make major changes in agricultural, environmental, and macroeconomic policy, at both the national and international levels, in developed as well as developing countries. These changes are needed to create the conditions for sustainable agriculture and for rural development. Their major objective is to increase food production in a sustainable way and to enhance food security. However, agricultural production can only be sustained on a long-term basis if the soil, water, and forests on which it is based are not degraded. To avoid this degradation, as is mentioned in chapter 14 of Agenda 21 , educational initiatives, utilization of economic incentives, and the development of appropriate new technologies must be involved, thus ensuring stable supplies of nutritionally adequate food, access to those supplies by vulnerable groups, and production for markets. This will also lead to employment and income generation, which will alleviate poverty, and to natural-resource management and environmental protection. Priority must be given to maintaining and improving the capacity of the higher potential agricultural lands to support an expanding population. However, conserving and rehabilitating the natural resources of lower potential lands to maintain a sustanable population density is also necessary. Vietnam has an underdeveloped agricultural economy. Nevertheless, this sector is vitally important as it accounts for more than 40% of the country’s gross domestic product (GDP) and about 60% of its employment. Increased food production, therefore, is critical as a means to improving nutrition levels, which are inadequate at present, and the overall quallty of life. The country has an area of more than 330,000 km 2 and a population of 71 million. However, cultivated land is very limited — less than 0.1 ha/capita — and although natural resources are diversified, their reserves are generally limited. For sustainable development, Vietnam must engage its abundant labor force, make effective use of its natural resources, improve its physical environment, and broaden its cooperative relations with foreign countries. However, economic growth might lead to disputes over the use of natural resources. For this reason, the national program for sustainable development stresses the need to build a general plan for natural-resources development based on key national objectives, the imbalance in natural-resource allocation in different areas, the assets and incomes of the people, and the effects that one economic sector or one activity may have on another Thus, conflicts anlong different branches of development and areas of the country concerning the use of natural resources should be avoided. Although, in the coming years, agriculture will still play an important role in the national economy, the old policy of “food self-sufficiency at all costs” has been replaced by a more comprehensive food strategy that accounts for the interrelationships between agriculture and industry, between food crops and industrial crops, between cultivation and animal husbandry, and between ecological conservation and agricultural productivity.

1 Vice-Minister, Ministry of Science, Technology and Environment, 39 Tran Hung Dao Street, Hanoi, Vietnam. Because cultivated land is so limited and there must be land for the construction of industrial and infrastructural projects in future, integrated planning is needed to optimize land use. Agricultural land should be broadly classified on the basis of ecological conservation and economic efficiency. If agriculture in lowland areas can be intensified, the need to cultivate areas less suited to such use and thus more prone to degradation will be reduced. Given rapid population growth, there is a risk that watersheds will become degraded because of deforestation, hill-slope erosion, and soil exhaustion by such unsustainable agricultural practices as shifting cultivation. Great attention must be paid to developing and promoting sustainable cultivation systems for hillside areas. Some combination of agroforestry, contour planting, tree cropping, and terracing will be involved, depending on the prevailing specific conditions. The management of problem soils of the Mekong River Delta is also important. Some 40% of the Delta is made up of acid sulfate soils. Another 700,000 ha of saline soil could be highly fertile if seawater intrusion could be prevented. An important part of the southern coastal areas is occupied by mangrove forests. However, their utilization and protection must be planned, because of their importance as buffer zones against storm surges and typhoon damage, coastal erosion, and flood control, as well as their prime role as the breeding, feeding, and nursery grounds for commercially important coastal organisms. Water resources are of crucial importance for the development of agriculture, which depends on irrigation, drainage, flood control, and control over waterlogging and salinization. Water- management policies should be established within a system that aims at integrating the management of water and land resources for their sustainable development and use by human settlements. Agricultural production must be intensive, but farmers should be encouraged to apply scientific and technological advances to their work so as to improve productivity and the quality of agricultural produce and to reduce losses during and after the harvest. In this way, the value of the agricultural produce can be raised. However, efforts to increase production should, to the greatest degree possible, avoid agricultural pollution from the overuse of agrochemicals. According to the Report of the World Commission on Environment and Development, about 10,000 people die each year in developing countries from pesticide poisoning, and about 400,000 more people suffer from related illnesses. The use of organic and biofertilizers should be encouraged. Although the use of chemical pesticides in Vietnam is low relative to other countries, it is likely to increase and some negative effects of pesticide pollution have been observed already. Integrated pest management (IPM), which combines biological control, host-plant resistance, and appropriate farming practices and minimizes the use of pesticides, is the best way to implement sustainable agriculture, as it guarantees yields, reduces costs, and is environmentally friendly. IPM should go hand-in-hand with regulations on storage, transportation, handling, and use of pesticides, including restrictions on the types of pesticides that can be used in the country. The flora and fauna of Vietnam are diverse, and are characterized by a high degree of endemism. Greater attention must be paid to the conservation and sustainable utilization of plant and animal genetic resources for food and sustainable agriculture. On the social aspect, sustainable agriculture must not be considered separately from rural development. Agricultural policy should strengthen the awareness of the population, improve farm production and farming systems through diversification of farm and nonfarm employment and infrastructure development, ensure people's participation, and promote human-resource development for sustainable agriculture. We are deeply aware of the need to implement a sustainable agriculture, especially at the early stages of the development of the country when 80% of our population lives in the rural area. It will demand greater efforts from the government and the population and, at the same time, broader international cooperation and assistance.

46 Le Quy An Research organization and management: a strategy and a weapon

Byron Mook 1

Research organization and management covers a wide range of topics — from setting priorities, to planning programs, to monitoring progress, to disseminating results, to administering finance, personnel, and physical facilities. However, this paper focuses on only two issues: • How should a manager identify the strengths and weaknesses in the organization? • What is the single most important resource that a manager can use to improve the efficiency of the organization?

The strategy: identifying organizational problems

Two hypotheses are important as starting points. First, all management change should be based on a systematic diagnosis of what is wrong. Second, this diagnosis should focus on three levels: people, organization, and environment. The challenge to a good manager is to analyze these three levels continually and then to draw the appropriate conclusions about the levels at which change is most possible.

The people level The logic here is that management problems are mainly people problems In other words, the organization does not function as it should because the people in it have one, or more, of three characteristics: • They have the wrong values (culture); • They have been badly trained (education); and • They are “bureaucrats.” Culture. Do “cultural” values have an important impact on organizational performance? Management consultants often talk about a “Japanese style of management.” They say that Japanese organizations are the way they are “because the Japanese are Japanese.” What does this mean? Is there something in the Japanese culture and people that determines how Japanese organizations perform? Similar questions could be asked in Vietnam. How fair or correct would it be to say that the agricultural research organizations in Vietnam are influenced by Vietnamese culture? If they are, what particular parts of that “culture” have the most effect on management? Education. The argument here is that the educational system produces people who do not work well in organizations. New recruits may be overqualified, or underqualified, or maybe just trained in the wrong ways. For example, in India, the level of formal qualification required to get an entry-level government job has risen dramatically over the last 30 yr. Whereas, formerly, a person with a primary education could become a clerk, now an advanced secondary qualification is required. The result may be low motivation and low performance because the new recruit feels overqualified. This “diploma disease,” therefore, does raise formal qualifications, but it also often encourages students to think only of passing exams and not of learning.

1 International Service for National Agricultural Research, P.O. Box 93375, The Hague 2509 AJ, The Netherlands. 1. The “Black Box” model of interorganizational research systems.

Bureaucracy. The reasoning here is that people become more “bureaucratic” the longer they are in an organization. They “follow the rules” and do things today in almost the same way as they did them yesterday. They do not take the initiative because most promotions are based on seniority. I have a good example from South India, where I once spent almost 2 yr with agricultural extension and village-level workers. To an outside management specialist (as I then was), many of the attitudes and behaviors of these officials seemed irrational or even irresponsible at first . After closer observation, however, I became convinced that they were actually very rational and very responsible. The problem was, quite simply, that the officials were protecting themselves by following the rules and being content with low standards — that is, by being bureaucratic.

The structural level On the structural level, the logic is more traditional: the problem is not the people, but rather the structure of the organization, the management processes within it, or both. The manager who wants to improve things must draw a new organization chart or modify some processes: have more or fewer departments, new budgeting procedures, new reporting requirements, and so forth. This approach to management change is traditional and very common. However, the perceptive manager should treat it cautiously. A new structure will do no good at all if the basic problems are with the people or with the organizational environment. Similarly, reforms in structure will bring no benefit if they are not accompanied by changes in processes, that is, in the ways things are done.

The environmental level The argument at the environmental level is similar to that at the structural level — but is probably less familiar. The hypothesis is that the problem is neither the people nor the structures and processes, but rather the relationships between organizations. Maybe too many organizations are involved in doing the same thing and the degree of overlap and duplication needs to be reduced. Maybe, for example, the manager needs to think about a new unit to “coordinate” things or to put more emphasis on “planning.” One way to begin to think about this interorganizational issue is to visualize (or even draw) the “managerial world” of the research leader. Usually, the first representation drawn by research managers is what might be called the “Black Box” model (Fig. 1). Here, some organizations provide input to agricultural research and others receive the output. The flow, or the traffic, is completely one-

48 B. Mook 2. The “ABC“ model of interorganizational research system. way The second model — which is almost never drawn by research managers - is an “interaction model” (Fig. 2) in which the traffic is two-way and in which all organizations with which agricultural research has contact both provide inputs and get outputs. This second model involves a lot of “ABC”: A lliances. B argaining, and C ompromise. The hypothesis here is that the most important determinant of efficiency and effectiveness for an organization may be its ABC environment — rather than its people or its structure. There are many good examples from agricultural research. Several countries in Asia have “agricultural research councils”: Bangladesh Agricultural Research Council (BARC), Indian Council of Agricultural Research (ICAR), Malaysian Agricultural Research and Development Institute (MARDI), Pakistan Agricultural Research Council (PARC), Philippine Council for Agriculture and Resources Research and Development (PCARRD), and Council for Agricultural Research Policy (CARP) in Sri Lanka. All of them try to make alliances, to bargain, and to compromise (ABC) with other organizations such as ministries, universities, donors, political parties, and farmers. Some of these councils are much stronger than others, and I would argue that the weaker ones are weaker mainly for ABC-type reasons rather than for personnel or structural reasons.

The weapon: a management information system

Good information is a prerequisite for good management — Information is power An agricultural research manager cannot plan, set priorities, monitor progress, evaluate results, or supervise budget and staff if good information is not available. Over the past few years, the International Service for National Agricultural Research (ISNAR) has been working with several national agricultural research systems (NARS), mostly in Asia, on developing simple management information systems (MIS) for agricultural research managers. Each research organization in Vietnam — a ministry, a department, an institute, a station, or a program — already has some kind of MIS. It has information: it moves it, manages it, and uses it. These MISS probably consist of information on the four subjects listed down the left side of Table 1. The second and third columns contain the words most commonly used when we talk about planning/programing and monitoring/evaluation on each of the four subjects. For example, for money, when we plan/program, we call it “budgeting,” and when we monitor/evaluate, we call it “accounting.”

Research organization and management 49 Table 1. Matrix for management information systems.

Subject Planning Monitoring

Projects Strategy, tactics Output, impact People Recruitment, careers, training Performance Money Budgeting Accounting, auditing Objects Procurement Stock control

3. Sample output from “Reflex” for rice research in Sri Lanka by discipline, 1993.

The MIS in Sri Lanka The country with which ISNAR has worked most closely on MIS development is Sri Lanka, so the following examples are from there. The Sri Lankan agricultural research system consists of 18 main institutes, with about 450 scientists, and about 1,700 research projects. The data in the Sri Lankan MIS are updated annually. The users of the system are program directors and managers at individual institutes, as well as managers at the national level. Literally at the touch of a few buttons, they can see several types of information. • Last year, 1993, 61 Sri Lankan scientists were involved in 229 rice research projects. A printout generated from the MIS — with projects arranged from the smallest (in financial terms) to the largest — showed that one project used 8% of the total national budget for rice research. What was it? “Foundation Seed Production,” which is not strictly a research project at all but simply an essential job that researchers must do. Armed with such information, research leaders can argue that the budget for research is not completely what it seems because it also includes the provision of essential services • Another printout showed the same projects arranged by lead scientist. A striking finding here was that some scientists were managing more than 10 projects. A supervising manager can use such information as the basis for several questions. Does each scientist have a balanced and coherent research portfolio and are some scientists trying to do too much? • A third printout, a bar chart (Fig. 3), shows the disciplinary mix within the national program. “Breeding/genetics” and “Soils” together take up more than 50% of the budget. How might a national manager react to such figures? What would be the comparable figures in Vietnam? • A fourth and final printout, a pie chart, shows the geographic and organizational spread of the rice research program (Fig. 4). The smallest slices of the “pie” are quite small. The six sites that have the biggest “slices” take more that 80% of the budget. Again, how might a national manager react to such figures? How would the situation in rice research in Vietnam compare?

50 B. Mook 4. Sample output from “Reflex” for rice research in Sri Lanka by research institution, 1993.

Resources required for an MIS All this may look and sound complicated, but it is not. Sri Lanka began 5 yr ago with no computers, no MIS experience, no people assigned to do MIS jobs, and no MIS procedures. Managers and scientists had to deal with four issues: technology, data content, data collection, and data management. Technology. The key is easy-to-use computers (hardware) and programs (software). The hardware that Sri Lanka has chosen to use is the basic, standard personal computer (PC). The software is a commercially available database called “Reflex” (which sells for under US$150). A research manager with no previous computer experience can learn to use it reasonably well in 4–8 hr and no programing is required. Data content. Small is better. ISNAR has experimented with various types of project descriptions and with various types of data on human and financial resources. In Sri Lanka, the data being collected are very simple: for projects, only about 10 items. and for people about the same. Data collection. Simple is best. The goal has been to develop a data-collection method that takes very little time. Scientists and managers often complain, rightly, that they receive too many visitors and questionnaires. The result in Sri Lanka has been a procedure in which the director of the institute gives each scientist a short form, which can usually be filled out in 15–25 min, once each year. Data management. Put the system close to its users. The issue here is one of centralization versus decentralization (or top-down versus bottom-up). The MIS in Sri Lanka begins and ends at the institute level. The data are collected there and the main users are there. The role of the national headquarters in Colombo is only to set standards, to encourage adherence to procedures, and to develop national aggregate tables.

Conclusion Probably the best way to get started with an MIS is with one institute or station. Collect some basic data and produce some basic reports. Managers will probably not know exactly what they want at the beginning. However, it is almost certain that they will soon become victims of what one of my ISNAR colleagues has called “the bowl of salted peanuts” syndrome. A manager who has taken one handful of nuts, one set of reports, will always come back for more!

Research organization and management 51

Varietal improvement

Vietnam-IRRI collaboration in rice varietal improvement

G.S. Khush, 1 Vo-Tong Xuan, 2 Nguyen Van Luat, 3 Bui Chi Buu, 3 Dao The Tuan, 4 and Vu Tuyen Hoang 5

Abstract. Vietnam and IRRI have collaborated in rice varietal improvement since 1969. As a result of this collaboration. 63 IRRI breeding lines have been released as varieties in Vietnam. These varieties have high yield potential, shorter growth durations, multiple resistance to diseases and insects, and tolerance to soil problems such as acidity. Some are adapted to flood-prone os upland environments. Large-scale adoption of these varieties has resulted in crop intensification, changes in cropping patterns, and major increases in rice production. Many IRRI breeding lines have been used as parents in the local hybridization programs and several improved varieties have been developed from such crosses. Future collaboration should aim at developing varieties with grains suitable for the export market. Such varieties should have higher yield potential; long, slender, and aromatic grains; durable resistance to diseases and insects; and tolerance to soil problems such as acidity and salinity. Because of the emerging opportunities to export rice to Japan, rices with japonica grain quality should be developed.

Vietnam and IRRI have collaborated in rice varietal improvement since the introduction of IR8 to Vietnam in 1969. Since then a large number of IRRI varieties and breeding lines have been introduced and evaluated in the country. Sixty-three IRRI breeding lines (Table 1) have been released as varieties and are widely grown all over the country. In the Mekong River Delta. as much as 70% of the rice area s now planted to IRRI-developed varieties. Many IRRI breeding lines have been used as parents in the local breeding program and, as a result, several varieties have been developed (Table 2).

Accomplishments to date

IR8 was released as TN8 in South Vietnam and as NN8 in North Vietnam. IR5 and IR22 were also released in both parts of the country but IR20 and IR1529-80-3-2 were released only in South Vietnam. These five varieties were widely grown but were susceptible to brown planthopper (BPH). During the South Vietnam-IRRI Rice Improvement Project (1972-–75) more than 400 breeding lines were introduced and evaluated in the country. Many of these lines were resistant to BPH. When a large-scale outbreak of BPH occurred in 1974–75, three BPH-resistant varieties – TN73-2 (NN23), IR26, and IR30 — were released. Dr. Vo-Tong Xuan introduced 300 breeding lines from IRRI in 1977 and a visiting IRRI team under the leadership of Dr. N.C. Brady, then Director General of IRRI, took seeds of 100 breeding lines to Vietnam in May 1978. Since 1979, breeding lines have been introduced through the nurseries

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 2 University of Cantho, Cantho. Vietnam; 3 Cuu Long Delta Rice Research Institute Omon, Cantho, Vietnam; 4 National Agricultural Sciences Institute, Van Dien, Tu Liem. Hanoi. Vietnam, 5 Food Crops Research Institute, Tu Loc, Hai Hung, Vietnam, and Ministry of Agriculture and Food Industry, Ngoc Ha, Bach Thao, Hanoi, Vietnam. Table 1. IRRl breeding lines released as varieties in Vietnam.

Breeding line Variety BPH- Breeding line Variety BPH- name resistance name resistance gene gene

lR5-47-2 (IR5) TN5, NN5 0 IR17494-32-3-4 IR17494 Bph3 IR8-288-3 (IR8) TN8, NN8 0 IR18189-2-3-2 MTL 54 Bph1 lR532-E576 (IR20) TN20 0 IR18348-36-3-3 (IR64) IR64 Bph1 a lR579-160-2 (IR22) TN22, NN22 0 IR19728-9-3-2-3-3 MTL 61 bph2 IR1529-6-80 TN73-1 0 IR19746-11-3-3 CN2 bph2 IR1561-228-3-3 TN73-2, NN23 Bph1 IR19960-131-3-3-3-3 IR19660 Bph1 IR1541-102-7 (IR26) IR26 Bph1 IR21015-80-3-3-1-2 OM86 bph2 IR1820-210-2 IR1820 Bph1 lR25588-7-3-1 OM88 bph2 lR2153-159-1-4 (IR30) IR30 Bph1 lR28224-3-2-3-2 (IR68) IR68 Bph3 lR2070-747-6-3-2 (IR32) IR32 bph2 lR28527-1-1-2 MTL 64 bph2 IR2070-199-3-6-6 NN8A bph2 lR29723-143-3-2-1 MTL 83 Bph3 lR2070-734-5-4 NN4A bph2 lR29725-76-3-3-2 MTL 68 Bph3 lR2070-423-2-5-6 (IR38) IR38 bph2 IR31802-48-2-2-2 OM87-1 bph2 IR2071-625-1-252 (IR36) NN3A bph2 IR31864-64-2-3-3-3 OM87-9 bph2 IR2071-586-5-6-3 (IR42) NN4B bph2 lR32307-3-2-2 (IR66) IR66 bph2 IR2071-119-3-4 NN5A bph2 lR32429-47-3-2-2 OM86-9 bph2 IR2151-96-1-5-3 IR2151 Bph2 IR35366-90-3-2 (IR72) IR72 Bph3 IR2153-26-3-5-6 IR2153 Bph2 lR35546-17-3-1-3 OM90-9 Bph3 lR2307-247-2-3 NN6A bph2 lR39323-110-5-2-2 MTL 85 Bph3 lR2823-399-5-6 NN2B bph2 lR42859-3-3-1-1 MTL 93 Bph3 lR2797-115-3 NN3B bph2 lR44595-70-2-2-3 OM90-2 ? lR4570-83-3-3 (IR48) NN5B bph2 lR47686-1-5-1-1 LC88-67-1 0 IR8423-132-6-2-2 CR203 bph2 lR47686-1-4 LC88-66 0 IR9129-169-3-3-3 MTL 36 bph2 IR50401-77-2-1-2 MTL 88 Bph3 IR9129-192-2-3-5 NN7A bph2 lR50404-57-2-2-3 MTL 87 Bph3 lR9224-73-2-2-3 OM33 bph2 IR53936-97-2-2-3-3 MTL 119 Bph3 lR9729-67-3 IR9729 bph2 lR54742-23-19-16-10-3 MTL 110 –b lR9782-111-2-1-2 MTL 63 bph2 lR54751-2-34-10-6-2 MTL 103 –b IR13240-10-1 NN9A bph2 lR54751-2-41-10-5-1 MTL 105 –b IR13240-108-2-2-3 MTL 58, TN108 bph2 lR54751-2-44-15-24-3 MTL 98 – b IR13429-299-2-1-3 IR60A bph2 lR56420-28-2-2 MTL 99 Bph3 IR17433-1 MTL 60 ?

a IR64 has another gene for moderate resistance to BPH in addition to Bph1. b These lines have an undesignated gene from O. officinalis. of the International Network for Genetic Evaluation of Rice (INGER) or on the basis of requests from Vietnamese scientists and 55 additional varieties have been released. In addition to the improved plant type, wide adaptation, and high yield potential, these varieties have some of the following characteristics: resistance to BPH and blast, cold and flooding tolerance, tolerance to acid sulfate soil (ASS), improved grain quality, adaptation to upland conditions, and short growth duration.

Resistance to BPH The first five varieties — IR5, IR8, IR20, IR22, and IR1529-680-3-2 — were susceptible to BPH. Therefore, when the outbreak of BPH occurred in Vietnam in 1974–75, these varieties were quickly replaced by IR1561-228-3-3, IR26, and IR30, which had the Bph1 gene for resistance. They were widely grown in the Mekong River Delta and IR1561-228-3-3 in the north as well. However, they became susceptible to BPH because of the development of a new biotype in 1978 and large-scale damage was caused by BPH that year. Varieties with resistance to this new biotype, having the bph2

56 Khush et al Table 2. Rice varieties developed in Vietnam from crosses involving IR varieties and breeding lines as parents.

Cross Name of Cross Name of variety variety released released

Siyamhalus/lR9728-111-2-1-2 MTL 129 IR661-140/IR22 X2 lR9728-111-2-1-2/CR190-12-3 MTL 94 IR262/IR579-48-1 X3 IR18189-2-3-2/CR190-12-3 MTL 95 IR8/IR127-8-1 X10 lR9782-111-2-1-2/IR29 MTL 113 Thiet Cot 31/IR30 X11 IR9782-111-2-1-2/Suweon 332 MTL 138 IR8/Bao Thai Lun MK46 lR49687-89-1/lR29 MTL 134 IR8/lR22//IR19746-11-3-3 VX83 IR29/IR19782-111-2-1-2 MTL 135 lR8/IR579-48-1 V13 IR1016-129-3-4/IR66 MTL 140 IR8/Lomello//Laotim V18 lR18189-23-2/IR36 KBS54 V18/IR8423-132-6-2-2 79-1 lR8/Lemello L 13 IR8/Loc Beo NK14 IR8//813//NN1 NN75-1 900/IR747-B2-6 OM91 IR5/314 NN 75 -2 lR36/IR5853-229 OM80 IR24/IR1112-9-6 NN 75 -6 Hungary/IR48 OM576 IR8/IR22 NN75-10 OM91/IR9782-111-2-1-2 OM59-7 IR8/Du//lR24///IR24 C10 OM91/lR9782-111-2-1-2 OM59-71 IR1529-680-2/813//IR8///IR5 U17 IR48/Than Nong Do OM296 IR8/813//C4-63 C15 OM90//IR36//IR5853 OM44-5 IR5/Chiem 262 386 Nep Thom//lR19794-8-3-1 OM43-26 IR5/Chiem 314//IR2031-354-2 V14 lR32843/IR2307-247-2-2-3 OM269 IR8/Chiem 501 Thanh Hoa C37 lR2307-247-2-2-3/A69-1 OM723-11 IR8/Chiem 501 Thanh Hoa C180 Colombia/IR64 OM997 gene for resistance, were quickly identified and multiplied. In fact, so alarming was the situation that Dr. Vo-Tong Xuan, who had selected IR36 from among the introduced materials, produced about 2,000 kg of IR36 and sent University of Cantho students to different provinces in the Mekong River Delta in November 1978, each with 2 kg of seed and asked them to plant and multiply the seed for distribution to farmers (see Xuan, this volume, page 21). IR36 became the most widely planted variety in Vietnam in the early 1980s. Several other varieties with the bph2 gene for resistance to BPH — NN6A, NN7A, OM33, and NN8A — were released. Another variety, MTL 58 (TN108), was released in the early 1980s. It had somewhat higher yield potential than IR36 which it replaced in the mid-1980s. Many other varieties with the bph2 gene for resistance to BPH were released in 1980s (Table 1). A new biotype of BPH emerged in 1989-90 and these varieties became susceptible. Dr. Vo- Tong Xuan introduced a further 254 breeding lines into Vietnam in 1991. Some of these had the Bph3 gene for resistance and the others inherited their resistance from a wild rice, Oryza officinalis. Other breeding lines with Bph3 were introduced through the INGER nurseries. Several varieties with resistance to a new biotype of BPH (Table 1) were released in 1992 and 1993 and these have almost replaced the varieties with bph2.

Blast resistance Most of the varieties introduced from IRRI are resistant to blast. However, some such as IRl820-210-2 and CR203 were particularly selected for blast resistance. CR203 was the most widely planted variety of rice in northern Vietnam until recently.

Rice varietal improvement 57 Cold tolerance The winter-spring rice crop planted in December in northern Vietnam suffers from low temperature at the seedling stage. IR8 is highly adapted for this season and outyields all other varieties tested during this season. It is still popular for the winter-spring season in northern Vietnam.

Flooding tolerance NN4B, NN5B, and MTL 83 were released for medium deepwater areas (20-40 cm water depth) because they are relatively tall. NN4B is most popular in this ecology and has been planted on 250,000 ha of medium deepwater lands annually in the southern provinces. It also has some tolerance to salinity.

Tolerance to acid sulfate soils Large areas of ASS occur in Vietnam. Such lands suffer from aluminum and iron toxicity and phosphorus (P) deficiency. Dr. Dao The Tuan and his colleagues have screened a large number of IRRI breeding lines for tolerance to ASS and identified and released several acid sulfate-tolerant varieties — IR2151-96-1-5-3 and IR2153-26-3-5-6 are most tolerant, Dr. Nguyen Van Luat and his colleagues have identified acid sulfate-tolerant varieties such as IR68, MTL 61, MTL 64, MTL 83, and MTL 87 for southern Vietnam. The popular variety MTL 58 (TN108) is also tolerant of acidity.

Grain quality Most of the IRRI breeding lines released in Vietnam — with the exception of IR5 and IR8 — have medium long, slender, and translucent grains with high milling recovery. However, with the exception of IR64, they have high amylose content and so they cook dry and fluffy. IR64 has a desirable combination of grain-quality characteristics such as intermediate amylose content, intermediate gelatinization temperature, and long, slender, and translucent grains that remain soft and moist upon cooking. Thus, of all the IR varieties, IR64 has the best grain quality. Because of this and its high yield potential, it has become the most widely planted variety not only in Vietnam but also in Indonesia and the Philippines. It is also widely grown in India. Other varieties that match the grain quality of IR64 are OM87-1, OM86-9, and OM87-9.

Upland conditions To date, very little progress has been made in developing improved varieties for upland conditions. However, two breeding lines from IRRI’s upland breeding program were released for upland conditions — IR47686-1-4 and IR47686-1-5-1-1 were released as LC88-66 and LC88-67-1, respectively. These varieties have excellent blast resistance and are adapted to infertile upland soils.

Short growth duration Next to high yield and BPH resistance, the shorter growth duration of IR varieties is the most important characteristic responsible for their widespread acceptance in Vietnam. Availability of short- duration varieties has led to major changes in cropping patterns and crop intensification. Conversion of deepwater areas in the Mekong River Delta to double cropping with high-yielding varieties is an outstanding example of the value of shorter growth duration in modifying the cropping patterns. TN73- 2 (NN22) and IR30 were the first short-duration varieties introduced into Vietnam, followed by NN3A, NN6A, and NN7A. Most of the later introductions are also of shorter growth duration and mature in 105-110 d. CN2 has the shortest growth duration (90 d) and has been widely grown in northern Vietnam. MTL 61, released for southern Vietnam, also matures in 90 d.

58 Khush et al Impact of modern varieties

Large-scale adoption of improved varieties, improved management practices, development of irrigation facilities, and benign government policies have led to major increases in rice production. For example, rice production in the Mekong River Delta increased from 5.3 million t in 1980 to 9.7 million t in 1990, an increase of 80% in a decade. From being a net importer of rice in the 1970s, Vietnam surprised the world by exporting 1 million t in 1989. Since then, the country has exported 1–2 million t of rice every year. In An Giang Province, which is a major rice-producing province. rice production tripled from 0.5 million t in 1976 to 1.5 million t in 1991.

Future challenges and opportunities for collaboration

Vietnam has the potential to continue to be a major exporter of rice. The country is endowed with excellent land and water resources, year-round rice-growing environments, and hardworking people. However, to be competitive in the International market, it must produce high-quality rice. It must also continue to emphasize the development of rice varieties with higher yield potential and multiple resistance to diseases and insects. Because a large proportion of the rice-growing areas has low pH (that is, ASS), development of varieties with higher tolerance to acidity should receive priority. Improved germplasm for medium deepwater and upland areas should be continuously sought. The following areas of collaboration between Vietnam and IRRI would be mutually useful: grain-quality improvement, improvement of yield potential, selection of germplasm with multiple resistance to diseases and insects and with tolerance to ASS, and selection of improved germplasm for flood-prone and upland areas.

Grain-quality improvement There is a distinct preference for long, slender, and aromatic rices in the international market. None of the high-yielding varieties, however. are aromatic. IRRI has developed aromatic germplasm with long, slender grains — it should be evaluated in Vietnam. Moreover, Vietnam must develop proper facilities for milling rice and for grading and packaging milled rice. With the opening of the Japanese rice market, there will be opportunities for exporting rice with japonica grain quality to Japan. IRRI is developing improved japonica germplasm adapted to the tropics. It should be evaluated in Vietnam to identify varieties with grain quality suitable for the Japanese market,

Improvement of yield potential A major project was launched at IRRI in 1989 to develop rice germplasm with a yield potential of 13-15 t/ha in the tropics and subtropics. Considerable progress has been made and prototype lines with high yield potential have been developed. These should be collaboratively evaluated in Vietnam.

Germplasm with multiple resistance to diseases and insects Efforts should be continued to incorporate new genes for durable resistance to diseases and insects into the improved germplasm. IRRI has transferred genes for resistance to BPH, bacterial blight, and tungo virus from wild species of rice. Novel genes for resistance are being introduced into improved germplasm through genetic engineering. This germplasm will be shared with Vietnam for developing durably resistant varieties.

Rice varietal improvement 59 Germplasm with tolerance to acid sulfate soils Several collections of Oryza rufipogon from the Plain of Reeds (in the Mekong River Delta) are highly tolerant to ASS. These have been crossed with elite germplasm at IRRI and segregating populations will be grown on ASS in Vietnam. Improved germplasm with high tolerance to acidity will be selected on the basis of this “shuttle” project.

Improved germplasm for flood-prone and upland areas IRRI has extensive breeding programs for flood-prone and upland environments. Improved germplasm developed for these ecologies will be shared regularly with Vietnam through the INGER nurseries or on the basis of direct contacts with breeders in the Vietnamese research institutes.

60 Khush et al Sustaining rice productivity in Vietnam through collaborative utilization of genetic diversity in rice

Nguyen Huu Nghia, 1 R.C. Chaudhary, 2 and S.W. Ahn 2

Abstract. The International Network for Genetic Evaluation of Rice (INGER) has supported improved rice production in Vietnam. Through evaluation and follow-up trials of selected INGER entries, 42 rice cultivars and breeding lines have been identified and released as varieties in Vietnam. Many entries have been found to be consistently promising and several promising lines have been used in hybridization programs to develop new improved varieties. Potential donors for various biotic and abiotic stresses have been routinely evaluated and several are used as resistance sources.

Rice is the main food crop in Vietnam providing about 80% of the carbohydrate and 40% of the protein intake. There are 6.3 million ha of rice land occupying 60% of the total agricultural land (IRRI 1993). The two major rice-growing areas in Vietnam are located in the Mekong River and Red River deltas. The total rice-cropping area has increased at 0.7% per year during the last decade (Nghia 1993), while annual growth rates of rice production and yield have been 5.1% and 4.4%, respectively (Table 1). Since 1980, total rice production in Vietnam has almost doubled. In 1993, about 1.7 million t of rice was exported making Vietnam the world's third largest rice exporter. Availability of improved rice varieties to rice farmers and changes in rice-cropping seasons are the main factors for this impressive increase. The rice-improvement program in Vietnam has greatly benefited from the International Network for Genetic Evaluation of Rice (INGER, formerly the International Rice Testing Program, IRTP) coordinated by IRRI, through which diverse rice germplasm and improved breeding lines have been introduced and utilized. Sustaining current high levels of yield and preparing for potential problems appear important and require consideration and good coordination with the nationwide varietal improvement program in Vietnam. This paper reviews past collaboration between the Vietnam rice-improvement program and INGER and discusses future plans for collaboration.

Role of INGER in varietal improvement in Vietnam

As one of various mechanisms for international cooperation initiated by IRRI, INGER has effectively facilitated the needs of different national agricultural research systems (NARS) in genetic improvement of rice since its inception in 1975. The objectives of INGER are To make the world's elite rice germplasm available to all rice scientists for direct use or for crosses within breeding programs;

1 National Agricultural Sciences Institute, Van Dien, Tu Liem, Hanoi, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099,Philippines. Table 1. Rice production in Vietnam, 1980-92.

Crop season Year

1980 1990 1991 1992

Winter-spring Area (1,000 ha) 1,703 2,073 2,158 2,279 Production (1,000 t) 3,867 7,845 6,787 9,144 Yield (t/ha) 2.30 3.80 3.16 4.01

Summer-autumn Area (1,000 ha) 680 1,214 1,369 1,399 Production (1,000 t) 1,591 4,110 4,761 4,804 Yield (t/ha) 1.82 2.81 3.07 3.43

Late-summer crop a Area (1,000 ha) 3,159 2,737 2,769 2 , 744 Production (1,000 t) 6,119 7,268 7,876 7,552 Yield (t/ha) 1.89 2.68 2.80 2.75

a Including monsoon local rice crop.

• To provide rice scientists with the opportunity to assess the performance of their own advanced breeding lines over a wide range of climatic, cultural, soil, disease, and pest conditions; • To identify genetic sources of resistance to major biotic stresses and of tolerance for abiotic stresses; To monitor and evaluate the genetic variation of pathogens and insects; • To serve as a center for information exchange on how varietal characteristics interact with diverse rice-growing environments; and To promote cooperation and interaction among rice-improvement scientists. IRRI coordinates the network, as well as participates in it as one of its members. Rice scientists in Vietnam have participated actively in the network and benefited from this important international cooperation. A total of 279 sets of different types of INGER nurseries were dispatched to Vietnam from 1990 to 1994 (Table 2). Major participating research institutes in recent years were Vietnam’s National Agricultural Sciences Institute (INSA), Cuu Long Delta Rice Research Institute (CLRRI), Mekong Delta Farming Systems Research and Development Center of the University of Cantho, Food Crops Research Institute, Plant Protection Research Institute, Institute of Agricultural Sciences of South Vietnam, and Binduc–An Gang Rice Research Station. In 1993, INGER trials were conducted in 18 locations by a total of 49 scientists from different institutions. The 1993 INGER nurseries consist of 806 entries that originated from 41 different countries and five international agricultural research centers (IARCs): Centro Internacional de Agricultura Tropical (International Center for Tropical Agriculture, CIAT), International Institute of Tropical Agriculture (ITTA), International Rice Research Institute (IRRI), Institut de Recherches Agronomiques Tropicales et des Cultures Vivrieres (IRAT), and West Africa Rice Development Association (WARDA) (Table 3). Thus, rice scientists in Vietnam have been able to obtain and utilize diverse rice germplasm and elite breeding lines for future varietal improvement.

62 Nghia et al Table 2. INGER nurseries dispatched to Vietnam. 1990-94.

Nursery type Year Total

1990 1991 1992 1993 1994

Irrigated rice Yield (very early, early, medium) 22 13 7 12 8 62 Observational 3 5 4 5 10 27

Upland Yield (early, medium) 3 2 4 – 2 11 Observational 3 3 4 8 5 23

Rainfed lowland Yield (early, medium) 4 2 2 3 – 11 Observational 3 2 2 2 3 12

Deepwater Yield 1 1 – – 1 2 Observational 3 2 2 1 4 12

Hybrid rice – – – – 1 1

Stress resistance and tolerance Problem soils 8 7 3 3 2 23 Drought 4 1 2 – 2 9 Blast 3 5 3 7 2 20 Bacterial blight 3 3 3 4 – 13 Tungro 2 1 1 – 1 5 Brown planthopper 5 4 4 7 – 20 Whitebacked planthopper 2 1 1 1 1 5 Stemborer 3 1 – 1 – 4 Gall midge – 1 – 2 – 3 Ufra nematode – 4 – – – 4

Total 77 61 43 57 41 279

Impact of INGER

After intensive evaluation and subsequent follow-up trials of selected INGER entries, a total of 42 rice cultivars have been identified and released as varieties in Vietnam (Table 4). Many entries have been found consistently promising in terms of yield or performance under stress (Annex 2 and 3). Also, location-specific promising lines were identified in each year and utilized in hybridization to develop new improved varieties (Annex 4 and 5). Many potential donor lines for various stresses — including diseases. insect pests, drought, and problem soils — were routinely evaluated and have been used as sources of resistance or tolerance. Use of diverse sources of' rice germplasm would greatly enhance the stability of rice production in Vietnam by widening the genetic base. An active breeding program, complemented with systematic monitoring of pathogen and insect populations, is a crucial step toward effective gene deployment to minimize disease and insect damage.

Genetic diversity in rice 63 Table 3. Origin and types of entries in the 1993 INGER nurseries.

Nursery a Entries National IARCs a (no.) programs (no.) IRRl CIAT IlTA IRAT WARDA IRGC (no.) (no.) (no.) (no.) (no.) (no.)

IIRYN-E 30 19 10 – – – – – IIRYN-M 30 18 9 1 1 – – – IIRON 124 79 34 4 4 – – – SARBON 75 47 28 – – – – – IRLYN-E 18 16 2 – – – – – IRLYN-M 22 17 2 – 3 – – – IRLON 85 35 35 – 13 – – 2 IURON 100 54 14 13 13 2 2 2 IDRON 44 29 15 – – – – – IRCTN 73 62 11 – – – – – IRSSTON 63 30 31 – – – – 2 IRBN-S 81 53 17 – 1 – – 10 IRBBN 66 32 31 – – – – 3 IRBPHN 63 33 21 – – – – 9 IRGMN 37 20 5 – – – – 12

a See Annex 1 for full names. b IARC, International Agricultural Research Center; IRRI, International Rice Research Institute; CIAT, International Center for Tropical Agriculture; IITA. International Institute of Tropical Agriculture; IRAT, lnstitut de Recherches Agronomiques Tropicales et des Cultures Vivrieres, WARDA, West Africa Rice Development Association; and IRGC, International Rice Germplasm Center.

Sustaining rice production

Because rice land in Vietnam covers a wide range of ecological conditions, the breeding objectives are quite specific for each rice ecosystem. For the irrigated ecosystem, early and high-yielding cultivars with good grain quality and resistance to major insects and diseases, such as brown planthopper (BPH), blast, and bacterial blight, are in high demand from the farmers. Early maturing (90-100 d) varieties are required for intensive rice-growing areas. Those that can tolerate low temperature at the seedling stage are needed for the winter-spring season in northern Vietnam. The rainfed ecosystems are very diverse and crops often suffer drought, waterlogging, pests, and soil stresses such as acid sulfate or salinity (Buu 1993). Suitable improved varieties are quite limited. Intensified rice cultivation often invites second-generation problems such as diseases and insects. Blast is considered as the most potentially dangerous disease in northern Vietnam. In 1992, a total of 336,000 ha of winter-spring crop was damaged by blast and more than 9,000 ha suffered total crop loss (Trung 1993). Blast populations in different rice-growing areas of Vietnam appear to be quite distinct (Table 5). For example, IR17494-32-3-4 was heavily damaged by blast in Quang Nan-Da Nang area but is still widely grown in Nam Ha Province where CR203 was highly susceptible. Continuous monitoring of virulence changes and identification of suitable resistant cultivars are needed. The latest outbreak of BPH occurred in 1988-89 in the Mekong River Delta area. Rice varieties carrying the bph2 gene such as IR42 and NN6A were damaged in 1988. NN9A, and MTL 58

64 Nghia et al Table 4. INGER entries released as varieties in Vietnam.

Designation Origin Name given Year released b

b Biplab Bangladesh – a – C22 Philippines C22 1985 C70-2043 Taiwan (China) C70 1993 C71-2035 Taiwan (China) C71 1993 IR13240-10-1 IRRl NN9A – b

IR13240-108-2-2-3 IRRl TN108 1988 b lR1529-680-3-2 IRRl TN73-1 – IR1561-228-3-3 IRRl TN73-2 1981 lR1820-210-2 IRRl IR1820 1987 b IR20 IRRl TN20 – lR2070-199-3-6-6 IRRl NN8A 1983 lR21015-80-3-3-1-2 IRRl OM86 1988 b IR22 IRRl NN22 – lR2307-247-2-2-3 IRRl NN6A 1980 lR5588-7-3-1 IRRl OM88 1988

b IR26 IRRl IR26 – IR2797-115-3 IRRl NN3B 1980 lR2823-399-5-6 IRRl NN2B 1980 b IR30 IRRl IR30 – lR31802-48-2-2-2 lRRl OM87-1 1988 lR31868-64-2-3-3-3 IRRl OM87-9 1990 b IR32 IRRl IR32 – lR32429-47-3-2-2 IRRl OM86-9 1988 lR33059-26-2-2 IRRl IR33059 1993 IR36 IRRl NN3A 1980

b IR38 IRRl IR38 – IR42 IRRl NN4B 1981 lR47686-1-4-B IRRl LC88-86 1993 IR48 IRRl NN5B 1983 a lR49517-15-2-2-1-2-2 IRRl – 1993

a lR49517-23-2-2-3-3 IRRl – 1993 b IR5 IRRl TN5 – lR50401-77-2-1-3 IRRl IR50401 1993 IR51673-172-1-3 IRRl lR51673 1993 IR56450-28-2-2 IRRl MTL 99 1993

IR64 IRRl IR64 1985 b IR8 IRRl NN8, TN8 – lR9224-73-2-2-2-3 IRRl OM33 1983 IRAT216 Cote d’lvoire LC90-5 1993 a b Jaya India – –

Khao Dawk Mali 105 Thailand Khao Dawk Mali 1993 a Pelita I-1 Indonesia – – b a Name given probably same as designation. b Year released unknown.

Genetic diversty in rice 65 Table 5. Varietal reaction a to rice blast in the 1992 inter- national nursery in Vietnam.

Designation Location

Omon Nghi Kim Long Dinh

Tetep 1 0 2 Suweon 351 1 3 3 ClCA 8 1 7 4 IAC 150/76 5 3 2 IR8 1 1 8 Chianung si-pi 661020 3 1 8 C101TTP-1 9 9 9

a Reaction on a scale of 1 (highly resistant) to 9 (highly susceptible).

Table 6. Varietal reaction a to brown planthopper of some selected entries in the 1991 IRBPHN at three locations in Vietnam and at IRRl in the Philippines...

Designation Origin Vietnam IRRl

An Chem Tien Bio- Bio- Bio- Khan Giang type type type 1 2 3

TN1 Taiwan 9 9 9 9 9 9 9101 (Acc74588) China 9 3 4 7 9 7 IR26 IRRl 5 9 7 3 9 5 Milyang 54 Korea 3 3 7 3 7 7 Milyang 63 Korea 5 3 5 3 9 9 RP1976-1689-24-211 India 3 9 2 1 1 7 Straw 23-446 (Acc38434) Bangladesh 5 3 3 1 3 7 PTB33 India 0 1 1 1 1 1

a Reaction on a scale of 1 (highly resistant) to 9 (highly susceptible).

were also affected in 1989. The 1991 International Rice Brown Planthopper Nursery (IRBPHN) indicated the presence of distinct BPH populations in different areas in Vietnam (Table 6). Increasing emphasis on intensification of rice cultivation in Vietnam may increase the vulnerability of rice plants to various biotic stresses. Well-coordinated efforts are needed to establish a research plan and a varietal-deployment scheme to minimize potential losses.

Strengthening future genetic improvement activities in Vietnam

As breeding activities in Vietnam are strengthened, the need for suitable parents, donors, and evaluation environments will increase correspondingly. Moreover, improved evaluation schemes and techniques will become essential. INGER will continue its crucial role of facilitating provision of both diverse and useful rice germplasm and improved evaluation-screening techniques. Various joint site

66 Nghia et al visits organized by INGER have provided opportunities for Vietnamese scientists to interact with other national scientists to exchange information. The recent initiation of a hybrid rice nursery (IRHON) and a supplementary trial on partial resistance to rice blast (IRBN-S) reaffirm INGER’s efforts to respond to the changing needs of national programs. The gradual increase in the number of elite breeding lines from Vietnam’s varietal improvement program selected for INGER nurseries indicates strong collaboration among rice scientists. Greater efforts will be directed toward generation of useful base information on rice genotype × environment interaction that will be useful for selecting location-specific, as well as broadly adaptable, rice cultivars. Intensive evaluation in a reduced number of key sites, therefore, appears to be crucial to improve the efficiency of INGER trials in Vietnam. The international coordinating mechanism facilitating the exchange of genetic materials and information on varietal improvement should be strengthened further.

Conclusion

Varietal improvement is a continuous process to meet the demands and challenges of changing environments and society. The dynamic response of the Vietnamese rice-improvement program to these challenges is a key to further improving the country’s rice production. INGER will continue to play an important role in assisting Vietnam’s rice-improvement program by promoting genetic diversity and making available the world’s elite rice germplasm. High yield potential and genetic resistance of these lines to pests and diseases should help Vietnam sustain its productivity.

References cited

Buu B C (1993) Rice breeding for the problem soil areas in the Mekong Delta, Vietnam. Pages 39-43 in Report of an INGER Problem Soils Monitoring Visit to Thailand and Indonesia. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. IRRI — International Rice Research Institute (1993) IRRI rice almanac, 1993-1995. P.O. Box 933, Manila 1099, Philippines. 142 p. Nghia N H (1993) Highlights of 1992-1993 INGER activities in Vietnam. Paper presented at the 16th INGER Advisory Committee Meeting, 8-10 December 1993. Hangzhou, People’s Republic of China. Trung H M (1993) Present status of rice diseases and their control with emphasis on the use of resistant varieties in Vietnam. Pages 44-49 in Report of an INGER Disease Resistance Monitoring Visit to Indonesia and Philippines. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines.

Genetic diversity in rice 67 Annex 1. Abbreviations for INGER nurseries.

IDRON International Deepwater Rice Observational Nursery IDRYN International Deepwater Rice Yield Nursery IIRON International Irrigated Rice Observational Nursery IIRYN-E International Irrigated Rice Yield Nursery – Early IIRYN-M International Irrigated Rice Yield Nursery – Medium IIRYN-VE International Irrigated Rice Yield Nursery – Very Early IRBBN International Rice Bacterial Blight Nursery IRBN International Rice Blast Nursery IRBN-S International Rice Blast Nursery – Supplemental IRBPHN International Rice Brown Planthopper Nursery IRCTN International Rice Cold Tolerance Nursery IRDTN International Rice Drought Tolerance Nursery IRGMN International Rice Gall Midge Nursery IRHON International Rice Hybrid Observational Nursery IRLON International Rice Lowland Observational Nursery IRLYN-E International Rice Lowland Yield Nursery – Early IRLYN-M International Rice Lowland Yield Nursery – Medium IRSBN International Rice Stemborer Nursery IRSSTON International Rice Soil Stress Tolerance Nursery IRTN International Rice Tungro Nursery IRWBPHN International Rice Whitebacked Planthopper Nursery ITRON International Tidal Rice Observational Nursery IURON International Upland Rice Observational Nursery IURYN International Upland Rice Yield Nursery IURYN-E International Upland Rice Yield Nursery – Early IURYN-M International Upland Rice Yield Nursery – Medium SARBON South Asian Rice Boro Observational Nursery

68 Nghia et al Annex 2. INGER entries in the ecosystem-based nurseries identified as promising for yield in Vietnam, 1987-92.

Nursery a No. of Designation Origin Years of good trials performance

Irrigated rice IIRYN-VE 17 BG1203 SriLanka 1987, 1988, 1989 BG731-2 SriLanka 1987, 1988 IR66 lRRl 1987, 1988 AT77-1 SriLanka 1988, 1989 lR50404-57-2-2-3 IRRl 1989, 1990, 1991

IIRYN-E 13 lR25840-83-3-2 IRRl 1987, 1988

IIRYN-M 9 BR203-70-B-2 Bangladesh 1988, 1989 B3894-22C-78-5 Indonesia 1988, 1989 OR367-SP-11 India 1991, 1992

IIRON 9 Pusa44 -33 lndia 1987, 1988 BG951 SrlLanka 1987, 1988 lR44592-62-1-3-3-2 IRRl 1988, 1989

Rainfed-lowland rice IRLYN-E 1 IR21567-9-2-2-3-1-3 IRRl 1987 IR13240-39-3-3-3-PI IRRl 1987 Ratna India 1987 IR33383-23-3-3-3 IRRl 1987

IRLYN-M 1 IR13146-45-2 IRRl 1987 lR26707-78-2-1-1 IRRl 1987 Mahsuri Malaysia 1987 SPT7106-2-3-3-1 Thailand 1987

IRLON 1 NC505 lndia 1987 RP1579-1863-73-32-53 India 1987 RP894-61-1-3-72 lndia 1987 Upland rice IURYN-E 3 CR222-MW1 India 1987, 1988 NDR97 India 1987, 1988

IURYN-M 5 IR43 IRRl 1987, 1989

IURON 5 lR47719-2-2-1-2 IRRl 1991 , 1992 Deepwater rice IDRYN 1 DWCB-B-110-H-3 Bangladesh 1988 BKNFR76001-50-2-1-1-1 Thailand 1988 NC492 lndia 1988

IDRON 4 B5316-12d-Mr-4-2 Indonesia 1987, 1990 lR39536-1-3-5-1-2-1 IRRl 1988, 1990 VK1-9 Vietnam 1990, 1991 Tidal wetland rice ITRON 1 B5278-13d-Mr-5-4 lndonesia 1988 IR6402-TR-7-1 IRRl 1988 Rohyb6-War6-2-B-2 Sierra Leone 1988 a See Annex 1 for full names.

Genetic diversity in rice 69 Annex 3. INGER entries in the stress-oriented nurseries rated good for stress tolerance in Vietnam, 1987-92.

Nursery a Test Designation Origin Years rated good sites (no.)

Abiotic stress Temperature IRCTN 3 K39-96-1-1-1-2 India 1988, 1991

Moisture lRDTN 4 Agulha Brazil 1991, 1992 IAC47 Brazil 1989, 1990 lR47686-31-1-1 IRRl 1990, 1991 lR47686-4-4-B-1 IRRl 1990, 1991 lR47686-6-1-2 IRRl 1990, 1991

Soil Acid lowland 4 IR26 IRRl 1988, 1991

Biotic stress Diseases IRBN 5 lR31892-46-3-2 IRRl 1987, 1990 Milyang 82 Korea 1987, 1989 RAU4072-46 India 1989, 1990 Tetep Vietnam 1987, 1989, 1990, 1992

IRBBN 10 Camor (Accl7366) Indonesia 1987, 1988 lR32822-94-3-3-2-2 IRRl 1988, 1989 lR4442-46-3-3-3 IRRl 1988, 1989, 1990 RP2151-192-2-5 India 1989, 1990 lR22082-41-2 IRRl 1989, 1990 IR20 IRRl 1989, 1992 Cisadane Indonesia 1989, 1992 RP2090-71-5-2-2 India 1991, 1992

IRTN 1 lR33383-23-3-3-3 IRRl 1990 RP1125-290-1-2-1 India 1990

Insects IRBPHN 8 PTB33 India 1987, 1988, 1990, 1991 lR13540-56-3-2-1 IRRl 1988, 1990 lR35353-94-2-1-3 IRRl 1988, 1990

IRWBPHN 2 WC1240 (Acc13742) India 1988, 1990

IRSBN 4 lR28154-101-3-2 IRRl 1987, 1988 IR39385-124-3-3-2-3 IRRl 1988, 1989

a See Annex 1 for full names.

70 Nghia et al Annex 4. Promising entries at different test sites in Vietnam based on 1992 INGER trials.

Nursery a Test site Entries

IIRYN-E Tien Giang lR53970-100-3-3-2, lR46446-94-3-1-2, lR57301-195-3-3, lR59606-119-3

An Khanh, Ha Tay lR1067-84-1-3-2-1, BR1067-96-6-2-1

IIRYN-M Ho Chi Minh City lR49461-113-3-2-3, lR53964-39-1-2-3-3, lR58123-61-2-2-3, ITA304, MR84

Van Dien BR1257-31-1-1, BR4363-8-11-4-9, CR367-SP-11, lR58109-109-1-1-3

IIRON Tien Giang lR50930-51-3-3-6, lR56422-109-2-1-2-3, lR56427-213-3-2- 3-2, lR56431-85-3-3-3-1, lR58115-103-3-1-1, lR59601-304- 2-1 0

Van Dien ECIA67-S64-4, L 71-1-1-2-1

IURYN Nghi Kim, Nghe An lR55411-50, lR55423-15, RP2235-35-40-5

IRLYN-E Van Dien RP2167-253-3-2-1

IRDTN Nghi Kim, Nghe An lR30716-8-1-8-1-2, lR55543-16, lR55548-5, RP2469-4216-6450-6509

IRBBN Con, Hue IRBB4, IRBBB5, IR46329-SRN-31-3-2-1, lR42221-145-2-3- 2, IR46329-SRN-34-3-1-2, GH305, BR808-17-1-3

IRBPHN An Khanh, Ha Tay BR1709-40-2-1-1, BR1711-7-2-3-2, PTB33, BG367-2, lR21188-87-3-3-2-2, lR22107-14-2-1, lR26707-78-2-1-1, lR31432-9-3-2, lR13540-56-3-2-1, IR41996-163-2-1-2, lR43559-25-5-3-2, RP1607-1240-42, RP2068-18-2-11, RP1579-52, RP2346-684-6, RP2397-406-50 a See Annex 1 for full names.

Genetic diversity in rice 71 Annex 5. INGER entries used in hybridization programs of Vietnam.

Improved Cross combination Year of Area of use in Vietnam variety release

KSB218-9-3-3 lR32429-122-2/IR8423-132-6 1993 intensive, southern

OM269-65 IR32843/IR2307-247-2-2-3 1993 intensive, southern (NN6A)

OM723-11 lR2307-247-2-2- 1993 acid sulfate soils, 3//Pokkali/B4380.2 southern

V18 IR8/Lomelo//Laotim 1993 intensive, northern

79-1 V18/IR8423 (CR203) 1993 intensive, northern

A20 Mutant lR2070-199-3-3-6 1993 intensive, northern

CR01 BG90-2/Balachiem HT//Tetep 1993 intensive, northern

C15 IR8/813//CH 1993 acid sulfate soils, northern

OM987-1 Tunsara/IR64 (OM89) 1993 intensive and acid sulfate soils, southern

Xuan-So 5 Xuan-So 2/2765 1992 intensive and acid sulfate soils, southern

DH60 VN10/Norin 15 1993 intensive, northern

N28 IET1785/Chianung sen yu 1993 intensive, northern

Dong 256 N11/VN10//IR64 1992 intensive, northern

Xuan-So 4 1623/Xuan-So 2 1992 intensive, northern

X11 Thiet-cot 31/IR30 1992 drought-prone, northern

72 Nghia et al Current status and future outlook on hybrid rice in Vietnam

Nguyen Van Luat, 1 Nguyen Van Suan, 2 and S.S. Virmani 3

Abstract. Hybrid rice research in Vietnam aims to develop heterotic rice hybrids with yield potential significantly higher than — and grain quality comparable to — the best available inbred varieties. It is also involved in developing hybrid seed production technology and agronomic management practices to optimize yield of rice hybrids and in studying the economics of the technology. Some rice hybrids bred at IRRI and in China yield more (by 1 t/ha) in the Mekong River and Red River deltas, respectively, and seed production technology is being developed using the models developed in China and IRRI. Seed yields of 0.2–2.15 t/ha have been observed in different areas and seasons. However, much adaptive research is needed to package the hybrid seed production technology to give consistently high seed yields. Fertilizer management strategy for rice hybrids is also being investigated and prospects and problems associated with direct seeding of hybrids in the Mekong River Delta are being studied The future outlook for hybrid rice technology is bright provided an integrated national program on hybrid rice research and development is established in the country.

Rice is the main food crop in Vietnam, providing 80% of carbohydrates and 40% of the protein intake of an average Vietnamese. The crop is cultivated on 4.1 million ha (about 6 million ha of cropped area, including double-cropped areas), which produced 21.86 million t of rough rice in 1993, Since 1990, Vietnam has exported about 1.7 million t of milled rice annually. This has been accomplished by expanding the double-crop rice area planted to short-duration, high-yielding varieties and by reducing the area under monsoon-season rice, which was planted to photoperiod-sensitive rice varieties. Rice yields between 3–4 t/ha in irrigated areas. compared with 1.5–2.0 t/ha in rainfed lowland areas. The highest recorded yields are 10 t/ha (for the winter crop) and 6 t/ha (for the summer crop). The population in Vietnam is currently about 71 million; it is expected to increase to 86 million by 2000 and 121 million by 2020. Per-capita rice consumption, which was 149 kg/yr in 1983–85, is expected to increase to 159 kg/yr in 2000 and 173 kg/yr in 2020. To meet the consumption requirements and export targets, rough-rice production must increase to 32.3 milllon t by 2025. Strategies to increase rice production are twofold: first, introducing short-duration varieties possessing higher yield potential in irrigated rice areas and, second, increasing yield in rainfed environments. Yield potential of inbred rice varieties grown under irrigated conditions has plateaued and the use of hybrid rice is considered as a valid strategy to break this yield plateau. Research on hybrid rice in Vietnam started in 1983 at Hau Gang (10°N latitude) in the Mekong River Delta after reports on successful development and commercial cultivation of hybrid rice in China (Lin and Yuan 1980) and the occurrence of significant heterosis in some experimental rice hybrids at IRRI (Virmani et al 1981, 1982). This paper discusses the current status of and future outlook for hybrid rice in Vietnam.

1 Cuu Long Delta Rice Research Institute, Omon. Cantho, Vietnam: 2 Rice Research Institute, National Agricultural Sciences Institute, Van Dien, Tu Liem, Hanoi, Vietnam: 3 International Rice Research Institute, P.O. Box 933, Manila 1099. Philippines. Objectives of hybrid rice research Hybrid rice research in Vietnam has four aims: • To develop suitable rice hybrids possessing a yield potential that is significantly higher than and grain quality comparable to the best available inbred rice varieties in irrigated areas in the Red river Delta (RRD) and Mekong river Delta (MRD); • To package the seed-production technology in a form suitable for the country; • To develop agronomic management practices for optimizing yield of hybrid rices; and • To study the economics of hybrid rice cultivation and seed production.

Performance of hybrids Significant heterosis in rice was reported in 1985 (Luat et al 1985). Since then, several experimental rice hybrids introduced from IRRI and produced locally have shown 18–45% yield superiority over the best local inbred checks at Cuu Long Delta Rice Research Institute (CLRRI) (Table 1). In the RRD, some rice hybrids from China (for example, Shan You 63, Shan You Gui 99, Shan You Quang 12, and Bo You 64) yielded 6.5–8.5 t/ha, 13–14% higher than the local check variety CR203 (Luat et al 1992). Some farm-level data gathered by IRRI economists showed that the Chinese rice hybrids gave an average yield of 7.0 t/ha compared to conventional rice varieties yielding 5.6 t/ha. In 1993, Chinese rice hybrids were planted on about 40,000 ha in the RRD. Some farmers harvested up to 10 t/ha in Dien Chou (Nhge An Province) and at Phu Xuyen (Ha Tay Province). Trials conducted with IRRI rice hybrids at CLRRI during 1990–92 led to release of two rice hybrids: IR58025A/IR29723-143-2-1R (as UTL 1) and IR62829A/IR29723-143-3-2-1R (as UTL 2) for regional testing in the MRD (Luat et al 1993). Results from trials conducted at CLRRI during the 1993 wet season led to the identification of several IRRI rice hybrids that outyielded the check varieties by more than 20% (Table 2). The mountain region of northern Vietnam appears to be highly suited to hybrid rice from China. Chinese rice hybrids yielded 14.0 t/ha in Dien Bien (Lai Chau Province), 12.0 t/ha in Hoa An (Cao Bang Province), and 12.6 t/ha in Van Quan (Lang Son Province). However, they did not perform well in the MRD. IRRI-bred rice hybrids were introduced in the RRD for evaluation during 1993; however, results are still awaited.

Table 1. Yield comparison of some experimental rice hybrids with inbred checks.

Year/season a Hybrid Yield % of Check b (t/ha) check variety

1989/90 DS IR54752A/IR64R 7.5 131* OM80 IR54752A/IR64R 7.2 125* OM80 IR54752A/OM80R 6.7 118* OM80

1990 WS IR58025A/IR29723R 7.6 143* MTL 58 IR62829A/IR29723R 6.7 126* MTL 58

1990/91 DS lR62829A/IR29723R 6.1 123* MTL 61 IR58025A/IR29723R 6.0 122* MTL 61

1992 WS IR58025A/IR52287R 6.7 131* IR64

1992193 DS IR58025A/IR32358R 6.8 145* IR64

a DS, dry season; and WS, wet season. b * Significantly higher than check variety at 5% level using LSD test.

74 Luat et al Table 2. Some new IRRI-bred rice hybrids found outyielding check varieties in trials conducted at CLRRI, 1993 WS.

Hybrid Maturity Yield % of Check group (t/ha) check a variety

IR64608A/lR53970R Very early 5.0 125* OM987-1 IR58025A/IR35366-62R Early 4.6 142* OM269 IR58025A/lR46R Medium 4.5 129* lR29723 lR58025A/lR32809-314R Medium 4.5 129* lR29723 IR58025A/lR21567-18-3R Medium 4.3 123* lR29723 IR58025A/IR20933-68 Medium 6.2 177* IR29723

a * Significantly higher than check variety at 5% level using LSD test.

Table 3. Characters of cytoplasmic male sterile (CMS) lines at CLRRI, Vietnam, 1993 wet season.

CMS lines CMS Origin Pollen Spikelet Panicle Days to Plant Grain RSV d source a sterility sterility exsertion 50% height shape c reaction (%) (%) (scale) b flowering (cm)

IR58025A WA IRRl 95 95 7 81 68 LS S IR62829A WA IRRl 95 98 5 72 68 LS R IR64608A WA IRRl 97 99 7 73 69 M S IR67684A WA IRRl 100 100 7 78 78 LS S IR64607A WA IRRl 98 100 7 84 71 LS MR IR66707A O. perennis IRRl 100 100 3 81 71 LS R PMS1A WA India 100 100 7 87 73 LS S PMS8A WA India 100 100 7 83 66 LS S PMS10A WA India 100 100 7 83 65 LS S Madhuri A MS 577 India 95 100 7 74 54 M R Pragathi A MS 577 India 97 100 7 74 54 M R Pushpa A MS 577 India 95 100 7 74 90 M R Krishna A WA India 93 99 7 67 57 M S Krishna A Kalinga I India 100 100 7 63 54 M S CNTBR 10A WA Thailand 100 100 7 88 95 L R RD25A WA Thailand 100 100 1 68 78 L R HD21A WA Thailand 100 100 1 90 113 L R V20A WA China 100 100 7 62 61 M S

a WA, Mild abortive. b Scale from 1, most exserted to 9, least exserted. c LS, long slender; L, long; and M, medium. d RSV, ragged stunt virus disease; R, resistant; MR, moderately resistant; and S, susceptible,

Performance of A, B, and R lines Eighteen cytoplasmic male sterile (CMS) lines have been introduced and evaluated at CLRRI. Of these, 10 possessed stable mate sterility and good agronomic characteristics, others were found to be unstable showing 2–5% seed set on bagging (Table 3). IRRI CMS line IR58025A possessed desirable grain quality (long, slender, translucent grains) but it was susceptible to a new biotype of brown planthopper (BPH), the key pest in the MRD. Three other CMS lines, IR62829A, IR64607A, and IR64608A, showed tolerance to BPH under field conditions. Days to 50% flowering of CMS lines ranged from 62 (V20A) to 90 (RD21) implying that hybrids with desired growth duration can be developed using

Hybrid rice 75 Table 4. Prospective maintainer and restorer lines identified for the CMS lines IR58025A and IR62829A in Cuu Long Delta.

CMS line IR58025A CMS line IR62829A

Maintainer Restorer Maintainer Restorer

OM43-26 OM53-71 lR44595-70 OM1037 OM59-7 OM80 OMCS6 lR42068 OM576 OM725 lR35546 MTL 58 OM269 IR35311 MTL 61 lR52287-15 lR44595-70 lR9729 lR50404 IR64 lR52280 IR42068 lR19725 S818B

these lines. At the National Agricultural Sciences Institute (INSA), several IRRI-bred and Chinese CMS lines were introduced during 1983-88. Most of the IRRI-bred CMS lines were unstable for pollen sterility and the Chinese CMS lines were susceptible to BPH and bacterial blight. New IRRI-bred CMS lines IR58025A and IR62829A introduced during 1992-93 were relatively stable for male sterility.

Identification of maintainers and restorers

Hybrid rice breeders at CLRRI have been identifying maintainers and restorers for two IRRI-bred CMS lines (IR58025A and IR62829A) possessing WA (wild abortive) cytoplasm. Several locally adapted high-yielding varieties bred locally or introduced from IRRI have been found to be maintainers and restorers (Table 4). Recently, test crosses have also been made with newly introduced CMS lines, IR66707A, PMS10A (from India), and RD25A (from Thailand). No restorers have been identified for IR66707A (possessing Oryza perennis cytoplasm). The identified maintainers are being used to develop new CMS lines, whereas restorers are being used to breed new experimental rice hybrids locally. At INSA also, some maintainers and restorer lines of WA CMS lines have been identified.

Hybrid rice seed production in Vietnam Hybrid rice seed-production technology developed at IRRI (Virmani and Sharma 1993) was used (without gibberellic acid, GA 3 , as it was too expensive) to multiply seeds of CMS lines and produce hybrid seeds during dry and wet seasons (Table 5). Outcrossing rates of 15-38% and seed yields of 0.8-2.15 t/ha were obtained. Seed yields appeared to be higher in the dry season than in the wet. In the 1993 wet season, a seed-production experiment was conducted to study the effect of GA 3 , urea, and Komix (a growth regulator formulation marketed in Vietnam) sprayed during initial to 20% flowering. GA 3 (90 ppm) spray gave the highest seed yield followed by Komix (3%) and urea (2%) treatments (Table 6). Experience with hybrid seed production of Chinese rice hybrids in the RRD was not encouraging in 1992 and 1993. Seed yields on CMS multiplication plots ranged from 0.4 to 1 t/ha and on hybrid seed production plots from 0.2 to 0.4 t/ha. Lower seed yields are attributed to nonsynchronization of flowering of A and R lines, unfavorable weather during the wet season, and lack of experience of scientists and seed producers in hybrid rice seed production. Seed-production plots in the 1994 dry season look better than in previous years and are expected to yield 1.5-2t of seed/ha.

76 Luat et al Table 5. Cytoplasmic male sterile (CMS) and F 1 hybrid seed production at CLRRI.

Combination Outcrossing Seed yield in rate (%) CMS line (t/ha)

Dry season 1990/91

IR62829A/IR29723R 38 2.15

Wet season 1992

CMS seed production IR58025A/B 25 1.45 IR62829A/B 21 1.20

Hybrid seed production a 25A/IR10198R 21 1.18 25A/IR29723R 15 0.80 29A/IR29723R 19 1.04 29A/IR40750R 17 1.02 29A/lR44675R 16 1.00

a 25A, IR58025A; and 29A, IR62829A.

a Table 6. Effect of gibberellic acid (GA 3), urea, Komix, and flag-leaf clipping on hybrid seed yields, CLRRI, 1993 wet season.

Treatment Seed yield (kg/ha)

GA 3 (90 ppm) 600 Komix (3%) 480 Urea (2%) 460 Flagleaf clipping 360 Control 280 LSD (5%) 100

a Komix is a growth-regulator formulation marketed in Vietnam.

These results indicate that hybrid seed yields of up to 2.0 t/ha are attainable in Vietnam. However, much adaptive research needs to be done using locally adaptable and commercially usable CMS lines to get such seed yields consistently.

Agronomic management of hybrid rice

The response to fertilizer of the hybrid UTL 1 (IR58025A/IR29723R) and check variety OM90-9 was studied in the 1992 wet season. Both the hybrid and the conventional variety showed maximum response at an NPK fertilizer rate of 80-60-30kg/ha. The hybrid UTL 1 outyielded OM90-9 at all fertilizer rates (Table 7). The experiment on the effect of transplanting space on the yield of hybrid rice (variety UTL 2) showed that the highest yield, 5.78 t/ha, was recorded at the transplanting space 25 × 30 cm and this

Hybrid rice 77 Table 7. Fertilizer response of hybrid rice UTL 1 as compared to conventional variety OM90-9.

NPK fertilizer Yield (t/ha) a rate (kg/ha) Hybrid rice Conventional rice UTL 1 OM90-9

00-00-00 3.80 3.33 40-60-30 4.80 4.06 80-60-30 5.33 4.60 120-60-30 5.26 4.86 160-60-30 5.13 4.86

aLSD (5%) between varieties = 0.11; between fertilizer rates = 0.45.

Table 8. Effect of transplanting space on the yield of hybrid rice UTL 2 in the 1992/93 dry season.

Transplanting Yield space (cm) (t/ha) a

20 × 15 5.08 20 × 20 4.83 20 × 25 5.35 25 × 25 5.74 25 × 30 5.78 30 × 30 5.69

a LSD (5%) = 0.56. was significantly higher than the yields obtained from the closer transplanting spaces of 20 x 15 cm and 20 × 20 cm (Table 8). Because direct seeding is very common in the MRD, an experiment on direct seeding of hybrid rice was carried out at CLRRI in the dry season of 1992/93. Keeping the high cost of hybrid seed in mind, only low seed rates (20, 30, 40, and 50 kg/ha) were used in this experiment following three methods of direct seeding (broadcasting, line-seeding, and hole-drilling). Although there was no significant difference in the yields of the hybrid UTL 2, which ranged from 5.32–5.89 t/ha at various seeding rates and under three methods of direct seeding, line-seeding consistently gave the lowest yields and hole-drilling the highest. The results indicated that direct seeding of hybrid rice could be used at very low seeding rates.

Hybrid rice research at IRRl relevant for Vietnam

Since 1979, IRRI has been actively involved in hybrid rice breeding and seed-production research for tropics and subtropics. Over the years, considerable progress has been made and some of the results have relevance for Vietnam. • Several heterotic rice hybrids adaptable to the tropics and showing significant yield superiority over inbreds have been developed and supplied to Vietnam for evaluation. UTL 1 and UTL 2 were selected among these in 1992 for regional testing in the MRD. • Several CMS maintainer and restorer lines adapted to the tropics and subtropics have been developed. These lines possess grain quality comparable to inbred rices and are suitable for

78 Luat et al developing heterotic rice hybrids adapted to rice-growing conditions in Vietnam. New CMS maintainer and restorer lines were supplied to Vietnamese hybrid rice breeders for use in breeding programs. • Hybrid seed production technology for the tropics has been developed and “packaged” in the form of a seed-production manual (Virmani and Sharma 1993) and a video movie. These can be translated into Vietnamese and used for training seed growers in Vietnam. A temperature-sensitive genetic male sterility (TGMS) system has been developed in collaboration with Japan and some TGMS lines have been shared with Vietnam for preliminary evaluation. The TGMS system is considered more efficient than the CMS system for hybrid rice breeding. • CMS maintainer and restorer lines and TGMS lines are being developed in the genetic background of tropical japonica (javanica or bulu) rices for developing indica/tropical japonica rice hybrids possessing a higher heterosis level than that in indica rice hybrids. These materials will be available to Vietnamese rice breeders within 3 yr. • Agronomic management strategies to maximize performance of tropical rice hybrids are being developed. Information collected will be useful for developing a package of agronomic practices for hybrid rice cultivation in Vietnam. • A methodology for studying the economics of hybrid rice seed production and cultivation has been developed. This can be used by Vietnamese economists • IRRI has developed training courses on hybrid rice breeding and seed production. Vietnamese rice breeders and seed-production specialists can use these courses to develop their staff capability.

Constraints

Development of hybrid rice technology in Vietnam is constrained because of insufficient trained staff and insufficient funds for hybrid rice research. Also, the on-going research programs in the country are not coordinated and the responsibilities of various research institutions working on hybrid rice are not clearly defined. Although the seed-production infrastructure available in the country is suitable for inbred-line multiplication, expertise in hybrid seed production is minimal. Rice hybrids introduced from China in the RRD have yielded better than the inbreds in the farmers’ field but they are susceptible to BPH, leaffolders, thrips, and bacterial and sheath blights and possess poorer grain quality than the farmers’ varieties. As a result, the hybrids fetch lower prices in the market and the farmers do not get the expected higher profit compared to inbred rices. In the MRD, although several IRRI-bred rice hybrids have been found to be higher yielding than the inbred rices, adoption of hybrid rice is constrained by the fact that farmers practice direct seeding for crop establishment using very high (150–200 kg/ha) seeding rates. This makes hybrid seed unaffordable.

Future outlook Rice hybrids have shown about 1 t/ha yield superiority over inbreds in the RRD in northern Vietnam and the MRD in southern Vietnam. Encouraged by the performance of Chinese rice hybrids in the RRD, the Vietnamese government plans to cover about 500,000 ha with hybrid rice in northern Vietnam by the year 2000. It is a challenging target. To meet it, high-yielding rice hybrids possessing grain quality comparable to or better than inbred rices must be introduced from China or IRRI.

Hybrid rice 79 Seeds of parental lines of the selected hybrids should be available freely along with hybrid seed production technology giving economic seed yields above 1.5 t/ha. Seed-production infrastructure in the country needs to be developed to produce hybrid seeds locally. Intensive hands-on training of seed-production supervisors and seed growers should be done urgently in collaboration with China and IRRI. In the MRD, where large-scale adoption of hybrid rice is restricted by the direct seeding practice, the transplanted rice area needs to be targeted in the first instance. A coordinated hybrid rice research and development program consisting of two components (one for the RRD and the other for the MRD) should be organized in collaboration with China and IRRI. The research program should focus on introducing and breeding heterotic rice hybrids (yielding at least 1 t/ha higher than inbreds), possessing acceptable grain quality, resistance to major diseases (that is, blast, bacterial blight, and sheath blight) and insects (that is, BPH and green leafhopper). The CMS system should be used for the purpose, and prospects of the TGMS system should be explored for future use. The program should also conduct adaptive research on hybrid seed production to develop a locally adapted package of seed-production technology. The two research components should be multidisciplinary involving plant breeders, agronomists, geneticists, entomologists, plant pathologists, economists, and seed-production specialists. They should be closely linked to exchange breeding materials, information, and monitoring tours. The research components in northern and southern Vietnam should also establish close liaison with seed- production agencies operating in their respective areas to produce foundation seeds of A, B, and R lines and certified seeds of F 1 rice hybrids. Seed-industry infrastructure in Vietnam needs considerable strengthening. Financial support should be sought from external sources to develop the seed industry. Prospects should be explored with private seed companies, recently permitted to operate in the country, to determine if they can undertake hybrid rice seed production and marketing. Large-scale adoption of hybrid rice in the MRD is contingent upon the commercial success of hybrid rice under direct-seeding conditions. Preliminary studies have shown that hybrid rice can yield as well in direct seeding as in transplanting. Agronomic research is needed to determine the minimum possible seeding rate for cultivating hybrid rice under direct seeding. Agricultural engineers at IRRI are developing seeders that may help to economize hybrid seed under direct seeding. Vietnamese and IRRI economists should make an ex-ante economic analysis of hybrid rice cultivation and seed production in Vietnam and specify the circumstances and target areas under which the technology can have the required effect.

References cited

Lin S C, Yuan L P (1980) Hybrid rice breeding in China. Pages 35–51 in Innovative approaches to rice breeding. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Luat N V, Bong B B, Chandra Mohan J (1985) Evaluation of F 1 hybrids in the Cuu Long Delta, Vietnam. IRR Newslet. 10(3):19. Luat N V, Minh H T, Suan N V (1992) Progress of hybrid rice research in Vietnam. Paper presented at the Second International Symposium on Hybrid Rice, 21–25 Apr. 1992, International Rice Research Conference, Los Baños, Philippines. Luat N V. Mui H T. Voc P C, Hung V M, Bong B B, Virmani S S (1993) Two promising IRRI rice hybrids named in Vietnam. IRR Newslet. 18(2):22. Virmani S S, Aquino R C, Khush G S (1982) Heterosis breeding in rice. Oryza sativa L. Theor. Appl. Genet. 63:373–380. Virmani S S, Chaudhary R C, Khush G S (1981) Current outlook on hybrid rice. Oryza 18:67–84. Virmani S S, Sharma HL (1993) Manual on hybrid rice seed production. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. 57 p.

80 Luat et al Classification of traditional rice germplasm from Vietnam based on isozyme pattern

Luu Ngoc Trinh, 1 Dao The Tuan, 1 D.S. Brar, 2 B.G. de los Reyes, 2 and G.S. Khush 2

Abstract. Starch gel electrophoresis was used to classify 643 traditional rice cultivars from Vietnam representing various types on the basis of isozyme pattern. Cultivars that originated from northern Vietnam belonged to group I and group VI whereas those from southern Vietnam belonged only to group I. Previously, all traditional aromatic rices in Vietnam were considered to belong to the indica group; however, isozyme analysis shows that of 37 aromatic rice cultivars from northern Vietnam, five were japonica. The allele 4 for Amp1 was more frequent in Vietnamese rice germplasm. A new variant allele 3 for Enp1 was detected in 6 of the 643 cultivars.

Rice shows wide varietal diversity in a broad region from Nepal to northern Vietnam (Chang 1976). Within Vietnam, geographic and ethnic diversity, as well as the long tradition of rice cultivation and the diversified farming practices, have resulted in great diversity in traditional rice germplasm. In the higher areas of the Red River Delta (RRD) where irrigation is not used, plain upland rice is cultivated. The winter rice cultivated in northern Vietnam is characterized by high resistance to blast and tolerance to adverse ecological conditions. Glutinous and aromatic rices grown in RRD have an excellent aroma. The indigenous rice in southern Vietnam is less diverse than that of the north. The most interesting germplasm is that of lowland and deepwater rice, which is a rich gene source for tolerance to acid sulfate and saline soil conditions. As early as the 18th century, the Vietnamese encyclopedist Le Quy Don evaluated and described many indigenous cultivars — his work is still valuable for plant breeders and scientists in various fields (Dap 1980). The Vietnamese have traditionally classified rice cultivars in various cultivated types (see Table 1). Like the Chinese, the Vietnamese also differentiated rices as Tien and Canh , Vietnamese words that are synonymous with Tsien and Keng in Chinese. Germplasm classification is important for the efficient use of genetic resources. Kato et al (1928) differentiated rice cultivars into two groups — calling them indica and japonica — based on geographic distribution and F 1 intervarietal hybrid fertility. Terao and Nizushima (1942), also using F 1 partial sterility, suggested that the rice varieties could be divided into five groups. Matsuo (1952), using various agronomic characters, differentiated rice cultivars into three types — round grain (A), large grain (B), and slender grain (C) — corresponding, respectively, to japonica, javanica, and indica (Morinaga 1954). Jacquot and Arnaud (1979), using multivariate analysis based on morphological characters, also separated Asian rice varieties into the japonica, javanica, and indica groups. Second (1982) surveyed 25 polymorphic isozyme loci in rice and found a clear tendency for varieties to cluster into the indica and japonica groups. Glaszmann (1987) classified Asian rice varieties based on isozyme pattern in six groups, the two main ones being indica and japonica, groups I and VI respectively, the remaining four groups (II, III, IV, and V) are distributed principally from western Asian countries to northern Myanmar. In this communication, we report the classification of 643 traditional rice cultivars from Vietnam based on isozyme pattern.

1National Agricultural Sciences Institute, Van Dien, Tu Liem, Hanoi, Vietnam: 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Table 1. Rice cultivars classified on the basis of isozyme pattern.

Material Number of cultivars in different varietal groups

Group I Group VI Unclassified

Cultivars from northern Vietnam Plain early rice 54 4 1 Plain upland rice 12 3 1 Plain glutinous rice 27 11 – Plain late and deepwater rice 107 1 – Aromatic rice 30 5 2 Winter glutinous rice – 3 – Winter nonglutinous rice 65 1 – Mountain upland early rice 6 2 – Mountain glutinous rice 22 4 – Mountain upland late rice 2 6 1 Mountain lowland late rice 78 2 3 Mountain rice from central plateau 9 2 –

Cultivars from southern Vietnam Plain early rice 29 – – Plain medium rice 70 – – Plain lowland and deepwater rice 80 – –

Total 59 1 44 8

Materials and methods

Materials. The experimental material consisted of 643 traditional rice cultivars, 90 brought from Vietnam and 553 from the International Rice Germplasm Center at IRRI. The materials were chosen to represent all cultivated types of Vietnamese indigenous rices (Table 1). Electrophoretic analysis. Starch gel electrophoresis was used following the procedures of Glaszmann et al (1988). For a given cultivar, two plants were analyzed together. When heterogeneity (mixture) or heterozygosity was detected within a variety for one of the five loci used for classification, the analysis was repeated on individual seeds. Isozyme analysis and varietal classification. We analyzed 10 enzymes representing 19 isozyme loci. Varietal classification was based on Glaszmann's method using five isozyme loci: Pgi1, Pgi2, Amp1, Amp2, and Amp3 (IRRI 1987).

Results and discussion

The results of isozyme analysis are shown in Table 1. Of the 464 cultivars from northern Vietnam, 412 (88.8%) belong to group I or indica rice, 44 (9.5%) belong to group VI or japonica rice, and 8 could not be classified. All cultivars originating from the Mekong River Delta in southern Vietnam were indica rice. Of the 37 aromatic rice cultivars, 30 belong to group I (indica rice), 5 to group VI (japonica), and 2 could not be classified. Our results agree with Glaszmann's conclusion on the genetic structure of rice germplasm. In East and Southeast Asia, the variation is reduced to the group I and group VI extremes (Glaszmann 1987). The genetic structure of traditional germplasm from northern Vietnam differs from that from the south.

82 Trinh et al Table 2. Rice cultivars carrying variant allele 3 for Enp1.

Cultivar Accession Varietal Distribution Culture type number group in Vietnam

Ca nhan 32099 I Northern Early, plain area Sai Hai Duong 47551 I Northern Winter rice Du Hai Duong 60726 I Northern Aromatic rice Khau dan 73201 I Northern Mountainous rice Doc Phung 201 I Southern Lowland rice, plain area Lua noi 10242 I Southern Lowland rice, plain area

The finding that Vietnamese aromatic rice belongs to group VI (japonica) is of interest to plant breeders. In Vietnam, it had been assumed that all traditional aromatic rices were indica — this is true if aromatic rice is classified only by morphological characters and photoperiod sensitivity. Previous analyses have shown that allele 4 is a rare allele of Amp1 (Glaszmann et al 1988). In our study, however, allele 4 was more frequent. In Oryza sativa, only two alleles (0 and 1) for the Enp1 (endopeptidase) locus are known (Glaszmann et al 1988). Another allele, designated as Enp1 2 was identified in the wild species O. nivara (Acc 104443) and Enp1 was located on chromosome 6 through primary trisomic analysis (Brar et al 1991). A new allele 3 at this locus was detected in six of the Vietnamese cultivars (Table 2). The new allele exhibits intermediate mobility between allele 1 of O. sativa and allele 2 of O. nivara. The six Vietnamese cultivars with the new allele (Enp1 3) are group I (indica) and are nonglutinous. It is interesting to note that some of the cultivars with the new allele are from the north and others are from the south and grow in a variety of ecosystems ranging from lowland to mountainous.

References cited

Brar D S, de los Reyes B G, Panaud O. Sanchez A, Khush G S (1991) Genetic mapping in rice using isozyme and RFLP markers. Pages 137-145 in Rice genetics II. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Chang T T (1976) The origin, evolution, cultivation, dissemination and diversification of Asian and African rices. Euphytica 25:425-441. Dap B H (1980) Cay lua Vietnam. Nha Xuat Ban Khoa Hoc Ky Thuat. Hanoi, Vietnam. Glaszmann J C (1987) Isozyme and classification of Asian rice varieties. Theor. Appl. Genet. 74:21-30. Glaszmann J C, de los Reyes B G, Khush G S (1988) Electrophoretic variation of isozymes in plumules of rice ( Oryza sativa L.) — A key to the identification of 76 alleles at 24 loci. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Research Paper 134. IRRI — International Rice Research Institute (1987) IRRI highlights 1986. P.O. Box 933, Manila 1099, Philippines. Jacqueot M, Arnaud M (1979) Classification numérique de variétés de riz. Agron. Trop. (Paris) 33:157–173. Kato S, Kosaka H, Hara S (1928) On the affinity of rice varieties as shown by the fertility of rice plants. Centr. Agric. Inst., Kyushu Imp. Univ., Jap. 2:241-276. Matsuo T (1952) Genealogical studies on cultivated rice. Bull. Nat. Inst. Agric. Sci. Jap. D 3:l-111. Morinaga T (1954) Classification of rice varieties on the basis of affinity. Pages 1-14 in Report of the 5th Meeting. Working Party on Rice Breeding, International Rice Commission. Second G (1982) Origin of the genetic diversity of cultivated rice (Oryza spp.): study of the polymorphism scored at 40 isozyme loci. Jap. J. Genet. 57:25-57. Terao H, Nizushima U (1942) Some consideration on the classification of Oryza sativa L. into two subspecies so-called japonica and indica. Jap. J. Bot. 10:212-258.

Germplasm classification 83

INSA-IRRIcollaboration on wild rice collection in Vietnam

Dao The Tuan, 1 Nguyen Dang Khoi, 1 Luu Ngoc Trinh, 1 Nguyen Phung Ha, 1 Nguyen Vu Trong, 1 D.A. Vaughan, 2 and M.T. Jackson 2

Abstract. Vietnam and IRRI undertook two joint collecting trips for wild rice in 1989 and 1990. The first was in the northwest provinces of Vietnam where seven samples of Oryza rufipogon and two samples of O. granulata were collected. The second was in the Mekong River Delta where 56 samples of O. rufipogon, 2 samples of O. officinalis, and 1 sample of weedy O. sativa were collected. All samples were described during or after the collection trips. Like the landraces of cultivated rice, wild rice in Vietnam is under serious threat of genetic erosion. It must be collected under a new collaborative project in the near future.

As in other Asian countries, wild rice species are widespread in Vietnam. Since French colonial times, various botanists studying the flora of Indochina have found wild rice species in Vietnam. After the reestablishment of peace in Indochina in 1954, Vietnamese scientists continued to study wild rice. Based on existing publications and continuing research, such wild species as Oryza rufipogon, O. officinalis, O. granulata, O. nivara, and weedy races of O. sativa have been identified in Vietnam (Dap 1980). According to some publications, O. minuta and O. latifolia have also been identified in Vietnam (Dap 1980) but this was the result of confused nomenclature because the former is found only in the Philippines and the latter in Latin America (Vaughan 1989). The University of Hanoi has a herbarium sample of O. meyeriana collected at Huu Lung District, Lang Son Province, in 1972, but certainly that sample should be classed as O. granulata because the distribution of O. meyeriana is limited to the archipelagos of the Philippines and Indonesia (Vaughan 1989). Oryza granulata and O. meyeriana can be confused easily because the species have many similar morphological characters.

Table 1. Distribution of wild rice in Vietnam.

Species Areas of distribution Collected Threat of in genetic 1989-90 erosion

Oryza rufipogon Dien Bien Phu valley Yes High Western part of Mekong River Delta Yes High O. officinalis Along Vietnam-China border No High Eastern part of Mekong River Delta Yes High O. granulata Highland and mountain areas in northern Vietnam Yes Low Central plateau No Medium O. nivara Along Vietnam- border No High O. sativa (weedy rice) Western part of Mekong River Delta Yes High

1National Agricultural Sciences Institute, Van Dien, Tu Liem, Hanoi, Vietnam; 2International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. 1. Collection sites for wild rice germplasm in northwestern Vietnam, 1989.

2. Collection sites for wild rice germplasm in the Mekong River Delta, 1990.

Table 2. Wild rice samples collected in Vietnam by two Vietnam-IRRI collaborative collection trips, 1989 and 1990.

Species No. of samples Year of Places of collection collected collection

Oryza rufipogon 7 1989 Dien Bien Phu valley O. granulata 2 1989 Hoa Binh and Son La provinces O. rufipogon 56 1990 Mekong River Delta O. officinalis 2 1990 Tien Giang Province O. sativa (weedy rice) 2 1990 Kien Giang Province

Since the early 1960s, a high rate of forest destruction, plowing virgin soil, and changing cultivation patterns have resulted in changing habitat and, consequently, the distribution areas of wild species and weed races have been considerably reduced. Today, they no longer exist in the Red River Delta or the coastal areas of northern and central Vietnam. Oryza rufipogon exists only as a small

86 Tuan et al Table 3. Some morphological and genetic characters of Oryza rufipogon samples a collected in the Dien Bien Phu valley.

Mean S.E. CV Range Number of (%) samples

Grain length (mm) 7.5 0.6 8.3 6.4–8.4 7 Grain width (mm) 2.0 0.1 4.7 1.9–2.2 7 Ratio L/W 3.7 0.3 7.6 3.2–4.1 7 Panicle length (mm) 189.6 34.4 18.0 141–221 5 Awn length (mm) 28.6 9.7 34.1 20–43 5 Anther length (mm) – – – 4.8–4.7 2 Genetic make-up b – – – 1 7 Seed production b – – – 2 7 Fertility b – – – 4–7 7 Degree of introgressionb – – – 1–2 7 Species diversity b – – – 2–3 7

a Collection numbers: VN89-W11 to VN89-W20. b Genetic makeup, 1 = heterozygous, 2 = homozygous; seed production, 1 = low, 2 = high; fertility, 0 = completely sterile, 9 = completely fertile; degree of introgression (scale of 9) , 1 = none, 9 = 90% O. sativa; species diversity (scale of 9), 1 = uniform, 9 = complex,

Table 4. Some morphological and genetic characters of Oryza rufipogon samples a collected in the Mekong River Delta.

Mean S.E. CV Range Number of (%) samples

Grain length (mm) 8.6 0.3 3.2 8.0–9.3 55 Grain width (mm) 2.3 0.2 9.7 1.9–2.8 55 Ratio L/W 3.7 0.4 10.8 3.0–4.4 55 Panicle length (mm) 262.4 34.1 12.9 147–323 55 Awn length (mm) 55.2 12.8 23.3 35-88 55 Anther length (mm) 5.6 0.5 8.3 4.8-6.5 49 Genetic make-up b – – – 1–2 53 Seed production b – – – 1–2 54 Fertility b – – – 2–5 55 Degree of introgression b – – – 1–2 54 Species diversity b – – – 2–4 50

a Collection numbers. VN90-W1 to VN90-42, VN90-45 to VN90-50, VN90-50. and VN90-54 to VN90-60. b Genetic makeup. 1 = heterozygous, 2 = homozygous; seed production, 1 = low, 2 = high; fertility, 0 = completely sterile, 9 = completely fertile; degree of introgression (scale of 9) , 1 = none, 9 = 90% O. sativa; species diversity (scale of 9). 1 = uniform, 9 = complex. population in the Dien Bien Phu valley and the Mekong River Delta. Of the other species, O. granulata exists in the central plateau and mountain areas in the north, O. officinalis in some parts of the Mekong River Delta and along the Vietnam–China border, O. nivara in small areas along the Vietnam–Cambodia border, and the weed races of O. sativa in some areas of the Mekong River Delta (Table 1). No germplasm of wild rice from northern Vietnam had been preserved in the germplasm collection before these trips. Only two northern Vietnamese locations were recorded for wild rice in herbaria: one in the herbarium in Ho Chi Minh City of O. rufipogon from the Dien Bien Phu valley

Wild rice collection 87 and the other in the herbarium at Hanoi University of O. granulata from Lang Son Province. In southern Vietnam, after 1975, some research and training institutions preserved samples of wild rice collected in the Mekong River Delta.

INSA-IRRI joint collection trips

The need to use species related to cultivated rice as gene donors in rice breeding has been increasing and, like the landraces of cultivated rice, wild rices in Vietnam are under threat of genetic erosion. Therefore, IRRI and Vietnam collaborated to collect wild rice germplasm with the National Agricultural Sciences Institute (INSA) as the coordinating institution for Vietnam. Two collection trips were made: • 21 Oct to 5 Nov 1989 in the northwest provinces of Vietnam, and • 17 Dec 1990 to 1 Jan 1991 in the Mekong River Delta. The collection sites are shown in Figs. 1 and 2 and the number of collected samples are given in Table 2.

Description of collected samples

All samples were described during or after the collection trips. Among the three wild species and one weed race collected during these two trips, samples of O. rufipogon are the most numerous. It is the most widespread species of wild rice in Vietnam. Oryza rufipogon is the direct ancestor of cultivated rice O. sativa, so its gene sources are of more general value (Oka 1988). Tables 3 and 4 show the characterization data of some morphological and genetic characters of O. rufipogon samples collected.

References cited

Dap B H (1980) Cay lua Vietnam. Nha Xuat Ban Khoa Hoc Ky Thuat. Hanoi, Vietnam. Oka H I (1988) Origin of cultivated rice. Japan Scientific Society Press, Tokyo, and Elsevier, Amsterdam, Netherlands. Vaughan D A (1989) The genus Oryza L.: current status of taxonomy. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Research Paper 138.

88 Tuan et al Ecophysiology of rice-crop establishment in wet direct seeding in Vietnam with emphasis on anaerobic seedling growth

Minoru Yamauchi, 1 Pham Van Chuong, 2 and Nguyen Minh Chau 3

Abstract. The cultural practice in direct seeded rice differs between the northern and southern parts of Vietnam. In the Mekong River Delta (MRD, south), rice is produced in two or three crops per year mostly by direct seeding under puddled tillage, minimum tilled, or zero-tilled conditions. When the drainage is difficult, the seeds are sown into standing water (water seeding). Occurrence of weedy rice (noncultivated rice in the cultivated rice fields) is spreading in the region. Weedy rice was better in seedling establishment in flooded soil than cultivated rice, indicating that it is anaerobic tolerant. In the Red River Delta (RRD, north), rice is grown twice per year, followed by a winter nonrice crop. Because the seedlings for transplanting are often damaged by cold injury and because direct seeding is advantageous in reducing labor cost and in grain yield over transplanting, farmers practice direct seeding wherever the irrigation system is improved. The cultural practice in the RRD is intensive and the soil is well puddled. Seeding rate is lower in the north than in the south. The common constraint to the adoption of direct seeding is the inconsistency in crop establishment. We studied the potential application of anaerobic seeding (sowing pregerminated seeds under the surface of puddled soil) in the fields of the MRD and the RRD. Crop establishment and grain yield of some anaerobic cultivars were better than or equivalent to the local check cultivars. Thus, anaerobic seeding technology could be promising in stabilizing crop establishment and in increasing grain yield.

Rice crops are established by transplanting or by wet or dry direct seeding. Wet seeding is rapidly being introduced by farmers in South and Southeast Asia where transplanting has been widely practiced. Apparently, farmers are developing a cultural practice of wet seeding based on their own knowledge and experience. In general, seeds are germinated and sown on the surface of flooded (water seeding) or water- saturated soil where oxygen (O 2 ) is available. However, rice species can germinate where O 2 is not available, that is, in anoxic conditions, and cultivars tolerant of such conditions are referred to as anaerobic cultivars. Postgermination growth differs significantly among rice cultivars when they are sown under the surface of flooded or water-saturated soil where O 2 is not available (Yamauchi et al 1993a). In the Philippines, pregerminated seeds sown under the surface of puddled soil (anaerobic seeding) established the crop and achieved high grain yield (Aragones et al 1993). Anaerobic seeding is practiced by sowing pregerminated seeds immediately after puddling (when the soil sulfate is soft) or using a seeding machine developed for this purpose. Anaerobic cultivars performed better than control cultivars even in water seeding (Pablico et al 1993).

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines: 2 National Agricultural Sciences Institute, Van Dien, Tu Liem, Hanoi, Vietnam; 3 Cuu Long Delta Rice Research Institute, Omon, Cantho, Vietnam. This paper analyzes the ecophysiology of the farmers’ practice of wet seeding in the Mekong River Delta (MRD) and in the Red River Delta (RRD) — particularly in Hanoi and Hai Hung — and evaluates the performance of anaerobic rice cultivars. Seedling establishment of weedy rice found in farmers’ fields of the MRD was analyzed in comparison with cultivated rice. The yield and crop establishment of anaerobic cultivars were tested in the experimental fields of Cuu Long Delta Rice Research Institute (CLRRI) and the National Agricultural Sciences Institute (INSA) together with local check cultivars.

Ecophysiology of wet-seeded rice in the Mekong River Delta

Rice is cropped two or three times per year in the MRD: the intensity being determined by the development of irrigation and drainage systems. In the rainfed-lowland ecosystem where water supply depends on the rainfall, dry seeding is practiced, followed by a second crop with transplanting or wet seeding. When drainage is difficult, transplanting or water seeding is practiced. The crop performance in the MRD is constrained by salinity during the dry season, acidity of acid sulfate soil (ASS), and deep water. Sowing onto puddled soil. The most common form of wet seeding in Asia is sowing onto puddled soil. In this practice, the soil is well puddled with adequate water and pregerminated seeds are sown on the drained soil surface. When the soil is too soft to hold the seeds on its surface, farmers delay sowing for 0.5–2 d so that soil surface becomes firmer. Sowing with minimum land preparation. Seeds are broadcast on the soil surface without puddling. Because water percolation is higher than in the puddled field and because O 2 may be contained in the spaces between soil particles, the seed environment may be more aerobic than in the puddled soil. Zero-tillage wet seeding. No plowing, harrowing, or puddling is conducted before sowing. Zero tillage seems to be practiced to reduce the turnaround time between the crops. Because the farmers in the MRD practice transplanting under zero tillage, direct seeding under zero tillage might be a reasonable development. At present, farmers harvest the rice crop by cutting the straw at knee height then threshing the grain. The straw is then spread on the rice stubble in the fields, dried, and burnt. Pregerminated seeds are broadcast after flooding the field. The turnaround time required for this system is 3-4 d. Burning rice straw in the zero-tillage system apparently is advantageous because it expels rats from the fields (they are a common problem in the zero-tillage system) and reduces disease pressure in the intensified cropping system. In addition, burning straw prevents ratoon crops and weeds and, because the turnaround time is short, no weed control is required at sowing. In addition, the contact of the sown seeds with the soil surface may be improved after burning because the crop residues that might prevent contact between seeds and soil are removed. In addition, straw burning may improve the crop establishment in wet seeding because rice-crop establishment may be inhibited by the products of anaerobic decomposition of rice straw (Cannel and Lynch 1984, Biswas 1994, Biswas and Yamauchi 1994). Rice-crop establishment by zero-tillage wet seeding was simulated in an experimental field at IRRI during the 1993 wet season (IRRI, unpublished data). Uniform crop establishment and normal grain yield were achieved, implying that zero-tillage wet seeding is a feasible technology. The zero- tillage wet-seeding technology must be evaluated further in terms of sustainability, increasing cropping intensity, and reducing production cost. Water seeding. Water seeding is practiced in fields where drainage is difficult, particularly at the end of the wet season or the beginning of the dry. Some farmers also use water seeding to suppress

90 Yamauchi et al weeds with flooding. At sowing, water depth may be as great as 30-50 cm, which is too deep for transplanting. Because water level decreases as the dry season proceeds, broadcast-seeded rice can establish the crop successfully. We simulated water seeding in containers with water levels of 10 and 25 cm and found that the percentage seedling establishment was more than 90% regardless of rice cultivar. In the fields of IRRI, however, water seeding was unstable because of biological stress (golden snails, Pomacea species, and unidentified factors). In addition, tungro was reported to increase in the water-seeded fields (Koganezawa et al 1993). Also, in the MRD, it is often reported that farmers use heavy rates of insecticide in water seeding to achieve successful crop establishment. It could be speculated that water seeding might be more difficult when cropping intensity is increased because biologcal stress might also increase in the field. The use of water seeding must be assessed in terms of environmental safety and stable crop production. A high seed rate (100-300 kg/ha) is used in farmers’ fields regardless of seeding methods described above. Some farmers find that a high seeding rate decreases the grain yield. However, they continue to use high rates to ensure crop establishment and to reduce weed infestation. Farmers often transplant seedlings from within the field to areas where crop establishment was poor in direct seeded fields.

Ecophysiology of wet-seeded rice in the Red River Delta

Although direct seeding is practiced less in the north than in the south, it is becoming popular as irrigation systems are improved and as herbicides become available. Rice is double cropped (first crop, February/March-June/July; second crop, June/JuIy-September), with a winter crop such as maize, soybean, or sweet potato. The second crop must be harvested before mid-September to avoid typhoon damage. In transplanting the first crop, rice seedlings in the nursery bed are often damaged by cold injury. It takes 55-70 d to grow seedlings in the nursery bed. Because plant density in transplanting is high (50-55 hills/m 2, 4 plants/hill), the area required for the nursery bed is large. Direct seeding must be used when the seedlings are damaged by cold or when farmers miss the time of transplanting and seedlings are too old. In addition, use of direct seeding increases the area of rice production because the area required for the nursery bed can be converted for production. Contrary to the variable cultural practices of direct seeding in the MRD, direct seeding in the RRD is practiced mostly in well-puddled fields. Seeds pregerminated for 3-7 d for the first crop or for 1.5-2 d for the second crop are broadcast sown on the surface of well-puddled soil. Time of seeding after final land preparation is carefully adjusted by farmers so that half of the seed body stays in the soil and the remainder stays in the air (Tong Khiem, Food Crops Research Institute, Hanoi, personal communication 1993) — another way of describing the timing is that seeds are broadcast sown so that they can be seen on the soil surface on the day of seeding and cannot be seen the next day (Tran Ngoc Trang, National Seed Agency, Hanoi, personal communication 1993). The time of seeding is, therefore, dependent on the intensity of land preparation and on the soil properties. Seed rate in the RRD is lower than that in the MRD: 80-100 kg/ha versus 100-300 kg/ha. Our field observations in Hai Hung indicated that plant spacing is well controlled so that the distance between the plants is about 5-10 cm. Grain yield of direct-seeded rice (5 t/ha) is equivalent to or higher than that of transplanted rice (4.5-4.8 t/ha) with a cultivar of 120-d growth duration, because the number of panicles per unit land area is higher (Nguyen Anh Huong, Trau Quy Agricultural Cooperative, Gia Lam, and Nguyen Van Thanh, General Secretary of Cam Binh, personal communications 1993). At present, adoption of direct seeding is limited due to the difficulty of drainage.

Ecophysiology of rice 91 Physiological constraints to direct seeding in Vietnam

The destruction of sown seeds by birds and rodents is a common problem of wet-seeded rice because seeds are sown on the soil surface. Lodging problems of wet-seeded rice could be attributable not only to surface seeding but also to the high seeding rate. These constraints could be reduced through the adoption of anaerobic seeding. Farmers use a high seeding rate to reduce the risk of failure of crop establishment. However, the high seeding rate and its attendant problems could be reduced if we could develop a technology that assures stable crop establishment. Seedling establishment often fails because of standing water in part of the field — complete drainage of the field is difficult except when the field is well-leveled. Pregerminated seeds sown in standing water apparently fail to establish because they do not become firmly anchored — because of buoyancy, the roots cannot penetrate the soil. In addition, the products of anaerobic decomposition of crop residues inhibit root and leaf development, thereby preventing establishment. We have observed that seedlings in standing water develop irregularly with twisted, short leaves and no roots. Because

Table 1. Seedling growth of weedy rice and cultivated rice collected from the Mekong River Delta in flooded soil in trays in the phytotron (29/21°C, day/night) at IRRI, 1993 wet season.

Rice cultivar/species Establish- Emergence Height Mesocotyl Germination (location) ment scorec (mm) length (%) a,b (mm) Percent Rate

Cultivated rice from dry-seeding farmers

Unknown (Ben Luc) 30.9d-g 1.09c-e 37c-f 1.2c-e 99a 0.97a OM96-6 (Ben Luc) 22.1e-g 0.50e 13ef 0.9c-e 100a 0.95ab OM90-2 (Ben Luc) 19.1fg 0.34e 4f 0.4de 99a 0.89a-d OM90-2 (Can Giuo) 33.3c-g 0.74de 14ef 0.6de 87b 0.92a-d Cultivated rice from wet- and water-seeding farmers

IR64 (Cai Lay) 20.6e-g 0.44e 10ef 0.3de 96a 0.86b-d lR13240-108 (Cai Lay) 33.8c-g 0.72de 13ef 0.5de 99a 0.96ab IR64 (Thot Not) 10.3g 0.24e 4f 0.2de 97a 0.82d Unknown (Cai Lay) 22.1e-g 0.31e 2f 0.2de 98a 0.83cd Unknown (Cai Lay) 38.2c-f 0.96c-e 25d-f 0.7de 99a 0.98a Weedy rice collected from Cai Lay

1. Yellow husk 70.6a 2.44ab 84b 2.6b 99a 0.93a-c 2. Brown husk 54.4a-d 1.60b-d 53b-e 1.9bc 99a 0.99a 3. Brown husk 57.4a-c 1.78bc 68bc 2.5b 96a 0.97a 4. Black husk 53.0a-d 1.72bc 62b-d 2.6b 99a 0.92a-d

Control cultivar from IRRl

I R36 22.0e-g 0.27e 1f 0.1e 99a 0.99a IR50 45.6b-e 0.90c-e 13ef 1.3cd 99a 0.99a IR72 25.0e-g 0.37e 6f 0.3de 99a 1.00a ASD1 64.7ab 2.81a 135a 5.3a 100a 1.00a Taothabi 70.6a 3.07a 150a 5.7a 99a 0.91a-d

a Means within a column followed by the same letter are not significantly different at the 5% level by Duncan's Multiple Range Test. b Pregerminated seeds were sown at 25-mm depth in soil and flooded to 30-mm depth. c The seedling establishment was analyzed 14 d after the seeding. Emergence score was taken as 0 = no emergence, 1 = coleoptile emerged, 2 = 1st leaf emerged, ... etc. Details were as described in Yamauchi et al (1993a).

92 Yamauchi et al toxic substances such as acetic acid decompose 2 wk after flooding, advanced flooding before seeding would reduce this constraint (Biswas 1994, Biswas and Yamauchi 1994). In Vietnam, further adoption of direct seeding is constrained by cold temperatures in the north and by soil problems (ASS and salinity), particularly during the dry season in the south. We lack of information regarding rice germination and crop establishment in problem soils. A particular problem that is emerging in the regions where direct seeding is practiced continuously is weedy rice (that is, uncultivated rice), which is taller than cultivated rice: this has been found in the MRD. In Malaysia, the grain yield is reduced through shattering and induced lodging of the cultivated rice (Hiroaki Watanabe, Japan International Research Center for Agricultural Sciences, personal communication 1994). In addition, the market value of the crop may be decreased because of the admixture of the red grains of weedy rice.

Seedling establishment of anaerobic cultivars in flooded soils

Seedling establishment of anaerobic cultivars was analyzed in flooded soils in containers at INSA (Chuong and Yamauchi 1994). The soils were collected from lowland, upland, and ASS fields. Seedling establishment differed significantly between the soils and between cultivars. It was consistently better in the soils from uplands than those from lowlands, which agrees with the results obtained from the Philippines (Yamauchi et al 1993b). Although the cultivars Kibi, CO 25, IR52341- 60-1-2-1, and ASD1 were superior to the check cultivars at INSA, more experiments are needed to confirm this. Seedling establishment in ASS was not consistent compared with that from lowland and upland soils (data not shown). Because the soil properties of ASS change according to the soil preparations and time after flooding, it seems to be necessary to simulate the field conditions more precisely to study the seedling establishment in ASS. Coating seeds with calcium peroxide (calper) improved seedling establishment in flooded soils (Chuong and Yamauchi 1994, table 2). Because the coating was effective even in ASS, the technology might be applied in the introduction of wet seeding to the ASS fields. It can be assumed that dry seeding cannot be practiced in the ASS because dryness increases the acidity.

Seedling establishment of weedy rice in flooded soil

We collected seeds of weedy rice and cultivated rice from farmers’ fields in the MRD and analyzed anaerobic seedling growth in the phytotron at IRRI (Table 1). The weedy rice was found in the fields of zero-tillage wet seeding in Cai Lay. The husk was yellow, dark brown, or black while the caryopsis was red to brown. Some of the plants had awns. The seeds of cultivated rice were collected from the farmers who practice wet or dry seeding. Weedy rice had superior seedling establishment in flooded soil over cultivated rice, suggesting that weedy rice is anaerobic. There was no difference in seedling growth between the farmers’ seeds from wet and dry seeding. Seedling establishment of weedy rice was the same as that of control anaerobic cultivars (ASDl and Taothabi) but higher than ordinary cultivated rice (IR36, IR50, IR72, and farmers’ seeds) (Table 1). Emergence score, seedling height, and mesocotyl length of weedy rice were equivalent or inferior to those of control anaerobic cultivars but superior to those of ordinary cultivars. Rate and percentage germination differed little among weedy rice, control anaerobic cultivars, and ordinary cultivars.

Ecophysiology of rice 93 Table 2. Crop establishment, yield components, and grain yield a of direct seeded rice in the Mekong River Delta (CLRRI) and the Red River Delta (INSA), 1993 wet season.

Location and cultivar Seedling Yield components Grain establish- yield ment b Panicles Spikelets Filled 1,000-grain (t/ha) (no./m2) per m2 per spikelets weight panicle (%) (g)

CLRRI

BR1870-67-1-3 400a 442a 126b 80.3a 22.7d 5.83a BR736-20-3-1 407a 410a 135a 78.7a 21.5e 5.20ab lR52341-60-1-2-1 406a 446a 65c 73.9a 27.5b 3.77b-d lR31802-48-2-2-2 401 a 527a 70c 63.4b 24.0c 3.40cd lR41996-50-2-1-3 400a 527a 44d 76.6a 29.5a 2.87d MTL 103 (check) 379b 471 a 77c 80.2a 28.1b 5.13ab MTL 114 (check) 375b 479a 82c 73.8a 27.7b 4.80a-c

r with grain yield c -0.28 -0.75 0.84* 0.62 -0.52 –

INSA

lR52341-60-1-2-1 293ab 306b 76a 86a 25.9c 5.15a lR31802-48-2-2-2 247bc 284b 75a 87a 24.0d 4.43b lR41996-50-2-1-3 223c 207d 71a 85a 28.7a 3.56c BR736-20-3-1 217c 247c 75a 80a 22.2e 3.27cd BR1870-67-1-3 217c 251 c 74a 82a 21.2f 3.24cd ASD1 230c 189d 71a 78a 27.9b 2.89d CN2 + calper (check) 297a 346a 80a 88a 20.0h 4.84ab CN2 (check) 243c 318ab 81a 86a 20.0h 4.45b CN5 (check) 233c 301 b 67a 85a 21.0g 3.57c

r with grain yield c 0.88** 0.81** 0.64 0.84** -0.23 –

a Within a column for each location, means followed by a common letter are not significantly different at the 5% level by Duncan's Multiple Range Test. b Pregerminated seeds were broadcast-sown immediately after land preparation at 400 and 330 per m 2 at CLRRI and INSA, respectively. c Coefficient of simple linear correlation with grain yield: *, significant at the 5% level; **, significant at the 1% level.

The anaerobic character of weedy rices may explain why they can establish seedlings in cultivated fields as weeds. Incorporation of anaerobic tolerance into cultivated rice might not only improve crop establishment but also increase weed competitiveness, thereby reducing the need for herbicides.

Grain yield of anaerobic rice cultivars

Yield potential of anaerobic cultivars was analyzed by broadcasting pregerminated seeds immediately after land preparation in the experimental fields at CLRRI and INSA. In this practice, sown seeds were placed under the surface of puddled soil. Seedling establishment at CLRRI was better than that at INSA (93–100% versus 46–89%). Percentage seedling establishment differed little between the cultivars at CLRRI; however, at INSA, the anaerobic cultivar IR52341-60-1-2-1 (89%) was higher than the best check CN2 (74%) and equivalent to calper-coated check CN2 (90%).

94 Yamauchi et al Grain yield among the tested cultivars was highest for anaerobic cultivars at bath locations (Table 2). At CLRRI, BR1870-67-1-3 yielded 5.8 t/ha whereas checks produced 4.8-5.1 t/ha. The BR cultivars had thick columns and large panicles even though the plant density was high. Although BR1870-67-1-3 had significantly higher spikelet numbers per square meter than checks, it did not significantly outyield the checks because 1,000-grain weight was low. Grain yield correlated highly with number of spikelets per panicle (Table 2). At INSA, anaerobic cultivar IR52341-60-1-2-1 significantly outyielded the checks (5.2 versus 3.6-4.5 t/ha) although the calper-coated check produced as much grain (4.8 t/ha). Yield-component analysis indicated that although the check cultivar CN2 produced more spikelets per square meter than IR52341-60-1-2-1, the latter had a higher grain weight, and so it outyielded the check (5.2 versus 4.5 t/ha). The grain yield was significantly correlated with number of panicles per square meter and seedling establishment, suggesting the importance of establishment in increasing grain yield. The plant type required for high grain yield in direct-seeded rice might differ between the fields of CLRRI and INSA. At CLRRI, panicle weight type (BR cultivars) yielded more than panicle number type (IR cultivars); however, at INSA, panicle number type produced higher yields. At INSA, the BR cultivars did not show the characteristics of panicle weight: the cause should be identified whether it was due to a difference in cultural practice or climate and soil fertility.

Acknowledgment

We thank Dr. Nguyen Van Luat, CLRRI, Dr. Dao The Tuan, INSA, and Dr. Nguyen Ngoc Kinh and the staff of the Vietnam-IRRI Office at the Ministry of Agriculture and Food Industry for coordinating the present study and Mr. A.M. Aguilar, IRRI, for technical assistance.

References cited

Aragones D V, Casayuran P R, Asis C A, Aguilar A M, Sta Cruz P C, Yamauchi M (1993) Evaluation of crop stand establishment by anaerobic seeding technology at two locations in the Philippines. Philippine J. Crop Sci. 18 (suppl. 1):36. Biswas J K (1994) Physiological aspects of seedling establishment of direct seeded rice under simulated lowland condition. Ph D dissertation, Central Luzon State University, Muñoz, Nueva Ecija, Philippines. Biswas J K, Yamauchi M (1994) Process of seedling establishment as influenced by organic matter application to flooded soil. Philippine J. Crop Sci. 19 (suppl. 1):82. Cannel R Q, Lynch J M (1984) Possible adverse effects of decomposing crop residues on plant growth. Pages 455-475 in Organic matter and rice. International Rice Research Institute, P.O. Box 933. Manila 1099, Philippines. Chuong P V, Yamauchi M (1994) Anaerobic direct seeding of rice in northern Vietnam. In Proceedings of the Workshop on Constraints. Opportunities and Innovations for Wet-seeded Rice, 31 May-3 June 1994, Bangkok, Thailand. International Rice Research Institute, P.O. Box 933. Manila 1099, Philippines. (In press). Koganezawa H, Pablico P P, Cabunagan R C, Tiongco E R. Cabangon R, Tuong T P, Yamauchi M (1993) Relationship between tungro (RTD) infection and water level in direct seeded rice, IRR Notes 18(2):28. Pablico P P, Yamauchi M, Tuong T P, Cabangon R C (1993) Effect of water level on the performance of direct seeded, anaerobic rice cultivars and on weed infestation. Philippine J. Crop Sci. 18 (suppl. 1):36. Yamauchi M, Aguilar A M, Vaughan D A, Seshu D V (19938) Rice ( Oryza sativa L.) germplasm suitable for direct sowing under flooded soil sulface. Euphytica 67:177-184. Yamauchi M, Aguilar A M, Sta Cruz P S (1993b) Anaerobic seeding with suitable germplasm. IRR Notes 18(1):36.

Ecophysiology of rice 95

Water and nutrient management

Leaching of acid sulfate soils and its environmental hazard in the Mekong River Delta

Le Quang Minh, 1 To Phuc Tuong, 2 and Vo-Tong Xuan 1

Abstract. More than 40% of the Mekong River Delta in Vietnam consists of acid sulfate soils (ASS). Reclamation of ASS involves leaching toxic substances from the topsoil. A Vietnam-IRRI collaborative project in 1989–93 studied the leaching process and quantified its environmental hazard. More than I m of water in a 4-wk leaching was not adequate to bring aluminum concentration (Al 3+) in the root zone of undisturbed ASS to a safe level for plant growth. Bypass flow was important in the leaching process. Land preparation by forming raised beds enhanced the leaching efficiency by increasing the bypass flow between soil lumps. Leaching released as much as 2 keq/ha (for rice cultivation) to 15 keq/ha (for upland crop raised beds) of Al3+per month. At the beginning of the rainy season, river discharge and rainfall were not adequate to dilute the released leachate. Thus, leaching of ASS could pollute the surface water to a level harmful to fauna within the project area and its surroundings. The negative effects of leaching of ASS on surface water chemistry and on the aquatic population make it imperative that development of ASS areas be carefully planned.

In the Mekong River Delta (MRD) of Vietnam, 1.8 out of 4 million ha of land consists of acid sulfate soils (ASS). Unfavorable chemical properties inhibit the use of these soils for agricultural production, The country was facing severe economic problems, a fast-growing population, and, until late 1989, food shortage, so that higher production by improved land use and expansion of agricultural land, even in the unfavorable acid sulfate areas, was urgently needed. Reclamation of ASS invariably involves, among other measures, leaching of toxic substances to reduce their concentration in the topsoil to a level that the roots of agricultural plants can tolerate. In the past, numerous trial-and-error attempts by farmers and state farms have led to mixed results. Even when it was successful, the reclamation process caused acid pollution to the surface water surrounding the reclaimed area. This led to severe problems of water quality and affected the important fishery resources in the MRD. A 1989–93 Vietnam-IRRI collaborative study was carried out to study the soil-water interactions and to quantify the amount of acid pollutant released during leaching of ASS in different conditions. This paper reports the findings of the study and discusses their implications.

Materials and methods

The study consisted of two main experiments and some supplementary field monitoring. In experiment 1, the effect of land preparation on leaching of ASS was studied in a field study at Cu Chi in the dry season of 1989 (Tuong et al 1993). The soil was a Typic Sulfaquept, with a jarosite layer extending from 40 cm depth to the sulfuric material at 135 cm. The whole soil profile was

1 University of Cantho, Cantho, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. 1. Layout of an experimental plot in cxperiment 1.

characterized by very low pH (2.5-3.5) and high exchangeable aluminum (Al 3+) — about 20 meq/100 g of dry soil — occupying about 80% of exchangeable cations. The treatments were three levels of land preparation before leaching: • Land was not prepared (P1); • Land was hoed once to 10-15 cm and dried in the sun for 2 wk (P2); and • Land was hoed twice to 20-25 cm and dried in the sun for 2 wk (P3). The treatments were arranged in a complete block design with three replications. Each plot was 1.5 x 1.5 m with sides made of wooden planks driven to depths of 20 cm (Fig. 1). The wooden sides were designed to reduce lateral seepage from the plot, and this was further minimized by 2.5 × 2.5 m “buffer zones” where the water level was kept at the same level as that in the inner plot. Leaching water was applied to the experimental plots from a calibrated tank and leachate was collected in drains surrounding the experimental plots. Each experimental plot was equipped with a set of six tubes to extract soil solutions at depths of 0-5, 5-15, 15-25, 25-35, 35-45, and 55-65 cm. The soil solution tubes were similar to those described by Breemen (1976) with some modification to ensure that there was no vertical leakage along the tube sides and to enhance free flow of soil solution into the tubes at the sampling depths. Samples were collected in pre-evacuated bottles at the start of the leaching treatment and 0.5, 1, 2, 4, 7, 14, 21, and 30 d thereafter. Two supplementary field monitorings were carried out to quantify the effect of drainage canals and floodwater on leaching of ASS under natural conditions at Cu Chi. In the first, soil solutions at depths of 10, 20, and 40 cm were taken along a transect perpendicular to a drainage canal. Sampling

100 Minh et al 2. Layout of a 900 × 400 m fish pond being reclaimed in an ASS, Cu Chi. Sampling sites along along transects I–V.

sites were 1, 2, 4, 8, 16, and 32 m from the canal. In the second one, pH of the surface water of a 900 x 400 m fish pond that had been under 6 mo of leaching with nearly neutral water at rate of 20 mm/d was monitored. Sampling sites were arranged in five transects at 0, 200, 400, and 600 m from the intake sluice (Fig. 2). On each transect, the sampling sites were at 0, 16, 48, 80, 112, 144, 176, and 208 m from the right peripheral (ring) canal, which ran along the side of the ponds. The pH and electrical conductivity (EC) of water samples were measured within 1 hr after sampling. Other constituents were analyzed as described in Begheijn (1980). To stop oxidation of ferrous ions during the storage before the analysis, a small portion of soil solution was fixed with 0.1 M HCl. Experiment 2 was carried out during the 1993 rainy season to assess leaching efficiency and the degree of pollution caused by three common agricultural land uses (rice, pineapple, and yam) in a newly reclaimed ASS area in Cai Lay District of Tien Giang Province. The soil was classified according to the US Department of Agriculture soil taxonomy as a Typic Sulfaquept with a dark humic topsoil (0–40 cm), a jarosite horizon (40-95 cm), and a pyrite horizon below 95 cm. The soil was extremely acid with pH of the topsoil and the jarosite layer of 3.3–3.4 and exchangeable Al3+ concentration of 13-16 meq/100 g of dry soil Previously, the area had been uncultivated with Melaleuca cajiputi as the natural vegetation. Since the completion of a network of canals in 1990, farmers have gradually reclaimed the area for rice, yam (Dioscorea esculenta), and pineapple. The latter were grown on raised beds — those for pineapple were higher than for yam because pineapple cultivation has a 3-yr cycle and the crop must survive the maximum annual flood depth, which was about 50 cm in November. From May to August 1993 (when the area was flooded and drainage was no longer possible), we monitored the discharge and quality of water drained from three blocks of land, each composed of one rice (R), one pineapple (P), and one yam (Y) farm. Each farm consisted of three adjacent plots, one has been reclaimed for 2 yr, one for 1 yr, and the other only 2 mo before the experiment in 1993.

Leaching of acid sulfate soils 101 3. Changes m pH of the soil solution at sampling depths (a) 5–15 cm and (b) 55-65 cm during the leaching process as influenced by land-preparation treatment.

TWO hours after each rain (or the next morning if rain occurred at night), leachate collected by ditches was drained to the surrounding canal network by opening the manually controlled sluices. Samples from drainage water were taken for chemical analysis. Methods of chemical analysis were similar to those of experiment 1. The amount of a certain pollutant released to the surrounding environment was derived from the product of its concentration and the drainage volume after each rain event. Flow pattern and bypass flow (Bouma and Decker 1978), that is, the amount of flow that bypasses the unsaturated soil matrix, in raised bed soils were studied in the laboratory, using soil cores (20 cm diameter × 25 cm long), simulated rainfall, and stain technique (Bouma and Decker 1978). Three samples were taken from each P and Y treatment in April (at the end of the dry season). Each soil core was subjected to three 30 mm/hr rainfalls, one per day for 3 consecutive d. Duration of each “shower” was 1 hr. The outflow rate, EC, and pH of the outflow were recorded every 5 min. After three showers, methyl blue was applied to stain the water-conducting pores.

Results and discussion

The results and discussion focus on the dissolved Al 3+ because of its potential toxicity to plant roots and to fish at concentrations exceeding 0.001 meq/liter to 1-5 meq/liter depending on variety or species and growth stage (Thawornwong and van Driest 1974, Singh et al 1988).

Leaching process: disturbed versus undisturbed ASS In experiment 1, pH of the soil solution at the first two sampling depths (0–5 and 5–15 cm) was raised by the leaching process (Fig. 3a), where the effects of land preparation were strongly apparent at earlier sampling times. For deeper sampling depths, pH remained rather constant throughout the leaching period (Fig. 3b) and no significant differences were found among treatments. Land preparation treatments significantly enhanced the leaching of Al 3+ (Fig. 4). Although the differences between the single- and double-hoed treatments (P2 and P3) were not statistically significant, they were noticeable even at greater depths at earlier samplings. As the leaching proceeded, its effects diminished: after about 1 wk (170 hr), A1 3+ concentration remained almost constant. In the nonhoed treatment (P1), A1 3+ concentration at all depths remained very high, far exceeding the tolerance level of rice plants, while in the hoed treatments it could be brought down to less than 2- 3+ 1 meq/liter. Variation in EC, pH, and SO 4 were similar to that of A1 .

102 Minh et al 4. Changes in A1 3+ of the soil solution at sampling depths (a) 5-15 cm and (b) 55-cm56 during the leaching process as influenced by land-preparation treatment.

3+ 2- 5. Variation of Al and SO 4 in soil solution at three different depths (10, 20, and 40 cm) as a function of distance from a drainage canal in the ASS area of Cu Chi.

Leaching of undisturbed ASS (treatment P1) was a slow and water-demanding process. It appeared that Al 3+ was particularly difficult to leach from undisturbed soils. Even 1 m of water was not adequate to bring its concentration in the root zone to a safe level for plant growth (Figs. 3 and 4). Results from field monitoring at Cu Chi indicated that leaching of undisturbed soils under natural conditions was not only a slow process but its effects were also limited to a small fringe of

Leaching of acid sulfate soils 103 6. pH of surface water along five transects and at various distances from the right ring canal of a fish pond after 6 mo of leaching with continuous water flow of about 20 mm/day.

about 10 m along the drainage canals where there was adequate exchange of water between the canal and the soil body (Fig. 5). The limited effects of leaching and flushing of undisturbed soil in the field are also shown (Fig. 6) by the pH of the surface water of a fish pond in the ASS area at Cu Chi after a 6-mo effort of leaching with nearly neutral water at a rate of 20 mm/day. A large area in the middle of the pond, with pH lower than 3.5, appeared not to be affected by the leaching process. The findings support previous investigators’ results. Sen (1988) found that Al 3+ in the soil solution remained as high as 6–18 meq/liter after 30 d of leaching with 450 mm of water. Konsten et al (1990) also reported slow leaching under natural conditions in Pulau Petak, South and Central Kalimantan, where annual rainfall is about 2,300 mm. They estimated that the annual leaching amounted to 1.3% of the total acidity present in the upper 65 cm. Thus, it will take at least 80 yr at the present leaching rate to neutralize the acidity and, in more poorly drained area, it may take longer. The findings in the reclaimed fish pond (Fig. 6) help explain why a large area of the Plain of Reeds in the MRD, which is flooded annually, remains acidic. The faster rate of leaching (Figs. 3 and 4) achieved by land preparation can be explained by the increased infiltration of the profile. Land preparation created macropores between the soil crumbs where water flow bypassed the soil matrix. Despite these bypasses, leaching efficiency, in terms of removal of A1 3+ per unit of water, of the hoed treatments was much higher than the nonhoed treatment (Fig. 7). This is particularly clear when the amount of water applied was less than 1,000 mm. The raised beds in experiment 2 were also composed of soil lumps that were excavated during the construction of the beds. Stains from the laboratory study of flow pattern indicated that most of the drainage water in the raised beds was bypass flow, confined to macropores between soil lumps. After 3 consecutive d, each with one 30 mm/hr rainfall, bypass flow in raised yam beds amounted to 54% (of rainfall applied) and did not change with land-use age. For pineapple, it decreased from 58% for newly constructed beds to 41% for beds that were 3 yr old. The decrease in bypass flow with land- use age in the pineapple beds was related to the decrease in macropore volume as a result of soil consolidation, In yam, consolidation did not occur because land preparation was needed annually before planting a new crop. In rice fields, soil was puddled and most of the water was drained as surface run-off. The A1 3+ concentration of drainage water (an indication of the amount of Al 3+ being leached by rainfall) from raised pineapple beds was higher, but not statistically so, than that from yam beds. Both were significantly higher than from rice fields (Table 1). Higher bypass flow was responsible for higher leaching efficiency and hence higher toxicity concentration in the leachate from the upland

104 Minh et al 7. Leaching efficiency expressed as (a) decrease in Al 3+ . concentration (compared with the original concentration) per 100 mm of water applied and (b) incremental decrease in Al 3+ concentration for each additional 100 mm (sampling depth 15–25 cm)

Table 1. Monthly average concentration (meq/liter) of Al 3+ in drainage water as influenced by land uses and land-use age.

Month Age Land use b, c, d (yr of cultivation) a Yam Pineapple Rice

May 0 4.4a 7.9a 4.2a 1 5.9a 7.6a 3.8a 2 4.3a 4.5b 3.7a Mean 4.8x 6.7x 3.9y

June 0 10.2a 12.3a 4.3a 1 7.1 b 11.4a 3.8a 2 8.7ab 7.2b 3.0a Mean 8.7x 10.3x 3.7y

July 0 11.1a 11.4a 4.1a 1 9.4a 9.7a 3.6a 2 8.9a 6.6a 3.5a Mean 9.8x 9.2x 3.8y

August 0 8.2a 7.6a nd 1 8.7a 6.1 b nd 2 8.4a 5.1 b nd Mean 8.4x 6.2x –

a 0, reclaimed 2 mo before the experiment. b Within a column, means following by a common letter (a, b, c) are not significantly different at the 5% level by Duncan’s multiple range test. c Within a row, means following by a common letter (x, y) are not significantly different at the 5% level by Duncan’s multiple range test. d nd, no drainage, rice vias harvested.

Leaching of acid sulfate soils 105 crops. For pineapple, A1 3+ concentration of the drainage water tended to decrease with land-use age (Table 1). This decrease was related to the decrease in macropore volumes and in bypass flow with respect to land-use age as discussed earlier. A similar observation that the leaching of acid from the topsoil of raised beds was mainly caused by bypass flow through cracks and macropores was reported by Sterk (1993). Because of the low hydraulic conductivity of soil lumps or peds, leaching by advective transport through them was very small. Water moving in macropores could much more effectively remove the toxicity that had been transported by diffusion from inside the ped to the ped surface (Ritzema and Tuong 1994). In other words, the diffusion transport and bypass flow play important roles in the leaching process. The diffusion process can be enhanced by changing the size of the soil peds. Decreasing the radius of the peds by a factor of 2 doubles the number of peds per square meter and increases the diffusion rate by a factor of 4, thus increasing the diffusion flow by a factor of 8 (Ritzema and Tuong 1994). Undisturbed soils, having much larger soil peds or clods, are leached much more slowly than soils whose structure has been modified by land preparation.

Acid pollution hazard to surface water Decreasing soil acidity for agricultural use by leaching necessarily involves transfer of the acidity and associated toxic substances from the soil to the surroundings. The leachate would be collected first in farm ditches and then drained to the surrounding canals. The total pollution depends on the concentration and the discharge of the drainage water. Table 2 presents the monthly total Al 3+ released in May–August 1993 at Cai Lay by different land uses and land-use ages of experiment 2. The amount

Table 2. Monthly total AI 3+ (eq/ha) released to the canal network as influenced by land uses and land-use age.

Month Age a Land use b,c,d (Yr of cultivation) Yam Pineapple Rice

May 0 3,222a 10,054a 1,988a 1 4,560a 9,971a 1,759a 2 3,481a 5,976b 1,836a Mean 3,757x 8,667y 1,861x

June 0 14,542a 19,052a 2,334a 1 10,694b 18,931a 2,879a 2 13,197ab 12,024b 2,347a Mean 12,811y 16,669y 2,520x

July 0 10,973a 12,837a 2,737a 1 9,514a 10,955a 2,394a 2 8,794a 7,353a 2,082a Mean 9,760x 10,381x 2,404y

August 0 12,821a 14,847a nd 1 14,371a 11,996b nd 2 13,891a 9,908b nd Mean 13,694y 12,250y –

a 0, reclaimed 2 mo before the experiment. b Within a column, means following by a common letter (a, b, c) are not significantly different at the 5% level by Duncan's multiple range test. c Within a row, means following by a common letter (x, y) are not significantly different at the 5% level by Duncan's multiple range test. d nd, no drainage, rice was harvested.

106 Minh et al of Al 3+ released monthly from the raised beds for upland crops (about 10-15 keq/ha) was about five times greater than from rice cultivation. This was due both to a lower concentration (Table 1) and a lower drainage volume in rice cultivation. Land-use age did not significantly affect the total amount released in rice and yam culture (Table 2). In pineapple, significantly less Al 3+ was leached from older raised beds than from the newly created ones. This resulted from the reduction in bypass flow and the increase in runoff in older pineapple beds as discussed earlier. Because the toxic threshold concentrations are often lower for aquatic organisms than for plant roots leaching of newly reclaimed ASS, especially by making raised beds for upland crops, may have serious consequences for fish and the aquatic food-production chain in the canal network. If the toxic substances are to be diluted to an acceptable level, for example, to 1 meq/liter, the surface runoff must be in the order of 1,000 mm/mo (equivalent to 1 × l0 4 m 3/ha per mo) for reclamation for upland crops and 200 mm/mo for rice. At the beginning of the rainy season, rainfall and discharge of the Mekong River were not adequate to supply such a runoff. As a consequence, it was not uncommon for the pH of surface water in reclaimed areas of the Plain of Reeds to remain below 3, with an A1 3+ concentration exceeding 10 meq/liter (Kham 1988). The pollution was not confined to the reclaimed areas. Through diffusion and mass transport by the flow of water, the acidity concentration was diluted as the water merged with that in the secondary and primary canals. At the same time, it contaminated a much larger surrounding area resulting in a large area of the Plain of Reeds with a pH of the surface water below 5 during the early part of the rainy season (Fig. 8). A high value of the pH, caused by the mixing of the river water at high tides, was only possible along a belt of about 10 km from the Mekong River, whose pH was 7.5-8.0. Similar contamination of a large area has been reported by Chairuddin et al (1990) for Pulau Patek in Indonesia.

8. Acid pollution and its effects on benthic communities in the Plain of Reeds, Vietnam. Shaded area: depressed benthic communities, June 1987 (from Grimas 1988). Area within the fine dotted line: Al 3+ in canal water >10 ppm, May 1987 (from Kham 1988). The dashed line is the pH 5 isoline, May 1985 (from Kham 1988).

Leaching of acid sulfate soils 107 Acid water contamination may result in the loss of wetland habitat and may have profound effects on the aquatic population of an area. Grimas (1988) reported a chronically depressed benthic population (both in abundance and diversity of benthic animals) in the center of the Plain of Reeds, approximately coinciding with the most heavily polluted area with an Al 3+ concentration above 10 ppm (Fig. 8). Fish production in the Plain of Reeds can be expected to be greatly affected by acidic pollution of the water or by the decrease of food (for example, reduced benthic communities). Similar pollution of surface water can be expected to occur in Ca Mau Peninsula of the MRD if reclamation of ASS is carried out at the same rate as that in the Plain of Reeds. The effects on the wetland habitat, however, can be more profound: the mangrove forests in the coastal lowlands, downstream of areas of ASS in Ca Mau Peninsula, are the base of the local food chain, which is often very sensitive to any change in surface-water chemistry. An example of the effects of acid pollution on aquatic populations can be found in South Kalimantan, Indonesia, where the number of fish species declined from 96 in an undisturbed area to only 29 species in a drained, acidified area (AARD and LAWOO 1992). Similar changes in fish population have been reported in eastern Australia (Callinan et al 1993, Willett et al 1993). Marius (1982) and Chairulddin et a1 (1990) also report strongly negative effects on shellfish, crustaceans, and fish, due to flushes of severe acidity from the reclamation of ASS.

Conclusions

When adequate fresh water is available, and if it is properly managed, leaching can turn ASS into productive soils. ASS leaching, however, is a highly water-demanding process. The opportunity cost of water use should be critically analyzed when irrigation water is also in high demand for other areas. Land preparation by forming raised beds can enhance the leaching efficiency by creating bypass flow and more contact surfaces between the moving water and the soil lumps. Leaching, particularly of raised beds for upland crops, however, creates pollution. Removing acidity by leaching and drainage necessarily involves the transfer of acidity and associated toxic substances from the soil to the surrounding water and brings about changes in the chemistry of surface water because of its low buffering capacity. This may change the populations of fauna and fish, both within the project area and downstream of it, and may make the effluent unsuitable for irrigation downstream. The negative effects of leaching of ASS on aquatic populations and the importance of fisheries for farmers’ income and diet make careful management of these resources in the development planning for ASS imperative. Simulation techniques may offer a predictive tool to study the degree and extent of pollution as a result of development plans and to ensure that the negative effects are within the “absorbing” or bearing capacity of the surroundings. To reduce the environmental hazard, it seems judicious to limit leaching to periods with high surface runoff, so that the acidic products are diluted as much as possible. Techniques of using floodwater of the Mekong River for leaching should be researched.

References cited

AARD and LAWOO — Agency for Agricultural Research and Development and Land and Water Research Group (1992) Acid sulphate soils in the humid tropics: ecological aspects of their development. AARD, Jalan Ragunan 29, Pasar Miggu, Jakarta 12520, Indonesia. Begheijn L T (1980) Methods of analyzing soil and water. Department of Soil and Geology, University of Agriculture, Wageningen, Netherlands.

108 Minh et al Bouma J. Decker L W (1978) A case study on infiltration into dry clay soil: 1 — Morphological observations. Geoderma 20:27–40. Callinan R B, Fraser G C. Melville M D (1993) Seasonally recurrent fish mortalities and ulcerative disease outbreaks associated with acid sulphate soils in Australian estuaries. Pages 403–410 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort, eds. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Publ. 53. Chairuddin G, Iriansyah, Klepper O, Rijksen H D (1990) Environmental and socio-economic aspects of fish and fisheries in an area of acid sulphate soils: Pulau Petak, Kalimantan. Pages 374-392 in Papers of the Workshop on Acid Sulphate Soils in the Humid Tropics, 20-22 Nov 1990. Agency for Agricultural Research and Development, Jalan Ragunan 29, Pasar Miggu, Jakarta 12520, Indonesia. Grimas U (1988) Water quality investigations in the lower Mekong Basin: biological monitoring — An evaluation. Paper presented at the Workshop on Surface Water Quality in the Lower Mekong Basin. Ho Chi Minh City, 7–13 Sep 1988. International Mekong Committee, Bangkok, Thailand. Kham T D (1988) Water quality reclamation in the Plain of Reeds in the 1980s. Paper presented at the Workshop of Surface Water Quality in the Lower Mekong Basin, Ho Chi Minh City, 7-13 Sep 1988. International Mekong Committee, Bangkok, Thailand. Konsten C J M. Suping S. Aribawa I B, Widjaja-Adhi I P G (1990) Chemical processes in acid sulphate soils in Pulau Petak, South and Central Kalimantan. Indonesia. Pages 109-136 in Papers of the Workshop on Acid Sulphate Soils in the Humid Tropics, 20–22 Nov 1990. Agency for Agricultural Research and Development, Jalan Ragunan 29, Pasar Miggu, Jakarta 12520, Indonesia. Manus C (1982) Vegetation et ecology des mangroves. Pages 103–136 in Proceedings of the Bangkok Symposium on Acid Sulphate Soils. H. Dost and N. van Breemen. eds. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Publ. 31. Ritzerna H P, Tuong T P (1994) Water management strategies as a tool for the sustainable use of acid sulphate soils. Paper presented at the Regional Workshop on the Sustainable Use of Coastal Land in South East Asia. 18–22 Apr 1994, at the Asian Institute of Technology, Bangkok, Thailand. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Sen L N (1988) Influence of various water-management and agronomic packages on the chemical changes and on the growth of rice in acid sulphate soils. University of Agriculture, Wageningen, Netherlands. Singh V P, Poernomo T, Brinkman R (1988) Reclamation and management of brackish water fish ponds in acid sulphate soils: Philippines experiences. Pages 214–228 in Proceedings of the Dakar Symposium on Acid Sulphate Soils. H. Dost, ed. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Publ. 44. Sterk G (1993) Leaching of acid from the top-soil of raised beds on acid sulphate soils in the Mekong Delta, Vietnam. Pages 241-246 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort, eds. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Publ. 53. Thawornwong N, van Driest A (1974) Influence of high acidity and Al 3+ on the growth of lowland rice. Plant Soil 41:141–159. Tuong, T P (1993) An overview of water management of acid sulfate soils. Pages 265-279 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort, eds. International Institute for Land Reclamation and Improvement. Wageningen. Netherlands. Publ. 53. Tuony, T P, Du L V, Luan N N (1993) Effects of land preparation on leaching of an acid sulphate soil at Cu Chi. Vietnam. Pages 281–287 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort, eds. International Institute for Land Reclamation and Improvement, Waginingen Netherlands. Publ. 53. van Breemen N (1976) Genesis and solution chemistry of acid sulfate soils. Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands. Agricultural Report 848. Willett I R, Melville M D, White I (1993) Acid drain waters from potential acid sulphate soils and their impact on estuarine ecosystems. Pages 419–425 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort, eds. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Publ. 53.

Leaching of acid sulfate soils 109

Dry seeding rice for increased cropping intensity in Long An Province, Vietnam

Tran Van My, 1 To Phuc Tuong, 2 Vo-Tong Xuan, 3 and Nguyen Thanh Nghiep 4

Abstract. Irregularity and low availability of rainfall are among the main constraints to increasing cropping intensity in rainfed lowland rice ecosystems. Farm surveys and field monitoring were carried out in the 1992 and 1993 wet seasons to better understand farmers’ practices and to identify factors affecting the performance of short-duration dry seeded rice (DSR) in enhancing cropping intensity in Long An Province, Vietnam. Most DSR farmers used 100-d varieties. The whole crop, from land preparation to harvest, used only 700-900 mm of rainfall. Harvest in August gave enough time and rainfall for another rice crop before the end of the rainy season. Farmers rototilled the land with heavy tractors before the onset of the monsoon season and seeded just before or at the onset of the rainy season. Irrespective of the seeding date, rice plants emerged almost at the same time — after 100 mm seasonal cumulative rainfall. The final rate of emergence declined with the time seeds stayed in the soil before emergence and ranged from 40 to 70%. A probability model, based on long-term rainfall data, suggests that seeding dates be between 1 and 14 May. Farmers spent 20-103 person-days/ha in hand weeding and redistribution of seedlings. Only 20% of farmers used herbicides. Yields averaged 4.3 t/ha. Short-duration varieties, timely land preparation, low soil permeability, and high water table were important factors contributing to the success of dry seeding in increasing cropping intensity and land productivity in Long An. This crop establishment technique can be expanded to other areas of the Mekong River Delta.

More than 60% of the Mekong River Delta is rainfed lowland. Traditionally, these areas were cultivated with a single transplanted rice crop. With the availability of modern short-duration varieties and other technologies, farmers in Long An have used dry seeded rice (DSR) to increase cropping intensity and productivity of their rainfed rice lands. DSR can be sown before the start of the wet season permitting use of early rainfall (Saleh et al 1993, Tuong et al 1993) and its early harvest generally improves the use of the remaining rainfall for a second crop. Dry seeding of modern rice has been studied elsewhere (Furoc et al 1978, Morris 1980, Denning 1991, Saleh et al 1993). Morris (1980) identified four interrelated factors — tillage, agrohydrology, nitrogen fertilization, and weed control — for successful adaptation of DSR and its related increased cropping intensity; but these factors have not been adequately studied in detail in actual farmers’ conditions. This study aimed at addressing these problems and quantifying the effects of agrohydrology on the seeding, emergence processes, seedling redistribution, and weeding for a better understanding of farmers’ DSR technology in Long An and identifying conditions where the technology can be app1icable. The findings are of importance in identifying other areas where the technology could be applied in the Mekong River Delta and elsewhere.

1 University of Agriculture and Forestry. Thu Duc, Ho Chi Minh City, Vietnam: 2 International Rice Research Institute, P.O. Box 933. Manila 1099. Philippines; 3 University of Cantho, Cantho, Vietnam; 4 Bureau of Agricultural Extension, Huong Tho Phu Village, Tan An, Long An, Vietnam. Methods

A 1992-93 study was carried out in four districts of Long An Province where the topography was flat with alluvial soil containing about 70% clay. Annual rainfall varied from 750 mm to 2,230 mm and averaged 1,640 mm of which 90% fell from May to November (Fig. 1). From curves of 10-d rainfall (Fig. l), even at 25% probability, there was no rain before 10 April, which is used as the starting date for computing seasonal cumulative rainfall in this paper. In the dry season and early part of the rainy season, surface water was affected by salinity intrusion. In the southern part of the study site, fresh water was limited to August-December (Region 1, Fig. 1) and in the northern part, August-February (Region 2, Fig. 1). In Region 1, rice was totally rainfed but, in Region 2, farmers near rivers could grow a third crop with supplementary irrigation during December-February. The study used a combination of methods: reconnaissance survey, detailed farmers’ survey, and field monitoring. The reconnaissance survey was carried out using a rapid rural appraisal (RRA) approach, in May 1992, to identify key issues and to design a questionnaire to be used in the detailed survey. Sixty-six farmers — 34 in Region 2 and 32 in Region 1 — were interviewed using a semi- structured, open-ended questionnaire during the 1992-93 dry season. Data collected included land preparation and establishment methods, timing of various activities, cropping pattern, variety selection, labor, input use, and yield of the 1992 wet-season crop and other farmers’ perceptions on DSR.

1. Ten-day rainfall at probability 25%, 50%, and 75% and in 1993 (until end of August) and period of fresh water in the southern (Region 1) and northern (region 2) parts of the study site, Long An.

112 My et al Farmers’ responses were further verified in 1993 wet season by detailed field monitoring of 20 randomly selected farms, 10 from each region. Monitored factors and the methods were as follows: • Land preparation methods, implements, and timing; • Seeding methods and timing; • Seeding rate and choice of variety — seeding rate was determined by the actual weight of the seeds used by the farmer divided by the area monitored; • Seed emergence was counted every 2 d from seeding to seedling redistribution in three l-m square quadrats randomly located in each of the monitored fields; plant density after redistribution was also determined from three similar quadrats and average values from the three quadrats were used in data analysis; Timing, labor, and methods of seedling redistribution and weeding were recorded with labor input converted to 8-h person-days from the observed number of people and their daily time spent on each activity; Gravimetric water content at depths of 0-5 cm and 5-10 cm were determined from three samples in each field every 4 d from 1 April until the soil became saturated, and whenever there was no standing water in the field; Ponding water depth (PWD) and groundwater table depth (GWTD) of two representative fields were measured every 4 d by sloping gauge (Wickham and Singh 1978) and by a groundwater tube of 2 cm diameter, perforated from depth 0.5 m to 2.0 m and installed to a depth of 2 m; • Amounts of inputs including fertilizer, insecticides, and herbicides were measured and their timing of application recorded; and The actual yield from each monitored field, after drying and cleaning, was measured.

2. Area under dry seeded rice (DSR) compared with transplanted rice (TPR) in summer-autumn cropping season at the study site, Long An.

Dry seeded rice in Long An Province 113 Field monitoring was also carried out far 1992 wet-season crop, but it was limited to land preparation, seeding, and emergence. Discussion in this paper focuses on the technical aspects of dry seeding technology.

Results and discussion

Dry seeding practice Traditionally, the study site was cultivated with one crop of rainfed transplanted rice (TPR) of a photosensitive local variety. As early as the 1970s, soon after the introduction of improved varieties, farmers started growing DSR and the area planted to DSR steadily increased, so that it now accounts for almost 100% of the summer-autumn rice-cropping area (Fig. 2). DSR fields are prepared before the start of the rainy season. Ungerminated seeds are broadcast on unpuddled dry (or moist) soil and remain in the soil until adequate moisture has accumulated for germination. After emergence, the rice plants grow in upland conditions until enough rainfall has collected to form a standing water layer in the field. At this point, farmers often redistribute the germinated seedlings to obtain a uniform stand in the field. Thereafter, with subsequent rains, fields are often submerged, unless there is a long dry spell, and the rice grows under lowland conditions until harvest. In general, the practices are similar to those in other DSR areas as reported by Moms (1980), Denning (1991), Fagi (1993), and Saleh et al (1993). DSR practices in Long An had, however, important details that were of importance for the stability and success of the system. These are discussed in the following sections.

3. Progress of dry seeded rice farming activities and cumulative rainfall (up to August) in the 1993 wet season at the study site, Long An.

114 My et al Land preparation All DSR fields were prepared by four-wheeled heavy-duty tractors (greater than 50 HP). Fewer than 10% of interviewed farmers owned tractors, and the rest had their field prepared by contract arrangement with tractor owners. Land preparation consisted of three activities: the primary (first) rototilling, mostly carried out before the onset of the rainy season (March and early April), the second rototilling, to form good soil tilth just before seeding, and the last rototilling right after seeding to bury the seed (Fig. 3) — the second and final rototillings were carried out in the same day. Most farmers completed land preparation by the end of April when seasonal cumulative rainfall reached 20–30 mm. The primary land preparation, which needed higher power and longer time to prepare a field, was carried out early to spread demand for the power (tractor) over a long period so that a larger area could be served by the available tractors. It also reduced the power and time needed for the subsequent rototillings so that seeding and land preparation could be completed before the land became too wet. Most farmers cited the availability of farm machinery for timely preparation of their heavy-soil fields as the most important single factor contributing to the success of DSR and its associated intensified cropping. The findings agreed with those of Morris (1980) who stated that successful adaptation of DSR depended on appropriate tillage operation. Fujisaka et al (1993) and Saleh et al (1993) also indicated that although timing of land preparation and sowing depends on availability of draft power and soil type, DSR farmers in Indonesia and the Philippines tried to prepare their land and sow the seeds very early at the onset of the rainy season. Delayed land preparation means loss of opportunity to make use of early rainfall. Late land preparation may also involve difficulties in maneuvering implements because of stickiness of clay soil.

4. Daily rainfall, soil moisture at two depths, 0-5 cm (SM. 0-5) and 5-10 cm (SM. 5-10), and survived emergence percentage (EM.) of two sampled dry seeded rice plots, 1993 wet season, Long An.

Dry seeded rice in Long An Province 115 With respect to rainfall, Long An farmers completed land preparation much earlier than farmers at Urbiztondo, Philippines, who carried out the first plowing after about 100-150 mm of rainfall and completed the land preparation after 150-300 mm (Saleh et al 1993). Earlier completion, despite heavier soils and low percentage of tractor owners, was attributed to the system of contract rototilling and spreading of the land preparation over a longer period before the start of the wet season.

Seeding and emergence Most farmers used 150-250 kg of seeds/ha. About 10% of farmers used 100-150 kg/ha and 3% used over 300 kg/ha. These rates were substantially higher than those used in controlled experiments by Furoc et al (1978) and Tuong et al (1993). Farmers cited insurance against low emergence as their main reason for a high seeding rate. In general, the interviewed farmers’ criterion for seeding date was “after a few rains.” It was observed in monitored fields that seeding dates varied over 1 mo from 17 April to 20 May in 1992 and 11 April to 18 May in 1993. In 1993, farmers in Region 1 in general seeded about 2 wk earlier than in Region 2 although rainfall in the two regions was similar. This indicated that seeding date also depended on the availability of the tractors, which moved from one region to another, for the second rototilling before seeding. The progress of seeding activity is shown in Fig. 3 (for simplicity, only data for Region 1 are shown). Most farmers completed land preparation and seeding after about 30 mm of seasonal cumulative rainfall. Corresponding values for Urbiztondo were 150-300 mm (Saleh et al 1993) although rainfall distributions during May-June at two sites were similar (data not shown). Early land preparation was the key for early establishment in Long An. Although seeded on different dates, most of the rice in the monitored fields started emerging almost on the same day (22-25 May in 1992 and 17-20 May 1993), after a few concentrated rainfalls (Fig. 4). Furoc et al (1978) also reported 90% emergence within a 3- to 4-d period around 26 May 1977 irrespective of planting date ranging from 20 April to 25 May.

5. Effect of time from seeding to emergence on final emergence percentage of dry seeded rice. 1993 wet season, Long An

116 My et al Small scattered showers did not affect the emergence of DSR. Emergence was triggered only when the soil moisture had been raised to about 30% (Fig. 4). For the two regions, the computed “needed seasonal cumulative rainfall at emergence” in 2 yr was about 100 mm. This value supported Furoc et al (1978) who reported that an accumulation of 50–125 mm was sufficient to trigger emergence. The final emergence percentage in monitored fields varied from 30 to 70% in 1992 and from 37 to 79% in 1993 and did not depend on varieties used. There was a significant negative correlation between the final emergence percentage and the duration from seeding to emergence (Fig. 5). The final monitored emergence percentage was lower than those obtained in experiments by Furoc et al (1978) and Tuong et al (1993) but Furadan was used for insect control in these experiments and it was not used in the farmers’ fields in Long An. The changes in soil moisture of the topsoil (Fig. 4) could also have affected the vitality of seeds that were not covered deeply enough. The longer the seeds stayed in the field, the more they were exposed to insect attack and moisture fluctuation, so that emergence was reduced. To obtain a final emergence percentage greater than 60%, seeds should not be in the field more than 2 wk before they emerged (Fig. 5). In other words, seeding should not be carried out more than 2 wk before a seasonal rainfall accumulation of 100 mm is expected. From Fig, 6, the 50% and 75% probability rainfall accumulation of 100 mm fell on 16 May and 27 May respectively; thus it can be suggested that seeding date be between 2 and 13 May (or for ease of extension work, the first 2 wk of May) to have a 50–75% probability that the emergence percentage will be equal to or greater than 60%

6. Emergence date and suggested seeding period (within 2 wk before emergence) for final emergence percentage greater than 60% at 50% and 75% probability levels ( P) for 100 mm of cumulative rainfall

Dry seeded rice in Long An Province 117 7. Relation between plant density after redistribution and emergence density.

Seedling redistribution Farmers redistributed seedlings when enough rainfall had accumulated to saturate the soil or to leave some standing water on the soil surface. In both 1992 and 1993, seasonal cumulative rainfall at redistribution ranged from 200 to 400 mm, and corresponded to 20-30 d after crop emergence (Fig. 3). Some variation in redistribution date could also be caused by the availability of labor. Plant density at redistribution varied widely, from 350 to 600 hills/m 2 . Most hills consisted of a single plant but some replanted hills had more. Plant densities before and after the redistribution were strongly correlated (Fig. 7). This suggested that farmers simply redistributed seedlings from within one plot to obtain a uniform stand rather than trying to get a “standard’ density by moving seedlings from other plots. Seedling redistribution was often combined with hand weeding and it was not possible to separate labor needed for redistribution alone. Similar situations have been reported in other areas where DSR is practiced (Fujisaka et al 1993).

Weed control Weeds were one of the constraints for DSR cultivation. In fact, farmers in Long An began dry seeding cultivation by removing weeds by hand and sickles a few days before the primary rototilling. Major weeds in monitored fields included Echinochloa crusgalli, E. glabrescens, and Fimbristylis miliacae. During crop growth, most farmers weeded three times, including once in combination with redistribution. The last weeding was often completed within 15 d after redistribution. Only 20% of interviewed farmers reported using herbicides. Interviewed farmers reported spending 80-130 person- days/ha on weeding and redistribution. Corresponding values observed in monitored fields were lower: 20-103 person-days/ha with an average of 47 (Table 1). The difference between farmer-recalled and monitored values could be because the latter are based on an 8-h day, whereas the farmer might have reported 1 d of work irrespective of the amount of time spent in the field.

118 My et al Table 1. Labor for weeding and redistribution of dry seeded rice, in Long An. Region Labor (person-days/ha) and Weeding Redistribution Weeding Total plot before and weeding at after redistribution redistribution redistribution Region 1 1 – 15 5 20 2 – 15 7 22 3 – 40 40 80 4 10 13 – 23 5 20 23 – 43 6 – 20 35 55 7 10 55 – 65 8 – 17 12 29 9 12 8 20 40 10 12 28 – 40 Region 2 a 2 11 9 14 34 3 15 20 20 55 4 32 50 – 82 5 35 45 – 80 6 8 16 4 28 7 – 33 53 86 8 – 16 16 32 9 13 90 – 103 10 – 16 33 49 a Plot 1 in Region 2 was changed to wet seeding and so was not monitored.

The findings differ from previous reports in two aspects. First, labor (monitored) for weeding was less than reported elsewhere (90 person-days/ha by Fujisaka et al 1993; 72–83 person-days/ha by Fagi 1993). The difference could be due to methods of collecting data or different degrees of weediness. In Long An, because of low soil hydraulic conductivity and high water-table, dry seeded fields became flooded within 3–5 wk after emergence and remained flooded for the rest of the season (Fig. 8), which helped suppress weeds. Double rice cropping (or sometimes triple, in Region 2) might have also reduced the weed population by putting weeds under constant competition and repeated hand weeding throughout the year. Second, herbicide was not commonly used, as it was elsewhere (Saleh et al 1993) — possibly because herbicides were still expensive for farmers and hand-weeding was more economical as it was primarily done by family labor in Long An.

Variety, yield, and other inputs Table 2 summarizes the varieties used, yield, fertilizer, and labor input in the monitored fields. The listed varieties were also the commonly used ones as obtained from the survey and all were bred for the irrigated rice ecosystem. Interviewed farmers cited high yield and pest and disease resistance as the most important criteria for their choice of variety. Although duration was not included in their cited criteria, all selected varieties matured in 95–105 d — short duration is important for increasing cropping intensity (as discussed later). In the 1992 interviews, only 8% reported yields less than 3 t/ha, 66% from 3–5 t/ha, and 16% greater than 5 t/ha. These values were confirmed in monitored fields in 1993 where yields varied from

Dry seeded rice in Long An Province 119 8. Daily rainfall, field water depth (groundwater table depth if negative: groundwater depth was -160 cm on 19 May) during dry seeded rice cropping, 1993 wet season, Long An.

3.0 to 5.2 t/ha with an average of 4.3 t/ha (Table 2). No significant correlation was found between yield and plant density, fertilizer, or total labor input. Reasons for the lack of correlation, especially with fertilizer input, need further research.

Discussion

DSR in Long An was a very rainwater-efficient system. Because of early land preparation and crop establishment, almost all early-season rainfall was effectively used for crop growth. In 1993, the whole crop production cycle, from land preparation to harvest used only 700–900 mm of rainfall (Fig. 3). In transplanted rice, almost this much water is needed to puddle the soil (Valera 1977, Saleh et al 1993). Growing DSR was a way to increase cropping intensity. Farmers reported that the possibility of having a second crop was the main reason for growing DSR. Early establishment and short-duration varieties permitted DSR to be harvested as early as August (Fig. 3) and this early harvest left enough time and rainfall to support another rainfed crop in Region 1. Some farmers in Region 2 could also grow a third crop with supplemental irrigation during December–February. Had farmers in Long An transplanted the first rice crop, they would have had to wait, as is done with transplanted rice in other areas in the Mekong River Delta until late July, to complete the transplanting and a second rainfed rice crop would not have been possible because of the delay in harvest. Farmers in Long An also avoided extending the second crop in the dry season by speeding land preparation between crops — the turnaround time was 10–15 d. Labor saving and spreading of labor intensity at crop establishment also facilitated crop intensification. There was not enough labor to transplant the whole area in a short time, even if enough rainfall had been accumulated early enough.

120 Myet al Table 2. Varieties, seedling density, fertilizers, labor, and yield of dry seeded rice in Long An. Region Varieties Seedling Fertilizers (kg/ha) Total labor Yield and density (person- (t/ha) plot (plants/m 2) N P K days/ha) Region 1 1 IR19660 349 72 54 4 20 5.2 2 IR66 486 68 46 - 22 3.0 3 OM86-9a 420 80 57 - 80 3.5 4 OM86-9 456 65 40 - 23 4.5 5 OM86-9 370 52 22 4 43 4.5 6 OM86-9 338 71 47 - 55 4.1 7 OM86-9 414 77 55 - 65 5.2 8 OM86-9 298 56 46 - 29 3.2 9 lR19660 446 91 26 - 40 3.4 10 IR19660 363 107 26 - 40 3.6 Region 2 b 2 lR9729-67-3 512 119 69 31 34 5.3 3 lR49517-23 524 83 49 20 55 4.8 4 lR50404-57 620 79 40 5 82 5.1 5 OM86-9 570 79 40 5 82 3.9 6 lR9729-67-3 399 86 38 30 28 5.1 7 KSB218 598 76 92 - 86 4.4 8 lR50404-57 411 94 93 10 32 5.1 9 MTL103c 588 106 59 6 103 4.0 10 IR50404-57 541 95 74 - 49 4.6 a OM86-9 = lR32429-47. b Plot 1 in Region 2 was changed to wet seeding and so was not monitored. c MTL 103 = lR54751-2-34-10-6-2.

Early DSR establishment in Long An was possible due to good farmer-contractorarrangements that allowed the full use of the limited number of heavy tractors in the area. Cost of land preparation was, however, high and contributed about 20-25% of the total cost of production of DSR. Further research is needed to reduce the cost of land preparation without sacrificing the timeliness of the operation. Land preparation research should also combine with seeding research (for example, seeding depth and implements) aimed at increasing the emergence rate even when seeds remain in the soil more than 2 wk. New short-duration varieties that have high weed competitiveness and allow stable and early establishment are also needed.

References cited

Denning G L (1991) Intensifying rice-based cropping systems in the rainfed lowlands of Iloilo, Philippines: results and implications. Pages 109-142 in Planned change in farming systems: progress in on-farm research. R. Tripp, ed. Wiley. Chichester, UK. Fag A M (1993) Strategies for improving rainfed lowland rice production systems with emphasis on central Java. Paper presented at the International Symposium of the Rainfed Lowland Rice Research Consortium, Semarang, Central Java, Indonesia, 8-13 Feb 1993. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Fujisaka J S. Moody K, Ingram K T (1993) A descriptive study of farming practices for dry seeded rainfed lowland rice in India, Indonesia, and Myanmar. Agric. Environ. Ecosyst. 45(1-2):115-128. Furoc R E, Magbanua R D, Gines H C, Morris R A (1978) Identification of criteria for date dry-seeded rice planting. Paper presented at the 9th Annual Scientific Meeting of the Crop Science Societies of the Philippines, Iloilo City, 11-13

Dry seeded rice in Long An Province 121 May 1978. Federation of Crop Science Societies of the Philippines, University of the Philippines at Los Baños, College, Laguna, Philippines. Morris R A (1980) Tillage and seeding methods for dry-seeded rice. Paper presented at the Cropping Systems Conference, 1980, International Rice Research Institute, Los Baños, Philippines. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Saleh, A F M, Lantican M, Bhuiyan S I (1993) Prospects of increasing productivity in a moderately drought-prone rainfed lowland rice system from the farmers’ perspective. Paper presented at the International Symposium of the Rainfed Lowland Rice Research Consortium, Semarang, Central Java, Indonesia, 8–13 Feb 1993. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Tuong T P, Ingram K T, Siopongco J D, Confesor R B, Boling A A, Singh U, Wopereis M C S (1993) Performance of dry seeded rainfed lowland rice in response to agrohydrology and N-fertilizer management. Paper presented at the International Symposium of the Rainfed Lowland Rice Research Consortium, Semarang, Central Java, Indonesia, 8–13 Feb 1993. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Valera A (1977) Field studies on water use and duration for land preparation for lowland rice. PhD dissertation, University of the Philippines at Los Baños, College, Laguna, Philippines. Wickham T H, Singh V P (1978) Water movement through wet soils. Pages 337–357 in Soils and rice. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines.

122 My et al Effect of phosphorus and growing season on rice growth and nutrient accumulation on acid sulfate soils

Phan Thi Cong, 1 Cong Doan Sat, 1 E.G. Castillo, 2 and U. Singh 2

Abstract. The effect of phosphorus (P) and growing season on rice growth and nutrient accumulation on acid sulfate soils of Tan Lap (Moc Hoa District, Long An Province) was determined in the dry and wet seasons of 1993. Single superphosphate (SSP), diammonium phosphate (DAP), and thermophosphate (TP) were used as P sources and applied at 0, 60, 120, and 180 kg P2 O 5 /ha. Selected soil properties were analyzed before the experiment and after each harvest. At harvest, grain and straw yield, total dry matter, and nitrogen (N), P, and iron (Fe) uptake were determined. Efficiencies of nutrient uptake and fertilizer recovery were also computed. The soil had high P adsorption capacity (350 µg P/g soil to attain a solution P concentration of 0.02 µg P/ml). The availability of P (Bray II) at harvest increased with P rates and differed among sources. Application of TP increased pH and reduced KCI-extractable aluminum significantly. P application increased grain yield almost threefold (1.6 to 4.5 t/ha) in the dry season but only from 0.8 to 1.6 t/ha in the wet season. TP was superior to SSP and DAP in terms of yield and nutrient uptake over both seasons. The application of 60 kg P2 O5 /ha may be recommended as the optimum P rate but 120 and 180 kg P2 O5 /ha also improved N fertilizer recovery and efficiency significantly.

Rice is the single most important crop in Vietnam. It is planted on 82% of the total farm area and it accounts for more than 85% of food-grain output. Acid sulfate soils (ASS) occur in 40% of rice areas, and are found in large areas in the Plain of Reeds, the Plain of Ha Tien, and scattered areas elsewhere throughout the Mekong River Delta, covering some 1.6 million ha (IRRI 1993). The soil is rich in humus and total nitrogen (N) but low in phosphorus (P) and bases. Aluminum (Al), iron (Fe), and hydrogen sulfide (H 2 S) toxicities limit crop yield (Dent 1986). P is the most important nutrient element for crop growth on ASS. Fertilization, particularly P application, has resulted in decreased Fe 2+ uptake, and the P status of the plants significantly affects the Fe content of the leaves (Prade and Ottow 1988). However, application of P fertilizer may not improve crop growth because phosphates are strongly adsorbed in these soils. The response of crop to P varies with the soil, rate and source of phosphates, water management, and season. Therefore, the optimum P rate for ASS varies from site to site and over seasons. Information on changes in selected soil chemical properties over seasons would be useful in developing fertilizer-management practices. This study had four objectives: • To determine changes of selected soil parameters across seasons; • To determine the effectiveness of three commonly used sources of P on rice growth and yield; • To evaluate the effect of P rates on growth, nutrient uptake, and yield of rice in ASS; and • To develop and modify existing methods and tools for fertilizer-management practices on ASS.

1 Institute of Agricultural Sciences of South Vietnam, 121 Nguyen Binh Khiem Street. 1st District, Ho Chi Minh City, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Materials and methods

The trials were conducted in the dry (December 1992–April) and wet (May–September) seasons of 1993 on the ASS at the experimental station of Agricultural Research Center of The Plain of Reeds, Long An Province. The site is about 600 m northeast of provincial road no. 49 that links Tan Thanh town and Moc Hoa district (10°50' N, 105°57' E). Some chemical properties of the experimental soils are given in Tables 1 and 2.

Table 1. Properties of the soil of experimental site, Tan Lap, Moc Hoa District, Long An Province.

Depth (cm)

0–5 5–15 15–30 30–50 50–70

Texture (%) Sand 9.4 11.1 7.8 2.8 6.1 Silt 25.5 21.3 30.5 25.9 23.9 Clay 65.2 67.7 61.8 71.3 70.1

PH

H2O 4.1 3.9 3.9 3.8 3.8 KCl 3.6 3.5 3.5 3.5 3.4

C (%) 5.15 4.19 3.53 2.47 2.94

Total N (%) 0.44 0.30 0.30 0.25 0.23

Total P 2 O 5 (%) 0.09 0.05 0.04 0.03 0.03

Exchangeable cations (cmol/kg) Ca 2.40 1.85 1.80 2.05 2.50 Mg 1.40 1.55 1.75 1.80 1.90 K 0.35 0.26 0.26 0.31 0.24 Na 0.79 0.45 0.45 0.39 0.38

Base saturation (%) 24.82 22.30 22.00 23.80 20.70

Fe 2 O 3 (%) 0.42 0.24 0.28 0.76 0.54

Table 2. Selected chemical properties of the soil before transplanting.

+ - Depth P AI NH 4 NO 3 - (cm) (Bray II) (ppm) + NO 2 (ppm) Extractable Soluble (ppm) (cmol/kg) (ppm)

1st crop (dry season 1992/93) 0-5 29.6 8.3 231 31.6 4.5 5-1 5 7.9 9.8 217 22.4 2.3

2nd crop (wet season 1993) a 0-5 39.0 9.9 342 12.9 6.0 5-15 19.6 9.9 315 7.8 5.2

a From control (zero P) plot.

124 Cong et al A randomized complete block design with four replications was used with four P rates and three P Sources combined into 21 treatments (Table 3). The plot size was 6 × 4.5 m. Single superphosphate (SSP), diammonium phosphate (DAP), and thermophosphate (TP) were used as P sources, Total P fertilizer was applied 1 d before transplanting the dry season crop in all plots. The treatments were identical for the second crop (wet season) except for treatments 7, 8, 9, 13, 14, 15, 19, 20, and 21 where P was applied in two splits: two-thirds as basal and one-third at maximum tillering. N was added in three splits at 140 kg N/ha in the dry season and 120 kg N/ha for the wet season. Blanket application of 30 kg K2O/ha was done at panicle initiation. Three 20-d-old seedlings per hill of IR50404-2-2-3, a commonly grown variety, were transplanted at 15 × 15 cm hill spacing. Initial site characterization was done with the soil from five depths: 0-5, 5-15. 15-30, 30-50, and 50-70 cm. P levels at different soil depths were determined using the method of Fox and Kamprath (1970). Soil samples after crop harvesting were collected from the 0–5 cm and 5–15 cm for analysis of pH (1:2.5 soil and water slurry), electrical conductivity (EC, 1:2.5 soil and water slurry), available P (Bray II), and KCl-extractable and soluble Al. Part of each sample was kept moist and + stored in an ice chest during transport and storage for fresh extraction of KC1-extractable NH 4 and - NO 3 Bulk density of these soil samples was determined using the core method. Plant samples from 16 hills per plot were collected at maximum tillering, panicle initiation, heading, and maturity to determine tiller number, plant height, and dry weight. N, P, and Fe content of plant samples were determined at all sampling times. Yield components were determined from the 16-hill samples at harvest. Grain and straw yield were collected from a 5-m2 harvest area. Grain yields were expressed at 14% moisture content. Data on plant and soil samples were analyzed using the IRRISTAT program.

Results and discussion

Soil properties P-fixing capacity of the ASS at Tan Lap was high, particularly for the surface (0–5 cm) and 5–15 cm layers (Fig. 1). The high sorption is related to high organic matter, iron oxide, and Al contents (Tables 1 and 2). The high P requirement (350 m g P/g and 600 m g P/g) for the top layer of the ASS to attain solution P concentrations of 0.02 m g P/ml and 0.10 mg P/ml were similar to those for highly weathered Oxisols (Singh 1985) but were higher than reported for Rangsit ASS from Thailand (Attanandana and Vacharotayan 1991). After dry-season harvest. All three sources of P increased ( P < 0.0 1 ) availability of soil P (Bray 11) in the top soil layer when determined at harvest of dry-season rice (first crop) This increase occurred despite the high buffering capacity of the soil (Table 4). P content (Bray II) of the second layer, however, was statistically similar to that of the control treatment (zero P). The increase in soil P status at rice harvest due to P application (different sources and rates) was confined to the top 5 cm. Among the sources, this increase in available P was significantly higher with SSP and DAP than with TP (Table 4). After the dry-season harvest, pH, EC, and extractable and soluble Al contents of the soil did not differ significantly among the treatments. Because of tillage and rice cropping (and consequent changes in hydrology), however, the soluble Al content of the soil was higher at harvest than before transplanting (Tables 2 and 4). After wet-season harvest. The available soil P in the top (0–5 cm) layer after the harvest of wet-season rice was higher ( P < 0.01) because of the effect of P fertilizer sources and rates (Table 5). In terms of their effect on available P, all three P fertilizer sources were statistically similar after the wet-season harvest. The soil P status in the top layer increased significantly with each additional

Phosphorus and growing season 125 Table 3. Phosphorus treatments for the experiment.

Treatment P Treatment P

Source a Rate b Sourcea Rate b (kg/ha) (kg/ha)

1 – 0 11 DAP 120 2 – 0 12 TP 120 3 – 0 13 SSP 120s 4 SSP 60 14 DAP 120s 5 DAP 60 15 TP 120s

6 TP 60 16 SSP 180 7 SSP 60s 17 DAP 180 8 DAP 60s 18 TP 180 9 TP 60s 19 SSP 180s 10 SSP 120 20 DAP 180s 21 TP 180s

a Composition of P sources. SSP = 16.5% P 2O 5 + 16.1% CaO + 0.8% MgO DAP = 46% P 2O 5 + 2.38% CaO + 0.9% MgO + 18% N TP = 15% P 2O 5 + 32 3% CaO + 17.3% MgO b s = Split application of P for this treatment in wet season crop (two-thirds as basal and one-third at maximum tillering).

1. P adsorption by ASS at Tan Lap. increment of applied P. Although soil P content in the 5-15 cm layer increased with increasing rates of P application and for all sources, these differences were not statistically significant. Effect over two seasons. The responses of soil P content to P sources were different in the dry and wet seasons (Fig. 2). With SSP as the P source, the P content of the 0-5 cm layer was significantly higher after the dry season harvest than after the wet-season harvest. The difference in available P content between 0-5 cm and 5-15 cm layers at the end of both dry- and wet-season

126 Cong et al Table 4. Effect of different P sources and rates on selected soil properties a after dry-season rice harvest (first crop), Tan Lap, 1993.

pH EC (mS/cm) Available P (ppm)

0-5 5-15 P b 0-5 5-15 P b 0-5 5-15 P b cm cm cm cm cm cm

P source c

Zero P 3.74ab 3.73a ns 0.64a 0.84a ** 39.0c 19.6a ns SSP 3.74ab 3.76a ns 1.38a 0.86a ** 81.5a 29.9a ** DAP 3.69a 3.71a ns 1.43a 0.90a ** 76.5a 21.5a ** TP 3.80a 3.73a * 1.44a 0.89a ** 65.3b 22.2a **

cv (%) 3.2 29.6 29.9

P rate (kg P 2O 5 /ha) 0 3.77a 3.73a ns 1.64a 0.84a ** 39.0c 19.6a ns 60 3.72a 3.69a ns 1.34a 0.80a ** 56.0bc 22.1a ** 120 3.74a 3.76a ns 1.43a 0.86a ** 63.6b 24.0a ** 180 3.78a 3.75a ns 1.49a 0.98a ** 103.8a 30.7a **

cv (%) 3.2 29.6 29.9

Extractable Al (cmol/kg) Soluble AI (ppm)

0-5 5-15 P b 0-5 5-15 P b cm cm cm cm

P source c

Zero P 9.91a 9.89a ns 342a 315a ns SSP 9.22a 9.92a * 332a 305a ns DAP 9.80a 10.80a ** 329a 288a ns TP 9.01a 10.23a ** 302a 295a ns

cv (%) 12.6 18.4

P rate (kg P 2O 5/ha) 0 9.90a 9.89a ns 342a 315a ns 60 9.47a 10.50a ** 329a 271a * 120 9.39a 9.90a ns 331a 314a ns 180 9.18a 10.55a ** 304a 304a ns

cv (%) 12.6 18.4

a Within a column for P sources or P rates, means followed by a common letter do not differ significantly at the 5% level by Duncans’s multiple range test. b P = probability that the difference between two depths is significant: ns, not significant: *, significant at 5% level; and **, significant at 1% level c Zero P, no P fertilizer, SSP, single superphosphate; DAP, diammonium phosphate: and TP, thermophosphate. harvests was greater ( P < 0.01) on application of P fertilizer (Fig. 2). However, after two seasons of rice crops, the available P content in the top two layers in the zero P treatment was statistically similar to the initial condition. After two seasons, TP application had a significant effect in increasing soil pH and reducing extractable Al (Table 5). Almost 50% of the composition of TP fertilizer is oxides of Ca and Mg and

Phosphorus and growing season 127 Table 5. Effect of different P sources and rates on selected soil properties a after wet-season rice harvest (first crop), Tan Lap, 1993.

pH EC (mS/cm) Available P (ppm)

0-5 5-15 P b 0-5 5-15 P b 0-5 5-15 P b cm cm cm cm cm cm

P source c

Zero P 3.88b 3.75ab * 0.45a 0.53a * 24.9b 10.9a ns SSP 3.91b 3.72b ** 0.47a 0.48a ns 70.5a 18.3a ** DAP 3.96b 3.71b ** 0.44a 0.47a ns 66.9a 17.6a ** TP 4.07a 3.83a ** 0.48a 0.49a ns 67.5a 16.9a **

cv (%) 3.3 14.6 37.4

P rate (kg P 2 O 5 /ha)

0 3.88b 3.75a * 0.45ab 0.54a * 24.9d 10.9a ns 60 3.92b 3.69a * 0.43b 0.46a ns 46.9c 11.2a ** 120 4.03a 3.78a * 0.49a 0.50a ns 72.0b 20.5a ** 180 3.98ab 3.78a * 0.47ab 0.48a ns 86.1a 21.0a **

cv (%) 3.3 14.6 37.4

Extractable AI (cmol/kg) Soluble Al (ppm)

0-5 5-15 P b 0-5 5-15 P b cm cm cm cm

P source c

Zero P 7.42a 9.93a ** 345a 383a ns SSP 7.39a 10.13a ** 367a 362a ns DAP 7.57a 10.23a ** 340a 370a ns TP 6.45b 9.78a ** 318a 333a ns

cv (%) 10.8 24.2

P rate (kg P 2 O 5 /ha)

0 7.42a 9.93a ** 345a 383a ns 60 7.48a 10.27a ** 359a 333a ns ** 120 6.95a 9.81a 322a 380a * 180 6.98a 10.00a ** 343a 353a ns

cv (%) 10.8 24.2

a Within a column for P sources or P rates, means followed by a common letter do not differ significantly at the 5% level by Duncans’s multiple range test. b P 1 probability that the difference between two depths is significant: ns, not significant; *, significant at 5% level; and **, significant at 1% level. c Zero P, no P fertilizer; SSP, single superphosphate; DAP, diammonium phosphate: and TP, thermophosphate. this may explain the observed rise in pH and the corresponding decline in extractable Al. After the harvest of dry-season rice (first crop), extractable Al in the top layer was negatively correlated with pH and available P (Table 6). The correlation between these variables was stronger at the end of the wet-season rice (second crop), The negative correlation of extractable Al with available P illustrates the “liming effect” of applied P. P application also resulted in more significant differences between the top two layers with respect to pH and extractable Al.

128 Cong et al 2. Available P at fertilizer rate of 180 kg P 2 O 5/ha through two cropping seasons.

Table 6. Correlation a matrix of selected soil properties.

EC Available Extractable Soluble P AI Al

After harvest of dry-season crop

PH 0.036ns 0.037ns -0.624** 0.077ns EC 0.588** -0.211ns 0.268* Available P -0.292** -0.027ns Extractable Al -0.165ns

After harvest of wet-season crop

PH 0.019ns 0.612** -0.799** -0.128ns EC 0.009ns -0.089ns 0.014ns Available P -0.758** 0.020ns Extractable AI 0.070ns

a Coefficients of correlation (Pearson's r ) are nonsignificant (ns), significant at P < 0.05 (*), or significant at P < 0.01 (*).

The available P content of the soil was statistically similar after the dry- and wet- season harvests (Tables 4 and 5). Soluble Al contents were also similar at the end of first and second rice crops. On the other hand, EC and extractable Al showed highly significant decreases after the second crop. The opposite effect was observed with pH. Some of these changes were cumulative effects of P addition (extractable Al and pH) whereas the decline in EC may be attributed to leaching of soil solution during the wet season. The lack of apparent change in soil P status at end of the first and second crops, for a given P treatment, may be a result of plant uptake and high P fixation in ASS. The available NH 4- N concentration at 0–5 cm declined from 3 1.1 m g N/g at the beginning of the dry season to 12.6 m g N/g after the dry-season harvest and to 7.5 m g N/g at the end of the wet- season harvest (data not shown). Similar depletion of NH 4 -N was observed in 5–15 cm layer with NH 4- N concentration declining from 22.6 m g N/g at transplanting to 12.0 m g N/g at the end of the first crop

Phosphorus and growing season 129 Table 7. Effect of different P sources and rates on yield and uptake a at maturity in dry-season rice, Tan Lap, 1993.

Uptake (kg/ha)

Grain Straw Total

N P Fe N P Fe N P Fe

P sourceb

Zero P 23.5c 5.6c 0.48d 20.5c 2.5d 1.02d 42.1c 8.0d 1.36d SSP 49.6b 19.0b 0.71c 38.9ab 6.1c 4.44c 88.5b 25.0c 5.14c DAP 53.5a 19.8b 1.04a 36.0b 7.0b 5.75a 89.6b 26.7b 6.78a TP 56.6a 24.1a 0.88b 41.2a 8.2a 5.24b 97.8a 32.3a 6.12b

cv (%) 7.9 7.9 7.7 16.9 16.5 17.3 6.2 6.0 10.0

P rate (kg P 2 O 5 /ha)

0 23.5c 5.6d 0.48c 20.5c 2.5c 1.02c 42.1c 8.0d 1.36c 60 50.9b 17.4c 0.82b 38.2b 6.8b 5.47a 89.2b 24.2c 6.28a 120 52.3b 20.8b 0.80b 36.0b 6.6b 5.63a 88.3b 27.4b 6.43a 180 56.6a 24.7a 1.01a 41.8a 7.8a 4.32b 98.4a 32.5a 5.34b

cv (%) 7.9 7.9 7.7 16.9 16.5 17.3 6.2 6.0 10.0

Yield (kg/ha) Plant height Tillers (cm) (no/m 2 ) Grain Straw (dry (14% mc) c weight)

P source b

Zero P 1,654c 1,679d 47.8c 346c SSP 4,079b 4,116c 59.1b 484b DAP 4,334b 4,538b 58.9b 497ab TP 4,840a 5,098a 63.3a 527a

cv (%) 7.9 10.1 4.9 11.0

P rate (kg P 2O 5 /ha) 0 1,654c 1,679d 47.8d 346b 60 4,120b 4,024c 56.5c 495a 120 4,277b 4,616b 60.3b 511a 180 4,856a 5,112a 64.3a 501a

cv (%) 7.9 10.1 4.9 11.0

a Within a column for P sources or P rates, means followed by a common letter do not differ significantly at the 5% level by Duncan's multiple range test. b Zero P, no P fertilizer; SSP, single superphosphate; DAP, diammonium phosphate; and TP, thermophosphate c mc, moisture content. and 6.7 µg N/g after the second crop. P fertilization did not affect soil-NH 4 status statistically although NH 4 -N content was higher in the zero P treatment

Grain yield, growth components, and nutrient uptake Dry-season rice. The application of P fertilizers to the dry-season rice not only resulted in improved P status of the soil but also gave higher grain yield, straw dry weight. total N and P accumulation, total

130 Cong et al grain uptake of P and N, straw uptake of P and N, and number of tillers ( P < 0.01). The grain yield increase due to the three P sources was 2.5–3-fold higher (Table 7). Performances of SSP and DAP were statistically similar and somewhat inferior to TP with respect to the grain yield, total N uptake, and grain P uptake. For straw yield, P uptake by straw, and total P accumulation responses the fertilizers were ranked TP > DAP > SAP (Table 7). The highest grain yield, straw weight, and N and P uptake were obtained with the highest P fertilization rate (180 kg P2 O 5 /ha). However, the optimum economic rate may be closer to 60 kg P2 O 5 /ha. The strong response to P application confirmed the limiting effect of P on crop growth in ASS. The high N accumulation in plants with P addition also indicates the need for N application if the full benefit from P application is to be realized. The higher uptake of N as a result of P fertilization may result from enhanced root growth and distribution and hence uptake capability, from greater plant N demand, and from higher soil N mineralization. Higher grain yield with TP fertilizer may be attributable to its high composition of bases (oxides of Ca and Mg). High base content reduced extractable Al in soil (Tables 4 and 5) and may have reduced P fixation by short-order (amorphous) Fe by reacting with it. The reduction in reactive Fe content of the soil is illustrated by the reduction in the total Fe uptake at 180 kg P2 O 5 /ha despite the high plant biomass at that rate (Table 7). The ranking of the fertilizers for Fe uptake was TP < SAP < DAP, whereas it was reversed for their base composition, TP > SSP > DAP. Although P is the major yield-limiting nutrient in ASS, Fe toxicity would be one of the major causes of yield loss in these soil. Thus, the positive effect of P fertilization and P sources with a high base content may be attributed to reduction in Fe toxicity as well as supply of P. Past research has shown reduction in Fe toxicity with P and K application (Benckiser et al 1984). Thus, dosage of P should not be based entirely on optimum economic rate but must consider positive effects of toxicity amelioration and high residual effect. The Fe content of young rice plants (21 d after transplanting) declined with increasing level of P application (Fig. 3) — TP was particularly effective in reducing Fe content of the plant. In our experiment, by providing 30 kg K2 O/ha at panicle initiation, we eliminated K deficiency and so reduced Fe toxicity during the physiologically active phase of plant growth. Wet-season rice. Grain yield and all crop growth parameters increased significantly with P application for the wet-season rice crop also (Table 8). However, the absolute increase in yield was

3. Plant Fe concentration at 21 d after transplanting (1993 dry season) at four levels of P fertilizer.

Phosphorus and growing season 131 Table 8. Effect of different P sources and rates on yield and uptake a at maturity in wet-season rice, Tan Lap, 1993.

Uptake (kg/ha)

Grain Straw Total

N P Fe N P Fe N P Fe

P source b

Zero P 12.2c 2.5c 0.18c 18.2c 2.8d 1.72c 30.4b 5.4c 1.9c SSP 16.5b 7.2b 0.27a 24.6b 6.5c 3.15a 43.3b 15.4b 3.4a DAP 16.6b 7.1 b 0.23b 24.4b 8.9b 2.95ab 42.4a 14.8b 3.2ab TP 20.0a 10.3a 0.21 bc 27.6a 10.2a 2.85b 43.9a 20.0a 3.0b

cv (%) 17.6 18.9 19.9 12.8 13.6 13.8 12.6 13.9 13.4

P rate (kg P 2 O 5 /ha)

0 12.2b 2.5c 0.18b 18.2b 2.8c 1.72c 30.4c 5.4d 1.9c 60 17.7a 6.7b 0.22b 25.6a 8.2b 2.61b 41.1b 13.2c 2.8b 120 17.5a 8.9a 0.23b 24.9a 7.6b 2.60b 41.0b 17.8b 2.8b 180 17.9a 9.0a 0.27a 26.0a 9.7a 3.73a 47.6a 19.3a 4.0a

cv (%) 17.6 18.9 19.9 12.8 13.6 13.8 12.6 13.9 13.4

Yield (kg/ha) Plant Tillers height (cm) (no/m2) Grain yield Straw (dry (14% mc) c weight)

P source b

Zero P 818c 1,679c 51c 139.4c SSP 1,329b 2,913b 59ab 173.0b DAP 1,333b 2,930b 57b 185.4b TP 1,665a 3,429a 61 a 214.8a

cv (0.6) 17.7 12.8 7.3 19.3

P rate (kg P2O5/ha)

0 818c 1,679c 51c 139.4b 60 1,378a 2,922b 57b 193.6a 120 1,454a 3,096ab 60a 188.4a 180 1,495a 3,254a 59a 191.2a

cv (%) 17.7 12.8 7.3 19.3

a Within a column for P sources or P rates, means followed by a common letter do not differ significantly at the 5% level by Duncan's multiple range test. b Zero P, no P fertilizer; SSP, single superphosphate; DAP, diammonium phosphate; and TP, thermophosphate. c mc, moisture content.

significantly lower than during the dry season. Although grain yield increased up to 180 kg P 2 O 5 /ha, it was statistically similar at 60 P 2 O 5 /ha. Responses to DAP and SSP were similar and TP remained the best P source. Split application of P did not have any advantage over single basal application (data not shown). However, with DAP, split application at 60 kg P 2 O 5 /ha gave lower yield, total dry matter, total N accumulation, and total Fe uptake ( P < 0.05). The low yield may be attributed to lower basal P rate

132 Cong et al 4. Plant Fe concentration at 21 d after transplanting with TP fertilizer (1993 dry and wet seasons).

Table 9. Effect a of different phosphorus sources and amounts on recovery and efficiency of N and P at maturity in dry-season rice.

Apparent recovery b (%) Physiological use Agronomic efficiency use efficiency

N P N P P

P source c

Zero P 30.1c – 39.6c 205.1 a – SSP 63.2b 16.0c 46.6b 163.9b 23.8b DAP 64.0b 18.0b 48.5ab 162.6b 26.6b TP 69.9a 22.6a 49.6a 151.6c 30.4a

cv (%) 6.2 8.6 5.6 3.9 12.7

P rate (kg P 2 O 5 /ha) 0 30.1c – 39.6c 205.1 a – 60 63.7b 26.91a 46.5b 171.5b 41.1a 120 63.1b 16.17b 48.7ab 156.6c 21.9b 180 70.3a 13.60c 49.4a 149.9d 17.8c

cv (%) 6.2 8.6 5.6 3.9 12.7

a Within a column for P sources or P rates, means followed by a common letter are not significantly different at the 5% level by Duncan's multiple range test. b Apparent recovery of N was not corrected for N uptake with no N fertilization. c Zero P, no P fertilizer; SSP, single superphosphate; DAP, diammonium phosphate; and TP, thermophosphate.

(40 kg P 2 O 5 /ha) applied at the time of transplanting when Fe and Al content in the soil is high, particularly, in the wet season. The mean grain yield for wet-season rice was 1.4 t/ha and for dry-season 4.1 t/ha. The corresponding straw weights at maturity were 3.0 t/ha and 4.3 t/ha. The large difference in harvest Index between the wet and dry seasons may be attributed to high rainfall. low solar radiation, high

Phosphorus and growing season 133 Table 10. Effect a of different phosphorus sources and amounts on recovery and efficiency of N and P at maturity in wet season rice.

Apparent Physiological Agronomic recovery b (%) use efficiency use efficiency

N P N P P

P source c

Zero P 25.3c – 26.4c 149.5a – SSP 34.3b 11.8b 32.3b 89.0bc 5.81b DAP 34.2b 12.1b 32.8b 90.8b 6.46b TP 39.6a 16.1a 34.9a 85.5c 9.03a

cv (%) 12.6 16.0 8.9 7.7 36.8

P rate (kg P 2 O 5 /ha)

0 25.3c – 26.4c 149.5a – 60 36.1a 17.9a 31.8b 104.5b 10.9a 120 35.4a 12.8b 34.4a 83.4c 6.1b 180 36.6a 9.3c 33.7a 77.4d 4.3c

cv (%) 12.6 16.0 8.9 7.7 36.8

a Within a column for P sources or P rates, means followed by a common letter are not significantly different at the 5% level by Duncan's multiple range test. b Apparent recovery of N was not corrected for N uptake with no N fertilization. c Zero P, no P fertilizer; SSP, single superphosphate; DAP, diammonium phosphate; and TP, thermophosphate.

respiration (little difference between day and night temperatures), and water management. Before the wet-season rice crop is planted, the field is dry for over 1 mo whereas the dry-season planting is delayed until the floodwater subsides. Thus, the inundation of the soil for wet-season planting would result in an increase in Fe 2+ during the early phase of rice growth. The run-on into the field and canal water also have toxic levels of Fe 2+ and soluble Al. The net effect of these influences was to double, approximately, the concentration of Fe in the young rice plant during the wet season when compared with the dry season (Fig. 4).

Nutrient recovery and use efficiency The uptake of both P and N at maturity was increased as a result of P application rates as well as with different P sources. The interactive increase in plant P and N accumulation at different combinations of P and N rates on ASS for Hoa An is reported by Guong and coworkers (this volume, page 151). The apparent recovery of P, defined as the difference in P uptake on P fertilized and P unfertilized plots as a percentage of the amount of P applied, was significantly higher for TP followed by DAP then SSP over both seasons (Tables 9 and 10). The agronomic P use efficiency (kg grain yield increase per kg P applied) was also consistently higher for TP over both seasons (Tables 9 and 10). The low recovery and uptake from SSP and DAP, however, led to higher physiological use efficiency of P (kg grain produced per kg uptake of P), As expected, the P recovery and agronomic use efficiency declined with increasing rates of P application. Across the seasons, the recovery, agronomic use efficiency, and physiological use efficiency of both P and N were significantly higher during the dry season. The N recoveries given in Tables 9 and 10 were not corrected for N uptake from zero N plots so that the true recovery values are higher. The relative increases, however, showed significantly higher

134 Cong et al recovery with TP in both seasons. The recovery of N was higher ( P < 0.01) with P than without P application and was improved with increasing rates of P. Similar increases in physiological N use efficiency were obtained with different P sources and P amounts applied. The results reconfirmed earlier findings that P application results in better utilization of other nutrients (Prade and Ottow 1986).

Conclusions

The P adsorption isoline for ASS at Tan Lap shows that the soil had high P adsorption capacity in the top $0–5 cm layer (350 m g P/g soil needed to attain solution P concentration of 0.02 m g/ml). The availability of P increased with P rates and P sources at the end of cropping seasons. Application of TP resulted in a significant increase in pH and reduction in KCl-extractable Al. In the dry season, P application resulted in an almost three-fold increase in yield (1.6 to 4.5 t/ha). The increase in yield due to P application was 0.8–1.6 t/ha in the following wet season. Among P sources, TP was superior to SSP and DAP in terms of yield and nutrient uptake in both seasons.

Although 60 kg P2O5/ha may be recommended as the optimum P rate in the wet season, a higher rate is desirable, particularly during the dry season, to get a better yield as well as to improve the soil. At P rates of 120–180 P 2O 5/ha, efficiency and recovery of N fertilizer also significantly improved. The development and refinement of existing methods to extrapolate results to other ASS should be the focus of future research.

References cited

Attanandana T, Vacharotayan S (1991) Nitrogen and phosphorus fertilization of acid sulfate soils of Thailand. Pages 185-189 in Production on acid soils of the tropics. P. Deturck and F.N. Ponnamperuma, eds. Institute of Fundamental Studies, Kandy, Sri Lanka. Benckiser G, Ottow J C G, Watanabe I, Santiago S (1984) The mechanism of excessive iron-uptake (iron toxicity) of wetland rice. J. Plant Nutr. 7:177-185. Dent D (1986) Acid sulphate soils: a baseline for research and development. Pages 82-83 in International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Pub. 39. Fox R. L, Kamprath E J (1970) Phosphate sorption isotherms for evaluating the phosphate requirement of soils. Soil Sci. Soc. Amer. Proc. 34:902-907. IRRI —International Rice Research Institute (1993) IRRI rice almanac 1993-1995. P.O. Box 933, Manila 1099, Philippines. 142 pp. Prade K, Ottow J C G (1988) Excessive iron uptake (iron toxicity) by wetland rice ( Oryza sativa L.) on an acid sulphate soil in the Casamance, Senegal. Pages 150-162 in H. Dost, ed. International Symposium on Acid Sulfate Soils, Dakar, Senegal. 1986. International Institute for Land Reclamation and Improvement, Wageningen, Netherlands. Singh U (1985) A crop growth model for predicting corn ( Zea mays. L) performance in the tropics. PhD thesis, University of Hawaii. USA. Univ. Mcrofilms Int., Am Arbor. MI. 389 pp.

Phosphorus and growing season 135

Improving nitrogen-use efficiency of direct- seeded rice on alluvial soils of the Mekong River Delta

Ngo Ngoc Hung, 1 U. Singh, 2 Vo-Tong Xuan, 1 R.J. Buresh, 3 J.L. Padilla, 2 Tran Thanh Lap, 1 and Truong Thi Nga 1

Abstract. Field experiments were conducted in 1989-92 in the Mekong River Delta of southern Vietnam. Nitrogen (N) management practices were studied in broadcast- seeded flooded rice, which is becoming an increasingly popular alternative to transplanting in this region. Plant density and timing, method, and rate of urea application were studied. N losses from urea (28 and 18%) were less than those normally reported for transplanted rice. Delaying the first application of urea until 10 d after seeding (DAS) has no adverse effect on yield of broadcast-seeded rice. Diammonium phosphate (DAP) and urea plus single superphosphate (SSP) were equally effective fertilizer sources. In the normal soil, 150 kg seed/ha is suggested for broadcast-seeded rice and close transplanting spacing (15 × 1.5 cm) is suggested for transplanted rice in acid sulfate soils. The different split applications of urea did not give differences in grain yield and N uptake.

Under irrigated conditions, rice is planted either by direct seeding or by transplanting in the Mekong River Delta (MRD) of southern Vietnam. Direct seeding has been adopted as the most efficient method of planting rice because of the availability of cost-efficient herbicides and where labour supply is limited. Urea is the main nitrogen (N) fertilizer applied to lowland rice in the MRD. However, information on the fate of N in broadcast-seeded flooded rice is limited. In numerous studies, only 20–40% of the applied N was recovered by the crop (De Datta 1986, Vlek and Byrnes 1986), because of extensive losses due to inadequate fertilizer management. Ammonia (NH 3 ) volatilization is a major cause of N loss from urea applied to tropical flooded rice (Mikkelsen et al 1978, Fillery et al 1984). Although thorough incorporation of urea into the soil without standing water, before transplanting, reduces the loss of NH 4 -N, the total N loss may still be substantial (De Datta et al 1987). In the MRD, however, many farmers do not apply N fertilizer as a basal incorporated treatment. A three-split N fertilizer is usually broadcast into the floodwater when the crop is established, about 10 d after sowing (DAS) the rice. In some cases, these farmers applied diammonium phosphate (DAP) as a one-third basal N dose. Application of urea in three splits rather than two or a single application promoted better crop growth and, thus, more efficient use of applied N with less risk of massive N loss through NH 3 volatilization, denitrification, and leaching (De Datta 1986). Patrick and Reddy (1976) found that split applications of fertilizer N resulted in higher recovery of N in the grain and straw and increased overall recovery over a single application. In studies on direct-seeded rice, Norman and Wells (1985) found that three top dressings of urea gave higher plant 15N recoveries

1 University of Cantho, Cantho. Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 3 International Center for Research on Agroforestry, P.O. Box 30677, Nairobi, Kenya. than a single preplant application. Research has demonstrated the importance of split application for reducing losses of fertilizer N. However, suitable N rate and split-application methods need to be studied more in the MRD to determine the best N management practices. The objectives of this study were fivefold: • To determine a 15N balance for applied urea; • To examine the effect of urea timing on response of rice to urea; • To compare the effectiveness of DAP and urea plus single superphosphate (SSP) as fertilizer sources for rice; • To determine the seeding rate and transplanting spacing for rice; and • To examine the split fertilizer-application methods for broadcast-seeded flooded rice in the MRD.

Materials and methods

Experiment I (dry season 1989/90) Four field experiments were conducted with broadcast-seeded flooded rice in the MRD. Table 1 shows the soil properties of the experimental sites. Experiments were established in a randomized complete block design with 12 treatments and 4 replications on 20 m 2 plots. Treatments included no applied urea and 50, 100, 150, 200, and 250 kg urea-N/ha applied as either an early or a delayed split. For the early split (ES), one-third of the urea

Table 1. Soil properties in the top 20 cm at experimental sites. a

Parameter Cantho Cai Lay Long Ho Binh Duc

pH 4.2 5.9 5.0 6.6 Organic C (g/kg) 2.8 10 28 10 Total N (g/kg) 2.5 1.2 2.5 1.3 CEC (cmol c /kg) 19 26 22 14 Clay (%) 42 67 68 42 Silt (%) 56 30 31 57

a Soil classification: Cantho, Thapto-Histic-Sulfic Fluvaquent; Cai Lay, Typic Tropaquept; Long Ho, Typic Tropaquept; Binh Duc, Typic Fluvaquent.

Table 2. Effect of urea timing on fate of 150 kg 15 N-labeled urea-N/ha at maturity of broadcast- seeded lowland rice, Cantho.

N timing 15 N recovery (% of applied N) Unrecovered (DAS) a 15N Grain Straw Root Soil depth (cm) (%)

0-5 5-15 15-30

10 15 11 1.9 20 1.9 1.1 49 20 33 19 2.1 17 2.7 1.8 25 44 44 28 1.4 13 1.3 1.1 11 LSD b (0.05) 21 5 ns ns 1.0 0.6 25

a DAS, days after sowing. b LSD, least significant difference; ns, not significant.

138 Hung et al was broadcast and incorporated into mud using rakes without standing water before sowing, one-third was topdressed at 20 DAS, and one-third was topdressed at 44–45 DAS For the delayed split (DS), one-third of the urea was broadcast into 5 cm of standing water at 10 DAS, one-third topdressed at 20 DAS, and one-third was topdressed at 14–15 DAS. In an additional ES treatment with 150 kg N/ha, the basal application of urea was replaced by diammonium phosphate (DAP). All treatments received 37 kg P/ha: the P was applied as single superphosphate (SSP) in all treatments except the DAP treatment in which P was applied as both DAP and SSP. The short-statured, modern rice variety IR66 was used and pregerminated seeds were sown at 200 kg/ha. The 15N balances were obtained from microplots (80 × 80 cm) in the 150 kg urea-N/ha treatment with DS application at Cantho and Cai Lay. At Cai Lay, each plot contained one microplot that received 15 N-labeled urea for each of the three application timings. At Cantho, each plot contained three microplots that received 15N -labeled urea for only one of the three N applications. Unlabeled urea was applied to microplots for the other two applications.

Table 3. Effect of location on fate of 150 kg 15 N-labeled urea-N/ha at maturity of broadcast- seeded lowland rice.

Location 15 N recovery (% of applied N) Unrecovered 15 N (%) Grain Straw Root Soil depth (cm)

0-5 5-1 5 15-30

Cantho 31 19 1.8 17 1.9 1.3 28 Cai Lay 27 35 2.4 14 2.6 0.7 18 S E a 4.8 1.9 0.5 1.5 0.5 0.1 7.2

a SE, Standard error of the mean.

Table 4. Combined analysis of variance for four locations. a

Source of df Mean squares variation Grain Straw Harvest Weight Filled Panicles Spikelets yield yield index per spikelets seed

Location (L) 3 154.89** 108.61** 0.4959** 257.45** 5,963** 12,063** 709** No N versus N (N) 1 43.05** 163.48 0.0072 2.79* 1,355** 26 2,395 Urea versus DAP (D) 1 0.20 3.09 0.0011 0.44 5 1 32 Among urea 9 3.79** 22.61** 0.0267** 3.20** 452** 67 183** Urea rate (U) 4 7.83** 45.51** 0.0586** 6.77** 1,007** 18 338** Urea timing (T) 1 0.69 10.92** 0.0026 0.01 42 514* 240* U x T 4 0.52 2.64 0.0009 0.43 1 3 13 L x N 3 2.63** 11.73** 0.0016 1.51* 116** 174 27 L x D 3 0.07 1.46 0.0012 0.21 43 65 56 L x U 12 2.06** 14.14** 0.0085** 1.15** 96** 85 81* L x N 3 0.09 2.43 0.0008 0.20 33 233* 169** L x U x T 13 0.21 0.62 0.0009 0.18 19 40 39

a *,** Significant at 0.05 and 0.01 probability levels, respectively.

N efficiency in direct seeded rice 139 Experiment II (dry season 1990/91) Four field experiments were conducted with broadcast-seeded rice in three sites, Cantho, Binh Duc, and Cai Lay, and transplanted rice in one site, Hoa An. The soil types for broadcast-seeded rice in those three sites were the same as those in experiment I. The Hoa An soil is classified as a Sulfic Tropaquept. The characteristics of the soil in the top 20 cm include pH (1:1 soil:water), 4.1; organic matter, 7.8%; total N, 0.38%; total P, 0.01% P 2 O 5 ; available P, 6.3 mg P 2 O 5 /100 g soil; and electrical conductivity (EC), 0.9 mmhos/cm. Experiments were established in a randomized complete block design with 4 replications and 12 treatments and a plot size of 20 m 2 . For the three broadcast-seeded rice sites, treatments were formed by two seeding rates (150 and 250 kg seed/ha) combined with six N rates (0, 40, 80, 120, 160, and 200 kg N/ha as urea). For the transplanted rice experiment, treatments were formed by two transplanted spacings (20 × 20 and 15 × 15 cm) and the same six N rates. Urea-N was applied in three equal splits: one-third at 10 DAS, one-third at 20 DAS, and one-third at 45 DAS. Supplemental fertilization was 60 kg P 2 O 5 /ha as SSP and 40 kg K 2 O/ha as KCl. IR66 was used for all four sites.

Experiment III (dry season 1991/92 and wet season 1992) Two field experiments were conducted with broadcast-seeded rice in Binh Duc and Cantho for dry season and wet season. The soil types were the same as those in experiment I. Experiments were established in a randomized complete block design with eight treatments and four replications and a plot size of 20 m2. Treatments (1) to (5) were 0, 40, 80, 120, and 160 kg urea- N/ha applied in three equal splits. Three additional treatments at an N rate of 80 kg N/ha with split applications were treatment (6) N applied in three splits, one-sixth, one-third, and one-half at 10, 20, and 45 DAS; treatment (7) N applied in three splits: one-sixth, one-half, and one-third at 10, 20, and

Table 5. Effect of urea timing on yield and yield components of broadcast seeded lowland rice.

Urea timing

Early Delayed P a

Grain yield (t/ha) b 5.5 5.6 ns Straw yield (t/ha) b 8.9 9.5 ** Harvest index b 0.38 0.37 ns Weight per seed (mg/seed) b 25 25 ns Filled spikelets (%) b 78 77 ns

Panicles (no./m 2 ) Cantho 458 565 ** Cai Lay 898 920 ns Long Ho 709 727 ns Binh Duc 639 636 ns

Spikelets (no./panicle) Cantho 45 36 ** Cai Lay 41 41 ns Long Ho 39 37 ns Binh Duc 47 47 ns

a P, probability that the difference between treatment timings were significant: **, at the 0.01 probability level; and ns, not significant. b Values are means for four locations.

140 Hung et al 45 DAS; and treatment (8) N applied in four splits: one-sixth, one-third, one-third, and one-sixth at 10, 20, and 45 DAS and heading. Pregerminated seeds of IR64 were broadcasted at 200 kg/ha. Supplemental fertilization with basal incorporation 1 d before seeding was P as SSP at 60 kg P 2 O 5 /ha and K as KCl at 40 kg K 2 O/ha.

Results and discussion

Experiment I Nitrogen-15 balance. Recovery of 15 N in the grain increased to 44% of applied N for the 44 DAS with increasing delay in application of the urea. However, recovery at 44 DAS was not significantly different from that for the 20 DAS treatment (Table 2). The pattern of 15 N recovery in the straw was the same but each increase was significant. When N fertilizer was surface broadcast at the panicle initiation (PI) stage, plant recovery of N was considerably higher than when it was surface broadcast at transplanting or at the early tillering stage (Zhu 1987); the reverse was true for N loss, which was very nigh (49%) for 10 DAS and lower (11%) for 44 DAS. From 17-25% of the fertilizer N was

1. Effect of urea timing and location on yield of lowland rice, dry season 1989/90.

N efficiency in direct seeded rice 141 retained in the soil and roots and there were no differences in 15 N recovery among timings. Distribution of 15 N in the soil plus roots suggests that leaching was not an important loss mechanism and, therefore, the N loss in this case is presumed to be due to NH 3 volatilization and denitrification. In comparing 15 N balances for Cantho and Cai Lay (Table 3), the retained fertilizer N in the soil and roots was not much different (17% and 14%, respectively, in the topsoil). However, the crop

Table 6. Effect of seeding rate on grain yield and yield components of lowland rice in the Mekong River Delta, dry season 1990/91.

Seeding rate (kg seed/ha) a

150 250 P b (1) (2)

Weight per seed (mg/seed) c 21 21 ns Filled spikelets (%) c 76 76 ns Grain yield (t/ha) Binh Duc 5.1 5.0 ns Cantho 5.2 4.9 * Hoa An 2.9 3.9 ** Cai Lay 5.3 5.3 ns

Panicles (no./m 2 ) Binh Duc 528 554 ns Cantho 814 1,088 ** Hoa An 499 651 ** Cai Lay 685 672 ns

Spikelets (no./panicle) Binh Duc 26 24 ns Cantho 42 31 ** Hoa An 56 54 ns Cai Lay 35 35 ns

a At Hoa An, rice was transplanted (not seeded) at two spacings: 1, 20 × 20 cm and 2, 15 × 15 cm. b P, probability that the seeding rates differed was significant; **, at the 0.01 level: *, at the 0.05 level; and ns, not significant at the 0.05 level. c Values are means for four locations.

Table 7. Effect of N rate on grain yield of rice at four experimental sites in the Mekong River Delta, dry season 1990/91.

N rate Grain yield (t/ha) a (kg N/ha) Cantho Binh Duc Hoa An Cai Lay

0 3.7c 3.0d 2.0c 4.0d 40 5.1ab 4.8c 3.0b 5.2c 80 5.9a 5.7ab 3.6a 5.8b 120 6.0a 6.0a 3.9a 6.1a 160 5.5a 5.6ab 4.1a 5.8b 200 4.6bc 5.2bc 3.8a 5.1c

a Within a column, means followed by the same letter do not differ significantly.

142 Hung et al recovery (grain plus straw) for Cantho was lower than recovery for Cai Lay (50% versus 62%) — in particular, 15 N recovery in the straw was much higher at Cai Lay than at Cantho (35% versus 19%). Because N uptake by rice at Cantho was lower, the N loss for Cantho was higher (28%) than Cai Lay (18%). In a previous 15 N balance study on broadcast-seeded flooded rice (BSFR) and transplanted rice (TPR) in Maligaya, Munos, Philippines (De Datta et al 1988), the 1 5 N loss was lower for BSFR (20%) than for TPR (32%). Yield and yield components. Yield and yield components differed significantly among the four locations (L) (Table 4). N application (N) significantly affected yield and yield components, except number of panicles which was also not affected by different urea-N rates (U). When DAP was used

2. Effect of N fertilizer rate on grain yield of rice in the Mekong River Delta. dry season, 1990/91.

N efficiency in direct seeded rice 143 as the first N basal application (D), yield and yield components were not significantly affected in comparison with urea application. The straw yield, panicles, and spikelets per panicle were different for different timing methods (T), but the grain yield, harvest index, weight per seed, and filled spikelets were not. Basal incorporation of urea is one of the strategies to reduce NH 3 loss. Basal incorporation of N fertilizer without standing water, but with soil saturation maintained for 4 d, greatly minimized NH3 loss and increased crop recovery of applied N and grain yield (De Datta et al 1990). In other studies using inhibitors, elimination of gaseous losses could have increased grain yield by as much as 6% in 1985 and 8% in 1986 (Buresh et al 1988). In this study, however, the early treatment with basal incorporation of N did not increase grain yield (Table 5), and the straw yield of early treatment was lower than that of delayed treatment (8.9 versus 9.5 t/ha). The panicles and spikelets per panicle were different with the two application timings at Cantho but not at the other three sites. For Cantho, the delayed treatment gave a higher number of panicles than the early treatment, but a lower number of spikelets per panicle. Yield response. The grain yield-response curves for the two timing methods for urea application (ES and DS) were almost similar for each location (Fig. 1). The recommended N rates were 100 kg N/ha for Cantho, Cai Lay, and Binh Duc and 50 kg N/ha for Long Ho. However, responses differed widely among sites; the response of grain yield at Binh Duc was very high (yield of more than 8.5 t/ha) at the recommended N rate (100 kg/ha).

Table 8. N rate and mean of grain yield and yield components of four experimental sites in the Mekong River Delta, dry season 1990/191.

N rate Yield and yield components a (kg N/ha) Grain yield Seed weight Filled Panicles Spikelets (t/ha) (mg/seed) spikelets (%) (no./m2) (no./panicle)

0 3.2c 20.8e 82a 557c 32c 40 4.5b 21.4cd 80a b 673b 36b 80 5.2a 21.8b 78 b 673b 39ab 120 5.5a 22.0a 77b 734a 40a 160 5.3a 21.5c 72c 718ab 40a 200 4.7b 21.3d 67d 706a b 40a

a Within a column, means followed by the same letter do not differ significantly

Table 9. Mean grain yield and yield components of rice at four experimental sites in the Mekong River Delta, dry season 1990/91.

Location Yield and yield components a

Grain yield Seed weight Filled Panicles Spikelets (t/ha) (mg/seed) spikelets (%) (no./m2) (no/panicle)

Binh Duc 5.0b 24a 85a 541c 25c Cantho 5.1ab 22c 81b 951a 36 b Hoa An 3.4c 16d 66d 575c 56a Cai Lay 5.3a 23b 73c 679b 35 b

a Within a column, means followed by the same letter do not differ significantly.

144 Hung et al Experiment II Grain yield did not differ between the two seeding rates at Binh Duc and Cai Lay (Table 6). In Hoa An, the highest yield was obtained from 15 × 15 cm spacing. Hoa An soil is classified as a acid sulfate soil (ASS), which limits plant growth, so this result is expected because, under less favorable conditions, closer spacing and planting of several plants per hill is recommended. In Cantho, even at

Table 10. Effect of seeding rate on biomass (t/ha) of lowland rice in the Mekong River Delta, dry season 1990/91.

Location and Seeding rate (kg seedha) a P b sampling day 150 250 (1) (2)

Cantho 31 DAS 1.7 1.9 ns 45 DAS 3.8 4.3 ns Harvest 10.1 9.9 ns

Cai Lay 31 DAS 2.1 2.2 ns 45 DAS 4.3 4.4 ns Harvest 10.1 10.1 ns

Hoa An 31 DAS 0.3 0.6 ** 45 DAS 1.7 2.7 ** Harvest 9.8 12.8 **

a At Hoa An, rice was transplanted (not seeded) at two spacings: 1, 20 x 20 cm and 2, 15 x 15 cm. b P. probability that the seeding rates differed was significant; **, at the 0.01 level; and ns, not significant at the 0.05 level.

Table 11. Mean grain yield of rice in two experimental sites in the Mekong River Delta, dry season 1991/92 (DS) and wet season 1992 (WS).

N rate Grain yield (t/ha) a (kg N/ha) Cantho Binh Duc

DS WS DS WS

0b 3.1d 1.9c 3.4c 1.1d 40b 4.4bc 2.3bc 4.3b 3.2c 80b 5.1 a-c 2.5ab 5.2ab 5.7a 120b 5.4ab 2.8ab 5.4a 5.6ab 160b 5.9a 2.9ab 5.2ab 5.3ab 80c 4.2c 2.8ab 5.2ab 5.1ab 80d 5.1a-c 3.1a 4.8ab 5.9a 80e 5.3ab 3.1a 5.3ab 4.4b

a Within a column, means followed by the same letter do not differ significantly. b N applied equally in three splits at 10, 20, and 45 DAS. c N applied in three splits: 1/6, 1/3, and 1/2 at 10, 20, and 45 DAS, respectively. d N applied in three splits: 1/6, 1/2, and 1/3 at 10, 20, and 45 DAS. respectively. e N applied in four splits: 1/6, 1/3, 1/3, and 1/6 at 10, 20, and 45 DAS and heading, respectively.

N efficiency in direct seeded rice 145 Table 12. Mean grain yield and yield components of rice in the Mekong River Delta, dry season 1991/92 (DS) and wet season 1992 (WS).

Location Yield and yield components a and season Grain yield Seed weight Filled spikelets Panicles Spikelets (t/ha) (mg/seed) (%) (no./m 2) (no./panicle)

Binh Duc DS 4.9a 27b 78c 798a 39b WS 4.8a 28a 82b 393b 49a

Cantho DS 4.8a 26c 86a 818a 33c WS 2.7b 27bc 65d 433b 43b

a Within a column, means followed by the same letter do not differ significantly.

250 kg seed/ha, the number of panicles was greater than at 150 kg seed/ha, but the higher number of spikelets per panicle at 150 kg seed/ha was the major yield component and resulted in a higher yield (5.3 t/ha) at that seed rate. The panicle number per square meter can be varied by varying plant density and tillering performance; however, beyond a certain density, the correlation between panicle number per square meter and spikelet number per panicle is negative (Yoshida 1983). There were no differences in weight per seed and filled spikelets between two spacings for all four experimental sites. Grain yield responded positively to increased applied N up to 80 kg N/ha at Cantho, Binh Duc, and Hoa An but to 120 kg N/ha for Cai Lay (Table 7, Fig. 2). Hoa An gave lower grain yield because its soil is ASS. Additional application of N after maximum yield reduces the grain yield because of- lodging. With excess N application, the height of the plant increases, the thickness of the stem decreases, and leaves become heavier so that the plant is less stable. Consequently, a high N supply aggravates lodging. N application affects each yield component with increasing N rate up to 120 kg N/ha: the weight per seed, panicles per unit area, and the number of spikelets per panicle (Table 8). However, the percentage of filled spikelets decreased when N rate increased, weight per seed also decreased with N rates above 120 kg N/ha. Of the four experimental sites, Hoa An gave the lowest grain yield but this was to be expected because of the ASS (Table 9) — seed weight and percentage filled spikelets were the lowest among the sites. Binh Duc, with the highest seed weight and percentage filled spikelets, however, did not fully compensate for the low number of panicles and spikelets per panicle; hence, the grain yield at Binh Duc was not highest. The effect of seeding rate (or transplant spacing) on biomass of rice was only significant in Hoa An where a transplant spacing of 15 × 15 cm gave higher biomass than 20 × 20 cm — the closer transplanting compensated for the poor growth on the ASS so that there was greater biomass in every growth stage (Table 10). There were no significant differences in biomass between the two seeding rates in Cantho and Cai Lay even at 31 DAS.

Experiment III Grain yield increased significantly in response to applied N up to 80 kg N/ha for Binh Duc and Cantho in the dry season 1991/92 and wet season 1992 (Table 11). Grain yield was higher in the dry season at both sites than in the wet season for almost all N rates.

146 Hung et al Table 13. N uptake (kg N/ha) in rice in the Mekong River Delta, dry season, 1991/92 (DS) and wet season 1992 (WS).

N rate Sequence sampling a (kg N/ha) 20 DAS 45 DAS 65 DAS Straw Grain

Binh Duc dry season 1991/92

0 b 23ab 58d 88e 40c 43d 40 b 23ab 68cd 104e 50bc 57cd 80 b 25ab 100b 152bc 61 b 82b 120 b 28ab 108ab 161ab 87a 91ab 160 b 33a 122a 179a 88a 107a 80 c 24ab 73cd 157b 49bc 85b 80 d 23ab 87bc 134cd 54bc 77bc 80 e 20b 76cd 129d 62 b 78 bc

Binh Duc wet season 1992

0 b 7c 13e 26d 23d 14d 40 b 11bc 22d 69bc 34c 33c 80 b 13b 29 b 88a-c 44bc 61a 120 b 18a 32 b 114a 48 b 65a 160 b 18a 42a 100ab 71 a 61ab 80 c 11bc 28bc 73 bc 42 bc 54ab 80 d 9bc 23cd 96a b 43 bc 60ab 80 e 8bc 20d 58c 40bc 48 b

Cantho dry season 1991/92

0 b 9d 29c 59d 40 b 16cd 55bc 100c 80 b 24a-c 56bc 133ab 120 b 27a 63b 161a 160 b 27a 94a 148a 80 c 20a-c 43bc 97c 80 d 22a-c 64 b 106bc 80 e 18bc 50bc 108c

Cantho wet season 1992

0 b 3a 10c 20d 40 b 4a 17bc 44c 80 b 3a 23ab 48c 120 b 4a 28a 62a b 160 b 5a 26a 73a 80 c 4a 17bc 44c 80 d 3a 21ab 54bc 80 e 4a 23ab 47c

a Within a column, means followed by the same letter do not differ significantly. b N applied equally in three splits at 10, 20, and 45 DAS. c N applied in three splits: 1/6, 1/3, and 1/2 at 10, 20, and 45 DAS, respectively. d N applied in three splits: 1/6, 1/2, and 1/3 at 10, 20, and 45 DAS, respectively. e N applied in four splits: 1/6, 1/3, 1/3, and 1/6 at 10, 20, and 45 DAS and heading, respectively.

N efficiency in direct seeded rice 147 Table 14. Mean N uptake (kg/ha) in rice in the Mekong River Delta, dry season 1991/92 (DS) and wet season 1992 (WS).

Location N uptake (kg/ha) and season 20 DASa 45 DAS 65 DAS Straw Grain

Binh Duc DS 25a 87a 138a 61a 78a WS 12c 26c 78c 43b 50b

Cantho DS 20b 56 b 113b – – WS 4d 21c 49d – –

a DAS, days after seeding.

During the rainy season in the tropics, solar radiation is lower so that plant growth tends to be tall and leafy because of higher temperature and less sunshine. Plants in the fields suffer from a shortage of light more seriously in the rainy season than in the dry season (Tanaka et al 1964). Different split applications at an N rate of 80 kg/ha (Treatments 3, 6, 7, and 8) did not significantly affect grain yield, except in the wet season at Binh Duc where the four-split treatment (Treatment 8) gave lower grain yield than three equal splits (Treatment 3). Therefore, there is no advantage in modifying the N the split application from the farmers’ present practice of three equal applications. The wet season in Cantho gave the lowest grain yield (2.7 t/ha) (Table 12). It is notable for its low percentage of filled spikelets. The percentage of filled spikelets is determined before, at, and after heading — unfavorable weather, such as low or high temperature at about reduction-division stage and anthesis, may induce sterility and, during ripening, it may reduce continued growth of some spikelets resulting in unfilled spikelets. Under most conditions, about 85% of spikelets filled is considered normal (Yoshida 1983). The N uptake tended to increase with increasing N rate from 0 to 160 kg N/ha at 20, 45, and 65 DAS, and at harvest (in straw and grain), except for 20 DAS at Binh Duc in the dry season and Cantho in the wet season (Table 13). In these two cases, plants may not have been well established. Numerous studies have also reported that total N content in the rice plant increases with an increase in N supply. Among different split applications (Treatments 3, 6, 7, and 8), the N uptake rarely differed. The N uptake in the dry season was always higher than that in the wet season for 20, 45, and 65 DAS, and in straw and grain (Table 14). N uptake in Binh Duc in the dry season was the highest at every stage in comparison with the others.

Conclusion

N losses from urea (28 and 18%) were lower than those normally reported for transplanted rice. Delaying the first urea application until 10 DAS had no adverse effect on yield of broadcast- seeded rice. DAP and urea plus SSP were equally effective fertilizer sources. The different splits for urea application did not give differences in grain yield and N uptake. In normal soils, 150 kg seed/ha is suggested for broadcast seeded rice and close transplanting spacing (15 × 15 cm) is suggested for transplanted rice in ASS.

148 Hung et al References cited

Buresh R J, De Datta S K, Padilla J L, Chua T T (1988) Potential of inhibitors for increasing response of lowland rice to urea fertilization. Agron. J. 80:947–952. De Datta S K (1986) Technology development and the spread of direct-seeded flooded rice in Southeast Asia. Exp. Agric. 22:417–426. De Datta S K, Obcemea W N, Chen R Y, Calabio J C, Evangelista R C (1987) Effect of water on nitrogen use efficiency and nitrogen-15 balance in lowland rice. Agron. J. 79:210–216. De Datta S K, Buresh R J, Samson M I, Wang K R (1988) Nitrogen use efficiency and nitrogen-15 balances in broadcast- seeded flooded and transplanted rice. Soil Sci. Soc. Am. J. 52:849–855. De Datta S K, Buresh R J, Mamaril C P (1990) Increasing nutrient use efficiency in rice with changing needs. Fert. Res. 26:157–167. Fillery I R P, Simpson J R, De Datta S K (1984) Influence of field environment and fertilizer management on ammonia loss from flooded rice. Soil Sci. Soc. Am. J. 48:914–920. Mikkelsen D S, De Datta S K, Obcemea W N (1978) Ammonia volatilization losses from flooded rice soils. Soil Sci. Soc. Am. J. 42:725–730. Noman R J, Wells R B (1985) Utilization and recovery of 15-N labeled urea in direct-seeded rice. Agron. Abstr. 1985:179. Patrick W H, Reddy K R (1976). Fate of fertilizer nitrogen in a flooded rice soil. Soil Sci. Soc. Am. J. 40:678–681. Tanaka A, Navasero S A, Garcia C V, Parao F T, Ramirez E (1964) Relationship of varietal characters to nitrogen response with special emphasis on mutual shading. In Growth habit of the rice plant in the tropics and its effect on nitrogen response. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Technical Bulletin 3. Vlek P L G, Byrnes B H (1986) The efficacy and loss of fertilizer N in lowland rice. Fert. Res. 9:131–147. Yoshida S (1983) Rice. In Potential productivity of field crops under different environments. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Zhu Z L (1987) 15 N balance studies of fertilizer nitrogen applied to flooded rice fields in China, In Efficiency of nitrogen fertilizer for rice. Proceedings of the International Network on Soil Fertility and Fertilizer Evaluation for Rice, Griffith, New South Wales, Australia. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines.

N efficiency in direct seeded rice 140

Nitrogen-use efficiency in direct-seeded rice in the Mekong River Delta: varietal and phosphorus response

Vo Thi Guong, 1 Tran Thanh Lap, 1 Nguyen My Hoa, 1 E.G. Castillo, 2 J.L. Padilla, 2 and U. Singh 2

Abstract. Recently, several improved rice varieties have been introduced to farmers in the Mekong River Delta. The need to evaluate rice yield response and N-use efficiency under different N-fertilizer regimes for these varieties prompted a series of field experiments on alluvial soils. Five varieties and four rates for nitrogen (0, 60, 120, and 180 kg N/ha) were tested using a split-plot design with four replicates. 15N was applied in the 60 and 120 kg N/ha treatments. Experiments were conducted at two sites and over two seasons. On acid sulfate soils (ASS), the experiment was conducted with one variety, three N rates, and four phosphorus (P) rates. In the dry season, grain yield showed high response at 60-120 kg N/ha with OM323-7 giving the highest yield (7.6 t/ha). In wet-season rice, grain yield was lower: however, the response to applied N was similar. Hybrid rice gave the highest yield at both locations during the wet season. Lower yields were obtained at high N rates because of lodging in some varieties. On ASS, yield response to N was significantly higher at 60-120 kg N/ha when applied in combination with 90 kg P 2 O 5 /ha. Agronomic efficiency (AE) was highest at 60 kg N/ha. In some varieties, AE was negative at 180 kg N/ha because of a high percentage of unfilled grains and lodging. Total N uptake increased continuously for all varieties during the crop growth period. 15N recovery was higher for 60 kg N/ha compared with 120 kg N/ha. In the dry season, high 15N recovety was found for OM323-7 (50.1%). In the wet season, IR64 and UTL 2 had the highest N recovery among varieties (60.5-68.3%). The recoveries of applied N based on 15N and apparent recovery methods were not consistent.

Rice is the main agricultural product of the lowland area of the Mekong River Delta, which supplies a large proportion of the rice for the whole country and for export. Fertilization with nitrogen (N) is one of the most important factors affecting rice production (Mikkelsen 1987) and N accounts for about 67% of the fertilizer applied to rice (Vlek and Byrnes 1986). Indeed, in the Mekong River Delta, about 75% of the total fertilizer used on alluvial soils is N. In a recent experiment, high rice yields were obtained at 100-120 kg/ha of N fertilizer addition (Tran Thanh Lap, unpublished data). Low efficiency of N fertilizer use is a cause for concern. In most studies on transplanted flooded rice, only 20-40% of the applied N is recovered by the crop because of N losses and poor fertilizer management (De Datta et al 1988, Vlek and Byrnes 1986). Varieties differ in response and ability to utilize soil and fertilizer N. These differences are clearer in the dry season than in the wet (IRRI 1985). Broadcast seeded rice in combination with cultivars with high lodging resistance resulted in high recovery of fertilizer N and high grain yield (De Datta et al 1988).

1University of Cantho, Cantho, Vietnam. 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Table 1. Soil properties of experimental sites.

a b c Soils pH N total NH 4 C P avall CEC K exch AI exch (%) (ppm) (%) (mg/100 g) (mmol/kg) In H 2 O In KCl

1 5.0 4.1 0.12 3.0 2.3 6.4 76 – – 2 5.3 4.3 0.17 2.5 4.2 3.0 122 – – 3 3.8 3.1 0.27 1.3 11.3 0.3 113 3.6 53.3

a Soil 1 — deposited alluvial (Fluvic Ustropept) at Binh Duc site; Soil 2 — undeposited alluvial (Typic Tropaquept, Fluvic) at Cantho site; and Soil 3 — Sulfic Tropaquept at Hoa An site. b pH in 1:2.5 soil:water slurry c CEC, effective cation exchange capacity (BaCI 2 unbuffered extraction).

Table 2. Varietal differences a of response to N rates in grain yield, dry season (DS) 1992193 and wet season (WS) 1993 on alluvial soil.

Varieties N rates Grain yield (t/ha)

Binh Duc Cantho

DS WS DS WS

UTL 2 0 4.7k 5.1cd 3.8k-I 4.8cd 60 5.5h-j 5.4b-d 5.2f-g 5.6ab 120 3.7l 6.0ab 4.0j-I 5.9a 180 2.5m 6.2a 3.6l 5.8a

IR64 0 5.1i-k 3.6h 4.6hi 3.4h 60 6.5c-e 5.0c-e 5.5c-f 4.3ef 120 6.3d-f 5.7a-c 6.0ab 5.4ab 180 6.4de 5.1cd 5.2f-g 4.0fg

MTL 105 0 5.5h-j 4.1gh 4.2i-k 3.3h 60 6.3e-g 5.2cd 5.4ef 4.6de 120 5.2h-k 5.0c-f 5.8b-f 4.8cd 180 4.9jk 3.8h 4.8gh 4.5d-f

OM723-7 0 5.7f-h 4.2f-h 5.9b-e 3.7gh 60 7.6a 4.8d-g 6.4a 4.8cd 120 7.3ab 5.2b-d 5.9a-d 5.2bc 180 6.9b-d 5.0c-f 6.0a-c 4.6d-e

MTL 119 0 5.6hi 4.3e-h 5.5d-f 3.7gh 60 6.7b-e 4.7d-g 6.2ab 4.8cd 120 7.1a-c 4.1 g-h 4.6h-j 4.7c-e 180 5.7g-i 2.6i 3.9kl 4.4d-f

CV (%) 7.7 12.0 10.9 6.7 LSD (0.05) 0.63 0.81 0.52 0.45

a Within columns, means followed by the same letters are not significantly different at 5% level.

In acid sulfate soils (ASS), a key yield-limiting factor is nutrient deficiency. Recent research has demonstrated good response of rice to phosphorus (P) application (Ren et al 1993) and, with an abundant N supply, response to P fertilizer was greatly improved (Mengel and Kirkby 1987). Applied nutrients would be used efficiently if the supply were synchronized with the demand of plant. Also,

152 Guong et al Table 3. Grain yield, a total N and P uptake, and apparent recovery of applied N and P 2 O 5 for rice on acid sulfate soils at Hoa An, wet season, 1993.

N rate P 2 O 5 Grain Total uptake Apparent (kg/ha) rate yield (kg/ha) recovery (%) (kg/ha) (t/ha) N P 2 O 5 N P 2 O 5

0 0 1.8b 43.1 35.3 – – 45 1.8b 36.2 37.9 – 5.8 90 1.9b 37.4 39.5 – 4.7 135 1.7b 33.6 40.6 – 3.7

60 0 1.9b 42.6 33.9 -0.8 – 45 2.5a 55.3 54.2 31.8 36.2 90 2.6a 65.0 62.2 46.0 25.2 135 2.5a 54.0 60.8 34.0 15.0

120 0 1.9b 65.8 46.1 18.9 – 45 2.6a 81.7 83.6 37.9 101.6 90 3.0a 83.5 78.8 38.4 43.7 135 2.7a 72.8 75.5 32.7 25.9

CV % 14.7 LSD (0.05) 0.49

a Within a column, means followed by the same letter are not significantly different at 5% level. from the point of view of economics, identification of rice varieties that use N efficiently could contribute to reduced losses of fertilizer and higher grain yields and thus increased net income for farmers. The objectives of this study were twofold: first, to determine the response to N fertilizer and N-use efficiency of five rice varieties using labeled N and, second, to investigate the P requirement of rice under various N regimes in ASS.

Materials and methods

N response on alluvial soil A field experiment was conducted in 1993 with five popular rice varieties at two sites (Cantho and Binh Duc) over two growing seasons (dry season and wet season) on alluvial soil. A split-plot design with varieties as the main plot and N rate as the subplot was used. The varieties were UTL 2 (hybrid), IR64, MTL 105 (IR54751-2-41-10-5-1), OM723-7 (selected breeding variety), and MTL 119 (IR53936- 97-2-2-3). The N rates were 0, 60, 120, and 180 kg N/ha applied as three splits at 10 d after emergence (DAE), 25 DAE, and 5-7 d before panicle initiation (PI), which was about 45 DAE. The plot size was 5 × 4 m. The seeding rate was 200 kg/ha. Blanket application of P and potassium (K) were basally incorporated at 60 kg P 2 O 5/ha as superphosphate and 30 kg K 2 O/ha as KC1. 15 N microplots (0.8 × 0.8 m) were installed in plots receiving 60 kg N/ha in the wet season and 120 kg N/ha in the dry season. These microplots were isolated from the main plots by a 40-cm high galvanized iron frame driven about 15 cm into the soil. Urea containing 5% 15 N was applied to the microplot. The microplots were sampled for soil and plants at maturity (Buresh et al 1982). Grain yield was determined from a 2.0 × 2.5 m area and was expressed at 14% moisture, Plants from four 0.5 × 0.5 m areas at the four corners were harvested for yield components. Dry weight and N content of plants were determined at 10 DAE, 25 DAE, 5-7 d before PI, 50% flowering, and harvest (straw and grain).

Direct-seeded rice 163 Table 4. Varietal differences in total N uptake of rice on alluvial soil, dry season (DS) 1992/93 and wet season (WS) 1993.

Variety N rate Total N uptake (kg/ha) (kg/ha) Binh Duc Cantho

DS WS DS WS

UTL 2 0 63.8 74.7 56.8 63.9 60 113.5 86.4 98.2 98.9 120 133.6 101.5 106.9 123.0 180 215.4 123.2 150.9 94.9

IR64 0 63.2 83.9 76.1 58.5 60 94.6 116.8 95.1 85.1 120 117.8 144.7 127.8 141.5 180 141.8 193.6 124.2 120.2

MTL 105 0 76.0 73.9 59.5 55.0 60 110.5 106.7 92.9 77.0 120 142.4 118.4 116.7 104.9 180 155.2 140.4 130.2 102.2

OM723-7 0 72.4 85.0 88.8 58.1 60 101.1 87.4 111.3 82.2 120 116.2 142.8 124.2 114.4 180 138.5 135.6 143.0 101.5

MTL 119 0 64.6 79.3 71.4 60.8 60 110.3 91.6 119.1 89.8 120 137.2 121.6 159.3 102.7 180 154.7 131.9 148.7 97.8

N and P on acid sulfate soils A second experiment was carried out in the 1993 wet season at Hoa An on ASS classified as Sulfic Tropaquept (Soil Survey Staff 1990). The treatments were arranged in split-plot design replicated four times with three rates of N (0, 60, and 120 kg N/ha) in the main plot and four rates of P (0, 45, 90, and 135 kg P 2 O 5 /ha) in the subplot. Blanket application of K at 30 kg K 2 O/ha was basally incorporated. Methods for fertilization and determination of grain yield and yield components were the same as in the first experiment. Soil properties for the experimental sites are as shown in Table 1.

Results and discussion

Grain yield and N uptake at maturity N application increased number of panicles per square meter, but tended to decrease the percentage of filled spikelets and the number of spikelets per panicle. These results were consistent for the five varieties over two seasons and at two sites. The effect of N application was similar on the alluvial soils and the ASS. In the dry season, grain yield was high compared with wet season except for hybrid rice, UTL 2, which had a very high percentage of unfilled grain (53–78%), and its grain yield declined sharply with increasing N rate (Table 2). At both Binh Duc and Cantho, the highest dry-season yields, 7.6 and 6.4 t/ha, respectively, were obtained with OM723-7 at 60 kg N/ha. The grain yield was

154 Guong et al Table 5. Agronomic efficiency (kg rice/kg N applied) and physiological efficiency (kg rice/kg N uptake) of N, dry season (DS) 1992/93 and wet season (WS) 1993.

Variety N rate Agronomic and (physiological) efficiency (kg/ha) Binh Duc Cantho

DS WS DS WS – UTL 2 0 – (73.7) – (68.3) – (66.9) (75.1) 60 12.9 (48.5) 5.3 (62.5) 24.0 (52.9) 13.8 (56.6) 120 -8.7 (27.7) 7.8 (59.1) 2.3 (37.4) 9.0 (48.0) 180 -12.1 (11.6) 6.3 (50.3) -0.9 (23.9) 5.6 (61.1)

IR64 0 – (80.7) – (42.9) – (60.4) – (58.1) 60 24.8 (68.7) 23.58 (42.8) 14.2 (57.8) 14.9 (50.5) 120 10.7 (53.5) 17.3 (39.4) 11.7 (46.9) 17.0 (38.2) 180 7.3 (45.1) 8.4 (26.3) 3.4 (41.8) 3.6 (33.3)

MTL 105 0 – (72.4) – (55.5) – (70.6) – (60.0) 60 13.3 (57.0) 17.5 (48.7) 20.7 (58.1) 22.0 (59.7) 120 -8.7 (36.5) 7.5 (42.2) 12.9 (49.7) 12.1 (45.8) 180 -3.4 (31.6) -1.7 (27.1) 3.7 (36.9) 6.3 (44.0)

OM723-7 0 – (78.7) – (49.4) – (66.4) – (63.6) 60 31.3 (75.2) 8.9 (54.9) 9.2 (57.5) 17.7 (58.4) 120 12.8 (62.8) 8.3 (36.4) 0.4 (47.5) 8.5 (45.4) 180 6.7 (49.8) 4.8 (36.9) 0.6 (42.0) 3.5 (45.3) – – – – MTL 119 0 (86.7) (54.2) (77.0) (60.8) 60 18.7 (60.7) 7.6 (51.3) 12.3 (52.1) 17.5 (53.4) 120 12.9 (51.7) -1.7 (33.7) -7.5 (28.9) 8.5 (45.8) 180 0.5 (36.8) -9.6 (19.7) -8.5 (26.2) 3.5 (44.9)

statistically similar for OM723-7 and MTL 119 at 120 kg N/ha. Thus, N addition for these two varieties beyond 60 kg N/ha did not significantly increase grain yield. The inherent high soil fertility at the Binh Duc site is reflected in consistently higher yields, particularly at low N input. The deposition of sediments every year during the flooded period at Binh Duc replenishes and improves the fertility of the soil. In the wet season, UTL 2 was the best yielder among the five varieties. It had a much higher percentage of filled grain than in the dry season. In general, yield responded significantly to applications of 60–120 kg N/ha. However, yields of several varieties were lower at 180 kg N/ha because of lodging. On ASS, increasing N application led to increased numbers of panicles per square meter, but there was no effect on filled grains per panicle. With the same level of N, increasing P application tended to increase the number of spikelets per panicle (data not shown). Yield did not increase significantly when N or P were not added (zero N and zero P treatment, Table 3). With P application, grain yield response to N addition was significant at 60 kg N/ha. Rice yields at 60 and 120 kg N/ha were statistically similar. Without added P, increasing N had no effect on rice yield. This result confirmed the conclusion of Xuan (1985) that, in acid soils, moderate liming and P application provide conditions for better utilization of applied N by rice. Apparent recovery of applied N increased with increasing rates of applied P up to 90 kg P2 O 5 /ha (Table 3). When only N was supplied, the higher rate of N gave a reduced effect. Rice yield did not increase significantly beyond P application of 45 kg P2 O 5 /ha in the treatments where N was

Direct-seeded rice 155 1. Total N uptake (kg/ha) of four varieties at different growth stages, Cantho, 1992/93 dry season.

2. Total N uptake (kg/ha) of four varieties at different growth stages, Cantho, 1993 wet season.

supplied. These results agree with the reported range of 50-100 kg N/ha and 30-60 kg P 2 O5 /ha for high rice yield (Ren et al 1993). The apparent recovery of a given application of P 2 O 5 increased with increasing rates of N application. On the alluvial soils, increasing N supply resulted in an increase in total N uptake (Table 4). At a high level of N fertilizer, grain yield decreased but total dry-matter production increased because of luxuriant growth — the grain:straw ratio decreased at N additions above the optimum rate. The ratio ranged from 0.38-0.45 at high levels of N (varieties MTL 119, MTL 105, and UTL 2) up to 1.11 at lower N fertilizer rates. These values agree with Chandler’s (1969) results that, for highly N-responsive varieties, the ratio was about 1.13 whereas, for poorly N-responsive ones, the mean ratio was 0.56. According to Yoshida (1972), the grain:straw ratio is clearly related to varietal characteristics.

156 Guong et al 3. Total N uptake (kg/ha) of four varieties at different growth stages, Binh Duc. 1993 wet season.

4. Total N uptake (kg/ha) of UTL 2 at four sites, 1992/93 dry and 1993 wet seasons.

Total N uptake during the crop-growth period continued to increase across varieties, sites, and seasons (Figs. 1, 2, and 3) in agreement with Atanasiu and Samy (1983). In general, the mean N- uptake responses among the varieties, sites, and seasons were similar. The response of UTL 2, however, was not consistent over the two seasons at Cantho and Binh Duc (Fig. 4). In the dry season, agronomic efficiency (AE) was highest at 60 kg N/ha for all varieties (Table 5) and ranged from 9.2 to 31.3 kg grain/kg of applied N. In both the dry and wet seasons, AE decreased at 120 and 180 kg N/ha. Some varieties had negative AE because unfilled spikelets (UTL 2) and lodging (MTL 119) increased with N application. Physiological efficiency (kg grain yield per kg N uptake) was higher during the dry season than the wet season in all varieties except UTL 2. UTL 2 had the highest physiological efficiency during the wet season at Cantho and Binh Duc.

Direct-seeded rice 157 Table 6. Nitrogen recovery a from fertilizer using 15 N. a Variety Season Nitrogen recovery Apparent recovery (%) (%)

Binh Duc Cantho Binh Duc Cantho

UTL 2 wet 56.2a-b 68.3a 19.5 58.3 dry 27.2c 44.2a 58.2 49.8 IR64 wet 60.5a 44.5b 54.8 44.3 dry 24.3c 37.0b 45.5 43.1

MTL 105 wet 42.4d 38.4b 54.7 36.7 dry 37.1 b 32.6b 55.3 47.7

OM723-7 wet 50.7b-c 35.9b 4.0 40.2 dry 50.1a 34.5b 36.5 29.5 MTL 119 wet 47.2c-d 35.7b 20.5 48.3 dry 38.3b 36.2b 60.5 73.2

a Within a column and a season, means followed by the same letter are not significantly different at 5% level. b N rate was 60 kg N/ha during the wet season and 120 kg N/ha during the dry season.

Nitrogen-15 recovery The total percentage recovery of 15 N fertilizer at 60 and 120 kg N/ha is presented in Table 6. The 15 N recovery is the total amount in straw and in grain. The dry season N application (120 kg N/ha) showed low fertilizer recovery compared with the wet season (60 kg N/ha). At the Binh Duc site, the highest level of N recovery was found in OM723-7 (50.1%) whereas UTL 2 showed the lowest value (27.2%). In the wet season, IR64 gave 60.5% 15 N recovery. At Cantho, UTL 2 gave the highest 15 N recovery for both dry and wet seasons. At 60 kg N/ha, UTL 2 showed 68.3% recovery. Based on apparent recovery, however, MTL 119 gave the highest N recovery during the dry season at both Binh Duc and Cantho. These differences demonstrate the need for multiple criteria to quantify N response and for efficient N management for a given variety, site, and season.

Conclusion

In the dry season, grain yield of the four rice cultivars responded more to applied N than in the wet season. Optimum N rate was 60 kg N/ha in both Cantho and Binh Duc for OM723-7 giving yields of 6.4–7.6 t/ha. The deposition of sediments after flooding during the wet season every year in Binh Duc replenishes and improves the fertility of the soil. Because of the inherent high soil fertility of the site, high grain yields are obtained in the dry season even at low levels of added N. In the wet season, yield response to added N ranged from 60 to 120 kg N/ha with UTL 2 producing the highest yield because of a higher percentage of filled grains as compared with the dry-season crop. Fertilization at 180 kg N/ha during the wet season caused lodging in the other varieties and so resulted in low yields. In ASS, addition of N leads to an increased number of panicles but no effect on filled grain percentage. With P application, rice yield responded to added N of 60 kg N/ha. Without P, increasing N rates to as much as 180 kg N/ha did not increase rice yields. Apparent recovery of applied N increased with applied P up to 90 kg P 2 o 5 /ha.

158 Guong et al References cited

Atanasiu N, Samy J (1983) Rice: effective use of fertilizers. Centre d’Étude de 1’Azote. Zurich. Switzerland. 93 pp. Buresh R J, Austin E R, Craswell E T (1982) Analytical methods of N-15 research. Fert. Res. 3:37-62. Chandler R F (1969) Plant morphology and stand geometry in relation to nitrogen. Pages 265-289 in Physiological aspects of crop yield. J.D. Eastin, ed. Crop Science Society of America and American Society of Agronomy, Madison, WI, U.S.A. De Datta S K, Buresh R J. Samson M I, Wang K (1988) Nitrogen use efficiency and N-15 balances in broadcast seeded flooded and transplanted rice. Soil. Sci. Soc. Am. J. 52:819-855. IRRl — International Rice Research Institute (1985) 25 years of partnership research. P.O. Box 933, Manila 1099, Philippines. Mengel K, Kirkby E A (1987) Principles of plant nutrition. International Potash Institute, Bern, Switzerland. 687 pp. Mikkelsen D S (1987) Nitrogen budgets in flooded soils used for rice production. Plant Soil. 100:71-97. Ren D T T, Guong V T, Hoa N M, Minh V Q, Lap T T (1993) Fertilization of nitrogen, phosphorus, potassium and lime for rice on acid sulphate soils in the Mekong Delta. Pages 117-151 in Selected papers of the Ho Chi Minh City Symposium on Acid Sulphate Soils. D.L. Dent and M.E.F. van Mensvoort. eds. International Institute for Land Reclamation and Improvements, Wageningen, Netherlands. Pub 53. Soil Survey Staff (1990) Keys to soil taxonomy (4th ed.). Cornell University, Ithaca, NY, U.S.A. Soil Management Support Services, Tech. Mag. 19. Vlek P L G, Byrnes B H (1986) The efficacy and loss of fertilizer N in lowland rice. Fert Res. 9:131-147. Xuan V-T (1985). Nitrogen management in rice-based cropping systems. Pages 329-338 in Nitrogen management in farming systems in humid and subhumid tropics. Institute for Soil Fertility, Haren, Netherlands. Yoshida S (1972) Physiological aspects of grain yield. Annu. Rev. Plant Physiol. 23:437-464.

Direct-seeded rice 159

Management of urea on degraded soils of the Red River Delta: effect of growing season and cultural practice

Tran Thuc Son, 1 U. Singh, 2 J.L. Padilla, 2 and R.J. Buresh 3

Abstract. Urea management practices to improve rice grain yield and modify floodwater conditions to reduce ammonia (NH 3 ) volatilization were implemented in three field experiments conducted during summer (July-October) 1989 and spring (February-May) 1990; summer 1990 and spring 1991; and spring 1992, summer 1992, and spring 1993. The experiments were conducted on degraded soil in the Red River Delta in Ha Bac Province of northern Vietnam. During the study, floodwater properties, plant growth, nitrogen (N) accumulation, and final yield were monitored. High temperature during summer and low cation exchange capacity (CEC) of the soils resulted in a very high potential for NH 3 volatilization as estimated from partial pressure of ammonia ( p NH 3 ). These conditions together with high rainfall emphasize the importance of N loss through runoff during the summer season. Basal incorporation of urea with no standing water effectively reduced p NH 3 . In addition, removing floodwater before urea application, thus reducing the chance of runoff loss immediately after urea application, and tillage may improve the yield as well. When integrated with farmyard manure (FYM), delayed application of urea (15 d after transplanting) gave higher yields than basal application. Optimum urea-N rate varied from 30-90 kg N/ha over seasons and years. Although plant growth was greater in summer with high solar radiation and temperature, this did not translate into higher grain yield. The best urea management strategy based on this study is a three equal- split application of urea as basal incorporation, at maximum tillering stage, and at 5-7d before panicle initiation. For best results, urea must be applied with no standing floodwater. The need to develop methods to extrapolate existing field data is discussed.

Increased fertilizer use has played leading role in increasing rice production in Vietnam to the current level. Almost two-thirds of the nation's inorganic nitrogen (N) fertilizer is used on rice and nearly all of the fertilizer is imported. The increased interest in N fertilization is also due to environmental implications. N is not only the nutrient most dependent on energy costs, but also the one most subject to losses (Boswell et al 1985). For example, urea-N is poorly utilized by rice and is prone to high losses through ammonia (NH 3 ) volatilization (De Datta and Buresh 1989). Although denitrification losses of applied N of economically significant magnitude have not been reported (Mosier et al 1990), N 2 O gas is a very potent greenhouse gas, almost 300 times more radiatively active than CO 2 on a mass basis (Rhode 1990). Also, N 2 O oxidation products, NO and NO 2 are involved in the destruction of stratospheric ozone (Crutzen 1976). Therefore, fertilizer N must be used effectively and economically. Because nutrients were inadequately replenished in the past, the soils of the Red River Delta (RRD) have become seriously degraded. Productivity of these soils can be enhanced, maintained, or restored by integrated management of nutrient inputs in conjunction with appropriate soil- and crop-

1Insitute for Soils and Fertilizers Research, Chem, Tu Liem, Hanoi, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 3 International Center for Research on Agroforestry, P.O. Box 30677, Nairobi, Kenya, management practices. The key issues in improving the efficiency of applied fertilizers are fourfold: first, effective management of inorganic fertilizers; second, effective integration of organic and inorganic fertilizers; third, use of economical fertilizer rates; and, fourth, use of appropriate and responsive varieties. We report here on the management of urea-N with respect to the first three issues. The research was conducted in northern Vietnam from 1990 to 1993 for the spring and summer seasons. Spring season (February-June) is characterized by low temperature and solar radiation during the later stages. The summer season crop (July-November) is established under high temperatures and grown during the period of highest rainfall. The effect of the seasons on floodwater chemistry, potential N loss, crop growth and development, and N uptake was evaluated. Because, in northern Vietnam, nutrients are also applied through animal wastes to rice fields, field trials were also conducted to identify relevant urea-N management in conjunction with farmyard manure (FYM).

Materials and methods

The first experiment was conducted on an alluvial soil (Aquic Ustifluvent) in the RRD (21°N) near Hanoi, Vietnam. Soil characteristics in the top 20 cm were air-dried pH (1:1 weight-to-volume water), 5.6; organic C, 12 g/kg; total N, 1.3 g/kg; CEC, 8 cmol c /kg; clay, 17%; and sand, 37%. Experiments two and three were conducted on degraded soils in Ha Bac Province also in the RRD. Soil characteristics in the top 20 cm were air-dried pH (1:1 weight-to-volume water), 5.8; organic C, 7 g/kg; total N, 0.68 g/kg; CEC, 4 cmol c /kg; clay, 5%; and sand, 46%. The daily rainfall, maximum and minimum temperatures, and solar radiation were recorded.

Experiment 1: floodwater depth and method of urea incorporation The first field experiment was conducted during the 1989 summer and 1990 spring seasons as a randomized complete block design (RCBD) with eight treatments and four replications. Before implementing the treatments, all plots were plowed and harrowed. The treatments were four methods of basal urea incorporation in factorial combination with two floodwater depths, 0 and 5 cm, during fertilizer incorporation. The four methods were broadcast application followed by harrowing and transplanting of rice; second plowing followed by broadcast application, harrowing, and transplanting; second harrowing followed by broadcast application and transplanting; and second harrowing followed by broadcast application (not transplanted with rice). CR203, a nonphotoperiod-sensitive indica rice, was transplanted with three to four seedlings per hill on 13 Jul 1989 and 15 Feb 1990. Hill spacing was about 13 × 21 cm (36 hills/m 2). This experiment has been fully described (Son and Buresh 1993).

Experiment 2: farmyard manure and urea-timing The second field trial was conducted during 1990 summer and 1991 spring seasons using an RCBD with six treatments and four replications. The treatments were a factorial combination of two FYM rates, 0 and 6 t/ha, and three urea treatment, no applied urea, 30 kg urea-N/ha basal incorporated, and 30 kg urea-N/ha delayed broadcast into floodwater at 14 d after transplanting (DAT) in summer and 16 DAT in spring. Three to four 30-d-old seedlings in summer and 42-d-old seedlings in the cool spring season were transplanted to each hill on 11 Jul 1990 and 19 Feb 1991, respectively. Planting density was maintained at 60 hills/m 2 (about 18 × 9 cm hill spacing). The full experimental details have been reported by Son and Buresh (1993).

Experiment 3 The third field experiment was conducted over three seasons: spring 1992, summer 1992, and spring 1993. The experiment was laid out in an RCBD with 12 treatments and four replications (Table 1) — the treatments were repcated in the same plots each season. The soil in all treatments was puddled by

162 Son et al Table 1. Urea treatments for 1992-93 field trial.

Treatment Urea rate N timing (kg N/ha)a number (kg N/ha) Basal 15 DAT Max T PI Heading

1 0 – – – – – 2 30 – 10 10 10 – 3 60 – 20 20 20 – 4 90 – 30 30 30 – 5 120 – 40 40 40 – 6 150 – 50 50 50 – 7 60 30 – – 30 – 8 60 – 30 – 30 – 9 60 20 – 20 20 - 10 60 – 20 – 20 20 11 60 – 15 15 15 15 12 60 15 – 15 15 15

a Timings Mere basal application, 15 d after treatment (15 DAT), at rnaximum tillering (Max T), panicle initiation (PI), and at heading.

1. Effect of growing season (summer 1989 and spring 1990) on floodwater properties at 1400 h after basal application of urea (from Son and Buresh 1993). flooding, plowing to about 10 cm depth with a water buffalo-drawn plow, irrigating to 5 cm depth, and then harrowing several times. All treatments received 60 kg P 2 O 5 /ha as single superphosphate basal incorporated and 30 kg K 2 O/ha as KC1 before transplanting. Additional 30 kg K 2 O/ha as KC1 was applied at 5-7 d before panicle initiation (PI). Basal N was incorporated by harrowing just before transplanting. All other urea-N applications (Table 1) were broadcast onto 2 cm of floodwater. Each plot (25 m 2) was surrounded by 15 cm-high bund to prevent water and N movement between plots.

Management of urea 163 Rice was seeded on 12 Dec 1991, 3 Jun 1992, and 26 Dec 1992 for each of the three seasons. The corresponding transplanting dates were 11 Feb 1992, 26 Jun 1992, and 5 Feb 1993. Three to four seedlings of CR203 were transplanted in each hill with about 18 × 9 cm hill spacing (60 hills/m 2). Phenological events were monitored in each plot Plant samples were collected from 0.8-m2 area from each plot at 20 DAT, maximum tillering, PI, and 50% flowering. Tiller number, aboveground dry weight, and N content using the micro-Kjeldahl method were determined. Grain and straw yields at maturity were determined from a 5-m 2 area in the center of each plot: grain yield is expressed at 14% moisture. N contents of grain and straw were also determined. Yield components were determined from four 0.25-m 2 areas at the four corners of the harvest area.

Results and discussion

Floodwater properties Floodwater temperature after each urea-N application was 4–22°C higher in summer (July) than in spring (February) (Figs. 1 and 2). During the 5 d after the basal urea-N application, floodwater pH at 1400 h was higher in both experiments in summer than in spring. N fertilization results in enhanced

2. Effect of growing season (summer 1990 and spring 1991) on floodwater pH and floodwater temperature after basal and delayed application of 30 kg urea-N/ha. Values for each sampling time followed by * or ** are significantly different at 0.05 or 0.01 probability levels, based on the least significant difference.

164 Son et al aquatic photosynthetic activity with consequent depletion of CO2 and increase in daytime floodwater pH (Fillery et al 1986). The higher floodwater pH during the summer season is related to greater aquatic photosynthetic activity. Reduced aquatic activity in the delayed N treatment during summer 1990 due to shading, high rainfall, and low solar radiation was reflected in smaller difference in floodwater pH between spring and summer seasons (Fig. 2). Because temperature affects crop growth, aquatic algal activity, and rates of N transformation and transport processes, the net seasonal effect on floodwater NH4 -N on basally applied N over the 2 yr was minimal (Figs. 1 and 3). The higher NH 4 -N amounts in the floodwater at 7-9 d after N application during spring 1990 than summer 1989 (Fig. 1) and at 2 d after delayed N application during summer 1990 than spring 1991 (Fig. 3) are attributed to greater floodwater depths during the respective periods (Son and Buresh 1993). The degraded soils of the experimental site have very low sorption capacity of NH4 (CEC, 4-8 cmol c /kg), so that heavy rainfall and greater floodwater depth after N application resulted in diffusion of NH 4 -N from the soil into the floodwater. These results show that runoff losses of N could be high in the farmers' fields after N application during both summer and spring seasons. High partial pressures of ammonia ( p NH 3) after basal N application in both the 1989-90 and 1990-91 experiments suggest a higher potential for NH 3 loss through volatilization during summer than spring season. The high p NH 3 in summer is attributable to much higher floodwater pH and temperature

3. Effect of growing season (summer 1990 and spring 1991) on NH4-N and partial pressure of ammonia ( p NH 3 ) after basal and delayed application of 30 kg urea-N/ha. Values for each sampling time followed by * or ** are significantly different at 0.05 or 0.01 probability levels, based on the least significant difference.

Management of urea 165 (NH 4 -N values were similar). The pNH 3 was somewhat higher in the degraded soil with lower CEC

(summer 1990) than in the alluvial soil (summer 1989). It must be noted that NH3 volatilization is a function of pNH 3 and wind speed. The relative difference in losses between spring and summer seasons will differ from p NH 3 estimates if the wind speed is much different. Among the options studied to reduce volatilization, delayed N application produced the desired effect (Fig. 3). Whether the reduced p NH 3 , a direct effect of lower floodwater pH, was because of management or rainfall is uncertain. The results from the incorporation study (Son and Buresh 1993) showed some reduction in p NH 3 during the first 4.2 d after urea application; however, these effects were not consistent over both seasons. Significantly lower p NH 3 values, particularly in the summer season, were obtained when urea was incorporated by harrowing with no standing water. None of the tested methods of urea incorporation eliminated potential N loss by volatilization. Considerable loss of N can be expected from urea incorporated by recommended methods on puddled soil (Diamond 1984, Padilla et al 1990). The results from both the 1990 summer and 1991 spring season trials indicate that the potential for NH 3 volatilization loss is not reduced when FYM is applied in conjunction with urea (Fig. 4).

Rice growth and nitrogen uptake Additional plowing before urea incorporation did not affect growth and N accumulation in young rice plants (34 DAT in summer 1989 and 28 DAT in spring 1990). Incorporation of urea by harrowing resulted in highly significant ( P < 0.01) increases in growth and plant N uptake of young rice plants in summer, and increased N uptake in spring (Table 2). Urea incorporation without standing floodwater improved N accumulation in both seasons and growth in the spring season ( P < 0.01). As mentioned earlier, it was essential to have no standing water to reduce p NH 3 during urea incorporation in summer, whereas increased growth and uptake occurred irrespective of water depth (Table 2). The results confirm that urea incorporation promotes early growth in transplanted rice when compared with surface application. FYM application had a significant effect ( P < 0.05) on early growth as measured by aboveground plant biomass at 31 DAT for summer 1990 and 33 DAT for spring 1991 (Table 3). Plant biomass and N uptake did not differ between basal and delayed application of urea. Both measures were, however, greater ( P < 0.01) for rice in summer than in spring.

4. Effect of farmyard manure (FYM) on partia1 pressure of ammonia (p NH 3) at 1400 h, averaged for two seasons. Values for each sampling time followed by * are significantly different at 0.05 probability level, based on the lead significant difference.

166 Son et al Table 2. Effect of basal urea incorporation method and floodwater depth during incorporation on growth and uptake of N in young rice plant (based on Son and Buresh 1993).

Treatment Biomass (t/ha) Plant N (kg/ha)

Summer Spring Summer Spring (34 DAT) a (28 DAT) (34 DAT) (28 DAT)

Incorporation method Transplanters 1.4 0.29 34 7.5 Harrow and transplanters 1.5 0.31 36 8.4 P b * ns ** *

Water depth (cm) c 0 1.5 0.32 38 8.8 5 1.5 0.28 34 7.3 P a ns ** ** **

a DAT, days after treatment. b P , probability that incorporation methods or water depths differed significantly: **, at the 0.01 level; *, at the 0.05 level, and ns, not significant at the 0.05 level. c Means for all three incorporation treatments with transplanted rice.

Table 3. Effect of farmyard manure (FYM), urea timing, and growing season on plant biomass and N accumulation of rice at 31 days after treatment (DAT) in summer and 33 DAT in spring (based on Son and Buresh 1993).

Treatment Biomass (t/ha) Plant N (kg/ha)

FYM No FYM 1.5 20 With FYM 1.6 22 P a * ns

Urea timing Basal 1.6 21 Delayed 1.6 22 P a ns ns

Season Spring 1.4 18 Summer 1.8 24 P a ** **

a P, probability that FYM, urea timing, or seasons differed significantly: **, at the 0 01 level; *, at the 0.05 level; and ns, not significant at 0.05 probability level.

Increasing dosage of urea-N (0-150 kg N/ha) application resulted in higher numbers of tillers, greater aboveground biomass production, and higher N accumulation in young rice plants (Table 4). This growth vigor continued through to maturity. The quick response of applied urea-N in terms of its availability to the rice plant and its utilization is illustrated by highly significant increases ( P < 0 01) in tiller numbers, biomass, and N uptake within 7-10 days after N application. For example. the first plant sampling was done about 5 d after the initial urea-N application for the spring 1992. summer 1992, and spring 1993. The results highlight the need to apply N in synchrony with plant demand because applied N that is not used by the rice plant (due to mismatch in timing and amount) will be lost. We have already shown high potential for NH 3 volatilization in these soils.

Management of urea 167 Table 4. Effect of urea-N rate and timing and growing season on plant biomass and N accumulation at various stages of growth. a,b

Season and N rate 20 DAT Max T PI FI PM treatment c (kg/ha)

Tillers (no./m 2 )

Spring 1992

T1 0 276bc 324a 327d 357a 332c T2 30 264c 326a 330cd 327a 326c T3 60 289ac 336a 342bd 339a 348bc T4 90 324a 368a 362ad 366a 375ac T5 120 290ac 371a 370ad 368a 434a T6 150 318ab 362a 393ab 390a 407ab T7 60 273c 340a 323d 340a 350bc T8 60 292ac 374a 402a 392a 409ab T9 60 286ac 337a 338cd 364a 350bc T10 60 302ac 358a 381ac 372a 382ac T11 60 320ab 369a 366ad 370a 378ac T12 60 270c 323a 331cd 331a 330c

Summer 1992

TI 0 390ad 415d 366b 310d 341c T2 30 414ab 438bd 384b 347cd 367bc T3 60 344d 430cd 398b 372bc 414ab T4 90 400ac 498b 447a 394ac 414ab T5 120 438a 486bc 385b 397ab 403b T6 150 442a 566a 455a 429a 455a T7 60 355cd 436bd 379b 352bd 400b T8 60 378bd 470bd 392b 355bd 384bc T9 60 393ad 435bd 386b 354bd 368bc T10 60 409ab 477bd 410ab 361bc 376bc T11 60 373bd 444bd 388b 359bc 386bc T12 60 374bd 416bd 382b 348bd 372bc

Spring 1993

TI 0 234g 350c 399d 331c 330d T2 30 252f 360ac 359bd 361ac 357bd T3 60 267de 352c 343cd 335c 338cd T4 90 284bc 363ac 363ab 353ac 357bd T5 120 296b 388ab 388ab 388ab 397a T6 150 318a 392a 392a 391a 393ab T7 60 270ce 369ac 362ad 353ac 352cd T8 60 272ce 356bc 376ac 371ac 372ac T9 60 281cd 360ac 355cd 346c 354bd T10 60 271ce 368ac 362ad 357ac 370ad T11 60 280cd 364ac 362ad 349bc 352cd T12 60 262ef 355bc 353cd 350ac 366ad Continued

a Within columns and parameters, means followed by the same letter do not differ significantly ( P < 0.05). b Stages of growth are 20 d after transplanting (20 DAT), maximum tillering (Max T), panicle initiation (PI), flowering (FI), and plant maturity (PM). c See Table 1 for treatments. d Being reanalyzed for % N.

168 Son et al Table 4 continued.

Season N rate 20 DAT Max T PI FI PM and treatment c (kg/ha)

Aboveground plant biomass (t/ha) Spring 1992

T1 0 0.17c 0.64de 2.10c 2.62f 4.99e T2 30 0.20bc 0.70be 2.64bc 3.49e 5.00e T3 60 0.22b 0.69be 3.15b 4.12cd 6.26bd T4 90 0.22b 0.79ab 3.35ab 4.31cd 6.77ab T5 120 0.23b 0.82a 3.30ab 5.06ab 7.12a T6 150 0.28a 0.76ac 3.86a 5.61a 6.54bc T7 60 0.23b 0.73ad 2.94b 4.19cd 5.80d T8 60 0.22b 0.70be 2.76bc 3.78de 6.06cd T9 60 0.23b 0.67ce 3.03b 4.60bc 6.61ac T10 60 0.22b 0.68be 2.72bc 4.02ce 6.30bd T11 60 0.23b 0.76ac 3.00b 4.27cd 6.44bc T12 60 0.22b 0.60e 2.82b 4.46c 6.41bc Summer 1992

T1 0 0.43a 1.23c 3.03f 3.87f 6.74f T2 30 0.42ac 1.23c 3.33ef 3.88f 7.77e T3 60 0.39bc 1.45ac 4.02bd 5.52bc 8.74ad T4 90 0.40ac 1.55ab 4.59ab 6.18ab 9.19ac T5 120 0.39bc 1.45ac 4.18bc 5.98ab 9.45a T6 150 0.39bc 1.63a 4.91a 6.78a 9.37ab T7 60 0.41ac 1.38bc 3.79ce 4.08f 8.33de T8 60 0.41ac 1.48ac 4.11cd 5.00ce 8.63bd T9 60 0.39bc 1.35bc 3.91ce 5.30bd 9.22ac T10 60 0.38c 1.43ac 3.75ce 4.72cf 8.49ce T11 60 0.40ac 1.38bc 4.32ac 4.24ef 8.49ce T12 60 0.42ab 1.33bc 3.53df 4.59df 8.58bd Spring 1993

T1 0 0.54ce 1.50d 2.44ef 4.39f 5.75e T2 30 0.47e 1.58d 2.90de 4.69ef 6.95d T3 60 0.52ce 1.53d 3.48bc 5.91ab 7.72ac T4 90 0.60bc 1.83c 3.73b 5.24be 8.04ab T5 120 0.65b 2.04b 3.84ab 5.94ab 8.05ab T6 150 0.74a 2.22a 4.23a 6.39a 8.29a T7 60 0.50e 1.53d 3.06cd 4.93cf 7.11cd T8 60 0.59bd 1.75c 2.61df 5.76ab 7.00d T9 60 0.51de 1.55d 2.39f 5.41bd 7.25cd T10 60 0.50e 1.55d 2.87df 4.77df 7.00d T11 60 0.47e 1.54d 2.89df 4.50f 7.15cd T12 60 0.47e 1.51d 3.53bc 5.53bc 7.50bd

Continued a Within columns and parameters, means followed by the same letter do not differ significantly ( P < 0.05). b Stages of growth are 20 d after transplanting (20 DAT), maximum tillering (Max T), panicle initiation (PI), flowering (FI), and plant maturity (PM). c See Table 1 for treatments. d Being reanalyzed for % N.

Management of urea 169 Table 4 concluded.

Season and N rate 20 DAT Max T PI FI PM treatment c (kg/ha)

N accumulation (kg N/ha)

Spring 1992

d T1 0 3.8c 13.0d 29.7e 29.5f 37.7d T2 30 5.2bc 15.0bd 41.7d 42.4e 37.8d T3 60 5.8b 15.5bd 48.9cd 50.1de 48.3c T4 90 6.0b 16.7ac 59.1bc 64.3b 55.9b T5 120 6.7ab 18.4a 63.3b 75.1a 65.0a T6 150 7.7a 17.4ab 78.2a 85.0a 58.5b T7 60 6.0b 17.4ab 46.9d 59.9cd 49.0c T8 60 5.8b 15.8ac 38.8de 51.0ce 48.3c T9 60 6.3ab 14.3cd 46.3d 62.2bc 56.3b T10 60 5.5b 15.1bd 37.9de 61.4bd 55.2b T11 60 5.5b 16.1ac 44.1d 57.9bd 57.9b T12 60 5.8b 12.8d 43.4d 62.7bc 58.0b

Summer 1992

T1 0 8.7c 20.6c 31.2g 34.0g 46.4f T2 30 9.7cd 20.9c 34.3fg 36.8g 56.1ef T3 60 9.9c 25.3bc 46.6ce 57.4cd 65.0ce T4 90 12.1ab 28.0ab 62.9b 64.7bc 76.1bc T5 120 11.6ab 26.5ab 66.5b 69.2b 83.9ab T6 150 12.6a 31.2a 73.6a 80.6a 88.6a T7 60 9.6cd 23.1bc 39.8ef 41.7fg 66.0ce T8 60 11.7ab 25.9bc 40.1ef 49.9df 62.8de T9 60 9.6cd 22.6bc 48.8c 55.5de 70.8cd T10 60 11.4b 24.8bc 36.6fg 47.7ef 69.5cd T11 60 10.2c 23.6bc 48.0cd 44.5f 64.4ce T12 60 9.2cd 21.0c 41.5df 46.2f 65.1ce

Spring 1993

T1 0 13.9e 26.4d 35.9f 38.7f d 44.2d d T2 30 13.6e 34.3c 46.7e 42.4f 48.3d T3 60 16.0de 34.9c 59.8d 63.9b 54.7c T4 90 18.8cd 41.4b 68.4c 61.3b 65.0b T5 120 23.3b 41.5b 77.9b 72.3a 63.7b T6 150 28.3a 58.0a 89.6a 80.1a 71.5a T7 60 16.2de 34.3c 51.2e 57.4be 55.9c T8 60 20.3c 37.5bc 42.7ef 55.4be 55.3c T9 60 14.9e 34.6c 48.9e 52.8de 54.4c T10 60 16.2de 33.5c 45.9e 54.5ce 56.5c T11 60 15.3e 35.6c 50.2e 51.5e 58.6c T12 60 13.6e 33.3c 62.2cd 62.6bc 57.6c

a Within columns and parameters, means followed by the same letter do not differ significantly ( P < 0.05). b Stages of growth are 20 d after transplanting (20 DAT), maximum tillering (Max T), panicle initiation (PI), flowering (FI), and plant maturity (PM) c See Table 1 for treatments. d Being reanalyzed for % N.

170 Son et al Biomass and N accumulation at the flowering stage responded significantly to N addition ( P < 0.05) at rates of up to 150 kg N/ha in all three crops — spring 1992, summer 1992, and spring 1993 (Table 4). The N response on tiller numbers at the flowering stage over the three seasons was inconsistent, illustrating the plasticity of tillering in rice plants. The greater number of panicles at maturity, however, indicated significant N response up to 60-90 kg N/ha. Similar response was obtained for total dry matter at maturity over all seasons. Significant increases in total N accumulation occurred up to 120-150 kg N/ha application. Plant growth and N uptake were greater for rice ( P < 0.01) in summer 1992 than in spring 1992 for all growth stages. These differences, however, were not significant when summer results were compared with spring 1993. Generally, higher growth in summer is attributed to higher temperature and solar radiation. The basal and delayed application of urea, and number of split applications (two, three, or four) at a total N rate of 60 kg N/ha did not statistically affect tiller number (final panicle number), total dry matter accumulation, or N uptake for all growth stages and seasons. However, based on biomass and N accumulation, the application rate of 60 kg N/ha was suboptimal so that the full effect of the various urea-N management regimes may not have been accurately reflected. Nonetheless, differences existed in uptake of N due to growth stage and season for urea management with two and three splits (Fig. 5). Based on N accumulation up to flowering stage, three split application of urea gave significantly higher uptake than two splits.

Grain yield and N uptake at maturity In the 1989-90 experiment, method of urea incorporation had no effect on grain yield and straw yield in either season (Table 5). In the 1990 spring season, incorporation of urea resulted in higher N uptake ( P < 00.01). Draining of the field before urea incorporation resulted in higher grain yield and higher uptake of N in spring although it did not influence volatilization potential (as indicated by p NH 3). Application of urea alone (combined basal and delayed) in both 1990 summer and 1991 spring season increased yield of grain and straw, and N uptake in grain and straw (Table 6). Basal and delayed application of urea were equally effective giving mean grain yields of 2.6 and 2.7 t/ha, respectively. The increase in all of these parameters was more marked in the summer crop than in the spring. Increases with urea in the presence of FYM were negligible in both seasons. However, the

5. Effect of number of split applications and timing of 60 kg urea-N/ha on plant N accumulation during 1992 summer season.

Management of urea 171 Table 5. Effect of basal urea incorporation method and floodwater depth during incorporation on rice grain yield and uptake of N at maturity (based on Son and Buresh 1993).

Treatment Grain yield (t/ha) Plant N (kg/ha)

Summer Spring Summer Spring

Incorporation method Transplanters 2.6 3.3 45 49 Harrow and transplanters 2.5 3.4 45 54 P a ns ns ns **

Water depth (cm) b 0 2.6 3.5 46 56 5 2.6 3.3 44 50 P a ns ** * **

a P, probability that incorporation methods or water depths differed significantly: **, at the 0.01 level; *, at the 0.05 level; and ns, not significant at the 0.05 level. b Means for all three incorporation treatments with transplanted rice.

Table 6. Effect of urea, farmyard manure (FYM), and growing season on yield and N accumulation at maturity.

Season and treatment Yield (t/ha) N (kg/ha)

Grain Straw Grain Straw

Spring

No urea / No FYM 2.0 2.6 23 20 No urea / With FYM 2.2 2.8 27 21 With urea / No FYM 2.3 2.8 25 21 With urea / With FYM 2.7 3.2 31 23

Summer

No urea / No FYM 2.4 2.8 23 18 No urea / With FYM 2.9 4.1 32 27 With urea / No FYM 3.0 4.2 31 29 With urea / With FYM 3.4 4.0 35 30

Source of variation df Mean squares a

Urea 1 1.812** 3.312** 185.6** 214.8** Urea x FYM 1 0.003 0.410** 9.2** 32.9** Urea x Season 1 0.173** 0.827* 18.8* 78.8* Urea x FYM x Season 1 0.013 0.706** 29.4** 53.4*

a *,** significant at 0.05 and 0.01 probability levels, respectively. delayed urea application in the presence of FYM was superior ( P < 0.01) to the basal application. Thus, for optimal benefit from the FYM and applied urea, the first urea application must be delayed up to 15 DAT. The application of FYM (23 kg N/ha) alone mimicked the effect of urea application at 30 kg N/ha. With increasing dosage of urea-N, number of panicles increased in all three seasons — 1992 spring, 1992 summer, and 1993 spring. The effect was more pronounced in summer with significant N response starting at 60 kg N/ha and continuing to the highest N rate (Table 7). High temperatures

172 Son et al Table 7. Panicle number, percent filled grains, 1,000-grain weight, and grain yield of CR203 in three seasons (spring 1992, summer 1992, and spring 1993).

Season and Panicles Filled grains 1,000-grain Grain yield N rate (kg/ha) (no./m 2 ) (%) weight (g) (t/ha)

Spring 1992 0 289b 94ab 23.5ab 2.74c 30 289b 95a 23.7ab 2.73c 60 276b 96a 23.9a 3.24b 90 304b 95ab 23.3ab 3.73a 120 290b 92b 22.7b 3.89a 150 354a 86c 21.4c 3.22b

Summer 1992 0 295d 86a 19.1a 2.47d 30 323cd 85b 18.9a 2.93c 60 377bc 85b 18.9a 3.32b 90 372bc 84bc 18.9a 3.52ab 120 395ab 82c 18.7a 3.74a 150 434a 78d 19.1a 3.58ab

Spring 1993 0 331b 93a 25.5a 2.97c 30 357b 93a 25.3a 3.68ab 60 388b 93a 25.0a 4.10a 90 357b 91ab 24.9ab 3.97ab 120 397a 89bc 24.9ab 3.83ab 150 393ab 88c 24.0b 3.61b

a Within a column, means followed by the same letter do not differ significantly at the 5% level by Duncan’s Multiple Range Test. during summer promoted higher panicle formation with increasing dosage of N. The fertility of grains (percentage of filled grains) showed negative response to addition of urea-N, particularly at 90-150 kg N/ha, in all seasons. The weight of 1,000-filled grains was much lower ( P < 0.01) in summer than in either spring seasons. The effect of N on this parameter was minimal; only at the higher N rates was grain weight lowered (Table 7). Despite the better growth (higher plant biomass and N accumulation) in summer, the grain yield was statistically similar to spring 1992 and 1993 yields, In spring and summer 1992, the optimum N rate was 90 kg/ha, whereas in spring 1993 it was 60 kg/ha (Table 7). Grain yield was higher when three equal splits of 60 kg urea-N/ha were applied as basal incorporation, at maximum tillering stage, and at 5-7 d before PI than with other timings (Table 8) in both spring 1992 and summer 1992. Plant biomass, N accumulation, and filled grain percentage were also higher with basal N incorporation. These results were consistent from spring 1992 to summer 1992. In spring 1993, all of the three N timing applications gave statistically similar responses for grain yield, yield and growth components, and N accumulation. The results from all three seasons confirmed that three equal split applications of 60 kg urea- N/ha was better than two equal splits (Table 8). Four equal split applications of urea had no yield advantage over three equal splits. In spring seasons, however, the recovery of applied N from four splits was higher than with three splits. In general, few variables showed significant differences. In an environment where grain yield is low, the slight yield advantage due to basal incorporation or to three N split application rather than two or none is worth pursuing.

Management of urea 173 Table 8. Effect of urea timing and number of split applications on grain yield and N accumulation.

Season Grain Straw N (kg/ha) Bio- Filled 1,000-grain and yield weight mass grain weight treatmenfa (t/ha) (t/ha) Grain Straw Total (t/ha) (%) (g)

Spring 1992 Three N split Basal, Max T, PI 3.67a 2.74 37.5a 18.7ab 56.3a 5.91 95a 23.8 15 DAT, Max T, PI 3.24b 2.87 30.8b 17.6b 48.3b 5.67 96a 23.8 15 DAT, PI, Head 3.24b 2.73 34.1ab 21.0a 55.1a 5.52 90b 23.5

Summer 1992 Three N split Basal, Max T, PI 3.91a 5.31 39.4 31.4 70.8 8.67 84a 18.9b 15 DAT, Max T, PI 3.32b 5.42 34.4 30.6 65.0 8.28 84a 18.9b 15 DAT, PI, Head 3.45b 5.04 38.1 31.4 69.5 8.00 80b 19.9a

Spring 1993 Three N split Basal, Max T, PI 3.74 3.23 35.1 19.4 54.4 7.25 92 25.2 15 DAT, Max T, PI 4.10 3.38 36.1 18.6 54.7 7.72 93 25.0 15 DAT, PI, Head 3.75 3.02 38.0 18.5 56.5 7.00 94 25.3

Spring 1992 Two urea-N split 3.21 2.49b 32.0b 16.7c 48.7c 5.25b 93 23.8 Three urea-N split 3.38 2.78a 34.1ab 19.1b 53.2b 5.70a 93 23.8 Four urea-N split 3.41 2.78a 37.1a 20.9a 58.0a 5.71a 93 23.9

Summer 1992 Two urea-N split 3.42 5.06 35.9 28.5 64.4 8.00 82 19.7a Three urea-N split 3.56 5.26 37.3 31.1 68.4 8.32 83 19.2ab Four urea-N split 3.52 4.98 36.6 28.2 64.7 8.01 83 19.0b

Spring 1993 Two urea-N split 3.64 3.09 35.5 20.0 55.6 7.01 91b 24.5b Three urea-N split 3.86 3.21 36.4 18.8 55.2 7.32 93a 25.2a Four urea-N split 3.78 3.24 39.2 18.9 58.1 7.32 92a 25.1a

a N treatments were basal, at 15 d after transplanting (15 DAT), maximum tillering (Max T), 5-7 d More panicle initiation (PI), and at heading (Head). b Within a column, means followed by the same letter are not significantly different at the 5% level by Duncan's Multiple Range Test.

Conclusions

From summer 1989 to spring 1993, the rice grain yield under optimum N rate and management ranged from 2.3 to 4.1 t/ha. The optimum N rates ranged from 30–90 kg N/ha. The season-specificity of grain yield response to N application and optimum N requirement is clearly illustrated. High temperature and resulting increase in floodwater pH in degraded soils with low CEC provides potential for high N losses through NH 3 volatilization. The high probability of rainfall after N application, particularly in summer, would also result in N losses in runoff. Thus, despite the poorer conditions for plant growth during spring, the grain yield is comparable to or even higher than in summer. Based on the results from these experiments, it appears that it is advantageous to have three equal split applications of urea with the first being basal incorporated followed by applications at maximum tillering and 5–7 d before PI. Urea should be applied with no standing water and when integrated with FYM it is better to have

174 Son et al the first dosage of urea applied at 15-18 DAT. These conclusions are, however, site, season, soil, cultivar, and management dependent. The large differences in results from the same site emphasize the urgent need to increase the explanatory and extrapolative power of field trial results — we need some recourse to mechanisms if results such as these are to be explained, or if we are to attempt to extrapolate such results across seasons and sites. One way in which this can be done is through the use of crop simulation models. These are far from perfect — they fail to include all the important factors that impinge on the farming environment (nutrients other than N, pests, weeds, diseases, and so forth). However, in their current state, models can simulate field trial results in carefully controlled plots.

References cited

Boswell F C, Messinger J J, Case N L (1985) Production, marketing, and use of nitrogen fertilizers. Pages 229–292 in Fertilizer technology and use (3rd ed). O.P. Engelstad, ed. Soil Science Society of America, Madison, WI, USA. Crutzen, P J (1976) Upper limits on atmospheric ozone reductions following increased applications of fixed nitrogen to the soil. Geophys. Res. Lett. 3:169–182. De Datta S K, Buresh R J (1989) Integrated nitrogen management in irrigated rice. Adv. Soil Sci. 10:143–169. Diamond R B (1984) Improving N efficiency for wetland rice. Page 286-310 in Soil test-crop response correlation studies: Proceedings of the International Congress Meeting of Commission IV, International Society for Soil Science. 1984. Bangladesh Agricultural Research Council and Soil Science Society, Dacca, Bangladesh. Fillery I R P, Roger P A, De Datta S K (1986) Ammonia volatilization from nitrogen sources applied to rice fields - II: Floodwater properties and submerged photosynthetic biomass. Soil Sci. Soc. Am. J. 50:86–91. Mosier A R, Mohanty S K. Bhadrachalam A. Chakravorti S P (1990) Evolution of dinitrogen and nitrous oxide from the soil to the atmosphere through rice plants. Biol. Fertil. Soils 9:61-67. Padilla J L, Buresh R J, De Datta S K, Bautista E U (1990) Incorporation of urea in puddled rice soils as affected by tillage implements. Fert. Res. 26:169-178. Rhode H (1990) A comparison of the contribution of various gases to the greenhouse effect. Science (Washington, D.C.) 248:1,217–1,219. Son T T, Buresh R J (1993) Incorporation of urea for transplanted rice as affected by floodwater and growing season. Fert. Res. 34(2):111–120.

Management of urea 175

Less-favorable ecosystems

Deepwater rice research in the Mekong River Delta

Vo-Tong Xuan, 1 Le Thanh Duong, 1 Nguyen Ngoc De, 1 Bui Chi Buu, 2 Pham Thi Phan, 1 and D.W. Puckridge 3

Abstract. Vietnam and IRRI have collaborated in deepwater rice research in the Mekong River Delta since 1973 when the University of Cantho and IRRI jointly established a deepwater rice-breeding program and then a research station in An Giang Province. Over the next few years, trials on introduced and local varieties and on fertilizer and cultural practices addressed mainly the floating-rice areas with very deep water. However, expansion of irrigation canals throughout the Delta after 1980 greatly reduced the area of floating rice. Recently, more attention has been given to the remaining 600,000 ha of medium-deepwater areas. Rainfed rice areas in eight provinces were surveyed in 1993; line transects were made across zones and farmers were interviewed to assess cultural practices, constraints to production, environmental conditions (particularly water depth), rice varieties, other activities, and socio- economic situations in each agricultural zone. The data from this survey are being used to identity plant types best suited for each zone and the potential for improving production. This information will be used to guide research in both agronomy and plant breeding by the University of Cantho and the Cuu Long Delta Rice Research Institute.

In Vietnam, the Mekong River Delta has an area of 3.9 million ha, about 12% of Vietnam's total land area. Each year, the Mekong River inundates most of the Delta from July to December and, 10 yr ago, these flooded areas were almost entirely sown to traditional deepwater and floating rice varieties that were adapted to water as deep as 3 m at flowering time and produced yields of 1-2 t/ha. Since 1983, however, new canals have allowed more than 300,000 ha of the floating rice land to be converted to double- or triple-cropped irrigated rice, yielding as much as 8 t/ha per year. Dry-season modern rice varieties increased from 0.56 million ha in 1975 to 1.05 million ha in 1992, and modern varieties in the wet season from 0.30 to 0.94 million ha. During the same period, the area of medium-deepwater rice decreased from 1.26 to 0.72 million ha. Rice production in the Delta increased from 5.3 million t in 1980 to 9.7 million t in 1990. Target production for the year 2000 is 14 million t. Farmers in the Delta are strong innovators, developing unusual methods of zero tillage, new methods for direct sowing of rice seed into standing water as deep as 50 cm (water seeding), and new techniques for ratooning to shorten crop duration of rainfed and irrigated rice so as to get an extra crop between floods. The results of irrigation, however, have not all been positive. Reduced fish production, environmental damage, and reduced economic efficiency have been linked to high fertilizer and pesticide use. Water seeding has involved heavy doses of toxic chemicals to control snails and fish that eat seeds, and farmers have been directed by government authorities to stop the practice. In contrast, other farmers have incorporated fish into their rice fields and, without losing yield, have eliminated the use of chemicals to control insects.

1 University of Cantho, Cantho, Vietnam; 2 Cuu Long Delta Rice Research Institute, Omon, Cantho, Vietnam; 3 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Table 1. Grain yields and related plant measurements of the four highest yielding entries in some deepwater rice (DWR) yield trials conducted by the University of Cantho, 1980-86.

Year DWR entries Flowering Height Panicles a Grain date (cm) (no./m 2) yield (t/ha) a

1980 Thanh An, Cantho. Eleven entries, maximum water depth 120 cm

Cu La 25 Nov 180 68 2.25 Chenab Sei 64-117 20 Nov 193 61 2.23 Leb Mue Nahng 111 30 Nov 191 46 2.22 BKN6986-29 23 Nov 166 58 2.17

1982 Thoai Son, An Giang. Five entries, maximum water depth 160 cm

Leb Mue Nahng 111 26 Nov 268 58bc 2.82a Pin Gaew 56 15 Dec 297 95a 2.72ab Cu La 20 Nov 256 91a 2.52bc Chenab Sel 64-117 22 Nov 264 51c 2.48bc

1982 Thanh An, Cantho. Ten entries, maximum water depth 100 cm

Pin Gaew 56 24 Dec 204 70bc 2.97a Nang Chet Cut 2 Dec 187 94bc 2.61ab Nang Tay Dum 9 Dec 197 78bc 2.48ab BKN76031-1-13-1 7 Dec 164 75bc 2.41ab

1982 Thoai Son, An Giang. Ten entries, maximum water depth 115 cm

Leb Mue Nahng 111 – – 75bc 3.21a BKNFR76031-1-13-1 – – 99a 2.85ab Nang Tay Dum – – 94ab 2.71ab Chenab Sel 64-117 – – 74bc 2.44bc

1982 Lang Bien State Farm, Dong Thap. Nine entries, maximum water depth 125 cm

Leb Mue Nahng 111 – – 70bc 2.79a Nang Tay Dum – – 98a 2.69a Cu La – – 74a-c 2.55ab Pin Gaew 56 – – 89ab 2.38a-c

1984 An Thanh State Farm, An Giang. Nine entries, maximum water depth 195 cm

Ba Bong – – 76 2.77a Nang Dum Nha Nuoc – – 83 2.74a Pin Gaew 56 – – 86 2.58a BKNFR76047-1-3-1 – – 93 2.55a

1986 Thanh An, Cantho. Five entries, maximum water depth 105 cm

BKNFR76047-1-3-1 – 238 113a 3.31a Leb Mue Nahng 111 – 250 84c 3.29a BKNFR76047-4-3-1 – 252 115a 3.21a Ba Bong – 255 114a 3.19a

a Within a column and a year, means followed by the same letters do not differ significantly at the 5% level.

This paper reviews some past Vietnam–IRRI cooperative research on deepwater and floating rice, and reports the results of a survey of coastal deepwater areas conducted in April 1993. Although most of the floating rice, grown in areas where flood depths range from 1.5 m to 3 m, has been

180 Xuan et al Table 2. Deepwater rice (DWR) breeding and crop physiology research conducted by the Cuu Long Delta Rice Research Institute, 1993.

Topic No. of District Province output entries

Yield trial of entries from 22 Omon Cantho HTAFR84036-9-3 and Trang Hoa Thailand Long Phu Soc Trang Binh (check)

Analyses of physiological 22 Omon Cantho HTAFR84036-9-3, Mot Bui, and traits of DWR lines from Trang Hoa Binh Thailand

Yield trial of promising lines Many Omon Cantho 18 lines of Mot Bui and 12 lines of from pure line selection of Tep Hanh Tep Hanh and Mot Bui

Demonstrations of Khao 1 - Long An and About 500 ha in total Dawk Mali 105 on farm Soc Trang scale

DWR yield trial 15 Omon Cantho Nam Bui, lR43262-B-87, and lR48927-8-8-8-20-B

Semi-DWR yield trial 15 Omon Cantho OM861 and IR42

DWR observation nursery 44 Omon Cantho NC490, Leb Mue Nahng 111, and RP2078-81-53

Local DWR yield trial 20 Omon Cantho Tau Lon and Mot Bui (E); Mong Chim Roi and Tep Hanh (L- group) replaced by irrigated dry-season rice, about 600,000 ha of medium-deepwater with floodwater depths of 30-100 cm remain near the coast. Most of the rice is rainfed, and is unlikely to be replaced by irrigation because of the increased likelihood of salt intrusion if more water is drawn from the rivers. Small areas of floating rice still remain and cropping systems incorporating floating rice followed by maize, sesame, peanuts, and mung beans in the dry season have been as profitable as two irrigated rice crops Fruit-tree gardens and rice-fish systems have also increased productivity. Future prosperity depends on careful planning and marketing.

Past research

The growing of high-yielding IRRI rice varieties in Vietnam began in the 1968/69 crop year with IR8 and IR5 introduced under a cooperative program of the United States Agency for International Development (USAID) with the Government of Vietnam. In November 1971, two IRRI personnel came to My Tho Province to construct experimental fields for irrigated rice. Dr. Dwight W. Kanter came as the IRRI plant breeder in April 1972, and soon thereafter began research on deepwater rice (DWR), which at that time was the dominant rice type in the Delta. A team under sponsorship of IRRI, composed of C.V. Hanh, N.H. Quyen, S.H. Ou, B.R. Jackson, and Vo-Tong Xuan, surveyed all the rice research stations in the southern part of Vietnam in April 1973 and recommended establishment of a DWR station in Long Xuyen in An Gang Province. Dr. Kanter started to test DWR in An Gang the same year.

Deepwater rice 181 Table 3. Research on farming systems and rice-based cropping systems by the Cuu Long Delta Rice Research Institute, 1991-93.

Year and topic District Province Output

1991 Farm household survey (100 farms Thot Not Cantho Farm situations, resources, and per site) Vinh Chau SOC Trang problems

1992 Cropping pattern, fertilizer Thot Not Cantho Performance of five cropping management, yield of peanuts in patterns floating rice area Gender analysis (40 farms) My Xuyen Soc Trang Role of women in farming Vinh Chau Soc Trang systems Thot Not Cantho Cropping pattern testing and farm Vinh Chau Soc Trang Rice + onion + Pachirizus tuber monitoring (recommended) Fertilizer management for peanut

1993 Rice plus peanut and farm monitoring Thot Not Cantho 100 ha in two villages Major cropping systems in floating rice Chau Phu An Giang – areas Farming system survey of 720 farms Hon Dat Kien Giang Application of geographic on coastal rainfed and DWR areas Tran Van Thoi Minh Hai information systems to Chau Phu An Giang analyzing and planning Omon Cantho Gender analysis Omon Cantho 200 farms

1994 Evaluating cropping systems floating Chau Phu An Giang Floating rice + hybrid maize rice areas, interviewing 100 farmers combinations with high- yielding varieties of rice Interview 150 farmers on hybrid Chau Phu An Giang New cropping systems maize, sesame, mungbean, cowpea, and watermelon production after floating rice

Topics of research work on DWR carried out by the University of Cantho from 1973 onwards are listed in Annex 1. Initially, most of the work was introducing breeding material from IRRI, and included a number of Thai varieties. Results of some of the varietal trials are shown in Table 1, which gives the four highest yielding entries in each of the trials. The results show that good yields can be obtained from DWR, but farmers were slow to change to new varieties because of the lack of seed, or because they preferred to continue using varieties that they considered reduced the risk of crop failure. DWR research has also been carried out by the Cuu Long Delta Rice Research Institute (CLRRI) since its establishment in 1977 (Tables 2 and 3). Subject areas have been allocated between the institutions to best use limited resources. Agronomy trials tested fertilizer and cultural practices. One of the most striking results was the improvement in production that can be made by providing shallow surface drains to remove acidity with the first rains. The soils in the floating rice areas were predominantly acid sulfate and, in the dry season, acidity built up sufficiently to severely affect the growth of rice sown at the beginning of the wet season. Table 4 shows the results of a trial testing the combined effects of nitrogen (N) and

182 Xuan et al Table 4. Effects of shallow drainage, phosphorus, and nitrogen on yield and yield components of Nang Tay Dum at Thoai Son, An Giang, 1983.

Treatment a Panicles Filled grains 1,000-grain Unfilled Yield (no./m 2 ) (%) weight (g) grains (%) (t/ha)

DPN3 155 122 23.4 10.1 3.73 DPN2 154 119 23.6 9.7 3.30 DPN1 149 114 23.5 10.6 3.18 DP 150 110 23.3 10.6 2.98

PN3 148 100 23.4 11.1 2.95 PN2 144 110 23.4 12.3 2.75 PN1 129 97 23.3 12.5 2.73 P 137 98 23.3 15.3 2.62

DN3 138 90 23.1 17.9 2.59 DN2 137 89 23.1 14.7 2.56 DN1 137 85 23.0 14.3 2.53 D 136 82 22.9 18.1 2.43

N3 131 76 23.0 18.9 2.26 N2 130 77 23.1 22.2 2.15 N1 124 79 22.5 16.8 1.79

Check 111 87 22.8 21.2 1.53

Drainage Phosphorus D x P D x P x N (D) (P)

CV % (yield) 5.9 3.2 7.5 11.7 LSD 5% (yield) 0.19 0.10 0.16 0.54

Note: Water depth: 110 cm (12 Nov 1983). Experiment: strip-split plot with three replications. a D, with shallow drainage (30 cm deep, 30 cm wide); P, 25 kg P/ha, N1, 23 kg N/ha. N2 46 kg N/ha, and N3. 69 kg N/ha. phosphorus (P) fertilizers with provision of shallow surface drains to drain water from the first rains into the nearest canal (Data are sorted by yield.) A combination of N, P, and drains gave the best resiults with yields over 3 t/ha at the highest N levels. However, P is very Important on these soils and, in the absence of P fertilizer, both N and drainage were relatively. ineffective. In other trials, N applications in the absence of P fertilizer have even depressed yields. As improvements in water distribution through canals in the Delta resulted in the replacement of floating rice, DWR research moved to cropping and farming systems, and has recently started to look at rice-fish production. However, there is still much to be done in the medium-deepwater areas, as shown by our recent survey.

Survey of rainfed and DWR areas

A survey was conducted in April 1993 in rainfed zones of the Delta (Fig, 1). At each location, a line transect of up to 5 km was made through the area. The land forms were mapped, and each location classified into different rainfed zones according to the characteristics listed in Table 5. Two transects from Zone 3 were discarded because of inaccuracies in the data. Results from 9 zones, 24 transects, and 191 households are reported, and examples of profiles from two transects are given in Figs. 2 and 3. These profiles show that, although considerable differences occur, the landscape is dominated by the distribution of rivers and canals with only slight changes in topography.

Deepwater rice 183 1. Locations for field survey in the Mekong River Delta conducted in April 1993.

The total number of family members in a household ranged from 2 to 15 with most households having 4–9 members: 47% had 5–6 members. Only 6% of farmers had completed high school (grades 10–l2), 16% secondary school (grades 6–9) and 34% primary (grades 1–5); 44% were illiterate. Only 10% of family heads were illiterate, 23% had attended secondary school, and 3% high school. The main labor force was 57% male and 43% female. The “minor” labor force (children and the elderly) was 53% male and 47% female. Costs of inputs in production of DWR included fertilizer (28.3%), fuel (3.0%), pesticides (7.l%), hired labor (41.4%), and agricultural tax (20.3%). The distribution of rice varieties is given in Table 6. Overall, 86 varieties were encountered. Most of the 191 farmers reported only one variety, but 20% grew two varieties and 3.5% grew three varieties. The most commonly occurring variety was Lun Can, which was used on 46 farms in two provinces. Most of the locations for Lun Can were in the range of 40–80 cm water depth, although it was spread over all water depths and five agroecological zones. Tai Nguyen was the second most common variety and the most widely spread, being found in five different provinces. Other varieties were generally found in only one or two provinces and in no more than three zones. Mean yields ranged from 1.8 to 4.8 t/ha, but comparison between varieties is difficult because of the different locations and different numbers of occurrences. The range of yields show that in some years the crop was lost. Of the total area of farms covered by the survey, 82% had maximum water depths of 40–80 cm (mean 58 cm), and 7% had water depths greater than 80 cm (Table 7). The mean crop area per farm was also greatest in the medium water depths (1.74 ha), but yields decreased with increased water depth, from 3.05 t/ha for the 30 samples with less than 40 cm maximum water depth to 2.14 t/ha for the deepest water.

184 Xuan et al Table 5. Characteristics and sampling details of the different rainfed zones sampled in a survey of rainfed rice in the Mekong River Delta, 1993.

Zone Dominant soil type Percent Saline Flood Rainfall range Sampling area conditions depth (mm) (mo) (cm) Transects Households Provincesa 1 Salic fluvaquents 70 12 Tidal 1,400-2,000 3 18 LA, ST, TV

2 Salic sulfaquents 65 12 Tidal 1,400-2,000 2 9 MH, TV

3 Typic sulfaquepts-salic 40 5 50-100 > 2,000 – – –

4 Sulfic tropaquepts-salic 46 5 < 50 1,800-2,000 5 39 KG, ST, MH

5 Typic tropaquepts-salic 60 5 50-1 00 > 2,000 1 12 MH

6 Typic tropaquepts-salic and Typic 80 5 < 50 1,800-2,000 – – – ustropepts-salic

7 Typic tropaquepts-salic and Typic 30 5 < 50 1,400-1,600 4 39 LA, BT, ST, TV ustropepts-salic

8 Fluventic tropopsamments 33 1-3 < 50 1.200-1,800 6 48 LA, BT, ST, TV

9 Typic sulfaquepts-salic 50 5 < 50 1,800-2,000 1 10 KG

10 Typic sulraquepts 65 1-3 < 50 1,800-2,000 1 9 KG

11 Aquic tropaquepts 25 1-3 < 50 1,400-1,600 1 7 LA a BT, Ben Tre; KG, Kien Giang; LA, Long An; MH, Minh Hal; ST, Soc Trang; and TV, Tra Vinh. Table 6. Distribution of most common rice varieties by agroecological zone, province, water depth, and mean yields in survey of rainfed rice, Mekong River Delta, 1993.

Variety No. of % Zone Province b Distribution Grain yield (t/ha) reports a (no. of reports) by water depth (cm)

< 40 40-80 > 80 Range Average

LunCan 46 21.4 2, 3, 4, KG,MH 14 24 8 0.4–6.0 3.1 9, 10 TaiNguyen 23 10.7 4, 5, 7, 8 LA, TV, KG, 8 14 1 0.0–6.0 2.7 ST, MH Nep Dai Loan 11 5.1 1, 7 ST 3 8 0 0.6–6.0 2.8 TrangChum 8 3.7 8 TV 2 6 0 0.6–4.2 1.9 MTL 83 8 3.7 7, 8, 11 LA, BT 3 4 1 0.0–6.6 4.5 Mot Bui Lun 9 3.8 4, 5 MH 5 4 0 0.3–6.0 3.2 MotBui 7 3.8 4, 7 KG, ST 3 3 1 0.1–3.6 2.5 F5 8 3.7 1 ST 3 5 0 0.6–6.0 2.9 NangThom 7 3.3 1, 8, 11 LA 6 1 0 0.0–6.0 3.3 CutLua 7 3.3 2, 3, 4 KG,MH 1 5 1 0.8–4.9 3.0 BaDuong 7 3.3 7 TV 2 3 2 0.0–4.0 1.8 Minh Hai Lun 6 2.8 9 KG 0 6 0 3.0–5.0 4.8 Lua Phi 6 2.8 8 TV 4 2 0 0.8–4.0 2.5 Mong Chim Lun 5 2.3 7, 8 ST 5 0 0 0.9–4.0 2.3 IR42 5 2.3 7, 8, 10 KG,ST 2 3 0 0.6–5.4 3.3 Trang Lun 4 1.9 3, 8, 9 LA, KG, MH 1 3 0 1.5–4.0 3.4 Mashuri 4 1.9 1 LA 0 4 0 0.0–6.0 2.9 Hai Hoanh Ran 4 1.9 8 ST 4 0 0 0.3–4.0 2.2

a Varieties reported more than four times. b BT, Ben Tre; KG, Kien Giang; LA, Long An; MH, Minh Hai; ST, Soc Trang; and TV, Tra Vinh.

Major problems in rice production Environmental problems. Drought at the beginning of the growing season, acidity that accumulates during the dry season, and salinity at the end of the growing season are the main environmental problems. In zones near the sea, salinity can increase to as high as 17 g/liter in April as water levels in the rivers drop — salinity decreases after the rains start in May. The water regime is also important and problems include tidal conditions, varying water depths, poor irrigation systems, and shortages of water Biological problems. Brown planthoppers (BPH) and stem borers are major pests. Deficiencies in rice varieties include lodging, mixed seeds, and low yield. Socioeconomic problems. Poor education, low income, high costs of production, and few opportunities for nonfarm income do not give farmers much opportunity to improve their situation.

Needs for research and development Varietal testing. Five areas of research have been identified in varietal testing. Observation and yield trials for specific water conditions and high grain quality, with resistance to BPH and stem borer if possible; For water depths less than 40 cm — Plant type similar to TR42 is required; resistance to BPH; growth duration of 120-130 days (nonphotoperiod-sensitive); and height of 110-120 cm; For water depth 40-80 cm — Plant type like RD19, Lun Can, and Tai Nguyen; plant height of 130-145 cm; adaptable to tidal conditions; with resistance to lodging, stem borer, and BPH; • For water depths greater than 80 cm — Plant type similar to Huntra 60 and Ba Duong; height

186 Xuan et al 2. Transect of rainfed and deepwater rice area in Long An Province. 3. Transect of rainfed and deepwater rice area in Kien Giang Province. Table 7. Results of survey of rainfed areas in the Mekong River Delta, 1993.

Range of maximum water depth (cm)

< 40 40-80 > 80

No. of samples 30 143 18 Mean depth (cm) 24 58 82 Percent of surveyed area 11 82 7 Mean farm area (ha) 1.13 1.74 1 .20 Mean rice yield (t/ha) 3.05 2.76 2.14

of 120–150 cm with elongation ability; harvest December - January; resistance to stem borer, and tolerance to salinity; • Grain quality — Development of varieties with long, slender grains, low chalkiness, and a high percentage of head rice. Cultural practices. Research is required on seedling age, plant spacing, and timing and rate of fertilizer application. Diversification of products. Cropping systems and off-farm opportunities need to be investigated to raise the standard of living for farm families.

Future research program

Research on rice and cropping systems in these medium-water depths will continue with the long- standing program of the University of Cantho, with its main emphasis on farming systems and varietal testing in specific areas of the Delta. This work will be complemented by the rice breeding and farming systems research programs of CLRRI in other locations. The aim is for sustainable agricultural systems in rainfed areas, particularly where any extension of the irrigation system is undesirable because of the increased likelihood of saline intrusion, and for improved production systems to raise the standard of living of the farmers.

Deepwater rice 189 Annex 1. Vietnam-IRRI collaborative experiments on deepwater rice (DWR) by the University of Cantho, 1973-93.

Year Type of experiment a Location Province

1973 IFRON Binh Hoa An Giang

1974 IFRON Binh Duc An Giang

1975 FROYT and Pure-line selection from variety Nang Tay Dum Vinh Trach An Giang

1977 IRDWON Binh Duc An Giang IRDWON Lang Bien Dong Thap

1978 IFRON Binh Duc An Giang

1979 IFRON Binh Duc An Giang IRDWON Cantho Cantho

1980 IFRON and FROYT Vinh Hanh An Giang DWRPYT and N fertilizer rates with DWR variety RD19 Thanh An Cantho

1981 IRDWON, FRPYT, and N and P trials on variety Nang Chet Cut Vinh Trach An Giang IRDWON Tan Hiep Kien Giang

1982 IRDWON, FRPYT, fertilizer trials with varieties Nang Tay Dum and Vinh Trach An Giang Nang Chet Cut DWRPYT and IRDWON with submergence tolerance, and fertilizer Thanh An Cantho management trials with variety Nang Tay Dum DWRPYT Hoa An Cantho FRPYT Lang Bien Dong Thap

1983 IFRON, FRPYT, and P and drainage trial with variety Nang Tay Dum Thoai Son An Giang FRPYT and P trials on variety Nang Tay Dum DWRPYT Chau Phu An Giang Vinh Trinh Cantho

1984 FRPYT and fertilizer management trials on variety Ba Bong An Thanh An Giang FRPYT and IFRON Dong Cat Dong Thap IRDWON Tan Xuan Dong Thap Cultural management of N fertilizer with DWR Cantho Cantho

1985 DWRPYT and fertilizer trials on variety Nang Tay Dum Thanh An Cantho

1986 IFRON Dong Cat Dong Thap Submergence-tolerance testing IRRI – N and drainage trial with variety Song Doi Thanh An Cantho

1987 FRPYT Dong Cat Dong Thap N and P and drainage trial with variety Song Doi Thanh An Cantho

1988 P and drainage trial on variety Nang Tri and assessment of grain Dong Cat Dong Thap shattering in floating rice

1989 P and drainage trial on variety Nang Tri and assessment of grain Dong Cat Dong Thap shattering in floating rice

1990-93 DWR farming systems Many places –

1990-92 Mixed seeding DWR with fish culture Co Do Cantho

a Abbreviations: DWRPYT, Deepwater Rice Preliminary Yield Trial; FROYT, Floating Rice Observational Yield Trial; FRPYT, Floating Rice Preliminary Yield Trial; IFRON, International Floating Rice Observational Nursery; IRDWON, International DWR Observational Nursery.

190 Xuan et al Opportunities for upland rice research in Vietnam

M.A. Arraudeau 1 and Vo-Tong Xuan 2

Abstract. The background for potential research projects on upland rice is described and two areas of opportunity — the central-southern plateau and the northern hilly areas — are proposed. Research in these areas would be complementary with close collaboration. Two sets of opportunities are addressed: scientific research and applied technologies that are appropriate for farmers in their own fields. Although upland rice contributes little to overall rice production in Vietnam, the knowledge gained from investigating traits specific to it will contribute to increasing productivity in this crop and to improving rice crops in other ecosystems. Although present practices with upland rice degrade the environment, it can become a sustainable crop through the use of improved germplasm and production techniques. Thus, within a cropping- or farming-systems context, upland rice improvement will reduce land degradation and contribute to the welfare of the upland peoples.

In Vietnam, upland rices have been surveyed, described, and studied to some degree for about a century. Even though it is limited, incomplete, fragmentary, and needing to be updated, there is quite a large body of information. Unfortunately, there is no single documentation center for upland rice and information is scattered and often hard to find. For the past few years, some research efforts have been made in upland rice areas, but they remain limited and few scientists are involved. However, there is a clear consensus that, for various reasons, most notably related to land degradation, research and extension in the upland rice areas must be reinforced. Because commitment and growing interest is there, it is obvious that strong opportunities exist to go further in research, beyond the existing, limited, research projects such as the Institute of Agricultural Sciences of South Vietnam-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (IAS-CIRAD) project, some International Network for Genetic Evaluation of Rice (INGER) trials, and farming system studies. Although many research topics are possible, those proposed here are considered to be the major ones to be implemented in the short to medium term. As we gain knowledge and a broader vision of the field through field visits, the topics can be refined progressively. This paper is intended only as a background for supporting research projects and addresses two sets of opportunities: scientific research and applied technologies that could be considered appropriate for farmers in their own fields.

Facts and figures

In Vietnam, upland rice — lua ray in southern Vietnam, lua can in the center, and lua nuong in the north — represented about 450,000 ha in 1993 or about 2% of the upland rice in the world. It is planted mainly as a major food crop in the humid forest zones by some 54 ethnic groups, of which 50 are

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 2 University of Cantho, Cantho, Vietnam. nomadic and practice shifting cultivation. The total affected area represents about 8 million ha where some 3 million ethnic minorities are living. The annual rainfall varies from 1,300 to more than 2,000 mm, but the usual range is 1,400–1,800 mm. It is very erratic and droughts are common everywhere. The rainy season starts in April–May, or even as late as early June, generally peaks in July–August, and ends in October–December. It is more uniform in the center-south and varies greatly in the north, even over short distances, where a range in elevation of 1,200–2,200 m over a few kilometers can be found. Temperatures are in the ranges of 15–25°C to 34–36°C during the cropping season. Slash-and-burn with shifting cultivation is the widely predominant traditional system. In the past, the fallow period was usually 12–15 yr or more; however, it is now only 3–10 yr because of increasing population pressure. Land degradation is an increasingly serious problem almost everywhere, but particularly in the north. For example, in Cao Bang Province, most of the land is denuded with only poor stands of grass and scattered forests remaining. Land ownership is very rare, representing less than 5% of the area — leaseholding is usual. Long-term leases were recently granted in some areas. The area planted to upland rice is generally declining. After an increase in 1980–85 because of food shortages, there has been a progressive decline in area. In Bac Thai Province, 4,500 ha were reported in 1990, then 3,900 in 1991 and 3,700 in 1992, which is less than 0.5% of the total provincial area. In Tuyen Quang, upland rice represents less than 1% of the total area of the province. It is more important in some provinces, such as Lai Chau, but rarely exceeds 2% of the total area. However, the impact on the environment is much greater and rough estimates give a total impact of 7–10 times more than the actual area of rice because of the slash-and-burn with fallow rotation. Therefore, from 5 to 20% of the provincial areas is in fact concerned. The upland soils are derived from diverse parent rocks, including granite, dacite, schists, and basalts, which are frequent in the high plateaus and on mountainous slopes. Red-yellow podzolic soils are widely predominant, but calcareous soils are located around the limestone hills that are scattered throughout northern Vietnam. Most of the soils are in the pH 4–5 range, with an estimate of up to 80% of soils having a pH below 5. In deforested areas (estimated at 9.75 million ha), the pH is 0.5 to 1 unit less than in the forest zones (estimated at 9.32 million ha). These soils have a high capacity for fixing phosphorus (P), some 700–1,000 ppm and up to 1,500 ppm at pH levels around 4, where soils show aluminum (Al) toxicity. Available P is very low everywhere, as is organic matter and cations, mainly calcium (Ca) and magnesium (Mg). The nitrogen (N) content is very low, and potassium (K) is variable, sometimes low. Under forest, it is estimated that soil losses are about 10 t/ha per year but, in the deforested grassy lands, they can reach hundreds of tonnes per hectare per year. Although chemical properties are usually very poor, soil physical properties are more often acceptable or even good, with a clay content in the 50–70% range. Some soils are quite light textured with 30% or more sand. However, this texture is fragile and is rapidly degraded with shallow soil preparation, such as the use of disc plowing in the rubber tree plantations, to create a hard pan. The traditional, and widespread, system of slash-and-burn consists of cutting the vegetation in March–April, then burning. Rice is planted using a stick with 5–10 seeds/hole and holes 20–30 cm apart. No fertilizers at all are used and weeding is the only form of field management. A single weeding, taking 10–40 person-daysha (usually about 20–25), is done. It is rare to do more, even if weeds are becoming serious. Harvesting is by hand, using sickles or small knives, or by stripping the panicles, and the harvest is stored on-farm in traditional granaries. The yield varies from about 0.6 up to 2 t/ha and declines rapidly after the first year, After 2 or rarely 3 yr, the farmers abandon the land, which returns to fallow, and restart the cycle elsewhere. In the slash-and-burn system, traditional cultivars are exclusively planted and it is estimated that there are probably more than 400 varieties planted in the country. Most of them are sticky

192 Arraudeau and Xuan varieties, with low amylose content; some are nep, meaning glutinous, and are usually used for alcoholic liquors. They appear to belong predominantly to the upland tropical japonica group — panicles are long to very long; grains are medium to large, relatively low in number, and frequently awned; tillering is low; and maturity is in the 100–160 d range, with 130–160 d range widely predominant. Several varieties are sometimes mixed in the same field, but usually they are grown more or less pure. Intercropping with another crop is infrequent, although maize, is sometimes planted. The major yield-limiting factors reported everywhere are poor soils and drought. Weeds, diseases, and pests — mainly insects with different species in different areas — are also noted but they are less important than the two major problems. Blast is never cited as being serious. The importance of nematodes is uncertain because of lack of information.

Opportunities for upland rice research

The contribution of upland rice to overall rice production in Vietnam is, and will remain, limited. Although an essential food crop for ethnic minorities, its production should be minimized in the future so as to allow an increase in other upland crops, such as fruit trees, as well as in cattle. There are, however, at least three reasons for upland rice research: • The knowledge gained from investigation of traits specific to upland rice, such as adaptability on poor soils and water-use efficiency, will not only contribute to increasing productivity in upland rice, but will also have a return for other rice crops, such as better use of limited water sources and more efficient use of nutrients. • Within a cropping- or farming-system context, upland rice improvement will have an important effect on reducing land degradation, and will also contribute to the economic growth and welfare of the peoples of the uplands. Although present practices with upland rice degrade the environment, it should and can be turned into a sustainable crop. The use of improved germplasm and production techniques will not be degrading, and will make a contribution to the long-term sustainability of the ecosystems concerned. In this paper, we consider two areas of opportunity: the central-southern plateau and the northern hilly areas. Research in these areas would be complementary and, with careful planning in successive phases, close collaboration between the two components is possible,

The central-southern opportunity The central-southern plateau includes seven provinces: Song Be, Dong Nai, Thuan Hai, Gia Lai, Kon Tum, Dac Lac, and Lam Dong. In 1991, an estimated 800,000–900,000 people were practicing shifting cultivation in these seven provinces. Dac Lac Province is suggested as the primary target at the beginning of the project for two reasons: • There is a very active university in Buon Ma Thuot, the Tay Nguyen University, which is already conducting research and extension activities in collaboration with the Eakmat Agricultural Research Center and the University of Cantho; and • The province is representative of both rubber plantations and the crop-farming systems of the ethnic minorities. In the vicinity of Buon Ma Thuot, there are two broad physiographic areas: the “Hauts plateaux” with basaltic rocks, low pH, and the usually poor, red-yellow feralitic soils that predominate in Dac Lac Province; and the mountains and foothills that predominate in Gia Lai and Lam Dong

Upland rice research 193 provinces, with diverse rocks such as schists and dacite, and very heterogenous soils that are frequently eroded because of serious deforestation in recent years. The rainfall in this area is around 1,500 mm/yr, with a rainy season from mid-April-early May until mid-October-early November (5–5.5 mo duration) with drought spells from time to time. The soils are poor to very poor everywhere and have a pH of around 4.0 up to 5.5. The upland crops are mainly upland rice, peanut, maize, sweet potato, cassava, sometimes soybean and mungbean as well as black bean, with such perennials as rubber tree, coffee, black pepper, and sugarcane. Livestock are represented by pigs, chickens, and cattle. The farmers’ equipment is limited and their cash resources are very low. Most are poor to very poor. Project goals. As migrants from northern Vietnam are predominantly in rainfed lowland-irrigated areas, the project should emphasize the ethnic minorities, particularly the Ede around Buon Ma Thuot in Dac Lac Province but also the Bahnar and Gia Lai. The research should target two cropping systems: young rubber plantations and traditional shifting cultivation and concentrate on the red-yellow podzolic soils. More specifically, the project should • Collect, protect, and make efficient use of any information or documentation that exists on upland rice from inside and outside Vietnam. There is already a large body of information, even if it is old, that could be of value for scientists and students if collected in a documentation center; • Address germplasm collection, characterization, and evaluation for local varieties, such as cuc, thai, ras, and nep materials, as well as for foreign improved varieties. Recombinants from diverse crosses focused on users’ needs, with primary attention on water- and nutrient-use efficiency, growth duration, and grain quality should be the major target for a short- to medium-term objective in plant breeding. • Address cropping systems, with a focus on upland rice productivity as well as on generating income through associated cash crops. Two cropping systems should be considered, both addressed with a “bottom-up’’ strategy, implemented with successive and progressive changes in traditional systems, accounting for the fact that the farmers would have very low resource levels at the beginning, but should progressively improve their food and cash resources. Collaboration. One very important aspect of this project is ensuring collaboration among institutions within Vietnam and IRRI. Tay Nguyen University could play a very major role (in collaboration with the University of Cantho) but support from agricultural, forestry, extension, and other institutions in the provinces concerned will be essential to take advantage of the available skills and expertise as well as to avoid duplication of effort. It is suggested that, at the beginning, one breeder and one agronomist-cropping systems specialist be involved full time with support for laboratory and field activities. IRRl could help with direct scientific and technical assistance in planning, experiments and field studies, reporting, and training. IRRl’s library could provide assistance in documentation.

The northern opportunity The area for the northern opportunity includes the provinces of Cao Bang, Ha Tuyen, Tuyen Qwang, Son La, Bac Thai, Lao Cai, Lai Chau, and Hoa Binh, but the surrounding provinces probably show strong similarities. The situation in this area is very different to that which prevails in the center-south. Three differences are particularly striking, but there are others. • The climate is much colder in winter and as hot, or even hotter, in summer. There are four seasons: a rainy season, June-October; a dry season, November-January; a “foggy season,”

194 Arraudeau and Xuan February-March, with almost permanent fogs and occasional showers accounting for around 30-80 mm of water supply; and finally, a second dry season, April-May. The overall rainfall regime is roughly bimodal with the rainy season from June-October accounting for 90% of the total rainfall. Serious typhoons can occur during the rainy season. • The landscape is much more mountainous, with some 75 to almost 90% of the total area of each province classed as hilly. These areas are rarely covered by primary forest, most frequently there is degraded secondary forest and large areas of highly degraded “bush” where slash-and-burn with shifting cultivation prevails. Generally, the valley bottoms are occupied by paddies, with roads and cities as well as most of the villages. • Where shifting cultivation exists, two situations prevail: either the area is close to communications and, consequently, to markets so that export of goods is relatively easy; or the area is far from usable roads and, consequently, it is much more difficult to gain access and there are problems in importing and exporting agricultural products out of the area. At present, rice supply is rarely a problem in the region except in the remote uplands where shortages can be up to 3-5 mo. Efforts have been made to address problems in the uplands in all provinces, for example, the on-going research and extension activities near Bac Can, about 120 km north of Hanoi. Upland rice is cultivated, frequently on very steep slopes, under slash-and-burn with shifting cultivation by ethnic minorities: the Tay, Dao, Cao Can, Nung, H’mong, Lao, and others. In Tuyen Quang, with a population of about 600,000 people, 50% belong to about 20 ethnic groups, with the Tay predominant. In this province, annual rainfall is around 1,600 mm, and 80% falls in mid-April-October. The rocks are mainly granite, but with sporadic scatterings of limestone. The farmers slash-and-burn, then grow crops (mainly upland rice) for 1-3 yr. They then abandon the land because yields decline sharply and the fallow period lasts from 6-7 up to 15-20 yr, most frequently around 10 yr. The major problems are drought resistance, because frequent dry spells can last up to 3 wk, and poor soils. Reforestation is on-going, with Acacia mangium among other species. According to the few samples observed, the traditional rice varieties are typical of upland tropical japonica, with quite long panicles and medium to 1arge grains in relatively limited numbers. Most of the varieties are low in amylose (sticky rice), but a few are waxy, Almost all have long to very long awns. The northern provinces together account for some 100,000–120,000 ha of upland rice, but the effect of upland rice is probably felt on around 1 million ha of land because of the shifting cultivation. Most of the land of Cao Bang Province is already completely devastated with no remaining forest. The situation there is extremely alarming, but some initiatives have been taken with reforestation. Almost no research was done in recent past years on upland rice, except extremely limited collections of varieties (in Cao Bang) and some cropping-systems activities. Although in the majority in total, the ethnic minorities living there have received little attention until recently. There is, however, a willingness to do more and what to do is being seriously considered. The average upland rice yield is about 1 t/ha, except in Son La where it is about 0.7 t/ha. Although blast is considered negligible, brown spot is very frequent. Weeds are the most serious problem in Son La, although apparently less so in other provinces. Three kinds of upland rice are grown, the medium amylose (the minority), the low amylose (the majority), and glutinous waxy nep rices, which are mainly used for liquor and other specific uses. There is some misinterpretation of upland rice varieties because of the strong influence of the irrigated plant type and there is a clear lack of knowledge about those varieties. Therefore, a comprehensive “germplasm strategy” is needed in this region. There is a willingness to develop activities on commodities, but they are apparently too “centralized” without well-organized planning to take care of ethnic minorities’ sensitivities, knowledge, and perceptions. Major objectives should be diversification, flexibility, and market

Upland rice research 195 orientation while simultaneously addressing quantity and, more importantly, quality targets. Topics include communications, crop ecosystem needs, and sustained income. Project goals. A multiple-focus approach to the project could include: • Crop diversification with tobacco, white potatoes, and legumes planted in the lowlands in rotation with rice; Fruit trees, with focus on high-quality apricots and plums; Ponds to produce quality fish; • Livestock, with focus on pork in the lowlands and cattle in the uplands; Poultry with chicken and ducks; Market organizations for collecting the output; and • Reforestation in the uplands as the area of upland rice declines progressively except in less hilly areas, where production could continue — land protection could use cash-crop hedgerows (for example, fruit trees) associated with pigeon pea or other crops, and crop rotations should include beans. A suitable area would be about 50 km from Cao Bang at the Bac Po historical location. Fresh water is freely available, fruit trees are growing, farmers are used to planting tobacco and white potatoes, and milk is produced. Slash-and-burn cultivation still exists, however, on steep slopes in forest areas. The local population includes Nung people, among others. The area of irrigated and rainfed rice is quite large. Although the road is in relatively poor shape, it would be adequate for marketing of produce. In most of the hills around Cao Bang and along the road toward Hanoi, denuded lands are common. In most of these areas, reforestation is a prerequisite, but should include resettlement of H’mong families as is done at present with land allocation to each family. The best improved lines from INGER experiments are yielding twice as much as the traditional checks at Cao Bang — yield of LC88-66 (IR47686 lines) is almost three times that of the traditional cultivar Te Meo under controlled experiments. Undoubtedly, higher yields can be achieved in the uplands through germplasm improvement.

General considerations For both regions, there are several common background principles. “Bottom-up’’ strategy. It is essential that indigenous knowledge and perceptions be incorporated into the decision-making process. Market potentials, communications, and infrastructures are essential components in directing the research priorities. Only by accounting for the present status of cropping systems can a development project be effective and efficient. In other words, new “high tech” practices, for which acceptance as well as impact on environment are unknown, should not be imposed. “Progressive-steps” strategy. Starting from a “low tech” level, it may take 5–10 yr to reach so-called modern cultivation techniques. This process should be soft and introduce successive components progressively. The elements to be addressed first should be the most serious agronomic and socioeconomic problems. “Flexible” strategy. The process should ensure that potential changes in crops, use of inputs, and other producing factors are adjusted to the needs of farmers and markets. Rapid changes should be possible whenever necessary. “Diversification” strategy. Uplands offer a wide diversity of commodities, from forestry to livestock and cash or food crops. Every region, down to the farm level, should adopt a range of

196 Arraudeau and Xuan activities, with a major focus on those generating income. However, food production should not be neglected as it is essential to keep the farmers from having to buy food so that they can use the income for productive items, including fertilizers and equipment. “Scientific-gain” strategy. A better understanding of the mechanisms and processes contributing to upland rice productivity is essential for ensuring efficiency of research outputs in both the short and long run. Considerable knowledge of plant-water-soilinteracting factors is needed for scientifically based sustainability of the system. “Learning” strategy. Progressive training of the scientists should be incorporated to improve skills in planning, monitoring, and reporting research, with a development-oriented presentation of documents, including the economic facets. “Documenting” strategy. A unique source of material could be created by gathering all existing documentation related to upland rice in Vietnam and building rapidly a reliable information and database center. There would be the potential later to extend this to other crops. with a “Vietnam Uplands for Life Center” perspective. “People-base” strategy. Last, but not least, all phases of the research projects should be monitored and assessed with the close assistance, comments, and advice of the final users, the farm families. Most of the activities should be on-farm, where excellent strategic research can be implemented. Although clearly research oriented, all activities should have a development-oriented target and, therefore, contribute to food security, resource-base protection, and the farmers’ welfare. With a per- capita income of US$6-8/mo at present for slash-and-burn farmers, the restraint of lack of capital is tremendous. The alternatives are simple — either the income of resource-poor people must increase where they live, or they will move toward other areas, mainly cities, and contribute to overurbanization with few chances for a better way of life. The remedy is surely not large subsidies, but helping the people to understand how they can progressively change with advice, training, and efficient extension services based on the output from economically and environmentally sound research.

Conclusion

There are several opportunities for initiating and implementing, as soon as possible, an upland rice research project in Vietnam under a Vietnam-IRRI collaborative agreement. • The economic growth favors the market economy and should generate more goods and income for the most underprivileged people who now live with subsistence cultivation practices. • The alarming process of deforestation should be reduced or stopped, The traditional slash-and- burn cultivation with logging and other causes has been responsible for 10 million ha that are already deforested. An ecologically sound improved cropping system will contribute to the success. • Traditional crops show a wide diversity. Their weaknesses, but also their strengths and comparative advantages, need to be assessed, and then improved for productivity gains. • There is a strong dedication and commitment among all institutions concerned in the uplands. • The uplands are already contributing to the development of Vietnam but could play a major role with a large “set” of commodities that cannot be grown in the lowland paddies under partial or total irrigation. Fruit trees, livestock, and annual food and cash crops should be

Upland rice research 197 associated with upland rice in well-designed and efficient production systems, through an integrated, complex process of food and cash crops. Although all the uplands of Vietnam deserve attention, research toward a development-oriented project based in two contrasting regions will serve as a node for progressive expansion of research findings and extension procedures to the uplands throughout the country. Through progressive improvements of the traditional system with step-by-step changes under flexible, diversified cropping patterns and wise use of local varietal resources, upland rice yield can be increased from the present average of 1 t/ha to at least 2 t/ha under optimized use of land and inputs.

198 Arraudeau and Xuan Pest management

Relationships between rice intensification, plant nutrition, and diseases in the Red River Delta

Ha Minh Trung, 1 Ngo Vinh Vien, 1 Dinh Thi Thanh, 1 Nguyen Thanh Thuy, 1 Ha Minh Thanh, 1 K.G. Cassman, 2 T.W. Mew, 2 P.S. Teng, 2 and R.M. Cu 2

Abstract. Average rice yield in the Red River Delta increased from 2.7 t/ha in 1985 to 3.7 t/ha in 1992. This increase was associated with intensification of input use, particularly nitrogen (N) fertilizer and pesticides. Despite an increase in fungicide use, however, disease pressure has also increased so that sheath blight, blast, and more recently a yellow-leaf disorder now cause yield losses of 20% or more on nearly 200,000 ha each year. In on-farm experiments in Ha Tay Province in the 1993 spring and summer rice-cropping seasons, the N and potassium (K) concentration in the uppermost leaves after the flowering stage indicated a deficiency for these nutrients with the farmers’ level of nutrient management. Increased rates of NPK fertilizer (P, phosphorus) increased yields by 14-19%; however, they were still limited by disease. Preventative fungicide application (PFA), in addition to the farmers’ fungicide applications, increased yields by 24-54% and the combined effects of PFA and increased NPK gave yield increases of 30-66% above farmers’ normal practices. Although normal farmers’ practices with fungicide had no effect on disease incidence or yield, PFA reduced disease incidence by 80-90%. In both seasons, yield loss from disease resulted mostly from a reduction in spikelet fertility. The potential roles of K deficiency, other nutrient imbalances, and other factors in predisposing the rice plant to disease infection need further elucidation. It is also clear that significant and large yield increases are possible from improved nutrient and disease management.

The Red River Delta (RRD) in northern Vietnam is the second largest rice-growing region in the country having about 800,000 ha of rice fields. Major increases have been recorded in rice production in this region in recent years. The average rice yield increased from 2.7 t/ha in 1985 to 3.7 t/ha in 1992 and annual production increased form 3.0 million t in 1985 to 5.1 million t in 1992. However, the problems of pests and diseases — particularly rice blast and sheath blight — have become severe along with the gains in rice production. The area affected by these diseases in 1992 was 195,816 ha or 2.7 times more than the area affected in 1985. Neck blast affected 138,000 ha in 1991 and sheath blight, 104,902 ha. The diseases reduced the average yield of spring rice to only 1.63 t/ha in 1991. Yellow-leaf syndrome and black rot of grain are diseases that occurred recently but their etiology is still unknown. They occur mostly in irrigated areas with high fertilizer inputs, particularly nitrogen (N). Soils in the affected areas are mainly old alluvial soils, low in organic matter, and slightly acidic. To develop an integrated management program for rice diseases in the RRD, the relationships between rice intensification, rice plant nutrition, and diseases must be examined. An initial study was conducted by the National Plant Protection Research Institute (NPPRI) in 1992 and 1993 at the Tan

1 National Plant Protection Institute, Chem, Tu Liem, Hanoi, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099. Philippines. Uoc Cooperative Farm in Thanh Oai District, Ha Tay Province. The study was done with the cooperation and assistance of the Entomology and Plant Pathology Division (EPPD) as well as the Agronomy, Plant Physiology, and Agroecology Division (APPA) of IRRI under the framework of the IRRI-Vietnam Collaborative Project.

Materials and methods

The Tan Uoc Cooperative Farm has about 648 ha of irrigated lowland rice in a total area of 835 ha. There are 1,800 households with 9,000 people. Before 1960, Tan Uoc was a low-lying area with rainfed lowland rice cropping. Rice was only grown during the dry or winter-spring season. During the summer months, most fields were flooded and rice could only be grown in higher areas. The main rice varieties planted then were such traditional varieties as Tam Den, Chum Bau, Te Tep; Gie Canh, and Nep Hoa Vang. These varieties are photosensitive and have law yield (1-2 t/ha). After 1960, when irrigation and drainage systems were installed, a new irrigated lowland cropping system was established. A third crop (winter crop) — commonly potato, maize, or vegetables — was grown on about 30% of the rice land during the rice interseason. At present, modern varieties such as CR203 are cultivated on 90% of the rice land. Nutrient inputs to rice are relatively high and include manure as well as chemical fertilizers of various grades. The new cropping system has produced relatively high yields (3.5-4.0 t/ha) but sustainability of rice production has been threatened by serious pests and diseases in the past few years. The soil type in the trial site is an old alluvial soil. The fields are not annually silted and are water-logged in lower areas. The field can become flooded for 1-2 wk if the rainfall exceeds 150 mm in 2-3 d. There are some difficulties with the water drainage at the end of the summer season. The soil has been modified during the intensification of rice production. It has a pH of about 4.5 to 5.5, fairly high humus content of 2.8%, high N content of 0.15-2.0%, and average levels of extractable phosphorus and potassium (P and K). These properties are typical for most soil types of irrigated lowland rice with low topography in the RRD. The experiment was conducted in nine farmers’ fields that were selected on the basis of three levels of productivity (low, medium, and high yield) based on historical records. The average yields for the spring crop were 4.5, 3.0, and 2.9 t/ha for high, medium, and low-yield farms, respectively. For the summer crop, the average yields were 4.5, 4.2, and 4.1 t/ha, respectively. Five treatments were used in this experiment for the spring season: • 1 — Farmers’ normal fertilizer practice (FNFP) + farmers’ pest control; 2 — FNFP + preventive fungicide application (PFA); • 3 — FNFP + additional NPK fertilizer, but without PFA; • 4 — FNFP + NPK + PFA; and • 5 — FNFP without fungicide application. FNFP was defined as the standard rate and timing of fertilizer and manure application practiced by the farmers in previous years (Table 1) and values represent the average fertilizer and fungicide use in the FNFP treatment. Manure and P as well as straw ash and lime powder were applied as basal treatment. N was generally applied in two equal splits: the first before transplanting and the second at 25-30 d after transplanting (DAT). The applied rates of N and P were lower than recommended for alluvial soils (90-120 kg N/ha and 30 kg P 2 O 5 /ha for the spring season and 60-90 kg N/ha and 30 kg P 2 O 5 /ha for the summer season). K was not supplied in either season although it was recommended at a rate of 20 kg K 2 O/ha for spring rice. The rates of fertilizer were reduced because diseases tend to be severe at higher N rates and because fertilizers are expensive.

202 Trung et al Table 1. Averages for land preparation, fertilizer and manure inputs, and fungicide use in the farmers’ normal practice treatments, 1993.

Spring Summer

Rough plowings (no.) 1 1 Harrowings (no.) 8 8 N (kg/ha) 53 48 33 16 P 2 O5 (kg/ha) K 2 O (kg/ha) 0 0 Manure (t/ha) 8.3 8.0 Straw ash (kg/ha) 0 90 Lime (kg/ha) 0 280 Fungicide applications (no.) 0.7 1.4

The additional NPK applied to Treatments 3 and 4 was 20-50-100 kg/ha with N, in the form of urea, supplied 21 DAT and P 2 O 5 and K 2 O, as superphosphate and KCl, supplied before transplanting. Fuji-1 and Validacin were used in some treatments to control rice blast and sheath blight — the fungicides were sprayed four times. First application of Validacin was sprayed on 25 Mar 1992, and the second, third, and fourth were applied at 10-d intervals after the first application. Fuji-1 was applied twice for leaf blast and before and after heading for neck blast. The cultivar CR203 was sown on 15 Dec 1992 and transplanted on 15–25 Feb 1993 with planting density of about 45–50 hills/m 2 . CR203 was selected from IR collection in 1978 and is the commonly used variety in northern Vietnam. It is resistant to brown planthopper (BPH) but susceptible to rice blast and sheath blight. The 1993 experiment included seven treatments: • 1 – FNFP + farmers’ pest control; • 2 – FNFP + PFA; • 3 – FNFP + additional NPK fertilizer but without PFA; • 4 – FNFP + NPK + PFA; • 5 – FNFP without fungicide application; • 6 – FNFP without manure but with additional PK; and

• 7 – FNFP without manure, but with additional NPK plus straw ash and ZnSO 4 application. Where applied, manure and lime were at a rate of 280 kg/ha, and straw ash at a rate of 90 kg/ha in fields with moderate and high yields, The rate of inorganic fertilizer was lower than the recommended rate. In treatments with additional NPK fertilizer (3 and 4), the rates as well as the application schedule were similar to that for the spring season. Treatment 6, the treatment without manure, received an additional 0-150-270 kg NPK/ha and 270 kg/ha of lime. Additional fertilizers and lime powder were applied as basal dressing. In Treatment 7 (FNFP without manure), additional fertilizers, straw ash, and ZnSO 4 were applied as a basal dressing (in kg/ha) of 300 ash + 15 N + 200 P 2 O + 250 K 2 O + 10 ZnSO 4 .

ResuIts

Meteorological data were taken at Lang Station, about 40 km from the experiment site, as the reference station for the area (Table 2). The weather data recorded at the Lang Station showed that it was favorable for rice production in both cropping seasons in 1993. Neither typhoons nor storms hit the

Rice intensification in the Red River Delta 203 Table 2. Climate conditions at a weather stationa near Tan Uoc Cooperative Farm.

Month Av. daily temperature (°C) Av. daily relative humidity (%)

1991 1992 1993 Av. b 1991 1992 1993 Av. b

Jan 17.5 15.8 16.2 15.7 84 79 74 82 Feb 19.0 16.5 19.1 16.8 79 82 83 84 Mar 21.5 19.8 20.4 19.9 91 87 85 86 Apr 23.4 24.1 24.0 23.5 83 86 86 86 May 27.4 27.3 27.0 27.3 81 83 85 82 Jun 28.9 28.9 30.2 28.8 82 81 76 82 Jul 29.3 28.5 30.2 29.2 81 82 78 82 Aug 29.0 29.6 28.9 28.6 82 78 82 84 Sep 28.6 28.1 27.8 27.3 78 83 81 82 c Oct 25.1 24.4 - 24.8 73 71 c – 82 Nov 21.1 20.2 - 21.1 76 75 c _ 79 Dec 19.4 19.6 - 17.8 79 79 _ 77

Month No. of raindays Av. monsoon rainfall (mm)

1991 1992 1993 Av.b 1991 1992 1993 Av. b

Jan 13 10 9 9 6 97 22 32 Feb 8 11 15 14 3 28 49 38 Mar 21 18 17 15 76 29 39 33 Apr 9 13 15 14 91 46 160 121 May 17 16 27 14 276 123 248 142 Jun 17 16 10 15 424 396 178 243 Jul 13 17 12 16 247 369 186 232 Aug 11 13 19 16 207 109 322 331 Sep 10 15 30 14 82 160 258 282 Oct 6 6 – 10 7 13 – 192 Nov 6 5 – 7 113 12 – 106 Dec 7 5 _ 7 16 36 – 9

a Lang Station — 21°02N, 105°51'E, 7 m above sea level. b Long-term average. c Data not available for October, November, and December 1993.

area. However, some changes in temperature and rainfall as well as relative humidity (RH) and the number of rain days and hours of sunshine had strongly affected the development of rice diseases, particularly sheath blight and blast. The spring climate in 1993 was warmer than the long-term average by 0.5-2.7°C (Table 2) and monthly precipitation was also higher than the long-term average by 10-100 mm. The warm, wet spring was not only favorable for growth of the rice plants but also conducive to the occurrence of rice diseases. Sheath blight occurred in all treatment plots. From heading stage, rice was severely infected with neck blast. The summer season for rice is June to October. June and July were relatively hot (30°C) and dry (76-78% RH). Therefore, the occurrence of sheath blight was late and the severity was low. In August and September, the temperature was similar to the long-term average of 27.5°C. The rainfall and humidity were high (258-322 mm/mo and 81-82% RH). This weather was conducive to rapid development of the plant canopy, which provided a microenvironment conducive to sheath blight development.

204 Trung et al Table 3. Disease progress of sheath blight, leaf blast, and neck blast, spring 1993.

Treatment a PI Pl+12 d 25% FL 25% FL 25% FL + 14d +21 d

Sheath blight b T1 6.0 27.5 36.6 54.1 – T2 5.5 9.7 11.3 15.5 – T3 5.8 26.1 32.3 52.9 – T4 5.8 9.7 8.1 15.2 – T5 6.3 28.0 38.6 58.4 –

Leaf blast and neck blast c T1 0.0 0.2 0.1 19.7 31.4 T2 0.0 0.0 0.0 2.8 5.2 T3 0.0 0.2 0.1 22.1 33.5 T4 0.0 0.1 0.1 3.8 6.0 T5 0.0 0.3 0.1 21.9 33.0

Note: PI, panicle initiation; and FL flowering. a T1, FNFP + farmer's disease control; T2, FNFP + Validacin and Fuji-1; T3, FNFP + NPK; T4, FNFP + NPK + Validacin + Fuji-1; and T5. FNFP + (no disease control). b Sheath blight (relative lesion height, as % of plant height). c Leaf blast severity (%) at PI, PI + 12 d. and 25% FL, and neck blast (% of infected panicles) after 25% FL.

Table 4. Grain yield, components of yield, and disease incidence, spring 1993.

Parameter a Treatment b CV

1 2 3 4 5

GY 3.43d 5.29b 4.07c 5.71a 3.48d 7.4 P/M2 362b 391a 377ab 376ab 376ab 4.7 TS/P 84b 88ab 85ab 89a 85ab 5.3 FS/P 57c 75a 62b 75a 56c 7.5 Fgr 67.4c 84.7a 73.5b 84.4a 66.4c 5.5 S/M2 30,355c 34,362a 31,946bc 33,405ab 31,845bc 6.2 Grwt 23.2c 24.9a 23.7b 25.1a 23.4bc 1.9 COY 472c 692a 553b 707a 492bc 11.5 SB 31a 4b 30a 5b 33a 31.8 IIndx 1,699a 81b 1,775a 108b 1,961a 49.5 LB 16.9a 8.2b 15.3a 10.0b 18.5a 27.1 NB 31.4a 5.3b 33.5a 5.7b 33.0a 32.9

Note: Within a row, values followed by the same letter do not differ significantly at the 0.05 level. a GY, grain yield, t/ha; P/M2, panicles/m 2 ; TS/P. total spikelets/panicle; FS/P, filled spikelets/panicle; Fgr, filled grain, %; S/M2. spikelets/m 2 ; Grwt, grain weight, g/1,000 grains; COY, components of yield and yield, g/m 2 ; SB, sheath blight incidence, %; Ilndx, infection intensity index, product of SB and RLH; LB, leaf blast at mid-grain filling; NB, neck blast at mid-grain filling; and RLH, relative lesion height (as % of plant height). b Treatments: 1, FNFP + farmers' disease control; 2, FNFP + Validacin and Fuji-I; 3, FNFP + NPK; 4, FNFP + NPK + Validacin and Fuji-1; and 5, FNFP + (no disease control).

The summer season of 1992 was quite different from that of 1993. High precipitation in June and July (369–396 mm/mo) caused seasonal flooding and damaged the newly transplanted rice. Precipitation in August, September, and October was only 109, 160, and 13 mm/mo, respectively (1ong-term averages are 331, 282, and 192 mm/mo). The average temperature for September was higher than the long-term average. These conditions were not conducive to sheath blight development

Rice Intensification in the Red River Delta 205 Table 5. Treatment effects on grain yield and leaf (upper two leaves) nutrient content, spring 1993.

Parameter a Treatment CV

1 2 3 4 5

GY 3.43d 5.29b 4.07c 5.71a 3.48d 7.4 SB 31 a 4b 30a 5b 33a 31.8 llndx 1,699a 81b 1,775a 108b 1,961 a 49.5 N1 2.80c 2.98b 3.19a 3.20a 2.74c 4.2 P1 0.5c 0.53b 0.53b 0.58a 0.48c 6.4 K1 0.90cd 0.94bc 0.98ab 1.01a 0.86d 5.4 N2 2.30c 2.57b 2.67ab 2.74a 2.21c 5.3 P2 0.40bc 0.42a-c 0.49a 0.47ab 0.38c 18.4 K2 0.61b 0.61b 0.65ab 0.69a 0.59b 8.1

Note: Within a row, values followed by the same letter do not differ significantly at the 0.05 level. a GY, grain yield, t/ha; SB, sheath blight incidence, %; Ilndx, infection intensity index, product of SB and RLH; N1, flag leaf N content at early flowering, %; P1, flag leaf P content (P 2O 5 ) at early flowering. %; K1, flag leaf K content (K 2O) at early flowering, %; N2, flag leaf N content at mid-grain filling, %; P1, flag leaf P content (P2 O5 ) at mid-grain filling, %; K2, flag leaf K content (K 2O) at mid-grain filling, %; and RLH, relative lesion height (as % of plant height). b Treatments: 1, FNFP + farmers' disease control; 2, FNFP + Validacin and Fuji-1; 3, FNFP + NPK; 4, FNFP + NPK + Validacin and Fuji-1; and 5, FNFP + (no disease control). but the unusual weather seemed to be conducive to black rot of grains and yellow-leaf disease. There were treatment differences between plots with and without additional application of NPK. Because of the warm, wet spring season in 1993, sheath blight appeared early in paddy fields. At panicle initiation (PI), the disease had occurred in all treatments (Table 3). Sheath blight was effectively controlled in plots that were sprayed with Validacin in the PFA treatments, but severity was high in plots without Validacin as well as in plots with the farmers' disease control program. The incidence of sheath blight differed statistically between treatments with and without Validacin (Table 4). Although the N content in leaves of Treatment 3 was statistically greater than that of Treatments 1 and 5, no correlation was found between disease and nutrient status of leaves (Table 5). Leaf blast was late and severity was low in spring. However, the incidence of neck blast was high at a later stage of growth (Table 3). The effect of treatments on both blast and sheath blight was similar. The nutrient content of leaves, particularly N, in the NPK-treated plot (Treatment 3) was higher than that of treatments without NPK. However, neck blast incidence was not significantly different between these treatments. Treatment significantly affected grain yield (Table 4). Treatment with NPK and PFA (Treatment 4) had the highest yield (5.71 t/ha) followed by treatment with PFA (Treatment 2, 5.29 t/ha) and treatment with only NPK (Treatment 3, 4.07 t/ha). Treatments 1 and 5 (FNFP and FNFP without PFA) had the lowest yield (3.43 and 3.48 t/ha, respectively). Except for Treatments 1 and 5, the differences of yields among plots were statistically significant. The increase of yield from NPK input, fungicide treatment, and NPK + fungicide were 19%, 54%, and 66%, respectively. The similar yields and disease incidences of the treatment without any fungicide applications (Treatment 5) and the treatment with the farmer's disease control program (Treatment 1) showed that the farmers' disease control program was not effective. The treatments also had effects on some components of yield, for example, the number of filled spikelets per panicle, percent of filled grains, and grain weight (Table 4). Sheath blight and grain yield ( r = 0.8**) and neck blast and grain yield ( r = 0.7) were highly correlated. The components of yield were also correlated with sheath blight and neck blast. Leaf blast had a lower correlation ( r = -0.5**) with grain yield than neck blast or sheath blight. The N contents of leaves at flowering

206 Trung et al Table 6. Effect of treatments on soil nutrient levels when sampled at panicle initiation, spring 1993.

Parameter a Treatment b CV

1 2 3 4 5

GY 3.43d 5.29b 4.07c 5.71a 3.48d 7.4 pH 5.04a 5.08a 5.10a 5.04a 5.05a 1.1 C 1.56a 1.55a 1.53a 1.58a 1.57a 4.6 N 0.19a 0.19a 0.20a 0.19a 0.19a 4.2 C/N 8.18a 8.19a 7.84a 8.18a 8.25a 6.2 P 72 a 72a 77a 77a 72a 13.5 K 89a 92a 93a 86a 81a 17.7

Note: Within a row, values followed by the same letter do not differ significantly at the 0.05 level. a GY, grain yield, t/ha; pH, soil pH; C, carbon, %. N, nitrogen, %; C/N, carbon: nitrogen ratio; P, phosphorus, ppm; and K, potassium, ppm. b Treatments: 1, FNFP + farmers’ disease control; 2, FNFP + Validacin and Fuji-1; 3, FNFP + NPK; 4, FNFP + NPK + Validacin and Fuji-1 ; and 5, FNFP + (no disease control).

Table 7. Treatment effects on grain yield and leaf (upper leaves) nutrient content, summer 1993.

Parametera Treatmentb CV

1 2 3 4 5 6 7

GY 4.17d 5.23b 4.76c 5.44a 4.17d 4.36d 3.90e 4.6 SB 33 b 4c 32 b 4c 31b 27b 43a 24.6 llndx 1,890b 57c 1,809b 60c 1,783b 1,497b 2,733a 34.2 N1 2.47ab 2.33b 2.41 b 2.54ab 2.62ab 2.62ab 2.75a 11.0 P1 0.38bc 0.38bc 0.43a 0.43a 0.40a-c 0.38bc 0.41ab 8.5 K1 1.09a 1.11a 1.18a 1.19a 1.19a 1.15a 1.14a 10.9 N2 2.07b 2.02b 2.14b 2.15b 2.07b 2.14b 2.46a 13.6 P2 0.37ab 0.33b 0.38ab 0.41 a 0.37ab 0.37ab 0.38ab 13.0 K2 0.91 b 0.95ab 0.98ab 1.01a 0.94ab 1.00a 0.95ab 9.9

Note: Within a row, values followed by the same letter do not differ significantly at the 0.05 level. a GY, grain yield, t/ha; SB, Sheath blight. %; Ilndx, infection intensity index, product of SB and RLH; N1. flag leaf N content at early flowering, %; P1, flag leaf P content (P 2O 5 ) at early flowering, %; K1, flag leaf K content (K 2 O) at early flowering, %; N2, flag leaf N content at mid-grain filling, %; P2, flag leaf P content (P 2 O 5 ) at mid-grain filling, %; K2, flag leaf K content (K 2O) at mid-grain filling, %; and RLH, relative lesion height (as % of plant height). b T1, FNFP + farmers’ disease control; T2, FNFP + Validacin and Fuji-1; T3, FNFP + NPK; T4, FNFP + NPK + Validacin and Fuji-1; T5, FNFP + no disease control; T6, FNFP + no manure but with P, K, and CaO; and T7, FNFP + no manure but with NPK, straw ash, and ZnSC 1,. and mid-grain filling of all treatments were not significantly different, and they were below the critical level of 2.5% N in treatments with farmers’ N management (Table 5). Although differences among treatments in P and K contents of leaves were significant, leaf K concentration was well below the 1 % critical threshold for sufficiency. Moreover, despite high rates of P and K application in some treatments, the effects of treatments on soil nutrient levels were not significant (Table 6). The mean levels of pH, C, N, P, and K and the C/N ratio did not differ among treatments. Sheath blight was the only disease of rice in summer 1993. Validacin was found effective against sheath blight in summer as well as in the spring season. Sheath blight incidence was low in Treatments 2 and 4 (4.4 and 4.3%, respectively), and disease incidence was high in treatments that did not receive PFA. As in spring 1993, the farmers’ disease control program was ineffective (Table 7) and there was a high incidence of the disease. Sheath blight incidence in Treatments 1, 3, 5, and 6 were not different statistically, but the incidence in Treatment 7 was significantly greater than all other

Rice intensification in the Red River Delta 207 Table 8. Grain yield, components of yield, and disease incidence, summer 1993.

Parameter a Treatment b CV

1 2 3 4 5 6 7

GY 4.17d 5.23b 4.76c 5.44a 4.17d 4.366d 3.90e 4.63 H/M2 47.8a 47.6a 47.4a 47.3a 47.9a 47.9a 47.4a 1.6 P/M2 392c 425b 427b 432ab 390c 424b 450a 5.2 TS/P 65a 66a 68a 68a 65a 66a 65a 6.6 FS/P 49b 57a 52b 59a 50b 51b 43c 7.6 Fgr 74.6b 86.0a 76.4b 86.0a 75.9b 76.8b 65.1c 6.1 S/M2 25,373b 27,964a 29,165a 29,480a 25,545b 28,081a 29,461a 6.5 Grwt 23.6ab 23.8a 23.5ab 23.8a 23.4b 23.6ab 23.4b 1.3 COY 445d 572 b 522c 602a 453d 505c 446d 5.5 SB 33b 4c 32 b 4c 31 b 27b 43a 24.6 llndx 1,890b 57c 1,809b 60c 1,783b 1,497b 2,733a 34.2

Note: Within a row, values followed by the same letter did not differ significantly at the 0.05 level. a GY, grain yield, t/ha; H/M2, hills/m2; P/M2, panicles/m2; TS/P, total spikelets/panicles; FS/P, filled spikelets/panicle; Fgr. filled grain (%); S/M2, spikelets/m2; Grwt, grain might, g/1,000 grains; COY, components of yield and yield, g/m2; SB, sheath blight incidence, %; Ilndx. infection intensity index, product of SB and RLH; and RLH, relative lesion height (as % of plant height). b TI, FNFP + farmers' disease control; T2, FNFP + Validacin and Fuji-1; T3, FNFP + NPK; T4, FNFP + NPK + Validacin and Fuji-1; T5, FNFP + no disease control; T6, FNFP + no manure but with P, K, and CaO; and T7, FNFP + no manure but with NPK, straw ash, and ZnSO 4 .

Table 9. Effect of treatments on soil nutrient levels when sampled at panicle initiation, summer 1993.

Parameter a Treatment b CV

1 2 3 4 5 6 7

GY 4.17d 5.23b 4.76c 5.44a 4.17d 4.36d 3.90e 4.63 pH 5.57a 5.58a 5.53a 5.57a 5.58a 5.60a 5.52a 1.74 C 1.66a 1.66a 1.64a 1.64a 1.65a 1.67a 1.64a 3.34 N 0.19a 0.19a 0.18a 0.19a 0.19a 0.19a 0.19a 5.71 C/N 9.02a 8.79a 9.00a 8.56a 8.78a 8.78a 8.59a 6.00 P 55b 59a b 59a b 66a 59ab 62ab 55b 12.5 K 88a 88a 90a 95a 91 a 94a 89a 9.7

Note: Within a row, values followed by the same letter do not differ significantly at the 0.05 level. a GY, grain yield, t/ha; pH, soil pH; C, carbon, %; N, nitrogen, %; C/N, carbon:nitrogen ratio; P, phosphorus, ppm; and K, potassium, ppm. b T1, FNFP +farmers' disease control; T2, FNFP + Validacin and Fuji-1; T3, FNFP + NPK; T4, FNFP + NPK + Validacin and Fuji-1; T5, FNFP + no disease control; T6, FNFP + no manure but with P, K, and CaO; and T7, FNFP + no manure but with NPK, straw ash, and ZnSO 4 . treatments. The addition of high rates of NPK and other amendments seemed to promote the incidence of sheath blight. Treatment effects on grain yield in the summer crop experiment were similar to the 1993 spring experiment. The highest yield, 5.4 t/ha, was from treatment with PFA plus NPK (Treatment 4), followed by treatment with PFA plus FNFP (Treatment 2, 5.3 t/ha), followed by treatment without PFA (Table 7). The lowest yield of 3.9 t/ha was from Treatment 7 (FNFP + NPK + straw ash and ZnSO 4 but no manure). Preventative fungicide application had a large, positive effect on filled spikelet percentage while increased NPK resulted in more panicles per square meter (Table 8). Also similar to the results in spring 1993, high rates of P and K fertilizer inputs had no detectable effect on soil-test values for these nutrients (Table 9).

208 Trung et al Discussion

Blast was the most important disease in the RRD, but sheath blight has replaced it. The reason for this is that the weather in the winter-spring season has been warmer in recent years and this has been accompanied by a delay in planting spring rice. These changes enable sheath blight to be more predominant in both spring and summer seasons, whereas blast is only common is the spring season. The addition of NPK fertilizers at a rate of 20–50–100 kg/ha to FNFP significantly increased the grain yield in both cropping seasons. The yield increase was also observed even in conditions of high disease intensity. The yield in plots with PFA (Treatment 4) was 40% higher than the yields in plots without PFA (Treatment 3) for both cropping seasons. The increase in grain yield due to fertilizer indicates a shortage of N in FNFP in this region. The fertilizer recommendations of the Institute for Soils and Fertilizers Research (ISFR) require an application of 90–120 kg N/ha and 30 kg of P 2 O5 /ha for summer cropping to achieve a yield target of about 4.5–5.5 t/ha. The farmers’ N rate was significantly lower than the ISFR recommendation, only about 53 kg N/ha for spring and 48 kg N/ha for summer season were applied. If we take into account some quantities of N released from manure, about 0.6% N in 8 t/ha of manure would yield another 48 kg N/ha. Thus, total N applied by farmers was about 100 kg N/ha, which is within the recommended range. The ISFR recommends a low rate of P and makes no recommendation for K. This recommendation might be based on older data, indicating that neutral and slightly acidic alluvial soil would not respond to P 2 O 5 and K 2 O in the absence of N. Where high levels of N are required for high yields, P 2 O 5 and K 2 O are needed in combination with N. The addition of NPK at 20–50–100 kg/ha has strongly contributed to yield increases even in conditions of high blast and sheath blight. Higher incidence of sheath blight, however, drastically reduced yield. It is important that the farmers in the RRD increase their fertilizer input to further increase yield. Because the incidence and severity of sheath blight and rice blast can also increase at increasing levels of fertility, fungicide that can effectively control the diseases should also be applied. The farmers’ disease control program was ineffective in controlling the disease. A review of the farmers’ timing and frequency of fungicide application should be initiated to improve their disease control program. For more than 30 yr, farmers in the RRD have not applied adequate amounts of P and K as indicated in the survey of farmers’ practices. Rice fields in the area might already be deficient in P and K because of intensive rice production without replenishment of these elements through fertilizer application. Results from the 1993 spring and 1993 summer field experiments showed that the extractable amounts of soil P and K did not change even at higher rates of applied P and K. The failure to change the extractable P and K contents of the soil with P and K addition suggests the possibility of soil fixation. Further work is needed on quantifying soil P and K fixation characteristics to explain the lack of increase in extractable P and K in treatments that received large amounts of fertilizers.

Conclusion

Results of field trials conducted in the Tan Uoc Cooperative showed that there is a great potential to increase the yield of rice in irrigated lowland areas of the RRD. Fertilizers, particularly N, are essential for increasing rice yield, but the severity of blast and sheath blight also increase with higher rates of fertilizers. Improvement in yield can also be achieved by effective control of sheath blight. The farmers’ disease control program was ineffective, Additional amounts of N are needed to improve yield, and the application of fungicide also appears to be needed for prevention of losses due to sheath blight

Rice Intensification in the Red River Delta 209 Tissue analysis of plants in both seasons indicated N and K deficiency at flowering. Extractable soil P and K did not change after the addition of large amounts of P and K fertilizer. This phenomenon has also been observed in the Mekong river Delta in southern Vietnam (Kim et al, this volume, page 211). Further study is needed to quantify the soil P and K fixation properties. This study could explain the lack of change in extractable P and K in soils treated with high levels of P and K. The ISFR fertilizer recommendation for the RRD should be adjusted to include amounts of P and K that can be used by the plant.

210 Trung et al Relationships between rice intensification, rice plant nutrition, and leaf-yellowing disease in the Mekong River Delta

Pham Van Kim, 1 R.M. CU, 2 P.S. Teng, 2 K.G. Cassman, 2 T.W. Mew, 2 Truong Thi Nga, 1 Nguyen Bao Ve, 1 and Pham Van Bien3

Abstract. Grain yields were high in plots with high levels of nitrogen (N) fertilizers, and potassium (K) at 200 kg K2 O/ha also significantly improved yield. Levels of N fertilizer were positively correlated with severity of leaf-yellowing disease (LYD), but phosphorus (P) and K had no effect on the disease. Leaf tissue analyses for N, P, and K indicated that N and K were deficient in both years at most locations, and high rates of supplemental N or K failed to increase the levels of N and K in the flag leaf above the critical values of 2.5% N and 1.0% K. This phenomenon suggests that the soil is possibly deficient in nutrients and fixed K strongly. Before this phenomenon can be interpreted, the procedures for tissue analysis and the equipment used in this experiment must be checked and calibrated. The distribution of LYD followed the distribution pattern of rice blast. It also appeared that the severity of LYD was correlated with the cropping intensity index — LYD was high in areas where three crops of rice were planted in a year, intermediate in areas where two crops of rice and a nonrice crop were planted, and low where only two crops were planted.

Leaf-yellowing disease (LYD) is a new rice disease discovered in southern Vietnam in 1987. Although, at first, LYD appeared unimportant at Cai Lay District, Tien Giang Province, it has spread over the years and become a very important disease of rice in Tien Giang, An Giang, and Dong Thap provinces. In 1990, rice fields in Tien Giang Province were severely affected by the disease. Losses caused by LYD had been studied (Hoa 1991) and have been estimated to reach about 50% in severely affected areas. The disease is particularly severe in areas of intensive cropping such as Tien Giang, An Giang, Dong Thap, and the northern part of Cantho provinces but is only mild to moderate in other areas with less-intensive cropping. The etiology of LYD is still not known but the effects of chemical fertilizers and some cultural practices on LYD have been, investigated. Some fungicides such as Benlate, Copper-B, and Topsin M have been reported to be effective for controlling the disease (Khoe 1990, Loc 1991). Du et al (1991) reported that Curvularia lunata was the causal organism of red stripe of rice in the Mekong River Delta (MRD). In 1992, two other researchers implicated Pseudomonas seritae pv. oryzae as the causal organism. A collaborative research project between IRRI and Vietnam was carried out to investigate the relationships between cropping intensity, nutrient status of the rice plant, and the expression of LYD.

Materials and methods Field experiments were conducted during the first crop of 1992 and the second crop of 1993. There were 29 sites in two areas on the same soil type, Ustropept subgroup (15 sites in Cai Lay District, Tien Giang Province, and 14 sites in Vung Liem District, Vinh Long Province). The 1992 experiment had

1Faculty of Agronomy, University of Cantho, Cantho, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 3Institute of Agricultural Sciences of South Vietnam, 121 Nguyen Binh Kiem, 1st District, Ho Chi Minh City, Vietnam. Table 1. Amount of fertilizer used by farmer cooperators in the Mekong River Delta, 1993 experiment.

Location Site Amount of fertilizer (kg NPK/ha)

Cai Lay 1 90-46-0 2 120-46-30 3 110-46-30 4 120-46-60 5 90-55-60

Vung Liem 6 75-46-0 7 75-30-3 8 80-40-0 9 90-45-5 10 80-46-5

Soc Trang 11 90-35-0 12 110-36-25 13 130-36-25

Thot Not 14 120-44-60 15 180-40-15 16 150-40-15

six treatments with various fertilizer regimes. Treatment 1 had 100-46-0 kg/ha of NPK fertilizer, Treatments 2 to 6 received the same amount of fertilizer as in Treatment 1 plus 40-0-0, 0-100-0, 0-0-200, 0-100-200, and 40-100-200 kg/ha of NPK fertilizer. Fertilizers were applied in three splits: one-third as basal before transplanting in Cai Lay or 10 days after seeding in Vung Liem for direct- seeded rice; one-third at about 20 d after sowing; and the last split was applied at panicle initiation (PI). The 1993 experiment had 16 sites in four areas (Table 1): five sites in Cai Lay, five in Vung Liem, three in Soc Trang Province, and three in Thot Not District, Cantho Province. Each site had three treatments replicated three times. All of the 10 sites in Cai Lay and Vung Liem, one in Soc Trang, and one in Thot Not had the same fertilizer regimes: Treatment 1 received NPK at 100-46-0 kg/ha, Treatment 2 had 140-146-200, and Treatment 3 was the farmers’ practice indicated in Table 1. There were also four sites, two in Soc Trang and two in Thot Not, with special fertilizer regimes: Treatment 1 was 100-105-0 kg NPK/ha, Treatment 2 was 140-334-240, and Treatment 3 was the farmers’ practice indicated in Table 1. Plot size was about 49 m 2 . The varieties used were those usually planted by the farmers. Disease was assessed at PI, 14 d after PI, flowering, and 15 d after flowering. From each plot, 60 tillers were selected for disease assessment. The intensity of the disease was scored based on the scale established by the Vietnamese Ministry of Agriculture (Table 2). Leaves were sampled for nutrient analysis at PI and at flowering for the 1993 experiment. Leaf samples for tissue analysis were collected from the five oldest tillers taken from six randomly selected hills in two 21-m2 areas from each plot. Leaves from sample tillers were divided into two groups. The upper-leaf group contained the three upper-most leaves including the flag leaf. The lower-leaf group contained the fourth, fifth, and sixth leaves. Leaves from the two sample groups were analyzed for available N, P, and K by the Department of Soil Science at the University of Cantho. Also in 1992, three soil cores were taken at

212 Kim et al Table 2. Scale used to assess leaf-yellowing disease severity.

Year Scale Area of LYD lesion (%)

1992 1 1-5 3 6-10 5 11-25 7 26-50 9 50-100

1993 1 1-10 2 11-20 3 21-30 4 31-40 5 41-50 6 51-60 7 61-70 8 71-80 9 81-90 10 91-100

Table 3. Nitrogen, phosphorus, and potassium levels of soil after the 1993 experiment.

Location Total N Total P Exchangeable (%) (%) K (meq/100 g)

Cai Lay 0.192a 0.067b 0.165b Vung Liem 0.152b 0.045c 0.181a Soc Trang 0.102c 0.079a 0.132c Thot Not 0.114c 0.077a 0.184a CV (%) 23.6 20.0 21.5

Note: Within a column, means followed by the same letter do not differ significantly by Duncan’s multiple range test. flowering from each of the first three treatments, then pooled. Soil sampling was done separately at two soil depths, an upper layer (0-10 cm) and a lower layer (10-20 cm). Soil samples were analyzed for pH, extractable P and K, and total C and N. Land owners were interviewed to collect data of cropping pattern and crop history of the fields in the past 10 yr.

Results and discussion

High severity of rice blast affected the 1992 experiment in Tien Giang Province, and mild sheath blight affected the 1992 and 1993 field experiments. Fuji-1 and Validamycin were used to control rice blast and sheath blight, respectively. Only two sites in Cai Lay were damaged by blast in 1992. Soils in Cai Lay had the highest total N content, but were lower in P and K that other areas. Soils in Soc Trang and Thot Not had high extractable P, and soils in Vung Liem and Thot Not had the highest extractable K content (Table 3). The organic matter content of soils in Cai Lay was lower than that of Vung Liem (Table 4).

Rice intensification in the Mekong River Delta 213 Table 4. Soil characteristics of fields in Cai Lay and Vung Liem, 1992.

Characteristics Cai Lay Vung Liem of soil

0-10 cm layer pH 5.547 5.207 Organic matter (%) 3.905 4.458 Total N (%) 0.193 0.176 Available P (mg/100 g) 7.331 7.466 Exchangeable K (meq/100 g) 0.255 0.186

10-20 cm layer pH 6.187 5.921 Organic matter (%) 2.511 3.424 Total N (%) 0.129 0.147 Available P (mg/100 g) 5.253 4.469 Exchangeable K (meq/100 g) 0.277 0.206

Table 5. Effects of fertilizers on grain yield and severity of leaf-yellowing disease, Mekong River Delta, 1992.

Site and treatment Grain yield Disease index Upper leaf N at (kg NPK/ha) (t/ha) (%) flowering (%)

Cai Lay 100-46-0 5.8a 55.7c 1.348b 140-46-0 5.7a 66.0a 1.764a 100-146-0 6.0a 54.8c 1.377b 100-146-200 5.8a 56.9c 1.415b 100-146-200 6.0a 58.2bc 1.403b 140-146-200 5.9a 63.7ab 1.740a

Vung Liem 100-46-0 5.0c 0.27c 1.142b 140-46-0 5.2bc 3.45b 1.439a 100-146-0 5.2bc 0.44c 1.141b 100-46-200 5.4ab 0.84c 1.181b 100-146-200 5.5ab 1.15c 1.114b 140-146-200 5.7a 7.66a 1.374a

Note: Within a column, means followed by the same letter do not differ significantly by Duncan's multiple range test.

LYD occurred late in 1992. The disease also occurred late during the second cropping season of 1993 in Cai Lay where the crop was sown early. In Vung Liem, where the crop was sown later than Cai Lay, LYD occurred early at about 14 d after PI. The disease, however, did not continue to develop after the flowering stage: disease severity was only mild during the 2 yr of field experiment. N fertilizer affected the severity of LYD in Cai Lay and Vung Liem in 1992 and 1993. An increase in N application in 1992 from 100 to 140 kg N/ha led to an increase in the severity of the disease (Table 5). Although leaf N concentration increased with higher N rates, leaf N content remained well below the critical value of 2.5%. Supplementation with 100 kg P 2 O 5 /ha and 200 kg K 2 O/ha did not show any effect on the disease. The 1993 experiment also showed an increase in LYD

214 Kim et al Table 6. Effects of fertilizers on grain yield and severity of leaf-yellowing disease, Mekong River Delta, 1992.

Site and treatment Grain yield Disease index Upper leaf N at (kg NPK/ha) (t/ha) (%) flowering (%)

Cai Lay 100-46-0 4.7b 27.14b 1.643a 140-146-200 5.2a 42.84a 1.775a Farmers’ practice 4.7b 28.29b 1.565a

Vung Liem 100-46-0 3.8a 1.55a 1.749a 140-146-200 4.0a 11.95a 1.723a Farmers’ practice 3.8a 8.27a 1.687a

Soc Trang 100-46-0 2.7c 6.75c 1.916a 140-146-200 3.4a 21.58a 1.919a Farmers’ practice 3.0b 14.24b 1.916a

Thot Not 100-46-0 2.6b 27.67b 1.934a 140-146-200 3.4a 39.09a 1.888a Farmers’ practice 3.1a 29.18b 2.037a

Note: Within a column, means follwed by the same letter do not differ significantly by Duncan’s multiple range test.

Table 7. History of cropping pattern of experimental fields in Mekong Delta.

Characteristics Cai Lay Vung Liem Soc Trang Thot Not

Rice crop intensity index 8.95 7.27 7.00 7.39 Lana plowing index 1.14 2.33 2.03 1.68 Total fallow period (d/yr) 88.60 141.80 50.30 43.10 Total flooded period (d/yr) 352.20 269.40 249.70 270.00 N fertilizer applied (kg/yr) 340.30 147.50 199.80 238.50 P fertilizer applied (kg/yr) 142.60 71.00 61.50 92.10 K fertilizer applied (kg/yr) 27.90 12.10 27.00 22.80 LYD disease index (mean) 41.46 0.93 6.75 27.66 severity at higher levels of fertilizer (Table 6). Results from both years have indicated a positive correlation between disease severity and high N fertility. The level of fertilizer input had a significant effect on grain yield in Vung Liem in 1992 (Table 5) and in Cai Lay, Soc Trang, and Thot Not in 1993 (Table 6). An increase of 40 kg N/ha was shown to improve grain yield as did 200 kg K 2 O/ha. However, an increase of 100 kg P 2 O 5 /ha did not show any improvement in yield in Cai Lay and Vung Liem. As in 1992, the 1993 experiment also showed the same yield responses to N and K. Results from these experiments strongly suggest that N and K are deficient and that about 200 kg K 2 O/ha is needed to improve grain yield. Leaf analyses showed that N was below the critical levels for rice (Tables 5 and 6). Leaf N at flowering was below the 2.5% critical value even in plots that received high N levels. K content of flag leaves at flowering was also below the critical value, 1%, and supplemental K, as much as 200 kg K 2 O/ha, did not increase the K content of leaf tissue to levels higher than the critical value.

Rice intensification in the Mekong River Delta 215 Cai Lay, where rice fields have been cropped three times a year for the past 10 yr, had the highest rice intensification index (Table 7). It was 8.95 compared with 7.00–7.39 in the other three sites where farmers plant rice twice a year only. The high cropping intensity at Cai Lay was also indicated by longer flooding periods that other areas (352 d versus 250–270) and higher NPK fertilizer inputs. Vung Liem and Soc Trang had a lower rice intensification index than Thot Not and the amount of N fertilizer used in those areas was lower than the amount used in Vung Liem also. As well as having the highest rice intensification index, Cai Lay also had the most severe LYD in 1992 (Table 5). Cai Lay and Thot Not had the highest LYD severity in 1993 (Table 6) and Liem and SOC Trang had low LYD intensity. The distribution pattern of LYD in the MRD also had the same distribution pattern as rice blast. Kim et al (1981) reported that the severe blast region in the MRD was in Tien Giang, Dong Thap, An Giang, and the areas north of Hau Giang Province (Thot Not). LYD was first discovered in Tien Giang (Cai Lay) in 1987 and it had spread throughout the MRD 2 yr later, but with severe LYD concentrated in areas where rice blast was severe. It also appeared that high severity of LYD was correlated with crop intensification. LYD in Cai Lay, where farmers plant rice three times per year, was consistently severe during the 2 yr of the experiment. In Thot Not, where farmers plant rice for two seasons followed by a nonrice crop in the third season, had intermediate severity of LYD. In other areas, where crop intensification index was low (farmers plant only twice per year), the severity of LYD was low.

References cited

Du P V, Lan N T P, Dinh H D (1991) Red stripe, a newly reported disease of rice in Viet Nam. Internat. Rice Res. Newsl. 18(3):25. Hoa T T (1991) Survey of leaf yellowing disease of rice on first crop of 1991 at Dong Thap Province [in Vietnamese]. BS thesis, University of Cantho, Cantho, Vietnam. 29 pp. Khoe L T (1990) Effect of seven fungicides to control leaf yellowing disease [in Vietnamese]. BS thesis, University of Cantho, Cantho, Vietnam. 31 pp. Kim P V, Nghiem N T, Len L, Kinh D N (1981) Survey of rice disease in the Vietnamese Mekong Delta from 1978 to 1980. Internat. Rice Res. Newsl. 6(5):14–15. Loc D V (1991) Effects of the timing and the number of sprayings of Copper-B to control leaf yellowing disease [in Vietnamese]. BS thesis, University of Cantho, Cantho, Vietnam. 30 pp.

216 Kim et al Reducing early-season insecticide applications through farmers’ experiments in Vietnam

K.L. Heong, 1 Nguyen Thi Thu Cuc, 2 Nguyen Binh, 3 S. Fujisaka, 1 and D.G. Bottrell 1

Abstract. Farmers’ insecticide use in Vietnam appears to be due to misperceptions rather than real needs. A large proportion of farmers spray early to control highly visible leaf-feeding insects, such as the leaffolders, because they believe that these insects can cause losses. However, field and laboratory research have shown that the rice crop can recover from leaf damage in the early season with no yield loss. When farmers were invited to participate in a simple experiment to evaluate the simple hypothesis that spraying for leaffolder control in the first 40 d after sowing was not necessary, farmers “discovered” that early spraying was unnecessary. Most farmer participants stopped early insecticide applications against leaflolders. With supporting extension activities, early insecticide spraying for leaffolder control in An Giang Province decreased dramatically. Farmers’ experiments thus serve as a usefu1 tool to initiate change in farmers’ perceptions of leaf-damaging pests.

Despite advances in pest-management research, pest-management practices have remained relatively unchanged in many developing counties in the 1ast two decades (Brader 1979). In the 1990s, this is still true in many countries: farmers rely mainly on pesticides to prevent crop losses (Lim and Heong 1984). For rice, numerous cultivars with multiple resistance have been developed (Khush 1989) but, in some countries, although these varieties have been widely adopted, farmers have increased their use of pesticides, particularly insecticides (Fig. 1). Farm surveys have shown that most rice farmers do not understand that resistant cultivars should receive less insecticide (Escalada and Heong 1993), but believe that most insects are harmful to the crop and that insecticides are the cure (Lim and Heong 1984, Escalada and Heong 1993). Pesticide advertising and the presence of pesticide sales agents, who often provide pest-management advice to farmers in rural communities, have influenced farmers’ unfavorable attitudes toward insect pests (Escalada and Heong 1993, Matteson et al 1994). In an information environment where messages to encourage pesticide use far exceed any other opinions, farmers have adopted extreme risk-averse attitudes with little economic rationale toward pesticide use. To improve on-farm pest-management practices, alternative approaches to warn farmers of this pesticide-dependent syndrome must be explored. Such approaches can serve to enhance field- training programs for farmers administered by the Food and Agriculture Organization of the United Nations (FAO) and the Ministry of Agriculture and Food Industry (MAFI) in Vietnam.

Pest-management practices of rice farmers in southern Vietnam

In May 1992, a survey of 685 farmers in the Mekong River Delta showed that the pattern of insecticide use by the farmers included early-season applications of broad-spectrum organophosphates for the control of leaf feeders (Mai et al 1993, Heong et al 1994). About 80% of the farmers applied

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 2 University of Cantho. Cantho, Vietnam; 3 Plant Protection Department, Long Xuyen, An Giang Province, Vietnam. 1. Proportion of farmers using pesticides in Nueva Ecija. Philippines. 1960-90. Arrows indicate introduction of IR varieties. Except for IR8, the new varieties are resistant to insect pests.

2. Distribution of first insecticide sprays after sowing in the Mekong River Delta.

their first insecticide sprays in the first 40 d after crop establishment (Fig. 2): their main pest target was the rice leaffolder, Cnaphalocrocis medinalis. Most farmers strongly believe that this pest will cause severe yield loss. Although damage by leaffolder may be highly visible, it is doubtful whether such damage can cause loss in yield. Bautista et al (1984) estimated the economic threshold at booting and heading stages to be 1.51 and 1.32 larvae/plant, respectively. However, they had grossly overestimated leaf

218 Heong et al consumption, 101.2 cm2/larva, whereas a larva could only consume 24.3 cm2 on plants at the favorable stage of 40 d after sowing (Heong 1990). The adjusted threshold should thus be 5 or 6 larvae/plant. Field estimates by Miyashita (1985) also showed that, at the tillering stage, crops with 67% damaged leaves did not suffer any yield loss. Using a computer-modeling approach, Graf et al (1992) provided a conservative threshold of 3 larvae/hill. Using a similar approach, Fabella et al (1994) suggested that leaf consumption by 20 larvae would still be insufficient to reduce crop yield significantly. In field populations, however, the pest density seldom exceeds 1 larva/hill (Guo 1990). Farmers seem to be overreacting to visible symptoms of damage and had overestimated yield losses associated with them (Escalada and Heong 1993). A similar tendency to overreact to certain insects was observed among Honduran farmers (Bentley 1989) who would spray insecticides on bean fields to kill Diabrotica beetles even though the damage was minimal. They had perceived these beetles as threatening because of their large size, bright colors, and ability to make large holes in the leaves. Similarly, rice farmers in southern Vietnam may overreact because of the highly visible larvae and damage symptoms. In addition, other factors may also influence insecticide use. These include the association of insecticides with modernism (Kenmore et al 1985, Bentley 1989), promotion campaigns for pesticides (Escalada and Heong 1993), farmers equating pesticides with medicine (Lim and Heong 1984, Bentley and Andrews 1991, Escalada and Heong 1993), and ease of use (Escalada and Heong 1993), and government-supplied pest-forecast information.

Communicating pest management through farmers’ experiments Widespread gaps in knowledge of farmers and unfavorable attitudes of farmers toward natural methods of pest management have encouraged pesticide misuse. Although rice farming without insecticides is economically competitive (Herdt et al 1984, Waibel 1986, Rola and Pingali 1993), most farmers are too well-indoctrinated to contemplate the possibility of not using them (Matteson et al 1994). This attitude prevails because of negative motivators — ignorance, fear. and passivity. In addition, chemical sales campaigns often exploit policymakers’ and farmers’ fears by portraying pesticides as valuable “insurance.” To end this pesticide-dependency syndrome, innovative communication approaches must be developed. Farmers’ participation in experimenting with a simple principle or “rule-of-thumb” has been used to encourage technology adoption (Bunch 1989). Such experiential learning processes have been demonstrated in the diffusion of both traditional and new technologies in maize and cassava growing in West Africa, soil-conservation techniques in the Philippines, and the making of contour ditches in Guatemala. In Vietnam, rice farmers were invited to experiment with a simple pest-management rule. The test principle was “early spraying for leaffolder control is not necessary.” To participate in the experiment, each farmer measured out an area of about 500 m2 in his or her rice field that would not receive any insecticide spray in the first 40 d for the control of leaffeeders. The rest of the field continued to receive the normal treatment. A total of 90 farmers from three provinces were invited to conduct the experiments (Table 1). During the season, farmers were visited by agricultural technicians and researchers to discuss the progress of the experiment. Each participating farmer was provided with supporting materials, such as a copy of Friends of The Rice Farmer (Shepard et al 1987), a record- keeping booklet, a ballpoint pen, and a sign board to be placed in the field. At the end of the season, a farmers’ workshop was organized and the participating farmers discussed the results of their experiments. At this workshop, farmers compared visual leaf damage and yields between the experimental plots and the rest of their fields. Generally, the number of insecticide sprays in the farmers’ experimental plots was reduced compared with the rest of their fields (Table 1). Yields of the two areas were, however, similar. All

Reducing early-season insecticide application 219 Table 1. Farmers’ experiments in southern Vietnam.

Province No. of Mean no. of sprays Mean yields (t/ha) farmers participating Experiment Main crop Experiment Main crop

Hau Giang 40 0.8 1.8 3.9 3.9 An Giang 18 0.8 2.3 6.7 6.7 Tien Giang 32 0.0 2.6 6.4 6.5

Table 2. Changes in farmers’ early spraying a for leaffolder, An Giang Province.

May 1992 Dec 1992

Number farmers interviewed 77 201 % farmers who sprayed early 91.1 21.4

a Winter-springcrop 1991/92 and summer-autumn crop 1992.

Table 3. Mean number a of insecticide sprays and yields of farmers’ experiments in Kien Giang Province.

District No. No. of insecticide sprays Grain yield (t/ha) inter- viewed Farmers’ Experimental Farmers’ Experimental plots plots plots plots

Rach Gia 16 1.27 (1.24) 0.13 (0.34) 5.71 (0.54) 5.68 (0.51) Hon Dat 7 3.14 (1.12) 1.29 (1.28) 4.76 (0.58) 4.47 (1.79) Tan Hiep 21 1.71 (0.93) 0.26 (0.39) 6.07 (0.69) 6.19 (0.74) Go Quuo 7 2.28 (1.28) 0 3.69 (1.45) 4.26 (0.35) Chan Thanh 13 1.54 (0.93) 0.08 (0.27) 5.88 (0.31) 5.92 (0.31) Giang Rieng 14 2.00 (1.20) 0.28 (0.45) 5.74 (0.70) 5.14 (0.71)

a Values in parentheses are standard deviations.

90 participating farmers decided that insecticide spraying for leaffolders in the first 40 d after sowing was unnecessary. When interviewed, some farmers inferred that there was no yield difference was because the crop could easily recover from the early damage by the leaffolder.

Multiplier effects In December 1992, a survey of 201 randomly selected farmers in Chau Thanh, Thoai Son, and Phuc Tan districts in An Giang Province was carried out to evaluate possible multiplier effects of the farmers’ experiments. Fewer than 22% of the farmers surveyed sprayed for leaffolder at the early crop stages (Table 2). This represented a substantial change from the 1991 crop season when most farmers believed that leaffolders were serious pests. This change was due to the additional extension activities of the Provincial Agricultural Authority of An Giang to actively promote the “no early spray” practice in 1992. These activities included radio broadcasts, farmers’ meetings, incorporating the practice into their training programs, and distributing 30,000 leaflets to encourage farmers not to use insecticides for leaffolder control in the first 40 d.

220 Heong et al Since 1992, these farmers’ experiments have been spreading rapidly to many other farmers in the Mekong river Delta. In the last winter–spring crop (1993/94) in Cantho Province, more than 600 farmers experimented with this simple rule. In Kien Giang, the provincial agricultural authority initiated a farmers’ experiment program involving 400 farmers in 1993. A sample of 77 farmers in six districts showed that the average number of insecticide sprays was reduced to fewer than one in the experimental plots (Table 3). There were no yield differences between the two plots.

Conclusions

Experiential learning from conducting a simple experiment to test a simple hypothesis is an effective way to improve farmers’ pest-management decision-making. It can eliminate earlier misperceptions that have often biased farmers’ attitudes toward insect pests. Farmers’ decisions are often based on normative rather than economic considerations (Mumford and Norton 1984). The behavioral-decision model proposed by (Mumford and Norton 1984) suggests that farmers’ decisions are more influenced by how they perceive the problem rather than the actual situation. The dynamic form of this model suggests that the outcome of an action taken in one time period can greatly influence perceptions in the next time period. Thus, the outcome of the experimental plots of the farmers served as a feed- forward mechanism to initiate change in perceptions, attitudes, and practices in the next time period. Thus, farmers’ experiments can serve as a tool to initiate changes in attitudes.

References cited

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222 Heong et al Characterization of pests, pest losses, and production patterns in rainfed lowland rice of the Mekong River Delta

H.O. Pinnschmidt, 1 Nguyen Dang Long, 2 Tran Tan Viet, 2 Le Dinh Don, 2 and P.S. Teng 1

Abstract. Holistic field surveys with integrated crop-protection treatments were conducted at four rainfed lowland rice (RLR) sites in the Mekong River Delta (southern Vietnam) in 1992. Data on crop development, yield, dynamics of disease and pest severities, weather, water conditions, physicochemical soil properties, and crop- and pest-management practices were collected. Weather-limited yield potentials of sites were estimated with the rice simulation model CERES (Crop Evaluation through Resources and Environmental Synthesis) and nitrogen-limited (N) potential yields were estimated based on an empirical model. Estimates of actual yield-gaps and yield losses were derived from these. Correlation, factor, and multiple-regression analyses were done to characterize patterns of and interrelations among cropping and pest-control practices, factors determining productivity level, physiological potential yield, and pest problems and to develop empirical methods for estimating yield potentials, pest- induced yield losses, and pest proneness of sites. High yields were closely associated with high soil productivity as indicated by high soil carbon content, high fertilizer input, and high pest-management intensity: low occurrence of vegetative drought stress; and high pest and disease severities whereas low yields were associated with the opposite conditions. The total yield-gap was estimated to range from about 20% to 70% and be due mainly to N-limitation: less than 10% was attributed to pests and diseases. Intensification of chemicalpest control significantly increased yield and pest- induced yield losses estimated at the field level were between about 10% and 20% with highest values at low-yielding sites. Chemical control did not significantly affect overall disease- and pest-severity levels. Disease and pest severities did not consistently positively correlate with yield-loss estimates adjusted for N-limitation or maximum yield per field. Key pests with regard to observed disease- or damage- severity level were sucking insects on panicles, the dirty panicle complex, stem rot, weeds, stem borers, other tiller-damaging pests, and brown spot. Leaf yellowing was only severe at Long An whereas root rot was severe at all sites except Soc Trang.

About 30%, or 1.76 million ha, of the total rice area in Vietnam falls into the category of rainfed lowland rice (RLR), producing a substantial proportion of the country’s total rice yield at average RLR yields of 2.0 t/ha (IRRI 1993). Although average losses due to rice pests have been estimated to be below 10% in the Red River Delta (RRD) for the past few years, losses in individual regions or fields can be much higher and rice pests and diseases are, thus, considered to be major constraints to agricultural production in this area. Simultaneously, the possibility of increased pest risks associated with the continuing increase in Vietnamese rice production and cropping intensification has been recognized. Risks might be amplified by lowered efficiency of control measures if new diseases, such as bacterial grain rot and leaf yellowing, emerge (Trung 1994).

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 2 Plant Protection Department, University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City, Vietnam. Although the actual worldwide importance of biotic yield constraints in RLR is not known because research in this agroecosystem has been neglected in the past (Heinrichs et al 1986), a survey in eastern India clearly indicated that diseases and pests, including weeds, belong to the top 10 technical constraints for higher RLR yields (Widawsky and O’Toole 1990). Some workers suspect that the disease and pest potential in RLR areas is as high or even higher than in irrigated rice, partly because the RLR environment is subject to rapid changes and extremes that favor the development of some diseases (Heinrichs et al 1986, Mew et al 1986). In view of the growing importance of RLR environments for future world rice production, it therefore seems advisable to pay attention to pest problems and to their efficient management in such ecosystems. Logical steps in employing a systems approach for developing improved pest-management concepts include the definition of pest problems and the pest-management domain and the identification of pest problems and corresponding intervention points (Teng and Savary 1992). Quantitative holistic surveys seem to be appropriate to provide the necessary information, especially with regard to identification of key pests, their patterns of occurrence, severity levels, and corresponding yield losses and with respect to baseline data on production situations, including weather conditions, soil properties, topographic features, and farmers’ crop- and pest-management practices. Such surveys were initiated in farmers’ fields at several key sites of the Mekong River Delta (MRD) in 1992. The four main objectives of this survey work were • To obtain baseline data to characterize RLR sites with regard to edaphoclimatic conditions, farmers’ cropping practices, site-specific cropping conditions, pest occurrence, yield, and yield losses; • To quantify pest-induced and other yield losses and identify key pests with respect to yield losses; • To analyze interrelations among variables and factors involved; and • To create a data base for further work on the development of disease management technologies for RLR. The work reported here will help supply the missing pest component in IRRI’s RLR research program to enhance its overall success with respect to sustainability of high RLR yields. This work is part of a 5-yr collaborative project of the German Agency for Technical Cooperation (GTZ), Justus Liebig University of Gessen (JLU), and IRRI on disease management in RLR funded by the German Ministry of Economic Cooperation (BMZ). Project activities and progress of the work have been documented recently (Pinnschmidt et al 1994a, 1994b). All activities in Vietnam were carried out by the collaborating team of the University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City.

Materials and methods

Four farmers’ fields were randomly selected in 1992 within a circle of 5 km in diameter at each of the four RLR sites — Bac Lieu, Ca Mau, Long An, and Soc Trang in the MRD — at the center of each 5-km circle was a weather station. In each field, three plots were laid out that received foliar sprays of fungicides and insecticides at different frequencies. Treatment 1 consisted of no sprays, treatment 2 was according to farmers’ practice, and treatment 3 involved very intensive applications of fungcides and insecticides at up to weekly intervals during the growing season. Before planting, the depth of the topsoil was measured and soil samples were taken from the top layer of each field. These were analyzed for pH, cation exchange capacity (CEC), exchangeable potassium (K), available phosphorus (P), and carbon (C), sand, silt, and clay contents. Each plot was visited four to six times during the growing season to collect data on crop development (growth stage after Zadoks et al 1974, plant height, number of culms/m 2, number of panicles/m2, mean number of leaves/culm, mean leaf area, and percentage crop canopy cover), soil-

224 Pinnschmidt et al and plant-water status (floodwater depth, estimated degree of soil hardness and dryness, and plant water-stress symptoms), and visual estimates of severity levels of biotic stresses (percentages of disease, insect, and other pest damage and percentage weed cover) as well as soil-related stresses (percentage nitrogen (N) deficiency and others). Harvest samples were obtained from three locations per plot. Farmers were interviewed for dates and amounts of fertilizer applications, pest control and other cropping practices, occurrence of special events, and other information on crop history. All these activities were carried out at all four sites during the first planting season in 1992, but only at Long An and Soc Trang during the second planting season. Variables were computed to characterize crop performance (mean grain yield, maximum plant height, final number of panicles, and so forth), crop- and pest-management intensity (total number of pest-control measures, total amount of fertilizer applied, and so on), and biotic and abiotic stress levels (occurrence of water stress, mean percentage severity levels of soil- and pest-related damage per day or maximum pest-severity levels during the season, and so forth) on a per-plot basis. Whenever mean severity levels per day were computed to characterize stresses, the computation was based on dividing the area under disease- (or damage-) progress curve (AUDPC) (for example, Madden 1983) of the given stress factor by the total crop growth duration in days (GDURAT). Some composite terms were computed to represent combined severity levels of various diseases or pest-damage types occurring on vegetative plant parts (VDIS, VINS) or generative plant parts and whole tillers (GDIS, GINS). Yield-gaps (YGAP1, YGAP2, and YAGP3) and parameters of yield loss (,YLOSSl, YLOSS2, and YLOSS3) were computed by relating actual plot yields to weather-limited potential yields (Yp) simulated with the CERES-rice model (Alocilja and Ritchie 1988), N-limited potential yields (YpN) estimated by a soil- and fertilizer-N driven empirical model (Neue 1985), and maximum yields per field (Ymax). The CERES-rice model was run based on weather data collected at the sites. Soil N content needed as an input in Neue’s model was estimated as the 10th fraction of decomposable soil C content (DCARB) which in turn was computed based on total soil C content (CARBON) adjusted for protection by clay (CLAY) (J.L. Gaunt, Natural Resources Institute, Kent, U.K., personal communication 1994). • Yp represents potential yields at yield-gap level 1 where deviations of actual yields from potential yields (= YGAP1) are caused by N-limitations, pests and diseases, and other abiotic stress factors. • YpN represents potential yields at yield-gap level 2 where deviations of actual yields (= YGAP2) are caused by pests, diseases, and abiotic stress factors other than N-limitation. • Y, represents potential yields at yield-gap level 3 where deviations of actual yields (= YGAP3) are caused by pests and diseases only. To obtain yield-loss estimates (YLOSSl, YLOSS2, and YLOSS3) that were independent of the respective yield-gap level, actual plot yields were related to potential yields at the respective yield-gap level. Thus, yield-gaps at level 2 were adjusted for N-limiting effects and yield-gaps at level 3 for N-limitation plus other abiotic stress and weed effects. Annex 1 provides a listing of all derived variables, computations and transformations, and variable abbreviations used in this paper. Data were subjected to variance, correlation, and multivariate-regression analyses, Parsimonious (fewest terms) and interpretable regression equations were sought to identify meaningful quantitative predictors of variables of interest such as yield, yield losses, and pest severities. To identify interrelated variables and separate them into groups according to their level of association, factor analyses were done using the principal component method for factor extraction. Because unrelated factors were desired, the factor matrix was subjected to orthogonal rotation under consideration of Kaiser’s varimax criterion. These analyses were first done separately for variables describing different aspects of the agroecosystem, such as soil and site conditions, crop and pest management, yield and yield losses, and disease and pest severities, respectively. Factors extracted from these subsets of variables were then subjected to another factor analysis to describe associations among them.

Characterization of production patterns 225 Table 1. Mean values of parameters a of crop performance, fertilizer input, pest management, and other cropping conditions in farmers' fields of RLR sites in the Mekong River Delta, 1992.

Bac Lieu Ca Mau Long An Soc Trang

1st 1st 1st 2nd 1st 2nd crop crop crop crop crop crop Crop performance YIELD 3.44 5.30 5.30 5.44 2.47 2.32 PAN 354.17 452.08 522.92 531.25 408.33 495.83 LAID 276.51 444.09 459.58 286.90 200.89 299.44 GDURAT 106.50 139.25 98.50 108.50 117.67 120.50 PHGHT 90.75 109.92 92.75 94.67 83.11 61.17

Fertilizer input NAPP 128.80 124.15 103.00 131.43 76.03 83.75 NONAPP 3.00 3.00 3.00 2.50 1.33 2.25 PAPP 61.88 77.45 48.50 61.05 19.93 19.50 KAPP 0.00 0.00 20.00 14.00 0.00 0.00

Pest management NOIAPP 4.75 3.50 1.25 5.00 0.00 1.00 NOFAPP 0.50 0.25 1.25 1.25 0.00 0.00 NOHWEED 0.25 0.25 1.75 0.50 1.00 0.00 NOHAPP 1.75 1.50 1.25 1.00 0.00 0.00

Other cropping conditions AYIELD 5.75 6.85 5.00 4.25 3.83 3.50 CPYEAR 1.00 1.00 2.50 2.50 2.50 2.50 FALLOW 7.00 7.00 3.00 0.00 3.33 0.00 CROTAT 0.00 0.00 0.00 0.00 0.33 0.00 SDATE 190.00 169.25 163.00 295.00 141.33 277.50 DSEED 1.00 1.00 1.00 0.75 1.00 0.75 VARIETIES IR64 IR42 IR50404 IR64 IR50404 IR64 IR42 lR9729 IR64 lR13240 lR9729 UNIFORM 42.50 100.00 65.00 60.00 100.00 100.00 NOVAR 3.50 1.00 4.25 2.50 1.00 1.00

Note: See Annex 1 for description of variables and units of measurement. a Data are from plots that received pest control according to farmers' practice

Results High-yielding IR varieties were planted at all survey sites. A relatively wide range of actual yields, long-term average yield estimates, final number of panicles, fertilizer inputs, and intensity of pest control was observed. The Soc Trang site placed last with regard to all of these variables whereas it placed first with regard to number of crops per year and varietal uniformity (Table 1). Soil texture and thickness of topsoil layer did not differ much among sites, whereas C-, K-, and available P-contents as well as CEC differed with the highest values observed at Ca Mau and Long An Lowest C-content, most frequent occurrence of drought stress, and highest severity ratings of N-deficiency symptoms were observed at Soc Trang (Table 2). Lowest severity ratings for pests and diseases. whether measured as composite terms (VDIS, VINS, GDIS, or GINS) or disease and damage caused by individual organisms, were observed at Soc

226 Pinnschmidt et al Table 2. Mean values of parameters a of soil conditions and abiotic problems in farmers’ fields of RLR sites in the Mekong River Delta, 1992.

Bat Lieu Ca Mau Long An Soc Trang

1st 1st 1st 2nd 1st 2nd crop crop crop crop crop crop

Soil conditions SAND 2.59 5.84 5.84 4.33 4.66 4.65 SlLT 42.21 40.96 44.41 43.60 42.27 42.48 CLAY 55.20 53.20 49.76 52.06 53.03 52.87 TLAYER 15.50 16.00 16.50 16.75 15.00 15.75 CARBON 1.30 1.93 2.07 2.22 1.12 1.08 PH 5.34 4.55 4.50 4.76 4.93 5.30 CEC 8.94 11.94 12.83 20.26 10.84 18.29 PAVAIL 19.6 42.8 48.2 32.7 15.2 14.8 POTASS 0.28 0.37 0.22 0.30 0.18 0.18 WCOND 0.00 1.00 2.00 2.00 0.00 2.00

Abiotic problems VFLOOD 0.00 0.00 0.00 0.00 0.33 0.00 SDROUGHT 1.00 0.25 0.25 0.00 1.00 0.75 VDROUGHT 0.75 1.00 0.25 0.00 1.00 1.00 GDROUGHT 0.00 0.25 1.00 0.00 1.00 0.00 ND 1.81 7.57 0.92 8.94 23.40 36.18 LDG 0.00 69.17 0.42 0.00 0.00 0.83

Note: See Annex 1 for description of variables and units of measurement. a Data are from plots that received pest control according to farmers’ practice.

Trang. Severity ratings at the other sites were usually higher although substantial variation occurred with respect to individual pests and diseases (Table 3). Sucking insects on panicles, the dirty panicle complex, stem rot, weeds, stem borers causing dead hearts and white heads, other tiller-damaging pests, and brown spot must be considered as key pests (in that order) at all sites with regard to observed severity ratings. Root rot — even though not clearly identifiable as a biotic disease — was recorded as severe at all sites except Soc Trang. High ratings for leaf yellowing were observed at Long An only. The average time profiles of some of the major diseases and pest damage types are shown in Fig. 1, indicating their temporal patterns of their dynamics. An analysis of variance identified highly significant effects of the factors “site,” “individual field, ’ and “pest control” treatment on plot yields (Table 4). However, the site effect was overriding. When relating individual plot yields to maximum field yields averaged across sites and fields, yield percentages were 98.4% (yield loss of 1.6%) for fully protected plots, 91.5% (yield loss of 8.5%) for plots receiving pest control according to farmers’ practice, and about 87.9% (yield loss of 12.1%) for plots receiving no pest control. Treatment effects on composite pest- and disease-severity parameters were either not significant or not highly significant, but site effects were highly significant. Thus, treatments are not clearly ranked with respect to disease or pest severity (Table 4). Weather-limited potential yields (Yp) estimated for each site by simulation runs of the CERES-rice model ranged from 6.9 to 8.1 t/ha. N-limited potential yields (Y pN ) estimated by Neue’s model and averaged across fields per site ranged from 2.4 to 6.5 t/ha and thus came quite close to observed maximum yields (Y max ) averaged across fields per site which ranged from 2.7 to 5.8 t/ha

Characterization of production patterns 227 Table 3. Mean values of parameters a of disease and other pest damage severitiesb in farmers’ fields of RLR sites in the Mekong River Delta, 1992.

Bac Lieu Ca Mau Long An Soc Trang

1st 1st 1st 2nd 1st 2nd crop crop crop crop crop crop

Composite damage terms VDlS 49.35 68.73 28.32 70.01 23.93 36.76 VlNS 10.09 17.45 7.70 8.73 3.59 11.50 GDIS 35.09 64.09 33.67 56.78 43.77 25.81 GINS 62.50 77.73 68.43 54.66 40.67 1 1.06

Damage on leaf blades LB 0.01 0.04 0.01 0.09 0.40 5.60 BS 3.87 3.42 2.51 8.62 4.90 2.64 BLB 3.03 2.36 0.88 1.86 1.29 0.52 LY 1.29 0.20 8.17 14.00 0.31 0.1 7 LS 8.60 4.47 0.41 0.55 1.81 0.04 LF 0.84 11.04 1.16 0.99 0.81 1.71 DF 2.88 2.04 0.08 3.66 1.29 0.28 WM 1.54 0.11 0.92 2.01 0.31 3.73 SIDL 0.46 0.55 3.50 0.00 0.20 0.30

Damage on leaf sheaths SHR 2.92 2.29 1.85 6.37 2.01 0.09 SIDS 4.19 0.13 0.00 0.00 0.00 0.00

Damage on panicles DP 26.50 15.00 23.58 2.75 38.67 11.50 SlDP 68.33 76.67 71.25 48.75 31.89 0.00

Foot and root damage RR 14.00 70.00 4.35 48.83 0.00 0.00 FR 0.17 0.00 1.69 3.50 0.00 0.00

Damage affecting whole tillers or hills DH 3.77 1.43 1.67 6.22 0.57 1.45 WM 1.12 0.00 1.02 14.58 1.51 4.04 R 0.40 3.92 1.45 3.30 1.04 8.33 RSV 0.00 0.00 0.00 0.00 0.00 12.71 SR 31.34 15.19 5.29 12.1 1 8.82 2.11 OTD 4.10 7.22 4.83 8.92 12.72 3.97 TV 0.00 0.00 0.25 0.00 0.78 3.58

Weeds WCOVER 19.37 19.93 8.95 0.38 4.98 3.23

Note: Data are from plots that received pest control according to farmers’ practice. a See Annex 1 for description of variables and units of measurement. b Only diseases and pest damage exceeding 3% severity at one site at least are show.

(Table 5). Thus, the mean total estimated yield-gap (YGAP1) per site ranged from 22.9% at Ca Mau to 67.1% at Soc Trang (2nd crop), the yield-gap due to biotic and all abiotic stresses except N-limitation (YGAP2) ranged from almost zero at most sites to almost 18% at Long An (2nd crop), and the yield-gap due to insect pests and diseases (YGAP3) was between 2.6% at SOC Trang (1st crop) and

228 Pinnschmidt et al 1. Time profiles of average severity levels of major diseases and pest damage types in farmers’ rainfed lowland rice fields in the Mekong River Delta. 1992. Note: BS, brown spot: LY, leaf yellowing. LS, leaf scald: SHB, sheath blight: SR, stem rot; DP, dirty panicle. WM, whorl maggot: DEF, defoliation. SIDP, sucking-insect damage on panicles. DHWH, dead hearts and white head; R, rats; and WCOVER, weed cover.

5.2% at Long An (1st crop). The yield-gap level-independent yield-loss estimates ranged from -3.4% to 17.6% (YLOSS2) and from 8.5% to 18.9% (YLOSS3) at yield-gap levels 2 and 3, respectively, with an indication of higher losses — especially with regard to YLOSS3 — at the low-yielding sites of Soc Trang and Bac Lieu compared with the other sites. Correlation analyses showed a complex structure of interrelations among variables (Table 6). In general, high positive correlations existed among actual yield (YIELD), variables that indicate soil- fertility level or water-holding capacity, or both (CARBON, DCARB, Y p N , and PAVAIL), parameters indicating crop- and pest-management intensity according to farmers’ practice (NAPP, NODISINF, and NOWEEDF), and severity’ levels of some pests (for example, SHR and SIDP) including most composite pest terms (VDIS, GDIS, and GINS). High negative correlations existed among YIELD and CARBON on one

Characterization of production patterns 229 hand and seedling and vegetative drought ( SDROUGHT and DROUGHT ) as well as N-deficiency rating (ND), on the other. Consequently, yield losses estimated at yield-gap level 1 (YLOSSl) were highly correlated with all variables that were highly correlated with YIELD, but the sign of the correlation coefficient was reversed. Interpretable high correlations between yield losses estimated at yield-gap levels 2 and 3 (YLOSS2 and YLOSS3) and other variables could only be found for severity of whorl maggot (WM) and white head (WH), which correlated highly positively with YLOSS2, and for the number of treatment-specific fungicide and insecticide applications (NOIAPP, NOFAPP, and NODISIN), which correlated highly negatively with YLOSS3.

Table 4. Effects of chemical disease- and insect-control measures on crop yield and parametersa of composite disease- and pest-damage severity in farmers’ fields of RLR sites in the Mekong River Delta, 1992.

Site, season, YIELD VDlS VlNS GDlS GINS and treatmentb

Bac Lieu 1st crop 1 3.25 47.85 12.39 34.40 62.05 2 3.44 52.75 11.72 38.62 66.37 3 3.85 47.44 6.15 32.27 59.07

Ca Mau 1st crop 1 5.30 63.93 21.91 61.28 78.45 2 5.34 80.18 17.87 75.01 77.75 3 5.78 62.08 12.56 55.98 76.98

Long An 1st crop 1 5.07 31.58 8.08 36.50 73.67 2 5.31 30.10 7.92 33.79 69.80 3 5.76 23.28 7.10 30.72 61.83

2nd crop 1 4.68 76.43 8.59 62.20 55.19 2 5.44 71.45 12.43 57.08 56.10 3 5.53 62.15 5.16 51.06 52.70

Soc Trang 1st crop 1 2.54 21.83 3.02 48.88 41.46 2 2.47 27.29 4.29 41.78 30.86 3 2.70 22.68 3.45 40.65 49.68

2nd crop 1 2.33 42.40 7.61 30.64 6.35 2 2.32 27.29 14.39 25.03 14.81 3 2.49 40.60 12.49 21.76 12.02

Treatment effect averaged across sites and fields (in % of maximum per field)

1 87.87 85.04 77.19 86.01 83.44 2 91.48 87.77 85.33 87.27 88.69 3 98.41 78.95 64.63 75.97 85.53 continued

230 Pinnschmidt et al Table 4 continued.

Significance levels of F values based on results of a nested-design ANOVA (using data on a per-plot basis)

Variable Effect of:

Treatment Field within site Constant Site and (df = 2,44) and season (df = 1,44) season (error 1) (df = 5,17) (df = 17,44)

YIELD 0.000 0.000 0.000 0.000 VCIS 0.291 0.003 0.000 0.000 VINS 0.030 0.332 0.000 0.001 GDIS 0.117 0.000 0.000 0.020 GINS 0.834 0.000 0.000 0.000

a Values are averaged across fields per site. See Annex 1 for further description of variables, units of measurement, and transformations. b Treatments: 1, no fungicide or insecticide used; 2, application of fungicides and insecticides according to farmers’ practice; 3, maximum use of fungicides and insecticides according to fixed spray schedule.

Variables YIELD, YLOSSl, YLOSS2, YLOSS3, composite pest-severity variables (VDIS, VINS, GDIS, and GINS), and weed cover (WCOVER) were subjected to multiple-regression analyses (Table 7). More than 70% of the variability of YIELD and YLOSS1 could be explained by the decomposable C-content of the soil (DCARB) alone. For YLOSS3, 18% of the variability could be explained by a negative effect of fungicide applications (NOFAPP). Around 20% of the variability of VDIS, GDIS, and GINS could be explained by positive effects of soil C-content (CARBON) in interaction with estimated effective fertilizer-N (FNe), N-limited yield potential (YpN) in interaction with soil silt content (SILT), and YpN, respectively. Of WCOVER, 53% was explained by positive effects of vegetative drought stress (VDROUGHT) and number of N applications (NONAPP). No interpretable equations could be established for variables YLOSS2 and VINS. Results of factor analyses are shown in Table 8. The number of factors extracted from the original variables varied from two to seven and total explained variance was usually high, ranging from about 77% to 87%. The factor loadings of the individual variables indicate how much they contribute in sharing a common factor and whether this contribution is negative or positive. Thus, soil and site factor SFACT1 mainly reflects soil C-content (CARBON) and its close negative association with drought stress during the early cropping season (SDROUGHT and VDROUGHT) whereas SFACT2 reflects soil sand content (SAND) in close positive association with available P (PAVAIL) and drought stress during the generative phase Crop- and pest-management factor CFACT2 reflects cropping intensity in terms of length of the fallow period (FALLOW) and number of crops per year (CPYEAR). in connection with number of herbicide applications (NOHAPPF)—CPYEAR logically having a negative contribution. CFACT3 indicates close associations among some farmers’ practices such as amounts of N and P applied (NAPP and PAPP) and numbers of insecticide applications (NOIAPPF) and of hand weedings (NOHWEEDF). with NOHWEEDF bearing a negative sign. Yield (YIELD) shares a common factor (YFACT1) with yield losses at yield-gap level (YLOSS1), while yield losses at yield-gap levels 2 and 3 (YLOSS2 and YLOSS3) make up a separate common factor (YFACT2). Pest variables split up into seven factors, each of them indicating associations among diseases and pests. Thus, total insect damage on generative plant organs and whole tillers (GINS) is closely positively associated with panicle damage due to sucking insects (SIDP), sheath rot (SHR), and other pests sharing pest factor PFACT1. Some factors are difficult to interpret, such as SFACT4, which has a high positive loading of POTASS and a high negative loading of CEC.

Characterization of production patterns 231 Table 5. Average estimates of potential yields, yield-gaps, a and yield-loss parameters b in farmers' fields of RLR sites in the Mekong River Delta in 1992.

Site Season Yield-gap level

1 2 3

Potential yield at respective yield-gap level Y P Y pN Y max Bac Lieu 1st crop 8.12 3.60 3.85 Ca Mau 1st crop 7.10 5.60 5.78 Long An 1st crop 7.73 5.99 5.78 Long An 2nd crop 6.94 6.46 5.55 Soc Trang 1st crop 7.67 2.53 2.77 Soc Trang 2nd crop 7.23 2.40 2.65

a % yield-gap in relation to Yp YGAP1 YGAP2 YGAP3 Bac Lieu 1st crop 56.72 -0.39 4.13 Ca Mau 1st crop 22.90 1.81 4.36 Long An 1st crop 30.39 7.89 5.19 Long An 2nd crop 24.83 17.94 4.86 Soc Trang 1st crop 66.49 -0.49 2.56 Soc Trang 2nd crop 67.09 0.29 3.72

% yield loss in relation to potential yield at respective yield-gap level YLOSS1 YLOSS2 YLOSS3 Bac Lieu 1st crop 56.72 -3.34 12.99 Ca Mau 1st crop 22.90 1.15 8.46 Long An 1st crop 30.39 8.89 9.84 Long An 2nd crop 24.83 17.56 9.02 Soc Trang 1st crop 66.49 -3.38 10.37 Soc Trang 2nd crop 67.09 28.46 18.86

Note: See Annex 1 for further description of variables and for units of measurement. a YGAP1, yield-gap presumably due to soil-N limitations, abiotic soil and water stresses, and biotic stress factors = YLOSS1; YGAP2, yield-gap presumably due to abiotic soil and water stresses and biotic stress factors: YGAP3, yield-gap presumably due to diseases and insect pests only due to differences in chemical pest-control measures.

The eight factors extracted in the final factor analysis explained 80% of the total variance. Although not all factors can be interpreted well, a picture of the strength and direction of linkages among important components of the agroecosytem is revealed. FACTOR1 indicates strong correlations among pest factor 1 (PFACT1), yield factor 1 (YFACT1), crop- and pest-management factor 1 (CFACT1), and soil and site factor 1 (SFACT1). It thus implicitly describes the close association among the orignal variables such as CARBON, SDROUGHT, VDROUGHT, NOVAR, KAPP, YIELD, YLOSSl, SIDP, GINS, SHR, and so forth. FACTOR8, having high loadings of CFACT4 and YFACT2, captures the strong negative correlation between the orignal variables NOFAPP and NOIAPP, which represent treatment-specific intensities of fungicide and insecticide sprayings, on one hand, and YLOSS2 and YLOSS3, which represent yield losses at yield-gap level 2 and 3, on the other hand. However, note that FACTOR8 does not explain much of the total variance of the data. Table 9 presents the scores of all extracted factors averaged by site. Because they are composites of all of the original variables that were important in making up a given factor, the factor scores characterize the conditions at each site with respect to the underlying original variables. For example, soil and site factor SFACT1, which is mainly made up of positive loadings of CARBON and negative loadings of SDROUGHT and VDROUGHT, has a high score at Long An, especially for the second crop, whereas its score at Soc Trang is very low. This corresponds to high CARBON and low SDROUGHT

232 Pinnschmidt et al Table 6. Correlation coefficients of relationships among yield and yield losses, soil properties, crop- and pest-management intensity, and pest-severity levels in farmers’ fields of RLR sites in the Mekong Delta, 1992.a

YIELD YLOSS1 YLOSS2 YLOSS3 CARBON NAPP NOWEEDF NODlSlNF VDlS VlNS GDlS GINS WCOVER

AYIELD 0.47** -0.43** -0.35* -0.10 0.25 0.28 0.52** 0.45** 0.37* 0.43** 0.29 0.65** 0.70** CARBON 0.84** -0.85** 0.26 -0.09 1.00** 0.44** 0.55** 0.51** 0.41** 0.10 0.42** 0.52** -0.19 DCARB 0.84** -0.85** 0.25 -0.10 0.99** 0.43** 0.54** 0.51** 0.40** 0.09 0.43** 0.52** -0.20 0.17 YpN 0.83** -0.84** 0.29 -0.08 0.95** 0.55** 0.59** 0.59** 0.43- 0.42** 0.55** -0.09 SAND 0.14 -0.17 -0.03 -0.08 0.05 -0.15 -0.00 -0.18 -0.07 0.12 -0.02 0.03 0.03

SILT 0.10 -0.09 -0.01 -0.00 0.12 -0.00 0.09 0.20 -0.01 -0.13 0.20 0.12 -0.15 CLAY -0.17 0.17 0.02 0.04 -0.15 0.07 -0.09 -0.12 0.05 0.08 -0.20 -0.13 0.13 TLAYER 0.34* -0.35* 0.42** 0.05 0.46** 0.16 0.12 0.40** 0.14 0.18 0.18 0.01 -0.23 VFLOOD -0.27 0.26 -0.20 -0.04 -0.22 -0.27 -0.03 -0.41** -0.17 -0.22 0.11 -0.04 -0.08 SDROUGHT -0.61** 0.65** -0.19 -0.00 -0.72** -0.18 -0.23 -0.26 -0.19 -0.14 -0.09 -0.34* 0.35*

VDROUGHT -0.52** 0.50** -0.20 -0.03 -0.63** -0.31* -0.38* -0.42** -0.10 0.20 -0.04 -0.27 0.51** GDROUGHT 0.45** -0.38* -0.15 -0.08 0.28 0.02 0.40** 0.08 -0.26 -0.01 -0.07 0.31* 0.14 PAVAIL 0.64** -0.63** -0.13 -0.18 0.39* 0.17 0.46** 0.36* 0.15 0.25 0.10 0.54** 0.15 CEC 0.04 -0.13 0.48** -0.00 0.21 -0.05 -0.44** 0.05 0.22 0.06 0.01 -0.35* -0.73** POTASS 0.31* -0.33* 0.14 0.05 0.35* 0.43** 0.19 0.46** 0.32* 0.31* 0.24 0.20 0.22

NAPP 0.39* -0.41** 0.16 0.06 0.44** 1.00** 0.25 0.52** 0.42** 0.01 0.27 0.31* -0.02 PAPP 0.51** -0.51** 0.05 -0.13 0.46** 0.64** 0.44** 0.59** 0.46** 0.30 0.34* 0.52** 0.36* KAPP 0.46** -0.43** 0.22 -0.00 0.61** 0.06 0.42** 0.33* 0.03 -0.16 0.22 0.25 -0.36* NOIAPP 0.22 -0.23 -0.08 -0.41** 0.11 0.17 0.04 0.26 0.16 -0.01 -0.01 0.06 -0.04 NOFAPP 0.21 -0.21 -0.15 -0.43** 0.13 0.04 0.06 0.14 -0.02 -0.22 -0.14 0.02 -0.12

NODISIN 0.24 -0.24 -0.11 -0.42** 0.13 0.13 0.05 0.24 0.10 -0.07 -0.05 0.05 -0.06 NODlSlNF 0.58** -0.58** 0.07 -0.02 0.51** 0.52** 0.43** 1.00** 0.54** 0.28 0.26 0.47** 0.11 NOWEEDF 0.62** -0.54** -0.29 -0.16 0.55** 0.25 1.00** 0.43** 0.17 -0.07 0.34* 0.84** 0.33* UNIFORM -0.25 0.16 -0.06 -0.04 -0.34* -0.31 -0.54** -0.54** -0.07 0.14 -0.09 -0.31* -0.06 NOVAR 0.32* -0.22 0.07 -0.00 0.41** 0.17 0.59** 0.49** -0.01 -0.14 0.07 0.35* 0.08 continued Table 6 concluded

YIELD YLOSS1 YLOSS2 YLOSS3 CARBON NAPP NOWEEDF NODISINF VDlS VINS GDlS GINS WCOVER

ND -0.56** 0.50** 0.04 0.12 -0.51** -0.26 -0.63** -0.55** -0.16 -0.08 -0.30 -0.50** -0.09 LDG 0.36* -0.38** -0.06 -0.06 0.20 0.34* 0.02 0.09 0.43** 0.53** 0.39** 0.18 0.28 LB -0.47** 0.39** 0.24 0.07 -0.41** -0.43** -0.76** -0.44** -0.08 0.06 -0.16 -0.65** -0.43** BS -0.10 0.04 0.09 0.05 -0.06 -0.07 -0.24 -0.02 0.24 -0.03 0.02 -0.27 -0.51** BLB 0.02 0.00 -0.13 0.15 0.06 0.27 0.35* 0.15 0.28 0.07 0.23 0.40** 0.14

LY 0.36* -0.35* 0.15 0.02 0.52** 0.26 0.44** 0.35* 0.02 -0.29 0.05 0.34* -0.35* LS 0.03 0.01 -0.46** 0.01 -0.19 0.05 0.41** 0.23 0.22 0.17 0.19 0.49** 0.59** LF 0.25 -0.27 -0.10 0.05 0.12 -0.00 0.10 0.10 0.29 0.67** 0.29 0.29 0.50** DF -0.00 -0.03 -0.23 -0.07 -0.12 0.05 0.07 0.10 0.40** 0.41** 0.28 0.13 0.32* WM -0.15 0.11 0.44** 0.16 0.00 -0.02 -0.39** 0.14 0.03 0.09 -0.10 -0.48** -0.48**

SIDL 0.25 -0.20 0.14 0.00 0.27 -0.10 0.18 0.00 -0.27 0.14 -0.26 0.03 0.03 SHR 0.47** -0.47** -0.16 -0.11 0.44** 0.43** 0.58** 0.38* 0.39** -0.07 0.37* 0.58** -0.12 SIDS -0.09 0.14 -0.23 0.10 -0.22 0.20 0.12 0.28 0.10 0.28 0.01 0.18 0.42** DP -0.11 0.20 -0.48** -0.06 -0.26 -0.23 0.34* -0.34* -0.39** -0.11 0.1 1 0.29 0.47** SlDP 0.60** -0.54** -0.38* -0.09 0.46** 0.31* 0.85** 0.43** 0.20 0.05 0.31* 0.98** 0.44**

RR 0.63** -0.66** -0.04 -0.16 0.57** 0.47** 0.50** 0.72** 0.83** 0.38** 0.66** 0.54** 0.16 FR 0.33* -0.32* 0.12 0.03 0.33* 0.24 0.23 0.31* -0.06 -0.21 -0.13 0.24 -0.21 DH 0.26 -0.27 -0.02 0.02 0.33* 0.20 0.24 0.36* 0.26 0.12 0.14 0.31* -0.14 WH -0.03 -0.03 0.34* -0.01 0.16 -0.03 -0.26 -0.07 0.06 -0.15 -0.01 -0.32* -0.74** R 0.01 -0.04 0.03 -0.17 -0.06 -0.07 -0.23 -0.13 0.22 0.44** 0.12 -0.06 -0.00

SR 0.33* -0.29 -0.1 7 -0.04 0.24 0.52** 0.49** 0.51** 0.46** 0.10 0.16 0.46** 0.36* OTD 0.10 -0.10 -0.00 -0.18 0.17 -0.04 0.07 -0.05 0.18 -0.00 0.48** -0.00 -0.01 TV -0.60** 0.56** 0.24 0.16 -0.48** -0.27 -0.73** -0.54** -0.27 -0.04 -0.29 -0.62** -0.33* VDlS 0.40** -0.46** 0.11 -0.06 0.41** 0.42** 0.17 0.54** 1.00** 0.40** 0.72** 0.24 -0.05

GDlS 0.37* -0.41** -0.04 -0.12 0.42** 0.27 0.34* 0.26 0.72** 0.19 1.00** 0.35* -0.01 VlNS 0.19 -0.22 0.09 -0.01 0.10 0.01 -0.07 0.28 0.40** 1.00** 0.19 0.14 0.30* GINS 0.63** -0.59** -0.35* -0.12 0.52** 0.31* 0.84** 0.47** 0.24 0.14 0.35* 1.00** 0.39** WCOVER 0.03 0.04 -0.38* -0.09 -0.19 -0.02 0.33* 0.11 -0.05 0.30* -0.01 0.39** 1.00**

Note See Annex 1 for description of variables, units of measurement, and transformations. a Minimum pairwise number of cases: 63; two-tailed significance: * = 0.01, ** = 0.001 Table 7. Results of multiple regression analyses of yield, yield losses, and pest severities on variables of soil and other site conditions, crop- and pest- management practices, and pest severities. a

Dependent Adjusted 2 variable R

YIELD YIELD = 2.205 x DCARB + 2.755 0.71 (0.171) (0.144)

YLOSS 1 YLOSS1 = -32.057 x DCARB + 64.145 0.72 (2.403) (2.019)

YLOSS2 (no equation could be established)

YLOSS3 YLOSS3 = -4.701 x NOFAPP + 10.68 0.18 (1.189) (1.246)

VDlS VDlS = 0.001034 x CARBON x FN e + 33.976 0.21 (0.0002398) (3.929)

VlNS (no equation could be established)

GDIS GDlS = 0.008869 x Y pN x SILT + 4.627 0.19 (0.002 159) (0.458)

GINS GINS = 7.736 x Y pN + 17.786 0.29 (1.434) (7.050)

WOVER WOVER = 1.921 x VDROUGHT + 0.025 x NONAPP - 0.022 0.53 (0.276) (0.00397) (0.339)

Note. For description of variables and transformations, see Annex 1 a N = 69; T values for all regression coefficients and F values for all equations significant at P = 0.001; standard error of regression coefficient in parentheses; only parsimonious and interpretable equations are presented.

and VDROUGHT at Long An and opposite conditions at Soc Trang. Yield factor YFACT1, which is formed by negative loadings of YIELD and positive loadings of YLOSS1, has a low score at Long An and a high score at Soc Trang: corresponding to high YIELD and low YLOSSl at Long An and the opposite conditions at Soc Trang. Similarly, the scores of the more complex factors, FACTOR1-FACTOR8, can be used to characterize and rank the sites with respect to a broader spectrum of variables. Thus, high scores of FACTOR1 at Long An reflect high scores of PFACT1, CFACT1, and SFACT1 and low scores of YFACT1 at that site which in turn corresponds to high GINS, SIDP, and SHR; high NOVAR, KAPP, and NOFAPPF and low UNIFORM; high CARBON and low GDROUGHT and VDROUGHT; and low YLOSS1 and high YIELD at that site. Low scores at SOC Trang indicate opposite conditions and intermediate scores at Bac Lieu and Ca Mau indicate intermediate conditions.

Discussion and conclusions The data obtained during the first survey year, 1992, cover a wide range of conditions with respect to many key variables such as soil C-content, yield, severity levels of pests and diseases, crop and pest management, weather, and drought stress and observations on many other biophysical and cultural factors relevant to crop-pest management. Thus, the data base has a high potential for site characterization on a wide scale of biophysical complexity of the agroecosystem. However, substantially more observations are needed to arrive at a sound basis for general conclusions with regard to pest problems in site-specific conditions.

Characterization of production patterns 235 Table 8. Results of factor analyses of variables that describe soil and other site conditions, crop- and pest-management, yields and yield losses, and pest situations in farmers' fields of RLR sites in the Mekong Delta in 1992. Only variables with highest factor loadings per extracted factor are presented including their factor loadings. a

Factors extracted from variables of soil and site conditions (cumulative % variance explained = 79.9)

Factor name SFACT1 SFACT2 SFACT3 SFACT4 SFACT5 Variance ex- plained (%) 31.9 17.2 13.2 10.0 7.7 Variables and CARBON 0.85 SAND 0.85 SILT 0.96 POTASS 0.77 VFLOOD 0.93 their factor SDROUGHT -0.82 PAVAIL 0.72 CLAY 0.90 CEC -0.72 loadings VDROUGHT -0.79 GDROUGHT 0.67 PH -0.62 TLAYER 0.62

Factors extracted from variables of crop and pest management (cumulative % variance explained = 80.8)

Factor name CFACT1 CFACT2 CFACT3 CFACT4 Variance ex- plained (%) 33.6 23.7 13.9 9.6 Variables and NOVAR 0.91 FALLOW 0.97 NAPP 0.88 NOFAPP 0.93 their factor UNIFORM -0.86 CPYEAR -0.91 NOWPPF 0.74 NOlAPP 0.93 loadings KAPP 0.84 NOHAPPF 0.59 NOHWEEDF -0.70 NOFAPPF 0.75 PAPP 0.59

Factors extracted from variables of yield and yield losses (cumulative % variance explained = 87.0)

Factor name YFACT1 YFACT2 Variance ex- plained (%) 58.4 28.6 Variables and YLOSS1 0.98 YLOSS2 0.89 their factor YIELD -0.97 YLOSS3 0.76 loadings continued Table 8 concluded.

Factors extracted from disease- and pest-severity variables (cumulative % variance explained = 76.6)

Factor name PFACT1 PFACT2 PFACT3 PFACT4 PFACT5 PFACT6 PFACT7 Variance ex- plained (%) 26.1 14.4 12.3 7.5 6.5 5.8 3.9 Variables and GINS 0.82 WM -0.82 VlNS 0.92 SlDS 0.82 SlDL -0.81 BS 0.72 OTD 0.92 their factor SlDP 0.79 DP 0.78 LF 0.80 BLB 0.58 DF 0.55 R 0.63 GDlS 0.59 loadings TV -0.75 WH -0.68 VDlS 0.54 FR -0.50 SHR 0.74 WOVER 0.65 LB -0.69 LS 0.57 RR 0.68 LY 0.65 SR 0.56 DH 0.53

Factors extracted from all previously extracted factors (cumulative % variance explained = 80.0)

Factor name FACTOR1 FACTOR2 FACTOR3 FACTOR4 FACTOR5 FACTOR6 FACTOR7 FACTOR8 Variance ex- plained (%) 179 148 11.0 9.5 7.6 7.3 6.1 5.7 Variables and PFACT1 0.92 PFACT2 0 88 PFACT6 -0.86 PFACT4 0.83 PFACT3 0.81 PFACT7 0.79 PFACT5 0.93 CFACT4 -0.90 their factor YFACT1 -0. 77 CFACT2 0 82 SFACT4 0.69 SFACT2 -0.76 SFACT3 -0.61 SFACT5 0.75 CFACT3 0.55 YFACT2 0.59 loadings CFACT1 0.70 SFACT1 0.66

Note: For description of variables and transformations. see Annex 1. a Method of factor extraction = principal component analysis, minimum eigenvalues for factor extraction = 1; orthogonal rotation of factor matrix according to Kaiser's varimax criterion. Table 9. Mean factor scores of factors extracted from variables representing soil and site conditions, crop and pest management, yield and yield losses, disease and pest severity, and previously extracted factors. a

Bac Lieu Ca Mau Long An Soc Trang 1st crop 1st crop 1st crop 2nd crop 1st crop 2nd crop

Soil and site factors SFACT1 -0.75 0.07 0.33 1.46 -0.88 -0.59 SFACT2 -1.02 0.94 1.37 -0.13 -0.17 -0.55 SFACT3 -0.11 -0.49 0.87 -0.43 -0.14 -0.10 SFACT4 0.73 0.74 0.54 -0.63 -0.03 -0.93 SFACT5 -0.49 0.05 -0.24 -0.15 1.44 -0.30

Crop and pest management factors CFACT1 0.49 -0.74 1.31 0.54 -0.68 -0.97 CFACT2 1.32 1.15 -0.15 -1.01 -0.25 -1.13 CFACT3 0.29 0.49 -0.63 0.90 -1.43 -0.03 CFACT4 0.10 -0.05 -0.11 0.32 -0.32 0.03

Yield and yield loss factors YFACT 1 0.59 -0.89 -0.75 -0.93 1.22 1.14 YFACT2 -0.48 -0.24 0.09 0.42 -0.68 0.93

Disease and pest severity factors PFACT1 0.33 0.37 0.53 1.02 -0.75 -1.69 PFACT2 0.37 0.74 0.33 -1.48 0.96 -0.68 PFACT3 -0.19 1.49 -0.22 -0.41 -1.25 0.27 PFACT4 1.63 -0.30 -0.58 -0.39 -0.16 -0.25 PFACT5 0.20 0.60 -1.41 0.67 0.22 -0.23 PFACT6 -0.30 -0.38 -0.43 0.53 0.29 0.36 PFACT7 -0.32 0.31 -0.15 -0.01 0.88 -0.48

Pooled factors FACTOR1 0.33 0.29 0.75 0.97 -1.05 -1.44 FACTOR2 1.07 0.83 0.23 -1.18 0.62 -1.11 FACTOR3 -0.05 0.57 0.50 -0.88 -0.53 -0.32 FACTOR4 1.79 -0.72 -1.03 -0.10 -0.01 0.04 FACTOR5 -0.15 1.41 -0.65 0.10 -0.82 0.35 FACTOR6 -0.45 0.22 -0.38 -0.05 1.43 -0.53 FACTOR7 0.08 0.63 -1.31 0.48 0.04 -0.34 FACTOR8 -0.02 0.04 0.32 -0.53 0.08 0.24

a See Table 8 for results of factor analyses and names of original variables.

Correlation and factor analyses showed that high yields, indicators of high soil fertility and water-holding capacity (such as high soil C-content), high fertilizer input and pest-management intensity, low occurrence of vegetative drought stress, and high pest and disease severities are closely associated with each other while the same is true for the opposite conditions. Although we cannot draw conclusions with respect to cause-effect relations based on these analyses, the results support the following hypotheses. • Yields are mainly determined by site-specific conditions that contribute to the level of soil productivity, which is indicated by the soil C-content that in turn indicates soil N content, soil

238 Pinnschmidt et al fertility, and water-holding capacity: • Farmers’ readiness for inputs might depend mainly on the soil productivity level; • Because of the high correlation between soil C-content and water-holding capacity, fewer drought problems are to be expected on soils rich in C; and • A high yield level (as determined by the conditions above) means that high pest-severity levels should be expected. Factor analyses enabled us to group interrelated variables into factors and thus show their level and direction of association. They also enabled us to reduce the large number of original variables to relatively few factors. Factor scores may then be used to characterize site or even single-field conditions with respect to the whole spectrum of original variables and their interrelations. Based on relating actual plot yields to measures of potential yield (attainable yield at various yield-gap levels), it can be concluded that total yield-gaps range from about 20% to almost 70%, depending on the site and field. The largest fraction of the total yield-gap is probably due to N limitation and less than 10% to pests and diseases. Therefore, soil C-content and related parameters that indicate soil N-content as well as water-holding capacity, which are both major indicators of the soil-productivity level, accounted for 70% of the observed yield and estimated total yield-loss variation. However, even when yield-loss estimates were adjusted for this overriding soil productivity effect, they did not display significant positive correlations, but sometimes even negative correlations, with pest severities. On the other hand, there was a significant treatment effect indicating increasing yields with increasing intensity of chemical protection. Also, there was the “open” yield-gap of less than 10%, which could not be explained by N-limitation or factors other than pests. This open yield-gap represents 10-20% yield differences measured in plots of individual fields and could be partly explained by the treatment-specific intensity of chemical control even though differences in disease and pest severities could not. All this makes it difficult to identify key pests with respect to yield constraints. However, with regard to observed severity levels and frequencies of occurrence, sucking insects on panicles, the dirty panicle complex, stem rot, weeds, stem borers causing dead hearts and white heads, other tiller- damaging pests, and brown spot can be considered as key pests (in that order) at all sites. Leaf yellowing was only severe at Long An whereas root rot was severe at all sites except Soc Trang. However, the damage status of root rot needs to be clarified. The unclear picture obtained with regard to linking key pests to yield losses might be due to several factors: • The remaining variability in yield data after adjusting for soil productivity effects is too “noisy”; • Pest-loss relations are masked by the high degree of pest species diversity among sites and fields and by methodological difficulties in pest assessment; • The model estimates for potential yield — especially N-limited potential yield — need to be improved; and • More data are needed, especially for applying factor analyses and other multivariate methods to the data. It remains a challenge to answer the question whether and under what conditions high pest- control inputs are justified. A relatively small percentage of yield increase at a high-yielding site such as Long An might repay inputs that are not returned from the same percentage of yield increase at a low-yielding site such as Soc Trang. On the other hand, there was an indication that percentages of pest-induced yield losses at the field level were higher at Soc Trang and Bac Lieu than at higher- yielding sites. Raising the yield level through higher fertilizer inputs or soil amendments might completely change the picture. This is where economic analyses will have to come into play in the future.

Characterization of productton patterns 239 References cited

Alocilja E C, Ritchie J T (1988) Upland rice simulation and its use in multicriteria optimization. International Benchmark Sites Network for Agrotechnology Transfer, Honolulu, HI, USA. Res. Rep. Series 01, 95 pp. Heinrichs E A, Katanyukul W, Resaulkarim A N M, Mishra B C (1986) Management of insect pests in rainfed lowland rice. Pages 349-358 in Progress in rainfed lowland rice. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. IRRI — International Rice Research Institute (1993) IRRI rice almanac, 1993–1995. P.O. Box 933, Manila 1099, Philippines. 142 pp. Madden L V (1983) Measuring and modeling crop losses at the field level. Phytopathology 73(11):1,591–1,596. Mew T W, Shahjahan A K M, Mariappan J (1986) Diseases and disease management of rainfed lowland rice. Pages 339-348 in Progress in rainfed lowland rice. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Neue H U (1985) Organic matter dynamics in wetland soils. Pages 109-122 in Wetland soils: characterization, classification, and utilization. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Pinnschmidt H O, Long N D, Mekwatanakarn P, Viet T T, Don L D, Teng P S, Dobermann A (1994a) Relationships between soil properties, crop and pest management practices, pest intensity, and crop performance in rainfed lowland (RLR) rice. Internat. Rice Res. Notes 19(2): in press. Pinnschmidt H O, Mekwatanakarn P, Long N D, Teng P S, Gaunt J L, Neue H U (1994b) Empirical estimates of yield and pest potentials of farmer’s fields of rainfed lowland (RLR) rice. Internat. Rice Res. Notes 19(2): in press. Teng P S, Savary S (1992) Implementing the systems approach in pest management. Agric. Syst. 40:237–264. Trung H M (1994) Pests and diseases: major constraints to agricultural production in the Red River Delta (RRD) of Vietnam. Report of the Vietnam-IRRI project, submitted to Entomology and Plant Pathology Division, International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. 16 pp. Widawsky D A, O’Toole J C (1990) Prioritizing the rice biotechnology research agenda for eastern India. Rockefeller Foundation, New York, USA. Res. Rep., 86 pp. Zadoks J C, Chang T T, Konzak C F (1974) A decimal code for the growth stages of cereals. Weed Res. 14:415-421.

240 Pinnschmidt et al Annex 1. List of abbreviations, computations, and variable transformations used.

A) Crop performance and yield losses, crop and pest YLOSS1: yield loss parameter 1 = YGAP1. management, and cropping conditions YLOSS2: yield loss parameter 2 = (1 - YIELD/Y pN ) × 100. YLOSS3: yield loss parameter 3 = (1 - YIELD/Y max) × 100. AYIELD: farmers long-term yield estimate per field in Y max: maximum measured plot yield per field in t/ha. t/ha. Y p : yield potential as simulated with the CERES-rice CPYEAR: number of crops per year. model in t/ha. CROTAT: crop rotation — 0 = not practiced, Y pN: N-limited yield potential in t/ha as estimated (from 1 = practiced in all cases. Neue 1985) by 2 DAS = days after seeding. Y pN = 0.05 x FN e - 0.000215 × FN e + 0.05 × FN e × 2 DSEED: planting method — direct seeding used = 1, not DCARB + (2.4152 × DCARB - 6.0882 × DCARB ) × used = 0. TLAYER. FALLOW: fallow period (from harvesting of previous crop until planting of current crop) in months. 0.9 B) Soil and water conditions and related problems FN e : 1.193 x NAPP . GDURAT: growth duration (from seeding until harvesting) CARBON: C-content in %. in Cays. CEC = cation exchange capacity in meq/100 g soil. KAPP: K O applied in kg/ha. 2 CLAY: clay content in 5%. LAID: leaf area index duration = leaf area index progress DCARB: estimated decomposable soil CARBON in % curve integrated over time. = CARBON - (1.64 + 0.16 × CLAY)/10. NAPP: N applied in kg/ha. GDROUGHT: drought stress during generative phase — NODISN(F): number of insecticide and fungicide 1 = occurred in all cases, 0 = never occurred. applications per season; plot-specific (farmers' LDG: maximum lodging in %. practice-specific). ND: mean N deficiency in % per day. NOFAPP(F): number of fungicide applications per season; PH: soil pH (measured in H 2 O). plot-specific (farmers' practice-specific). PAVAIL: available P (Olsen method) in ppm. NOHAPP(F): number of herbicide applications per season; POTASS: exchangeable K in meq/100 g soil. plot-specific (farmers' practice-specific). SAND: sand content in % . NOIAPP(P): number of insecticide applications per season; SDROUGHT: drought stress during seedline phase — plot specific (farmers' practice-specific). 1 = occurred in all cases, 0 = never occurred. NOHWEED(P): number of hand weedings per season; SILT: silt content in % . plot specific (farmers' practice-specific). TLAYER: depth of top layer in cm. NOPEST(F): NODISW(F) + NOWEED(F). VDROUGHT: drought stress during main vegetative phase NOVAP: number of varieties planted on land surrounding — 1 = occurred in all cases. 0 = never occurred. the surveyed field. VFLOOD: submergence stress during main vegetative NOWEED(F): number of herbicide applications and hand phase — 1 = occurred in all cases, 0 = never weedings per season; plot-specific (farmers' occurred. practice-specific). WCOND: 2 prevailing water management conditions at a PAN: (final) number of panicles/m . site — 0 = no water control possible, 1 = drainage PAPP: P O applied in kg/ha. 2 5 possible. 2 = irrigation possible, 3 = 1 and 2. possible. PHGHT: (maximum) plant height in cm. SDATE julian seeding date. UNIFORM: varietal uniformity = % surrounding area C) Biotic problems planted to the same variety as the surveyed field. VARIETIES: prevailing varieties in the area surrounding BLB: mean bacterial leaf blight severity in % per day. the surveyed field. BLS: mean bacterial leaf streak severity in % per day. YGAP1: estimated yield-gap 1 (due to N limitation, soil, BS: mean brown spot (on leaves) severity in % per day. water, and pest problems) in % CTT: maximum cut tiller damage incidence in %; each observed severity value was multiplied by DAS/GDURAT. = (1 - YIELD/Y p ) x 100. YGAP2: estimated yield-gap 2 (due to soil, water, and DF: mean other defoliation in % per day. DH: mean dead hearts in % per day; each observed pest problems) in % = YGAP1 - (1 - Y pN/ Yp ) x 100. YGAP3 estimated yield-gap 3 (due to pest problems only) severity value was multiplied by DAS/GDURAT. DP: maximum dirty panicle severity in %; each observed in % = YGAP1 - (1 - Y max /Y p ) × 100. YIELD: measured plot yield in t/ha. severity value was multiplied by DAS/GDURAT.

Characterization of production patterns 241 FR: maximum foot rot severity in %; each observed TH: mean thrips damage in %, per day. severity value was multiplied by DAS/GDURAT. THSBED: maximum thrips damage in % in seed bed. FSM: maximum false smut severity in %; each observed TV: mean tungro severity in % per day. severity value was multiplied by DAS/GDURAT. VDIS. total ”vegetative” disease severity (diseases on GDIS: total “generative” disease severity (diseases on vegetative plant organs) in % generative plant organs and/or whole tillers) = (1 - (1 - (LB + BS + SHBL + BLB + BLS + LY + = (1 - (1 - OTD/100) × (1 - RSV/100) × (1 - PB/100) LS + NBS + OLD)/100) × × (1 - DP/100) × (1 - FSM/100) × (1 - OPD/100) × (1 - (SHBS + SHR + OSD)/100) × (1 - CR/100) × (1 - RR/100) × (1 - FR/100) × (1 - RK/100)) × 100. (1 - (TV + OHD)/100) × (1 - (RSV + OTD)/ 100) × GINS: total “generative” insect (and other vertebrate pest) (1 - SR/100) × (1 - FR/100) × (1 - RR/100) × damage in % (1 - RK/100) × (1 - OAD/100)) × 100. = (1 - (1 - (WH + DH)/100) × (1 - (R + CTT)/100) VINS: total “vegetative” insect (and other vertebrate pest) × (1 - SIDP/100) × (1 - R/100)) × 100. damage in % LB: mean leaf blast severity in % per day. = (1 - (1 - (WM + TH + SIDL)/1 00) x LF: mean leaf folder damage in % per day. (1 - (LF + DF)/100) x (1 - SIDS/100) x (1 - DH/100) LS: mean leaf scald severity in % per day. × (1 - (R + CTT)/100)) x 100. LY: mean leaf yellowing severity in % per day. WCOVER: mean weed cover in % per day. NHS: mean narrow brown leaf spot severity in % per WH: maximum white heads in %; each observed severity day. value was multiplied by DAS/GDURAT. OAD: mean other area damage severity in % per day. WM: mean whorl maggot damage in % per day. OHD: mean other hill damage severity in % per day. OLD: mean other leaf disease severity in % per day. D) Variable transformations prior to statistical analyses OPD maximum other panicle disease or damage severity in %; each observed severity value was multiplied by Note: ** meansraised to the power of the value that follows. DAS/GDURAT. OSD: mean other sheath disease severity in %, per day. B**0.5 BLB**0.5 OTD: mean other tiller damage in % per day; each BLS**0.333 BS**0.5 observed severity value was multiplied by CB**0.25 CTT**0.333 DAS/GDURAT. DF**0.333 DH**0.333 PB: maximum panicle blast severity in %; each observed DP**0.5 FNE**2 severity value was multiplied by DAS/GDURAT. FSM**0.333 FR**0.333 R: maximum rat damage in %; each observed severity GDIS**0.5 LAID**0.333 value was multiplied by DAS/GDURAT. LB**0.2 LDG**0.333 RK: root damage by root knot nematode in % at LF**0.333 LS**0.333 maximum leaf area stage; each observed severity value LY**0.33 NAPP**2 was multiplied by DAS/GDURAT. NBS**0.5 ND**0.333 RR: root rot severity in % at maximum leaf area stage; NODISIN**0.333 NOFAPP**0.333 each observed severity value was multiplied by NOHWEED**0.333 NOIAPP**0.333 DAS/GDURAT. NONAPP**4 NOPEST**0.333 RSV: maximum ragged stunt virus incidence in %; each NOVAR**0.25 NOWEED**0.5 observed severity value was multiplied by OAD**0.333 OHD**0.333 DAS/GDURAT. OLD**0.333 OPD**0.5 SHBL: mean sheath blight severity (on leaf blade) in % OSD**0.5 OTD**0.5 per day. PAVAIL**0.333 PB**0.333 SHBS: mean sheath blight severity (on leaf sheath) in % R**0.333 RK**0.333 per day. RR**0.333 RSV**0.333 SHR: mean sheath rot severity in % per day. SHBL**0.25 SHBS**0.25 SIDL: mean sucking insect damage on leaves in % per SHR**0.5 SIDL**0.333 day. SIDS**0.333 SR**0.5 SIDS: mean sucking insect damage on sheaths in % per TH**0.333 TLAYER**0.333 day. TV**0.333 UNIFORM**4 SIDP: maximum sucking insect damage on panicles in % VINS**0.5 WCOVER**0.5 per day; each observed severity value was multiplied WH**0.333 WM**0.333 byDAS/GDURAT. YLOSS3**0.25

242 Pinnschmidt et al Surveys of pesticide use in three provinces of the Red River Delta

Ha Minh Trung, 1 Ngo Vinh Vien, 1 Dinh Thi Thanh, 1 Nguyen Thanh Thuy, 1 Mai Thi Lien, 1 Ha Minh Thanh, 1 P.S. Teng, 2 T.W. Mew, 2 and K.G. Cassman 2

Abstract. Surveys of three provinces — Thai Binh (rice-rice system: intensive, moderate yields), Ha Tay (rice-rice-nonricecrop system; intensive, moderate yield), and Vinh Phu (rice-rice-nonricecrop; low yields) — were conducted in the rice- cropping seasons of spring 1992, summer 1992, and spring 1993. Thirty farm families per province were interviewed to collect information on pesticide use. In spring 1992, the number of insecticide applications per field averaged 2.3, 2.9, and 0.7 for Thai Binh, Ha Tay, and Vinh Phu, respectively. Fungicide applications were 1.4, 1.5, and 0.8, respectively, for the same provinces. Corresponding values for summer 1992 were 1.9, 3.2, and 0.7 for insecticides, and 1.2, 1.4, and 0.5 for fungicides; those for spring 1993 were 1.2, 0.8, and 0.2 for insecticides and 0.8, 1.4, and 0.2 for fungicides in the three provinces. During spring 1992, fungicides were applied by 97, 90, and 63% of the interviewed farmers in the three provinces, and by 100, 97, and 47% in summer 1992. The most common insecticides were Monitor 60 EC, Padan 9.5 SC, Bassa 50 EC, and Mipcin 25 WP. The most common fungicides were Kitazin 50 EC, Fuji-1 40 EC, and Validacin 3 EC. No use of herbicides was reported. The results of this survey indicate relatively high pesticide usage and suggest an opportunity to reduce pesticide- related production costs through an integrated crop- and pest-management strategy.

Agriculture in northern Vietnam has made substantial progress toward increased production in recent years. These achievements were due to the new agricultural policies that permit farmers to rent government land on a long-term basis, and to intensive farming techniques and multiple cropping with greater inputs of fertilizers and introduction of shorter-duration varieties on irrigated land. However, insect pests and disease pressure have increased so that farmers apply larger quantities of pesticides to control these problems. The objective of the present study was to quantify pesticide use under farm conditions and to assess the need for current spray applications using on-farm surveys in the three major rice-growing provinces of the Red River Delta and in a vegetable-growing area near the capitol city, Hanoi.

Methods

Survey location Two surveys were conducted, the first during spring/summer 1992 and the second during spring 1993. Surveys were conducted in November 1992 in the following areas of the Red River Delta: • Thai Binh Province, an area with a tradition of intensive rice farming in northern Vietnam with

1 National Plant Protection Research Institute, Chem. Tu Liem, Hanoi, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. the first recorded yield above 5 t/ha in 1967/68. Present total annual grain output is nearly 10 t/ha produced in two rice-cropping seasons; Ha Tay Province, a rice-growing province along the banks of the Red River with annual rice yield of 12 t/ha per year in two cropping seasons: • Vinh Phu Province, a midland rice-growing area where rice yields are lower than in the other provinces of the Red River Delta; and A vegetable-growing area in the vicinity of Hanoi that supplies vegetables to the capital city.

Survey method The survey included two districts per province and two cooperative farms in each district. Within each cooperative, 15 families were selected at random for the survey. Farmers were interviewed and farms visited at different times during each growing season to record the following: Status of major insect pests and diseases; • Relationship between different provincial plant-protection services and the effect of their activities on pest and disease control conducted by small-scale farmers; Quantities and sorts of chemicals used; Varieties used; Farming patterns; Fertilizers used; and Yield of rice. In Thai Binh Province, the survey was conducted in An Le and An Vinh cooperative farms of Quynh Phu District where the cropping pattern is two rice crops per year (spring rice plus summer rice). Quynh Phu is an agricultural district where farmers mainly live on agriculture and have a tradition of intensive farming to increase the rice yield. Rice varieties in this province were VN10, CR203 (lR8423), and IR17494 in the spring crop and CR203, Moc Tuyen, and glutinous rice in the summer crop. Historically, rice blast often appeared in the spring crop, particularly on CR203, which was very susceptible to this disease. The two cooperative farms in Ha Tay Province were Song Phuong and Ha Mo of Dan Phuong District. These cooperatives are located in a rice-growing area with a complete irrigation system on the banks of the Red River. The farming pattern includes two rice crops plus one nonrice crop (spring rice plus summer rice plus winter nonrice crops such as maize, potato, or soybean). Major rice varieties are CR203, C712035, and glutinous rice in the spring season, and CR203 (80% of the planted area) in the summer season. Farmers in these two cooperative farms were experienced in intensive farming practices to increase yield of rice, and considered rice blast and brown planthopper (BPH) as potential constraints to production. Vinh Phu Province is an area with soils of low fertility where rice yield is low compared with the other provinces of northern Vietnam. Tien Chau and Tien Phong cooperative farms of Me Linh District were selected for the survey. The major cropping pattern was two rice crops plus one nonrice crop (winter–spring rice plus summer rice plus winter nonrice crops such as maize, potato, tomato, and soybean). Major rice varieties in the spring crop were CR203, IR8, Chiem 314, and CR203, Bao Thai Lun, and glutinous rice in the summer crop.

Results

General status of rice production in northern provinces The northern provinces of Vietnam (from Hue City northward) consist of those in the north of central Vietnam, in the Red River Delta, and in the mountainous regions. These collectively constitute the second largest rice-growing area in the country with the following cropping patterns:

244 Trung et al • Spring rice-summer rice-winter nonrice crops; • Food nonrice crops-summer rice; • Spring rice-summer rice; and • Spring rice-fish systems. Total area under rice in northern Vietnam in 1992 was 2.52 million ha of which winter-spring rice occupied 1.10 million ha (November–June), summer rice occupied 1.30 million ha (June–November), and early summer rice 0.12 million ha (May–August). Area under nonrice crops was 1.06 million ha including potato, maize, groundnut. and soybean. Total area of rice in the winter-spring season of 1993 in northern Vietnam was 2,600 ha less than the area in 1992. Thai Binh Province consists of eight districts, with 317 cooperative farms and 394,985 households. Total area under rice in the 1993 spring season was 79,842 ha. During 1993, in Quynh Phu District, cooperatives were selected at An Vinh and An Le. The district had 54,142 households and a total rice area of 11,816 ha. Rice varieties used were VN10 (80% of rice area), CR203 (11 % of rice area), DT10, and IR17494 (each about 4% of rice area), and the remainder with other varieties. Tien Hai District had 44,316 households with 10,861 ha under rice. Varieties used were VN10 (59%), CR203 (12%), DT10 (10%), IR17494 (5%), and OM80 (5%), and other minor varieties. Ha Tay Province consists of 14 districts and 517 cooperative farms, with 80,600 ha of rice in the spring 1993 crop. Dan Phuong District includes 22,878 households with 2,330 ha under rice in spring 1993. Varieties used were DT10 (40%), CR203 (34%). glutinous rice (8%), Chinese varieties (7%), C71 (3%), and other minor varieties. In Thanh Oai District, there were 42,116 households with 8,220 ha under rice. Varieties used were CR203 (47%), Chinese varieties (41%), glutinous rice (10%), and other minor varieties. Vinh Phu Province consists of 14 districts with a total of 72,484 ha under rice in 699 cooperative farms with 336,500 households. Me Linh District includes 51,000 households farming a rice area of 7,029 ha. Varieties used were CR203 (36%), NN8 (32%), DTl0 (14%), and CN2 (10%), and other minor varieties. In Vinh Lac District, there were 65,000 households farming a rice area of 12,200 ha. Varieties used were CR203 (42%), NN8 (33%), and DT 10 (18%), and other minor varieties.

General status of rice pests and diseases In 1992, six major insect pests and diseases were reported to cause damage in the northern provinces (Table 1). Rice blast and sheath blight were the most common diseases although neck blast was less widespread in spring 1993 than in 1992. Yellow leaf syndrome was also more prevalent in 1992. BPH was most prevalent in the 1992 spring season and less severe in 1993. Leaf roller was reported on a relatively large area in both years. In contrast, stem borer was reported on a very limited area. These data do not include quantitative measures of the severity of infestation by these insects and diseases; however, such data are available from other studies done under the Vietnam-IRRI cooperative project.

Chemicals commonly used in the rice fields District Plant Protection services appear to have introduced their own guidelines for farmers to apply the following chemicals for control of the recorded insect pests and diseases. For insecticides, the chemicals with guidelines were methyl Parathion 50 EC, Monitor 60 EC, Padan 95 WP, Bassa 50 EC, Mipcin 25 WP, and Mipcin 20 EC. Fungicides included Kitazin 50 EC, Fuji-1 40 EC, Hinosan 40 EC, Validacin 3 EC, and Dinazin 6.5 EC. The main chemical suppliers for the northern provinces are the Plant Protection Material Company No. 1 and the northern branch of the Vietnam Pesticide Company (VIPESCO). The total quantity of chemical released for sale in 1992 by these two companies was 1,880 t of which 1,310 t were insecticides and 570 t were fungicides. Total cultivated land area in northern Vietnam in 1992 was 3,585,400 ha. Thus, average quantity of chemicals used was 0.524 kg/ha. This value does not

Surveys of pesticide use 245 Table 1. Major rice pests and diseases and their infected area in spring season, 1992 and 1993.

Insect pests Infected area and diseases Spring 1992 Spring 1993

Total area (%) a Total area (%) a (ha) (ha)

Rice blast Leaf blast 192,000 17.48 175,000 15.95 Neck blast 217,000 19.76 65,000 5.93 Sheath blight 170,000 15.48 197,000 17.80 Brown planthopper 369,000 33.60 55,000 5.02 Leaf roller 81,000 7.37 51,000 4.66 Stem borer 15,000 1.36 2,588 0.23 Yellow leaf virus 100,000 9.11 46,000 4.19

Source: Plant Protection and Production Department, Ministry of Agriculture and Food Industry. a Area under rice: spring 1992, 1,098,000 ha; spring 1993, 1,095,000 ha.

account fully for total pesticide use because farmers used additional chemicals that were obtained from illegal importation or from left-over stocks from 1991 that were sold in the 1992 rice seasons. Results of the surveys indicate the intensity of chemical use by the interviewed farmers (Table 2). These results suggest that: • The level of chemical use for insect pest and disease control in Me Linh District of Vinh Phu Province was lower than in the other surveyed districts. • The highest rates of insecticide and fungicide use were in Ha Tay Province. • Only Dan Phuong among the three surveyed districts applied potassium (K) and a higher dose of farmyard manure. The average rice yield was also higher than in other districts. This district has a tradition of intensive rice farming. • In Quynh Phu District, Thai Binh Province, the highest level of chemicals used by a farm household was 1.7 kg/ha of insecticides and 2.7 kg/ha of fungicides in the winter–spring crop, and 3.7 kg/ha of insecticides and 2.9 kg/ha of fungicides in the summer crop. • In Dan Phuong District, Ha Tay Province, the highest level of chemicals used by a farm household was 7.9 kg/ha of insecticides and 3.2 kg/ha of fungicides in the winter–spring crop, and 6.0 kg/ha of insecticides and 2.8 kg/ha of fungicides in the summer crop. • In Me Linh District, Vinh Phu Province, the highest level of chemicals used by a farm household was 2.7 kg/ha of insecticides and 2.2 kg/ha of fungicides in the spring crop and 4.3 kg/ha of insecticides and 1.1 kglha of fungicides in the summer crop. In 1993, additional data were obtained by interviewing farmers at Tay Tuu village, Tu Liem, Hanoi, which is a major vegetable-growing area near Hanoi with a cropping pattern of vegetable crops in rotation with rice. The number of chemical applications, as well as the type of chemicals used kept changing according to the kind of vegetables grown (Table 3). Some species of insect pests have developed resistance to chemicals, particularly Plutella on cruciferous vegetables. The number of chemical applications in the vegetable-growing area was much higher than in the rice-growing areas (Table 3). Particularly for Plutella control, farmers often gave one chemical spray per week, which may facilitate development of resistance to chemicals in this pest. There have been 237 different commercial names for the 106 chemicals available in Vietnam as of March 1993: of these, 45 are insecticides, 35 fungicides, 25 herbicides, and 1 is a rodenticide.

246 Trung et al Table 2. Fertilizers and chemicals used in the Red River Delta, 1992.

Survey area a Planted Fertilizer used (kg/ha) area N P O K O FYM b (ha) 2 5 2

Winter-spring crop Quynh Phu 11,500 79 56 0 7,800 Dan Phuong 2,423 107 63 19 12,800 Me Linh 8,000 63 41 0 7,500

Summer crop Quynh Phu 11,500 76 35 0 8,400 Dan Phuong 2,477 115 64 32 13,900 Me Linh 7,000 66 38 0 74,700

Insecticide Fungicide Rice yield No. of Rate No. of Rate (t/ha) sprays (kg/ha) sprays (kg/ha)

Winter-spring crop Quynh Phu 2.30 1.83 1.40 1.87 5.03 Dan Phuong 2.90 2.75 1.45 1.82 5.65 Me Linh 0.9 0.6 0.7 0.8 3.16

Summer crop Quynh Phu 1.95 1.86 1.15 1.63 4.15 Dan Phuong 3.20 3.23 1.35 1.87 5.35 Me Linh 0.7 0.5 0.5 0.2 2.54

a For Quynh Phu District, Thai Binh Province, average values were obtained from An Vinh and An Le cooperative farms; for Dan Phuong District, Ha Tay Province, from Song Phuong and Ha Mo cooperative farms; and for Me Linh District, Vinh Phu Province, from Tien Chau and Tien Phong cooperative farms. b FYM, farmyard manure.

Table 3. Chemicals used in vegetable growing area in Hanoi, 1992.

Vegetable Insecticides Fungicides Major pests and diseases

No. of Rate No. of Rate sprays (kg/ha) sprays (kg/ha)

Snap bean 8.20 11.53 1.20 1.3 Pod borer; Rust Tomato 4.16 7.04 7.83 4.2 Heliothis; Phytophthora infestans Chinese mustard 3.80 7.84 – – Plutella

However, the types and number of chemicals used in the provinces under survey seem to be much simpler than the ones prevailing in the country as a whole. As the provinces under survey are densely populated, weeds were controlled manually and only insecticides and fungicides are used by farmers. The most common are the insecticides Monitor at 1.0 liter/ha, Padan 95 SC at 0.5 kg/ha, Bassa 50 EC at 1.5 liter/ha, Mipcin 25 WP at 2.0 kg/ha, and the fungicides Kitazin 50 EC at 1.5 liter/ha, Fuji-1 40 EC at 1.0 liter/ha, and Validacin 3 EC at 1.7 liter/ha. Quantities of insecticides and fungicides used in the spring season of 1993 were smaller than in the spring season of 1992 (Table 4 versus Table 2). This would be expected in light of the reported

Surveys of pesticide use 247 Table 4. Fertilizers and chemicals used in three provinces in the Red River Delta,-. spring- 1993.

Survey area a Planted Fertilizer used (kg/ha) area b (ha) N P 2 O 5 K 2 O FYM Thai Binh Province Quynh Phu 11,816 80 53 – 8,000 Tien Hai 10,861 126 67 – 7,500 Ha Tay Province Dan Phuong 2,430 105 54 16 13,900 Thanh Oai 8,220 64 73 – 7,450

Vinh Phu Province Me Linh 7,029 72 35 – 9,650 Vinh Lac 12,200 89 44 4 10,000

Insecticide Fungicide Rice yield No. of Rate NO. of Rate (ma) sprays (kg/ha) sprays (kg/ha)

Thai Binh Province Quynh Phu 0.94 0.49 1.03 1.05 4.51 Tien Hai 1.65 0.91 0.65 0.51 5.77

Ha Tay Province Dan Phuong 1.43 1.08 2.05 1.84 5.36 Thanh Oai 0.15 0.17 0.71 0.52 4.28

Vinh Phu Province Me Linh 0.17 0.03 0.28 0.15 3.78 Vinh Lac 0.25 0.20 0.03 0.09 4.41 * Quynh Phu District: average figures obtained from two cooperative farms, An Vinh and An Le; Tien Hai District: average figures obtained from two cooperative farms, Dong Quy and Tay Giang; Dan Phuong District: average figures obtained from two cooperative farms, Song Phuong and Ha Mo; Thanh Oai District: average ftgures obtained from two cooperative farms, Tan Uoc and My Hung; Me Linh District: average figures obtained from two cooperative farms, Tien Phong and Tien Chau; and Vinh Lac D istrict: average figures obtained from two cooperative farms, Tu Chung and Dong Lac. c FYM. farmyard manure. levels of insect pest and disease incidences in the northern provinces in the 2 yr (Table 1). In contrast, farmers applied about the same amount of fertilizer and manure in both 1992 and 1993 spring seasons. As found in 1992, the districts located in the intensive-farming area such as Quynh Phu and Tien Hai (Thai Binh Province) and Dan Phuong (Ha Tay Province) used a larger quantity of fertilizers and pesticides in rice and had higher yields of rice than those in Vinh Phu Province. Generally, almost all households used relatively high inputs of farmyard manure (at least 7,450 kg/ha) and, in most places in the survey, farmers used very little K on rice. Sites selected for this field survey cover three ecological regions that differ from one another in cultural practices, soil conditions, and varieties of rice grown. These environmental factors influence the occurrence and intensity of insect pests and diseases on rice and the control measures against them. The proportion of total rice area treated with pesticides was greatest in the three intensive-farming districts of Quynh Phu and Tien Hai (Thai Binh Province) and Dan Phuong (Ha Tay Province) compared with districts in Vinh Phu (Table 5 ). Plant protection is generally one of the largest costs for rice production particularly when pests

248 Trung et al Table 5. Percentage of rice area treated with chemicals against major rice pests and diseases, spring 1993.

Survey area Rice area % of rice area treated with chemicals against – (ha) Rice Sheath Stem Leaf Brown blast blight borer roller planthopper

Thai Binh Province Quynh Phu 11,816 65 16 9 76 – Tien Hai 10,816 33 24 38 92 –

Ha Tay Province Dan Phuong 2,430 4 85 25 53 8 Thanh Oai 8,220 34 8 – 1 8

Vinh Phu Province Me Linh 7,029 9 17 – 4 2 Vinh Lac 12,200 2 2 – 24 1

Table 6. Expenses on chemicals used in the districts surveyed.

Survey area Total revenue Expenses on chemicals Chemical cost (dong × 1,000) a as % of total revenue Yield In cash Total Insect- Fung- (kg/ha) (dong × 1,000) icide icide

Tha Binh Province Quynh Phu 4,505 5,406 124 53 71 2.3 Tien Hai 5,765 6,918 121 95 26 1.8

Ha Tay Province Dan Phuong 5,359 6,431 217 130 87 3.4 Thanh Oai 4,282 5,138 54 17 37 1.1

Vinh Phu Province Me Linh 3,780 4,536 6 2 4 0.1 Vinh Lac 4,411 5,293 12 11 1 0.3

a In 1994, 11,000 dong = US$1.

and diseases occur and infest large areas. Expenses for chemicals used for insect and disease control in the spring season 1993 are given in Table 6. These cost estimates exclude the cost of labor for chemical application because each household had a different valuation for their labor costs, and the labor costs differs from place to place. Among 180 farm households surveyed, 140 (78%) based their chemical application entirely on the forecasting notice and information provided by both local and central plant protection institutions [including plant protection warnings broadcast on radio and television). Forty households (22%) made their own decisions for chemical applications based on the results of their own field surveys. There were seven households (4%) who were able to combine forecasting information on pests and diseases provided by the plant protection institutions with the results of their own field surveys to warrant chemical application for pests and disease control. There were two households (1%) who misused a pesticide (Padan 95 SP) for neck blast control.

Surveys of pesticide use 249 Discussion

An agricultural extension system is needed to provide information to farmers on guidelines for integrated pest management. Part of its mandate includes the responsibility to help farmers recognize different insect pests and diseases and determine incidence or severity thresholds that justify treatment, and, when needed, it must supply suitable chemicals for their control. To minimize the number of chemical applications and to make chemical control more cost-effective, farmers need relevant guidelines to distinguish the natural enemies from the insect pests and so avoid unnecessary pesticide applications thus reducing chemical use in the field. It is necessary to conduct further studies and to encourage farmers to use balanced quantities of fertilizers with particular emphasis on the use of K and organic fertilizers in the field. Before 1990, the plant protection team on each cooperative farm was responsible for field control of insect pests and diseases. Nowadays, however, this is undertaken by the farmers themselves. Therefore, to make the best use of chemical control, the farmers must be given proper guidelines on identification of insect pests and diseases, on appropriate integrated crop-management measures that help to reduce pest pressure, and on assessing the severity of pest and disease pressure in their fields before deciding to apply pesticides to control insect and disease problems in rice.

250 Trung et al Nematode parasites of deepwater and irrigated rice in the Mekong River Delta

Nguyen Thi Thu Cuc 1 and J.-C. Prot 2

Abstract. The major root-parasitic nematodes present in deepwater and irrigated rice in the Mekong River Delta (MRD) are Hirschmanniella oryzae, H. mucronata, and Meloidogyne graminicola. The first two infest more than 90% of the fields and are potentially important pests of irrigated rice in the Delta: the third may be of local importance. Tiem Dot Sam disease (or ufra), caused by the nematode Ditylenchus angustus, was a major disease of floating, deepwater, and rainfed lowland rice in the MRD. The nematode is still present and the cultivars grown are susceptible but the incidence of the disease has been drastically reduced within the past 10 yr especially in areas where a winter-spring (W-S) crop is grown. To understand the factors that are responsible for this change, the effects of different water regimes and cultural practices were tested. Direct seeding into water, which is used by many farmers during the W—S cropping season, appears to reduce the invasion of the seedling by the nematode. The absence of deep flooding does not limit the reproduction of the nematode but reduces the severity of the disease and yield loss. The combination of direct seeding in water and water control during the W-S cropping season may be responsible for the decline in importance of Tiem Dot Sam disease in the MRD.

Many plant-parasitic nematodes are associated with deepwater, rainfed lowland, and irrigated rice. Those of proven or potential economic importance in South and Southeast Asia are rice-root nematodes, Hirschmanniella spp.; rice root-knot nematode, Meloidogyne graminicola; stem nematode, Ditylenchus angustus; and white tip nematode, Aphelenchoides besseyi (Bridge et al 1990). The rice-root nematodes are pathogenic to rice (Fortuner 1974, Babatola and Bridge 1979) and capable of causing yield losses under field conditions (Jairajpuri and Baqri 1991, Prot et al 1992). Meloidogyne graminicola causes damage in rainfed lowland and deepwater rice (Bridge and Page 1982, Jairajpuri and Baqri 1991). Aphelenchoides besseyi causes white tip disease, which is seed borne and subject to quarantine regulations — it can cause severe yield loss in severely infested fields (Fortuner and Orton Williams 1975). Ditylenchus angustus , the causal agent of Tiem Dot Sam disease (ufra disease in Bangladesh and India) occurs mostly in floating and deepwater rice. However, it can also cause serious damage in irrigated and rainfed lowland rice (Cuc and Kinh 1981). It was a serious problem in four provinces of the Mekong River Delta (MRD) of Vietnam: Dong Thap, An Gang, Hau Gang, and Cuu Long (Cuc 1982) and yield losses ranged from 50 to 100% (Cuc and Kinh 1981). However, its occurrence in the MRD seems to have been drastically reduced in the past 10 yr. Preliminary and limited surveys have been conducted previously (Cuc et al 1985) but information on the distribution and intensity of the major parasitic nematodes associated with rice in the MRD was limited. In addition, the distribution and importance of D. angustus, which has been reported to affect 60,000-100,000 ha of rice in the Delta (Catling and Puckridge 1984), must be reassessed. Moreover, it was important to identify the causes of the decline in importance of Tiem Dot

1 Plant Protection Department, Faculty of Agriculture, University of Cantho, Cantho, Vietnam; 2 International Rice Research Institute, P.O. BOX 933, Manila 1099, Philippines Sam disease. This understanding may result in better control of the disease in areas of the MRD where it still occurs as well as in other countries where it is still a major problem (Bangladesh and India) and prevent its resurgence in areas where it is currently under control. The objectives of the surveys and experiments reported here were twofold: • To assess the prevalence and intensity of parasitic nematodes associated with deepwater and irrigated rice in the MRD; and • To study the effects of different water regimes combined with transplanting and direct seeding on the infestation of the seedlings by D. angustus, the multiplication of the nematode, and the development of Tiem Dot Sam disease.

Materials and methods Surveys Two surveys were conducted to estimate the distribution and intensity (population density) of the major parasitic nematodes associated with irrigated and deepwater rice. During the first survey, 276 soil, root, and stem samples were collected in March 1989 in Hau Gang and Cuu Long provinces from the winter-spring (W-S) irrigated crop. During the second survey, conducted in November 1989 and November 1990, 1,640 (10 samples per field) samples of soil, root, and stem were collected in 164 deepwater fields selected at random over five provinces: An Giang (7 fields), Cuu Long (23), Dong Thap (8), Hau Giang (47), and Minh Hai (79). During both surveys, samples were collected between flowering and maturity stage. Information on the area of rice affected by Tiem Dot Sam disease and the area grown in deepwater rice and in irrigated rice during the W-S and the summer-autumn (S-A) cropping seasons since 1976 were collected from the plant protection services in each province. Nematodes were extracted from 200 cm 3 of soil with a combination of sieving and modified Baermann funnel methods (Hooper 1986a) and from 3 g of roots by macerating them for 15 s in a blender and then placing them for 24 h in a modified Baermann funnel (Hooper 1986b). Nematodes were also extracted from 30 g of stems by cutting the stems into 1-cm pieces, teasing them apart, and incubating them for 24 h in a modified Baermann funnel (Hooper 1986b). Effect of cultural practices and water regime on Tiem Dot Sam disease The specimens of D. angustus used in all experiments were derived from a culture maintained in a 15-m 2 bed at the University of Cantho on variety IR42. The soil used in all experiments was a clay soil collected from a rice field on the experimental farm of the university. This soil was sterilized by heating (100°C) for 30 min. IR42 was used in all experiments. At harvest of all experiments, nematodes were extracted from the stems by cutting the stems into 1-cm pieces, teasing them apart, and incubating them for 12 h in a modified Baermann funnel (Hooper 1986b). Effects on infestation. An experiment was conducted to study the combined effects of water regime and transplanting or direct seeding on the infestation of the young plants by D. angustus. The experiments was conducted in 17 cm diam × 20 cm high Wagner pots filled with 1 kg of soil. Three 8-d-old seedlings or three 3-d-old pregerminated seeds of IR42 were transplanted into each pot and at the same time 300 nematodes were inoculated at the soil surface. Fifteen days after inoculation, nematodes were extracted from the stems of the three seedlings. Eight treatments were used: direct seeding in saturated soil without standing water; direct seeding in 1, 5, 10, or 15 cm of standing water; transplanting in mud without standing water; transplanting in standing water reaching the apex of the stem, or the collar of the leaf sheath. Water levels were maintained at the same levels for the duration of the experiments by daily watering. Treatments were arranged in a randomized complete block design with 10 replications. Average numbers of nematodes observed in the stems in each treatments were compared in pairs using the Mann-Whitney U test. The experiment was replicated twice.

252 Cuc and Prot Effects of flooding on the nematode and the development of the disease. Two experiments were conducted in 75 dm 3 , 60-cm high pots filled with 10 kg of soil. In the first experiment, the soil was saturated and two 20-d-old seedlings were transplanted in each pot. Seven days after transplanting (DAT), 300 D. angustus were inoculated in half of the pots and the water level was raised to the level of the highest stem apex and four flood durations were tested in combination with presence and absence of the nematode. The treatments were maintained until 77 DAT; high water level maintained for 7 d, 3 wk, and 5 wk and then reduced to 5 cm. Numbers of stems and infected stems were recorded at 10, 20, 30, 40, and 55 DAT. At harvest, nematodes were extracted from the stems and the grain yield was measured. Treatments were arranged in a randomized complete block design with seven replications. Data were analyzed using the Mann–Whitney U test. In the second experiment, the soil was saturated and a 15-d-old seedling transplanted into each pot. Five days after transplanting, 150 D. angustus were inoculated in half of the pots. Five water regimes or treatments were tested in combination with presence and absence of D. angustus: water level raised to 5 cm above the soil surface and maintained at this level from 5 DAT until harvest; water level raised to the level of the apex of the stem at 5 DAT, at 15 DAT, at 25 DAT, or at 35 DAT, maintained at this level until 75 DAT, and then reduced to 5 cm until harvest. Numbers of stems and infected stems were recorded at 15, 25, 35, 45, and 55 DAT. Plants were harvested at the hard-dough stage and numbers of flowers and of filled spikelets were recorded. Nematodes were extracted from all the stems. Treatments were arranged in a randomized complete block design with six replications. Data were analyzed using the Mann-Whitney U test.

Results Surveys During the survey for root-parasitic nematodes conducted in W-S irrigated rice, Hirschmanniella oryzae was detected in all but one sample collected (Table 1). High population densities of this parasite were observed in more than 50% of the samples. Low population densities of H. mucronata were recorded in 75% of the samples. Meloidogyne graminicola was present in 57% of the samples but at high population levels in only 10% of these. With a prevalence (percentage of fields infested) of 99% and a mean intensity (population density) of 1,238/dm3 of soil, H. oryzae was the most prevalent root-parasitic nematode observed in deepwater rice (Table 2). Hirschmanniella mucronata was observed in 96% of the fields but at a lower intensity than H. oryzae. Meloidogyne graminicola was observed only in Hau Gang and Cuu Long provinces and Tylenchorhynchus annulatus in An Giang, Dong Thap, and Hau Giang provinces,

Table 1. Numbers of samplesa with low, medium, and high population densities of three nematodes from the winter-spring irrigated rice crop.

Population density b

Low Medium High

Hirschmanniella oryzae 16 108 151 Hirschmanniella mucronata 131 42 3 Meloidogyne graminicola 108 24 25

Source: Cuc and Prot 1992a. a Total of 276 samples taken. b Soil densities of nematodes (per dm3) are low, 0-200; medium, 201-1.000;and high, >1 ,000. Root densities (per g) are low, 0-20; medium, 21-100; and high, >100.

Nematodes in the Mekong River Delta 253 Table 2. Mean intensity (MI, per dm 3 of soil or per g of root) and prevalence (P, % of fields where the species was detected) of root-parasitic nematodes associated with deepwater rice in the Mekong River Delta.

Nematode species Mekong River Delta provinces and sample site An Giang Cuu Long Dong Tap MI P MI P MI P

Hirschmanniella oryzae Soil 63 100 1,402 100 526 100 Root 32 100 76 100 12 100

Hirschmanniella mucronata Soil 61 75 274 100 53 73 Root 7 100 3 100 2 87

Meloidogyne graminicola Soil 0 0 115 44 0 0 Root 0 0 36 52 0 0

Tylenchorhynchus annulatus Soil 0 0 0 0 550 50 Root 9 25 0 0 26 87

Mekong River Delta provinces

Hau Giang Minh Hai Total

MI P MI P MI P

Hirschmanniella oryzae Soil 1,224 98 1,353 100 1,238 99 Root 82 98 26 100 49 99

Hirschmanniella mucronata Soil 123 96 232 85 191 96 Root 5 96 4 63 4 77

Meloidogyne graminicola Soil 547 42 0 0 408 20 Root 43 42 0 0 39 20

Tylenchorhynchus annulatus Soil 30 10 0 0 261 5 Root <1 20 0 0 12 11

Source: Cuc and Prot 1992a.

Aphelenchoides besseyi and D. angustus were not observed in any of the samples collected at random. During the surveys, however, severe symptoms of Tiem Dot Sam disease were observed in Dong Thap, Cuu Long, and Hau Giang and D. angustus was observed in samples collected from these fields. When statistics on the areas of rice grown during the flood season and of rice affected by Tiem Dot Sam disease are compared, the decrease in Tiem Dot Sam disease seems to be related, at both the provincial (Table 3) and the district (Table 4) levels, to the reduction in area of rice grown during the flood season and an increase in the area of irrigated rice grown during the W-S season.

254 Cuc and Prot Table 3. Areas damaged by Ditylenchus angustus and of two forms of land use in five provinces of the Mekong River Delta.

Province Damaged Type of rice planted (ha) and area (ha) year Deepwater Winter-spring irrigated

Cuu Long 1985 2,798 141,970 40,824 1987 106 108,000 58,186 1988 1,133 105,845 75,366 1990 906 95,245 80,870

Dong Thap 1976 60,000 110,839 30,165 1980 32 110,000 72,059 1981 10,000 80,000 60,815 1983 30,000 na 61,785 1985 10 na 71,116 1988 8 59,000 99,273 1990 20 15,000 141,803 1992 0 7,000 na

Hau Giang 1982 17,900 320,517 27,378 1985 7,200 296,242 56,100 1988 1,284 252,068 71,287 1990 804 210,830 104,323

An Giang 1976 2,500 152,692 31,509 1980 210 145,875 79,066 1985 5 83,964 97,632 1990 0 37,347 141,210 1992 0 27,000 na

Note: na, not available.

Effect of cultural practices and water regime on Tiem Dot Sam disease In both experiments, the number of D. angustus observed in the stems of the seedlings 15 d after inoculation was significantly lower when pregerminated seeds were sown in 5, 10, and 15 cm of standing water than when seeds were sown in the absence of water or in 1 cm of standing water (Table: 5). When 8-d-old seedlings were used, the numbers of nematodes observed in the stems 15 d after transplanting did not vary with the water level and were not significantly different from the number observed after seeding in the absence of standing water.

Effects of flooding on Ditylenchus anguslus and Tiem Dot Sam disease In the first experiment, the number of stems observed at 40 and 55 DAT was significantly reduced in the presence of D. angustus in all treatments except when plants were maintained under deep flooding for 5 wk (Fig. 1). In the presence of the nematode and under all water regimes, the numbers of stems showing the symptoms of Tiem Dot Sam disease were smaller ( P < 0.05) than the total number of stems. The number of D. angustus present in the stems at harvest appeared to decrease when the period of deep flooding increased (Table 6) — the number of nematodes in plants flooded for 10 wk was

Nematodes in the Mekong River Delta 255 Table 4. Areas (ha) infested by Ditylenchus angustus and of two forms of land use in two districts of Hau Giang Province.

District Infested Type of rice planted (ha) and year area (ha) Deepwater Winter-spring irrigated

Phung Hiep 1982 2,560 27,006 1,034 1985 1,199 23,468 2,900 1988 620 22,550 4,355 1990 300 19,640 7,260

Ke Sack 1983 1,700 10,600 2,580 1985 1,300 9,070 8,000 1987 250 7,793 10,600 1990 185 7,913 9,587

Source: Cuc and Prot 1992b.

Table 5. Effects of establishment method and water regime on infestation of young seedlings of IR42 by Ditylenchus angustus.

Establishment method and Number of nematodes in the stems a,b water level above soil surface 1st 2nd experiment experiment

Direct seeding 0 cm 107a 20a 1 cm 73ab 15a 5 cm 9b 2b 10 cm 8b 0b 15 cm 13b 0b

Transplanting 0 cm 45ab 15a Stem apex 53ab 23a Top of sheath collar 34b 19a

a Average of 10 replications. b Within a column, values followed by the same letter do not differ significantly according to a Mann-Whitney U test ( P = 0.05). significantly smaller than in plants flooded for 1, 3, or 5 weeks. Under all water regimes, the grain yield was significantly reduced by the nematode. In the absence of nematode, the yield was significantly reduced by 10 wk of deep flooding when compared to 1, 3, and 5 wk of flooding. In the presence of D. angustus, the yield was independent of the duration of the deep flooding. In the second experiment, D. angustus did not significantly increase or decrease the number of stems observed until 55 DAT (Fig. 2). In nematode-infested plants, the number of stems showing the symptoms of Tiem Dot Sam disease was almost equal to the total number of stems in all treatments. The number of panicles was reduced in the presence of nematodes when deep flooding was started at 5, 15, and 25 DAT (Table 7). It was not affected when deep flooding was not applied or started at 35 DAT. In the absence of the nematode, there was no significant difference in number of

256 CuC and Prot 1. Effect of duration of deep flooding starting after transplanting on numbers of stems per two hills in presence or absence of Ditylenchus angustus and on the number of diseased stems in the presence of the nematode: A, 10 wk of deep flooding; B, 5 wk; C, 3 wk; and D, 1 wk. filled spikelets between plants subjected to different water regimes. When plants were not subjected to deep flooding, the number of filled spikelets was not reduced by the nematode. When plants were flooded, the number of filled spikelets was significantly reduced by the nematode. Deep flooding at 5, 15, and 25 d seemed to reduce the number of nematodes present in the stems at the hard-dough stage. However, this reduction was significant only when flooding was started at 15 DAT.

Discussion Hirschmanniella oryzae and H. mucronata are omnipresent in irrigated as well as deepwater rice. Their effect on deepwater rice has never been assessed but they can cause yield loss in irrigated rice (Jairajpuri and Baqri 1991, Prot et al 1992) — they are potentially important pests especially if irrigated rice replaces deepwater rice. Meloidogyne graminicola, present in 20% of the irrigated fields

Nematodes in the Mekong River Delta 257 Table 6. Effects of duration of deep flooding (first experiment) on numbers of Ditylenchus angustus and grain yield obtained at harvest of IR42 in presence and absence of nematodes. a,b

Period of deep flooding Number of Grain after transplanting nematodes yield (wk) in the stems (g)

Ditylenchus angustus present 10 551 b 45c 5 1,684a 60bc 3 1,805a 56c 1 2,481a 51c

Ditylenchus angustus absent 10 0 70b 5 0 94a 3 0 106a 1 0 100a

a Average of 7 replications. b Within a column, values followed by the same letter do not differ significantly according to a Mann-Whitney U test ( P = 0.05).

Table 7. Effects of time and duration of a deep flooding (second experiment) on numbers of panicles, filled spikelets, and Ditylenchus angustus observed at hard-dough stage with IR42 in presence and absence of nematodes. a,b

Period of Number of Number of Number of flooding panicles filled nematodes/ spikelets plant

Ditylenchus angustus present No flooding 9.5a 691 bc 2,480a 5-75 DAT 3.3bc 266c 1,355ab 15-75 DAT 4.0bc 357c 1,010b 25-75 DAT 2.7c 243c 1,417ab 35-75 DAT 7.2ab 560c 2,699a

Ditylenchus angustus absent No flooding 8.3a 870ab 0 5-75 DAT 8.2a 1,057ab 0 15-75 DAT 9.2a 1,206a 0 25-75 DAT 7.8ab 1,009ab 0 35-75 DAT 10.0a 1,435a 0

a Average of 10 replications. b Within a column, values followed by the same letter do not differ significantly according to a Mann-Whitney U test ( P = 0.05). c Days after transplanting. and 57% of the deepwater rice fields, may be of local importance. Because it can damage other crops, the economic importance of the rice root-knot may increase with any increase in crop diversification. Surveys conducted over the last 5 yr have indicated that the occurrence of Tiem Dot Sam has been drastically reduced but it still causes limited damage in Cuu Long Province and in other areas of the MRD. The decline in the importance of Tiem Dot Sam appears to be related to the reduction

258 Cuc and Prot 2. Effect of duration and time of deep flooding on numbers of stems per hill in the presence or absence of Ditylenchus angustus and on the number of diseased stems in the presence of the nematode: A, no deep flooding; B, deep flooding from 5 to 75 d after transplanting (DAT); C, deep flooding from 15 to 75 DAT; D, deep flooding from 35 to 75 DAT. in area of rice grown during the rainy season (Cuc and Rot 1992b). This reduction has come mainly from floating and deepwater areas. Many farmers who previously grew deepwater rice now maintain their fields fallow during the flood period and grow two irrigated crops during the W-S (December-March) and S-A (May-August) cropping leasons (Catling 1992). The nematode is still present in the fields and high-yielding modern cultivars grown during the W-S and S-A seasons are susceptible to the disease but, especially during the W-S season, only a few plants are damaged and yield is not affected. It has also been observed that Tiem Dot Sam disease is less severe in deepwater rice in areas where a W-S rice crop has been grown. Direct seeding into water reduces seedling infestation by D. angustus. A similar observation has been made with A. besseyi, the white tip nematode, that parasitizes rice leaves (Cralley 1956). Ditylenchus angustus, which swims in the water, may be unable to infest the seedlings when they are

Nematodes in the Mekong River Delta 259 totally submerged and may starve and lose its ability to invade the seedlings before they emerge from the water. Under conditions prevailing during our experiments, transplantation did not reduce the infestation and the water depth had no effect on seedling infestation by the nematode when seedlings were transplanted. In our experiments, the multiplication of D. angustus was not reduced in the absence of deep flooding. At the same time, however, deep flooding favored the expression of Tiem Dot Sam disease. In these experiments, the expression of the disease and the reduction in yield it caused were not directly related to the ability of the nematode to multiply but deep flooding, especially early flooding, seemed to increase the susceptibility of the rice plant to Tiem Dot Sam disease. The results obtained suggest: first, that direct seeding in water may reduce or prevent the infestation of the seedlings by the nematode D. angustus, the causal agent of Tiem Dot Sam disease. This mode of seeding, used by many farmers during the W-S cropping season, may be partly responsible for the decrease in occurrence of the disease in the MRD. Second, the absence of deep flooding does not result in a reduction of the multiplication of the nematode but in a reduction in the severity of the disease it causes. The absence of deep flooding during the W-S crop may partly explain why the yield loss caused by the nematodes on this crop is minimal in fields where it is present.

References cited

Babatola J O, Bridge J (1979) Pathogenicity of Hirschmanniella oryzae, H. spinicaudata and H. imamuri on rice. J. Nematol. 11:128-132. Bridge J, Luc M, Sikora R A (1990) Nematode parasite of rice. Pages 69-108 in Plant parasitic nematodes in subtropical and tropical agriculture. M. Luc, R.A. Sikora, eds. CAB International, Wallingford, Oxford, U.K. Bridge J, Page S L J (1982) The rice root-knot nematode, Meloidogyne graminicola, on deep water rice Oryza ( sativa subsp. indica). Revue Nematol. 5:225-232. Catling D (1992) Rice in deep water. MacMillan Press, London, U.K. 542 pp. Catling H D, Puckridge D W (1984) Report on a visit to Vietnam, October 1983. Deepwater Rice 1/84:3-4. Cralley E M (1956) A new control measure for white tip. Arkansas Farm Res. 5:5. Cuc N T T (1982) Distribution of ufra disease in the Mekong Delta of Vietnam and control methods [in Vietnamese]. Thong tin KHKT Hau Giang 1-2(4-5):6-9. Cuc N T T, Kha T M, Hien N X (1985) Preliminary survey on nematode parasites of rice in Hau Giang and Cuu Long [in Vietnamese]. Pages 353-356 in 1985 Faculty of Agronomy Report. University of Cantho, Cantho, Vietnam Cuc N T T, Kinh D N (1981) Rice stem nematode disease in Vietnam. Internat. Rice Res. Newsl. 6 (6):14-15. Cuc N T T, Prot J C (1992a) Root-parasitic nematodes of deep-water rice in the Mekong Delta of Vietnam. Fundam. Appl. Nematol. 15:575-577. Cuc N T T, Prot J C (1992b) Effect of changing the agricultural environment on ufra occurrence in the Mekong Delta. Internat. Rice Res. Newsl. 17(2):25. Fortuner R (1974) Evaluation des degâts causés par Hirschmanniella oryzae (Van Breda de Haan, 1902) Luc & Goodey, 1963, nematode endoparasite des racine du riz irrigué. Agron. Trop. Nogent 29:708-714. Fortuner R, Orton Williams K J (1975) Review of the literature on Aphelenchoides besseyi Christie, 1942, the nematode causing ‘‘white tip” disease in rice. Helminthol. Abstr., Ser. B: Plant Nematol. 44:1-40. Hooper D J (1986a) Extraction of free-living stages from soil. Pages 5-30 in Laboratory methods for work with plant and soil nematodes. J.F. Southey, ed. Ministry of Agriculture, Fisheries and Food, London, U.K. Reference Book 402. Hooper D J (1986b) Extraction of nematodes from plant material. Pages 51-58 in Laboratory methods for work with plant and soil nematodes. J.F. Southey, ed. Ministry of Agriculture, Fisheries and Food, London, U.K.. Reference Book 402. Jairajpuri M S, Baqri Q H (1991) Nematode pests of rice. Oxford and IBH Publishing, New Delhi, India. 66 pp. Prot J C, Cuc N T T (1990) Nematodes in irrigated rice after DWR in the Mekong Delta. Deepwater and Tidal Wetlands Rice 17:2-3. Prot J C, Soriano I R S, Matias D M, Savary S (1992) Use of green manure crops in controlling Hirschmanniella mucronata and H. oryzae in irrigated rice. J. Nematol. 23:127-132.

260 Cuc and Prot Social sciences

Change from deepwater to irrigated rice ecosystem in the Mekong River Delta: impact on productivity and on farmers' income

Mahabub Hossain, 1 Duong Ngoc Thanh, 2 and F.B. Gascon 1

Abstract. Since the early 1980s, provincial and district governments in Vietnam have made substantial investments in development and reconstruction of canals and embankments for flood control, drainage, and irrigation in the Mekong River Delta. The investment has converted the rice ecosystem from deepwater to irrigated lowlands, and the area under deepwater rice had declined from two-thirds to less than one-third of the rice area by the end of the 1980s. This paper evaluates the effect of the change on the productivity of agricultural resources and on farmers' income using data collected from farm households during the 1990/91 and 1992/93 crop years. Although the change has had a dramatic effect on rice production, the effect on agricultural production was less spectacular because high-value upland crops are substituted for rice. With a substantial increase in employment and use of modern agricultural inputs, the productivity of labor and capital declined. The change, however, has had a positive effect on both farm and nonfarm incomes.

The Vietnamese rice economy has made remarkable progress since 1980. Over the last 13 yr, the population of Vietnam increased by 35%, but rice production grew by 82% and rice yield by 58%. As a result, Vietnam has emerged as the third major exporter of rice in the world market, after Thailand and the United States. In 1989-92, Vietnam exported on average about 1.5 million t/yr of milled rice, which accounted for 11% of the world trade in rice. Two-thirds of the increase in rice production has come from the Mekong River Delta (MRD), which occupies 44% of Vietnam's rice land but accommodates only 24% of the population. The progress was made possible partly through massive investments in the development and maintenance of canals and embankments for flood control, drainage, and irrigation by the provincial and district governments as well as by farmers. The government covered the cost of construction of the main and secondary canals, but the cost of constructing tertiary canals and dikes and bunds surrounding the fields and the investment in irrigation pumps was borne by the farmers (Duong 1992). The farmers also bear the cost of operating and maintaining irrigation fields every year. The investment in water- resource development in the MRD has allowed farmers to change the traditional cropping pattern from deepwater rice (DWR) followed by one or two upland crops (such as sesame, maize, mungbean, watermelon, and various vegetables) to two irrigated lowland rice crops (ILR). In the deepwater ecosystem, farmers grow local varieties of rice from May to December, and sesame or watermelon as the first upland crop during the dry season of January-March. Some farmers grow maize or mungbean, cucumber, and watermelon as the second upland crop in April-June by broadcasting deepwater rice seeds as a relay crop in late May or early June (Duong and Xuan 1991).

1 International Rice Research Institute, P.O. Box 933, 1099 Manila, Philippines; 2 Farming Systems Research and Development Center, University of Cantho, Cantho, Vietnam Investment in canals, embankments, and pumps allows the deepwater ecosystem to be converted to the irrigated lowland ecosystem, and this permits farmers to grow two modern rice varieties, the first from mid-April to early August (autumn rice) and the second from mid-December to early April (spring rice). The land is fallowed in September–November, when the depth of flooding does not allow the dwarf modern varieties to be grown. In 1982, DWR occupied nearly 66% of the rice area in the MRD but, by 1989, the share had dropped to 38% (Duong 1992). The share of spring rice increased from 16% to 28% and that of autumn rice from 17% to 35% during this period. The conversion of the deepwater ecosystem to irrigated lowlands has been instrumental in the spectacular growth in rice production in recent years. However, it has been achieved at the expense of the production of upland nonrice crops, because rice monoculture is increasingly practiced. This change has raised the question of whether farmers’ income and levels of living have improved, because modern rice varieties require large investments in imported fertilizers and pesticides and the operation and maintenance of canals and pumps need additional investment. The sustainability of the irrigated ecosystem is also questioned, because negative effects of intensive rice farming on the quality of natural resources, and the effect of withdrawal of water for irrigation in the dry season on growing salinization in coastal areas are suspected. The main objective of this study was to obtain a comparative picture of the economics of agricultural production in the deepwater and converted irrigated ecosystems. The study attempts to estimate the effect of the investment in water-resource development on the productivity and efficiency in resource use, and on farmers’ incomes.

Data and methods

Sources of data The study is based on primary data collected from randomly selected farm households by administering structured questionnaires in the 1990/91 and 1992/93 crop seasons. Three sets of questionnaires were used for the survey — the first to obtain village-level data on farming practices and input-output prices, the second was applied to farm households to collect farm-level input-output information on crops grown in DWR and ILR ecosystems, and the third was administered to all rural households (including the landless) to record economic activities and income from off-farm and nonfarm activities. The survey was conducted by the Farming Systems Research and Development Center of the University of Cantho in collaboration with the Social Sciences Division of IRRI. The sample households were drawn from Chau Phu District of An Giang Province and the Lai Vung and Cao Lanh districts of Dong Thap Province. Chau Phu is a typical DWR area in the upper part of the MRD; the district town is about 25 km from the Cambodian border. The flooding pattern is influenced by impounded rainwater (poor drainage) and overflows of the Mekong River systems. Water levels begin to increase in August, peak in early October, and recede in December. For this survey, eight villages were selected from Chau Phu District, and one village each from Lai Vung and Cao Lanh districts, which were located on the same canal system that serves mainly the Chau Phu District. From each village, 10–30 households were selected at random depending on the size of the village. The total sample size consisted of 252 households of which 45 were landless. The sample villages were widely dispersed and could be reached only by boat. The surveys were conducted separately for the wet and dry seasons of the 1990/91 crop year to reduce errors in input-outputdata because of faulty memories. The same households were resurveyed during the 1992/93 crop year. In the later survey, some households were dropped because they were not available, or because of inaccuracy of information suspected during the processing of the data from the first survey.

264 Hossain et al The sample households were divided into two groups for the analysis — those following the traditional DWR plus upland cropping system and those who changed to the irrigated autumn rice followed by irrigated spring rice cropping system — and then various indicators of their production performance were compared at the system level. Households that followed both the DWR and the ILR cropping systems were excluded.

Measures of farm economy The main indicators of production performance used for the comparison in this study were value added, farm-family income, farm-operating surplus, unit cost of production, and employment and labor productivity. Value added. Value added is the gross value of production of all crops grown during the year minus the cost of current inputs (raw materials or intermediate consumption) used in the production process, that is, seeds, fertilizers, pesticides, and fuel for running irrigation pumps. This is a component of national income as it is contributed to by the primary factors of production — land, labor, and capital. Farm-family income. Farm-family income was calculated as the gross value of production minus the paid-out costs, which include the cost of current inputs, rental costs of draft animals and farm machinery, wage payments to hired labor, and the land tax paid to the government. Farm-operating surplus. Farm-operating surplus is the gross value of production minus the total cost of production: a measure of profits from farm operation. The total cost includes imputed value of family labor used in crop-production activities, the imputed rent of capital supplied by the household, and the imputed interest charges on working capital. Market wage rates and charges for hiring draft animals and farm machinery were used as the opportunity costs of family-supplied labor and capital. The paid-out cost was taken as a measure of the working capital, and a 6% rate of interest per month, which was found a common practice in the informal credit markets, was used to calculate the interest charges. Unit cost of production. Unit cost of production is estimated as the total cost per tonne of output. It is a measure of the efficiency of resource use. In market economies, the total cost should include the opportunity cost of land, which is a real cost to a tenant farmer who has to pay the stipulated rent to the landowner. In many South and Southeast Asian countries, the land rent varies from one-third to one-half of the gross produce in the share-cropping market. In Vietnam, however, the farmer has only the rights to use the land. The market for rent or for outright sales of landed property is virtually nonexistent. Thus, the cost of land to the farmer is the tax paid to the government: a meagre 7% of the gross produce for DWR land and 3.7% for ILR land. The nonexistence of the land market makes the unit cost of rice production very low in Vietnam. Employment and labor productivity. In labor-surplus economies, the scope of employment of family labor can be taken as an important indicator of economic progress. Because surplus labor will be wasted, and the peasant household has the obligation of maintaining the family worker, the household will take up an economic activity that generates more employment even when the marginal productivity of labor is lower than the market wage rate.

Method for estimating economic efficiency In the economic literature, a profit-function model derived by the application of duality relations between the cost and the production function is used to measure and compare economic efficiency and price efficiency for groups of farms (Lau and Yotopoulos 1971, 1972). Although the model has been severely criticized (Quiggin and Anh 1984, Chand and Kaul 1986) its use for empirical studies remains popular. We used the model for the present analysis because it helps us compare relative economic efficiency between users of the deepwater and the irrigated cropping systems.

Change from deepwater to irrigated rice 265 In the model, the farm is assumed to have fixed coefficients of land (A), family worker (N), and capital (K), which cannot be varied in the short run, but it can choose variable inputs of hired labor (L), and fertilizer (F), whose prices are W and Pf respectively. The amount of variable inputs that the farm decides to use is determined by setting the marginal cost of the input i, to 1/ P i times the marginal value product, where P is considered the opportunity cost of the input supplied by the farm family. The farm is called price efficient if P i = 1. One farm may be more technically efficient than another if it produces a larger quantity of output from the same quantities of measurable inputs. Technical efficiency may differ between two groups of farms by a multiplicative factor d. The difference in economic efficiency among groups of farms may be caused by differences in technical or price efficiency or both. Under the assumption of the Cobb-Douglas production function, the model yields a unit output price profit function:

[1] and the input demand functions:

[2] and

[3]

where p is the unit output price profit (gross revenue minus total cost of current inputs), W and P f are, respectively, labor and fertilizer prices normalized by the output price, and S is a dummy variable taking value 1 for farms that have changed to the irrigated system and 0 for farms still practicing deepwater cropping. The hypothesis of equal relative technical efficiency implies that d = 0. The hypothesis of equal relative price efficiency implies that a 11 = a 12 and a 21 = a 22 . The hypothesis of absolute price efficiency implies that, for farms adopting the irrigated system, a 11 = a 1 and a 21 = a 2 and, for nonadopter farms, a 12 = a 1 and a 22 = a 2 . The error terms are assumed to be additive with zero expectation and finite variance for each of the three equations. However, the covariances of error of either equation corresponding to different farms are assumed to be identically zero. Under this specification of errors, Zellner’s seemingly unrelated regression equation (SURE) provides an asymptotically efficient method of estimation (Zellner 1962). The model was estimated with the household-level data on the specified variables. To make the price variables exogenous to the household, the village-level price was applied to all sample households belonging to the village.

Results and discussion

Characteristics of the sample Farm characteristics. The average farm was larger in the deepwater ecosystem (2.00 ha) than in the irrigated ecosystem (1.14 ha). The farm size declined by 5% and 14%, respectively, in the two ecosystems over 1991-93. Apparently, because of higher productivity, the population pressure on land has been growing faster in the irrigated ecosystem. Owner operators comprised 96% of the farm households. The average household consisted of seven members, four of them participating in economic activities. The average age of the head of the household, who had an average of about 4 yr

266 Hossain et al of schooling, was 52 yr. The demographic characteristics of the farm households are the same in the deepwater and the irrigated ecosystem. Adoption of technology. In the deepwater ecosystem, all farmers used traditional rice cultivars, whereas those in the irrigated ecosystem all use modern cultivars. All households used direct seeding for crop establishment and mechanical threshers irrespective of the ecosystem. The major difference in the two ecosystems was found in the use of agrochemicals — in the irrigated ecosystem, all households used chemical fertilizers, whereas in the deepwater ecosystem, only 45% of the farmers used them. In 1993, the consumption of NPK fertilizer was 195 and 219 kg/ha in the autumn and spring rice crops, respectively, compared with only 27 kg/ha in the cultivation of deepwater rice. The use of fertilizers increased over 1991-93 in both irrigated and deepwater areas. In the irrigated ecosystem, 80% of the area under spring rice was treated with herbicides, and almost all the land was treated with insecticides. In DWR, herbicides were used by 22% of households and insecticides by 38%. In 1993, the average expenditure on pesticides was US$36/ha in spring rice compared with US$23 in autumn rice and only US$3.30 in the DWR. Cropping pattern. In early 1990/91, in the deepwater ecosystem, 30% of the land was cropped with traditional rice followed by sesame, and another 24% with traditional rice followed by sesame followed by another upland crop such as maize, melon, mungbean, cowpea, squash, cucumber, eggplant, or chili. In the irrigated ecosystem, 95% of the area was double cropped with two modern varieties of rice. The cropping intensity with rice was 97% in the deepwater ecosystem and 195% in the irrigated ecosystem. The conversion to the irrigated ecosystem has, thus, led to a shift from diversified crop farming to a monoculture of rice cultivation. The total cropping intensity increased from 178% to 195% in the deepwater ecosystem, and from 192% to 198% in the irrigated ecosystem in 1991-93.

Effect on farm economy The input-output relationships and the costs and profitability of rice cultivation in the two ecosystems are reported in Table 1 and the information on the upland crops in Table 2. Table 3 presents the same information at the system level, taking into account all crops grown during the year, Agricultural production. As expected, the conversion of the ecosystem has a spectacular effect on rice production. Total rice production was 10.8 t/ha per year in the irrigated ecosystem, compared with 2.4 t/ha per year in the deepwater ecosystem, a difference of about four times (Table 1). The difference in the gross value of production is, however, less dramatic because the DWR is of better quality and fetches a higher price in the market. In 1993, for example, US$1 would buy 12 kg of irrigated modern rice but only 9.5 kg of the deepwater traditional variety - the price difference was about 25%. The increase in rice production was achieved at the expense of the upland crops grown after harvesting the DWR. The gross value of production of the upland crop was estimated from the 1993 survey at US$367/ha (Table 2), equivalent to 4.43 t of irrigated rice at 1993 prices. When the loss of output of the foregone upland crops is taken into account, the increase in the value of agricultural production for the year as a whole is estimated at US$297/ha, a 49% increase over the value of the produce in the deepwater ecosystem (Table 3). Intermediate consumption. The conversion of the system has greatly increased the use of intermediate inputs (raw materials) in crop production. As mentioned earlier, farmers use chemical fertilizer and pesticides much more in irrigated modern rices than in traditional DWR. Farmers in the irrigated ecosystem also have to bear the cost of fuel and electricity for running the irrigation pumps. At the system level, the cost of intermediate inputs that are consumed in the production process is estimated at US$265/ha in the irrigated ecosystem, compared with US$l63 in the deepwater ecosystem, that is an increase of 63%. Value added in crop production. The net addition of value in rice production in a year is estimated at US$615/ha in the irrigated ecosystem compared with only US$215 for the deepwater

Change from deepwater to irrigated rice 267 Table 1. Costs and returns (per ha) in rice farming in Mekong River Delta, 1992/93.

Item Unit Deepwater Irrigated rice rice Autumn Spring harvest harvest

Yield t 2.4 4.9 5.9 Labor d 48 84 98 Fertilizer NPK kg 27 195 219

Paid-out costs Total US$ 103.4 240.5 249.1 Current inputs US$ 27.6 124.2 145.6 Capital rental charge US$ 23.9 57.4 48.4 Wage bill US$ 34.2 40.8 37.0 Land tax US$ 17.7 18.1 18.1

Imputed costs Total US$ 85.1 123.2 134.2 Family labor US$ 22.8 53.1 61.4 Family capital US$ 0.9 7.0 7.4 Interest charges US$ 61.4 63.1 65.4

Total cost US$ 188.5 363.7 383.3 Gross returns US$ 242.5 406.0 488.9

Evaluation of benefits Value added US$ 214.9 281.8 343.3 Family income US$ 139.1 165.5 239.8 Operating surplus US$ 54.0 42.3 105.6 Unit cost of production US$/t 79 74 65 Labor productivity US$/d 2.3 1.62 1.70 ecosystem, a spectacular increase of US$400/ha. However, the farmers in the irrigated ecosystem forego the value added of US$205 from the upland crops grown in the deepwater ecosystem. At the system level, the value added in the crop-production activities is estimated at US$615 in the irrigated ecosystem compared with US$420 in the deepwater ecosystem (Table 3). The net gain of agricultural incomes from the conversion of the system is thus estimated at US$195, a paddy equivalent of 2.35 t/ha. How does the gain compare with the cost of investment for the development and maintenance of the canal and embankment systems for flood control, drainage, and irrigation? A recent study of canal systems in Chau Phu, Cao Lanh, and Lai Vung estimated the investment cost per hectare of land as the equivalent of 2.5 t of paddy and the yearly operation and maintenance cost at 343 kg of paddy/ha (Duong 1992). If we assume that the canals and embankments need reconstruction every 10 yr, the cost of the conversion of the deepwater to the irrigated system is estimated at 593 kg of paddy/yr. Because the value added from the conversion of the system is estimated at 2.35 t of paddy/ha, the investment seems to be highly profitable to society. Cost of production of rice. Two measures of the cost of production have been estimated, the “paid-out cost” and the “total cost.” The “paid-out cost” includes the costs of seed, fertilizer, pesticides, irrigation, hired labor, and rental services for machines and draft power, whereas the “total cost” also includes the imputed value of family labor, capital, and foregone interest income on the use of working capital in crop farming. In making production decisions, small-scale farm households who have surplus

268 Hossain et al Table 2. Costs and returns (per ha) of upland crops in the deepwater rice ecosystem, 1991 and 1993.

Item Unit 1991 1993

Paid-out costs Total US$ 162.3 168.6 Current inputs US$ 135.5 135.2 Capital rental US$ 2.3 6.2 Wage bill US$ 24.5 27.2

Imputed costs Total US$ 110.6 112.9 Family labor US$ 49.0 46.3 Family capital US$ 19.0 22.3 Interest charges US$ 42.6 44.3

Total cost US$ 272.9 281.6 Gross value of production US$ 313.6 367.2 Value added US$ 178.1 232.0 Family income US$ 151.3 198.6 Operating surplus US$ 40.7 85.6 Employment d 54 62 Labor productivity US$/d 2.57 2.57

family labor and low opportunity cost of employing it elsewhere may give more weight to the paid-out costs than to total cost that is a more relevant variable for the large-scale farmers who have high opportunity costs for family labor and capital. The paid-out cost per unit of land also shows the working capital requirement, and the small-scale farmer may be in a more disadvantageous position to supply it than the large-scale farmer who has more savings and better access to credit from formal or informal sources. The paid-out cost was 1.3 times higher for autumn rice cultivation and 1.4 times higher for spring rice compared with that for the cultivation of DWR. The total cost was 93% and 103% higher than in DWR, respectively, for the autumn and spring rice (Table 1). At the system level, the paid out cost was 78% higher and total cost 57% higher for the irrigated ecosystem compared with those for the deepwater ecosystem (Table 3). The conversion of the ecosystem has thus greatly increased the scope of using both modern and traditional inputs in crop farming. Unit cost of rice cultivation. Although the cost of production per unit of land is higher in the irrigated ecosystem, the farmer is also getting a larger output. A measure of efficiency in rice cultivation is the cost of production per unit of output. The cost of producing 1 t of output was US$79 in the cultivation of DWR (Table 2), whereas it was US$74 for autumn rice, and US$65 for spring rice. Thus, as a result of the conversion of the system, farmers are getting a larger amount of paddy from the scarce factor of production, land, at a somewhat lower cost. Operating surplus. The measure of profits from the farm business operation is given by the “operating surplus” (gross value of production minus total cost). The operating surplus in the cultivation of two irrigated rice crops is estimated at US$148/ha, which is about 20% of the total cost and 30% of the paid-out cost. For DWR, the operating surplus is 44% of the paid-out cost. At the system level, the operating surplus is estimated at US$148/ha for the irrigated ecosystem compared with US$117 for the deepwater ecosystem — higher by about 26%. As a ratio of total cost, the operating surplus is 20% for the irrigated system compared with 25% for the deepwater ecosystem. Thus the conversion of the system has led to a decline in the rate of return on capital. However,

Change from deepwater to irrigated rice 269 Table 3. Comparative economics (per ha) of deepwater (DWR) and irrigated (ILR) rice-based cropping systems, average for 1990/91 and 1992/93 crop years at 1993 prices.

Item Unit Ecosystem Difference (ILR over Deepwater Irrigated DWR)

Paddy yield t 2.4 10.8 8.4 Gross value of crop production US$ 583 880 297 Current inputs US$ 163 265 102 Paid-out cost US$ 269 480 211 Imputed cost US$ 197 252 55 Total cost US$ 466 732 266 Value added US$ 420 61 5 195 Family income US$ 314 400 86 Operating surplus US$ 117 148 31 Employment d 106 180 74 Labor productivity US$/d 2.40 1.66 -0.78 Productivity of capital % 25.1 20.2 -4.9

because the investment in crop farming has increased greatly as a result of the change, the absolute profit per unit of land has increased in spite of the decline in the rate of return on capital. Household incomes from crop farming. Because land is the most scarce factor of production, the farmer is interested in maximizing the net return per unit of land. A peasant farmer may be interested in maximizing the net return to the labor and capital owned by the household, because these are sunk costs and the household has to maintain the family workers and farm establishments irrespective of whether they are used or not. The returns to family inputs (gross value of production minus paid-out cost) is estimated at US$400/ha of land in the irrigated ecosystem compared with US$314 for the deepwater ecosystem (Table 3). The household income from rice farming has thus increased by about 27% as a result of the conversion of the system. Employment and labor productivity. The main factor behind the increase in household income is the greater scope for the employment of family labor. In the deepwater ecosystem, 1 ha of land employed about 48 d of labor in rice cultivation, and another 54 d in upland crops. In the irrigated ecosystem, total employment in raising two irrigated rice crops is about 180 d/ha. Thus, there is a net gain of employment of about 74 d/ha per year. The imputed earnings from the use of family labor is estimated at US$115/ha for the irrigated ecosystem, compared with US$71 for the deepwater ecosystem — an increase of 62%. The average productivity of labor is higher than the market wage rate (about US$1.00/d) in both ecosystems. Thus, the farmers gain as the scope of employment of labor increases; however, the labor productivity declines with the increased use of labor. The net productivity of labor (the value of production minus the cost of nonlabor inputs divided by labor) is estimated at US$1.66/d for the irrigated ecosystem, compared with US$2.40 for the deepwater ecosystem.

Technical efficiency in input use The work on estimating the relative economic efficiency in the use of resources is still in progress. We report here some preliminary results obtained from the data collected during the 1990/91 crop year. Maintaining the hypothesis that the farmers are both absolutely and relatively price efficient in the use of hired labor and fertilizers and that constant returns to scale prevail, the following estimate of the profit function is obtained from the 1990/91 survey data:

270 Hossain et al ln p = 6.012 + 0.161 S - 0.493W - 1.027P f + 0.983A + 0.002K + 0.014L [4] (28.0) (2.41) (-2.863) (-0.103) (22.2) (0.83) (0.33) R 2 = 0.53 The variables are as defined previously and the values in parentheses are the estimated t values of the regression coefficients. The coefficients for the family-owned capital ( K ) and labor ( L ) are not statistically significant. It seems that farmers have surplus capacity in family workers and farm establishments so that their marginal contributions to profits are insignificant. Land is the only fixed factor of production that contributes to the increase in profits. The output elasticities of inputs (percent change in output due to 1% change in input) are estimated from the parameters of the profit function at 0.39 for land, 0.41 for fertilizer, and 0.20 for labor. The variable S is 1 for the irrigated ecosystem and 0 for the deepwater ecosystem. The value of the coefficient is the measure of technical efficiency in the use of inputs. The coefficient is positive and statistically significant. The estimate indicates that the technical efficiency in the use of inputs is about 16% higher in the irrigated ecosystem than in the deepwater ecosystem. Household incomes and its composition The estimates of total household income for all rural households (including the landless) and the composition of the income obtained from the survey are reported in Table 4. It can be seen that the per-capita annual income is very low in rural Vietnam, US$81 in the deepwater ecosystem and US$100 in the irrigated ecosystem. Income from rice farming accounted for only about 30% of the total household income in the deepwater ecosystem. Other major sources of income were cultivation of upland crops (32%), fisheries and livestock production (17%), hiring out of labor and capital services (8%), and various nonfarm activities such as trade, transport, and various service activities (13%). As expected, the conversion of the ecosystem has contributed to a substantial increase in incomes from rice farming, but at the expense of income from nonland crops and from fisheries and livestock. The share of rice farming in total household income was about 65% for the irrigated ecosystem.

Table 4. The structure of household incomes (average per sample household) in deepwater and irrigated ecosystems in Mekong River Delta, 1990/91 and 1992/93.

Source of income Deepwater ecosystem Irrigated ecosystem

1990/91 1992/93 1990/91 1992/93

On-farm Total 409 452 521 504 Cultivation of rice 181 145 459 445 Cultivation of other crops 151 199 3 5 Fisheries and livestock 77 108 59 54

Off-farm Total 42 39 64 70 Hiring-out of labor services 36 29 52 56 Hiring-out of capital services 6 10 12 14 Nonfarm activities 68 74 121 118 Total household income 519 565 706 692 Household size 7 7 7 7 Per-capita income 74 81 101 99

Change from deepwater to Irrigated rice 271 It is important to note that the incomes from off-farm and nonfarm sources are also substantially higher for the irrigated ecosystem compared with the deepwater ecosystem. As noted earlier, the intensification of rice farming has increased the demand for labor and has expanded the labor market and income-earning opportunities for those hiring-out labor services. The specialization in rice production and the growth in rice yield have had a substantial effect on marketed surplus for rice. The trading of surplus rice for other household necessities and modern agricultural inputs have generated additional economic activities in the rural trade and transport sectors. These are some of the factors behind the higher levels of income from nonfarm activities in the irrigated ecosystem compared with the deepwater ecosystem. In 1992-93, the income from off-farm and nonfarm sources was US$188/household, about 66% higher than the earnings from these sources in the deepwater ecosystem. The difference in income from farming activities between the two ecosystems was only 12%. Because the low-income households are involved more in off-farm and nonfarm activities than in farming, these findings suggest that the conversion from the deepwater to the irrigated ecosystem may have had a positive effect on socioeconomic equity and alleviation of poverty.

Summary and conclusions

The change from the deepwater to the irrigated rice ecosystem has had a dramatic effect on rice production, because farmers are getting nearly 10 t of paddy/yr from the two irrigated rice crops compared with 2.0-2.5 t they used to get from DWR. However, the gross value of agricultural production was only 50% higher, because of the higher quality of the deepwater rice that fetches nearly 25% more in the market, and the farmers foregone production of some high-value upland crops that are grown after harvesting rice in the deepwater ecosystem. The change has led to a decline in the productivity of labor and capital. However, the absolute profits and farm-family income were higher in the irrigated ecosystem by 26% and 27%, respectively, than in the deepwater ecosystem. The positive income effect was a result of two factors: The change in the cropping system allowed farmers to use more capital and labor per unit of land and Despite the diminishing returns, the average productivity was still higher than the opportunity cost of these inputs, so that farmers gain with additional use of inputs. For example, the market wage rate was US$1.00/d, whereas the net productivity of labor was US$1.66/d. Thus, with each additional day of employment, the farmer had a net gain of US$0.66. In the irrigated ecosystem, the employment per hectare of land was 74 d/yr higher than in the deepwater ecosystem. The change also has a positive effect on the rural nonfarm sector. The larger amount of marketed surplus from rice, and the expansion of the market for nonfarm goods and services generated additional employment and incomes in the rural trade, transport, and services sectors. Because these incomes accrue more to the lower-income households, the change in the ecosystem has had a positive effect on socioeconomic equity and the alleviation of poverty. The investment in water-resource development needed to convert the ecosystem seems to have been beneficial to society. The amortized investment and the operation and maintenance cost of the canal and irrigation system is estimated at 0.59 t of paddy/ha of land. The increase in crop value added as a result of the conversion of the system is estimated at 2.35 t of paddy/ha, about four times the cost of investment. This calculation, however, assumes that labor has no opportunity cost, and that the additional employment generated by the change has been a net gain to society. Even if we assume that

272 Hossain et al the additional labor in the intensified rice-farming activities was obtained through diversion from some other economic activities, the net gain to society in paddy equivalent is estimated at 1.46 t/ha, about 2.5 times the investment cost. The investment in the canal systems thus had very high rates of return.

References cited

Chand R, Kaul J L (1986) A note on the use of the Cobb-Douglas profit function. Am. J. Agric. Econ. 68(1):162-264. Duong L T (1992) Conversion from deepwater rice to irrigated lowland rice cultivation in Vietnam. University of Cantho, Cantho, Vietnam. Mimeo. Duong L T, Xuan V-T (1991) Rice based farming system in the Mekong Delta of Vietnam. University of Cantho, Cantho, Vietnam. Mimeo. Lau L J , Yotopoulos P A (1971) A test of relative economic efficiency and an application to Indian agriculture. Am. Econ. Rev. 61(1):94–109. Lau L J, Yotopoulos P A (1972) Profit supply and factor demand functions. Am. J. Agric. Econ. 45(1):11-18. Quiggin J, Anh B-L (1984) The use of cross-sectional estimates of profit function for tests of relative efficiency: a critical review. Australian J. Agric. Econ. 28(1):44-55. Zellner A (1962) An efficient method of estimating seemingly unrelated regressions and tests of aggregated bias. J. Am. Stat. Assoc. 57:348-368.

Change from deepwater to irrigated rice 273

Supply responses of rice and three food crops in Vietnam

Nguyen Tri Khiem 1 and P.L. Pingali 2

Abstract. Recent economic reforms in Vietnam agriculture consisted of a shift from collective agricultural production systems to an individual-oriented contract system (1981-88) and from 1989 onward to complete liberalization of input and output markets. This paper assesses the impact of market reforms on farmers’ crop choice, land and input allocation decisions, and food-crop productivity using cross-section time-series data from seven regions and 17 yr from 1976 to 1992. A system of equations of the supply-response model with the choice-of-technique framework were estimated. Two dummy variables for policy regimes were included in the system. Estimated elasticity of rice area-share with respect to rice revenue per hectare is negligible. Rice-yield elasticity with respect to its price ranged from 0.02 in the northern regions to 0.09 in the southern regions. The impact of reforms was more remarkable on crop yield and input demand and farmers’ private investment. A slight increase in total planted area and cropping intensity accompanied by a decline in rice area in the northern regions indicates that crop diversification is taking place. This diversification is induced by market price and by autonomous investment decisions of farmers that are made possible by the liberalization policy.

Over the past decade, Vietnam has made a dramatic transition from a collective socialist economy to a market-oriented economy. Although the economy is still in transition, one can clearly observe the positive productivity trends that are attributable to market reforms. Rice yield per hectare and total rice production, which were stagnant during 1976–80, grew at the rate of 3.23% and 3.14% per year, respectively, in 1981–87, and 2.05% and 5.02% per year, respectively, in 1988–92. Annual per-capita rice output in 1992 was 40 kg higher than it was in 1981. Vietnamese farmers have faced three distinct policy regimes since 1976: collective production, 1976-80; contract system of production, 1981–88; and the transition to a market economy, 1989 onward. Detailed discussions on these can be found in Tiem (1991), Cuc (1991), Pingali and Xuan (1992), and Khiem and Pingali (1994). Although Vietnamese economists and policymakers, studying the impact of the reforms, have concentrated on the aspects of the policy-making process and production trends (Cuc 1991, Tiem 1991, Lam et al 1992, Anh 1993), the “big story” is that farmers now have the freedom to respond to market signals. Pingali and Xuan (1992) quantified the impact on rice productivity of the transition from a collective to the contract system. Farmers’ response to the most recent set of reforms, which led to an almost complete liberalization of the food-production sector, has not been quantified. This paper assesses the impact of market reforms on farmers’ crop choice, land and input allocation decisions, and food-crop productivity. Using data from 7 regions over 17 yr from 1976 to

1University of Cantho, Cantho, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Table 1. Rice area, output and yield of the Mekong River Delta and the south, 1976-80.

1976 1977 1978 1979 1980

Rice harvest area (‘000 ha) All the south 2,909 3,034 3,010 3,011 3,236 Mekong River Delta 2,062 2,099 2,062 2,086 2,096 Rice output (‘000 t) All the south 6,346 5,887 5,014 6,431 7,207 Mekong River Delta 4,665 4,214 3,417 4,650 5,279 Rice yield (t/ha) All the south 1.98 1.94 1.66 2.13 2.23 Mekong River Delta 2.04 1.66 1.73 2.23 2.31

1. Average yields of rice, maize, sweet potato, and cassava, 1976-92

1992, we assess the supply response of improved market signals for rice and competing food crops, which include maize, sweet potato, and cassava, and provide empirical evidence to show that the process of decollectivization initiated in late 1980 and pursued through the early 1990s has had a significant effect on productivity.

Policy regimes and food production trends

Rice and other food-crop production patterns during 1976-92 reflected the effects of major government policy changes. Table 1 and Fig. 1 present the yield trend of rice, maize, cassava, and sweet potato from 1976 to 1992. Rice. Although the area of rice cultivation increased at a rate of 1%, total production stagnated at 11 million t from 1976 to 1980. Rice production in 1981-87 was marked by a sharp increase in yield and in output (3.23 and 3.14% per year, respectively, Table 2). Total rice production increased at 5% per year in 1988-92 of which an increase in area accounted for nearly 3% and in yield for 2%.

276 Khiem and Pingali Table 2. Food crops production performance, 1976-92.

Crop and period Growth (% per year)

Cultivated Yield per Total area ha production

Rice 1976-80 1.02 -0.55 ns 0.46 ns 1981-87 -0.09 ns 3.23 3.14 1988-92 2.96 2.05 5.02

Maize 1976-80 1.91 ns -0.04 ns 1.87 ns 1981-87 1.10 ns 4.45 5.55 1988-92 -2.65 -1.29 ns -3.94

Sweet potato 1976-80 13.78 5.96 ns 19.74 1981-87 -4.93 1.51 ns -3.42 ns 1988-92 4.13 2.89 7.03

Cassava 1976-80 15.11 -0.83 ns 14.28 1981-87 -3.70 2.94 -0.76 ns 1988-92 -2.64 0.44 ns -2.52

Source: Agricultural Statistics, General Statistic Office, Hanoi. Note: ns, growth rate is not significantly different from zero.

Expansion in rice area resulted mainly from conversion of single to double rice cropping in the Mekong River Delta (Fig. 2). Reclamation of marginal land in the Delta since 1975 has increased arable land by only l0%, but the area planted to short-duration, high-yielding rice varieties has increased more than three times. Rice area in the Mekong River Delta increased 583 thousand ha from 1987 to 1992 of which 183 thousand ha were from clearing new land and 400 thousand ha from a shift in cropping practice. Rice output of this region grew at 4.01 and 8.65% in 1981-87 and 1988-92, respectively. Maize. Maize area did not change significantly in 1976-86 although the pattern differed across regions. Maize yield increased significantly during 1981–87 through the introduction of hybrid varieties (Table 2). Growth pattern of maize was generally influenced by the intensification program of the Ministry of Agriculture. The Red River Delta (RRD) and the eastern Mekong River Delta (MRD) showed the largest increase in maize area in 1981-87 (5.4 and 3.3% per year, respectively) but both area and production declined during 1988-92 after a sharp increase in early 1988. Compared with 1987, maize production increased 45% in 1988 whereas the sown area expanded by 26%. Cassava and sweet potato. Cassava, a drought-tolerant crop, is grown mainly on degraded soils in the central and northern regions. The estimated area of cassava is about 300,000 ha. Most farmers do not apply any commercial inputs in cassava planting. There are about 300,000 ha of sweet potato in the country. The crop is grown mainly in the upland region of central coastal and northern provinces where most farmers do not use any commercial inputs except home-made manure. Sweet potato yield in these regons averaged 5-6 t/ha. In the MRD, farmers rotate sweet potato with rice using NPK fertilizers and good irrigation to obtain 12-16 t/ha. Sharp increases in the area of sweet potato and cassava in 1976-80 (Table 2) reflected a movement by farmers to these food crops, which were not generally covered by the government

Supply responses 277 2. Planted rice area, Mekong River Delta (MRD) and country total, 1976-93.

Table 3. Total irrigated areas (‘000 ha) of rice, industrial crops, and other annual crops, 1986-90.

Crop 1986 1987 1988 1989 1990

Rice 4,570 4,566 4,670 4,936 5,046 Industrial crops 178 174 176 169 176 Other annual crops 183 212 205 219 214 Total 4,931 4,952 5,021 5,324 5,436

Source: Irrigation Statistics: 5 Year Construction and Development, Statistic Publishing House, Hanoi, 1992. low-price procurement. Cassava area and production increased 15 and 14% per year, respectively, in 1976-80 but began to decline slightly afterward. Investment in irrigation. Collectivization in the south and cooperative consolidation in the north were closely linked with the government investment in irrigation and mechanization. Large-scale mass labor movement for water conservation was launched in every locality in the hope of achieving quick increases in food production. Total outlay in agriculture during 1976-80 accounted for 19-23% of total state investment; this was one of the highest levels during the 1976-92 period. Currently, Vietnam has an irrigation system to support 2 million ha of year-round agriculture and 400 thousand ha for one crop per year. Some 850 thousand ha are serviced by drainage schemes and 450 thousand ha are drained by electric pumping. Of the irrigated land, 20% is in the RRD and 40% in the MRD. On average, the irrigated area increased 122 thousand ha/yr in 1976-80, 62 thousand ha in 1981-85, and 70 thousand ha in 1986-90. Every year, a further 40 thousand ha were brought into cultivation through drainage projects. The increase in irrigated area was contributed principally by rice area (Table 3). Of the total of 6 million ha sown with rice in 1990, 5 million ha were irrigated: 2 million ha of spring rice, which is a dry-season crop, 1.1 million ha of autumn rice, and 1.9 million ha of the main wet-season rice crop. The drainage system has been particularly important in the RRD, which is more prone to excessive rain storms than the MRD. Although this system is well developed, 100-150 thousand ha

278 Khiem and Pingali are still subject to flooding during heavy rainfalls. The Red River irrigation system is a network of high dikes to hold back monsoon floods, pumping stations, and canals to drain excess waters in the wet season and provide irrigation in the dry season enabling two crops of rice to be grown in most of the Delta. Much of the irrigation and drainage system in the RRD is old and is suffering from degradation, which demands costly repairs, especially for the system of pumping stations. The existing system in the MRD operates mainly as an irrigation source, with transport of water to the fields being the responsibility of the farmer. The canals serve a dual purpose: as an irrigation-drainage system and for transport. After 1975, a plan was developed to build a series of large pumping stations similar to the pattern in the RRD; however, it soon became inappropriate. A system of canals and dikes to bring irrigation water and control flood water is being developed. Farmers in the MRD construct minor canals and dikes to control water in their fields. Fertilizer application. Figure 3 shows the very rapid growth in chemical fertilizer use during 1981-88. (Data were compiled from national statistics where quantities of different fertilizers was converted to urea equivalents.) About 400 thousand t of phosphate (P) fertilizers are produced each year and most nitrogen (N) and composite fertilizers are imported. Imported chemical fertilizers account for about 85% of fertilizer supply. About 70-75% of the quantity of chemical fertilizers imported and produced locally was applied to rice crops. Aggregate data on fertilizer use on crops other than rice were not available. Chemical fertilizer application in rice production increased at 11.5% per year from 1976 to 1992. The rate was much higher for 1981-90 where the expansion in the area sown to modern varieties in the MRD was most rapid. The rate of chemical fertilizer use on rice averaged 40 kg urea equivalent/ha in 1976-81; this country-wide average increased to 100 kg/ha in 1983-35 and 150 kg/ha in 1986-92. Farmers in the RRD apply 8-10 t of home-made manure per hectare of rice; in the central coast and northern highlands, the rate varies from 6 to 8 t/ha. Few farmers in the MRD use any manure. Fertilizer productivity in rice production shows a steadily declining trend. The average amount of paddy produced per kilogram of fertilizer declined from 50 kg in 1976-81 to 22 kg in 1991-92 (Fig. 4). The trend of fertilizer productivity in Indonesian rice production is shown for reference. Fertilizer productivity in the two countries shows a very similar declining trend.

Analytical procedures and data sources

The effects of market reforms and crop-specific policies on farmers’ crop choices and on land- and input-allocation decisions were estimated by a system of supply-response equations using the choice-of- technique framework developed by Mundlak (1988). The theoretical treatment of the choice-of- technique with sequential decision model and derivation of estimating equations are shown in Rosegrant and Kasryno (1992). Rosegrant and Kasryno (1992) and Kumar and Rosegrant (1993) used this framework to estimate endogenously and separately the effects of price and other policy variables on area allocation across crops, and yield and input demand by crop, in addition to the effects on output and total demand. Based on the formation of a multiperiod decision framework, three blocks of equations were developed (Rosegrant and Kasryno 1992): Equations that determine the quasi-fixed inputs that present investment in technology and in total area planted to crops; Equations that determine the allocation of total area to each of the four crops, conditioned on the level of quasi-fixed inputs; and A third block of equations that determine yield response and input demand, conditioned on the quasi-fixed inputs and the allocation of area across crops.

Supply responses 279 3. Fertilizer use in rice production, 1976-92.

4. Rice production per unit of fertilizer used, Vietnam and Indonesia, 1976-92.

This sequential decision framework can be used to capture the impact of the institutional change variables. Two dummy variables — D8188 and D8992 — are incorporated into the equation blocks representing the introduction of the contract system in late 1980 and market liberalization in 1988.

Quasi-fixed factor estimation Investment in quasi-fixed factors in a given sector is a function of the rates of return to that sector relative to other sectors. Expected prices of products and factors are traditionally treated as key variables eliciting responses in product supply and factor demand. In environments where technology is changing, expected net profits or revenues per hectare of land, instead of expected prices, guide land-allocation decisions (Evenson 1993). Revenues per hectare for each crop would be a better variable in a quasi-fixed inputs model. Conditioned by the availability of data, this study uses expected prices, which are defined as weighted averages of the prices in the previous 2 yr reflecting the lag in production-response decisions. Equations for determination of quasi-fixed inputs are:

280 Khiem and Pingali [1]

[2] where A is the total area planted to rice, maize, sweet potato, and cassava; AR is the total irrigated areas for all crops; PF and PI are the expected prices of the four food crops and expected price index of agricultural inputs, respectively; INV is state investment in irrigation; D8188 and D8992 are dummy variables as defined above; t is time trend; and e is the error term.

Area allocation estimation The second block of equations determines the allocation of total area to each of the four crops (rice, maize, sweet potato, and cassava) conditional on the level of quasi-fixed inputs estimated in the first block of equations. This subsystem of equations is derived from a multinominal logistic function specified as:

[3]

where w i is the share of the total area allocated to crop i, X is a vector of independent variables, B i is a set of parameters to be estimated, and u is the error term. Geometric transformation gives the linear version of the multinominal logit model:

[4]

where w i is individual crop share area; w* is the weighted geometric mean of the crop area-shares (ln w * = S wi ln w i ); P j is the expected price of jth crop, AR* and A* are the predicted values of irrigated area and total areas of four crops estimated from the equations of quasi-fixed inputs, and v i is the error term.

Yield-response and input-demand estimation The output-supply and factor-demand equations for empirical estimations are derived by assuming the underlying Generalized Leontief (GL) profit function, which is written as:

[5]

The corresponding output-supply and factor-demand system of the GL profit function is:

[6] where P i is crop and input prices, Z k is the crop-specific quasi-fixed inputs, and T is a policy dummy. The supply and demand equations derived from GL profit function are linear in the square roots of the ratio of prices. The symmetry constraint b ij = b ji ; i = j can be tested. Corresponding cross-price elasticities can be derived as:

Supply responses 281 [7] and elasticities for own-price as:

[8]

Data sources. The time-series cross-sectional data set covers seven regions and 17 yr (1976-92). Aggregate time-series data on crop production and area at provincial and regional levels were available in statistical yearbooks and various publications by the National Institute for Agricultural Planning and Projection (NIAPP), Ministry of Agriculture and Food Industry (MAFI). Data on irrigated areas for 1986-92 have been compiled and published by the Ministry of Irrigation and the General Statistic Office. Because the 1976-92 series for these variables was not continuous, estimation and interpolation had to be made based on available data on investment in irrigation and data from the provincial agricultural services and from the National Agricultural Sciences Institute. Data on prices at a regional level were compiled from the Central Commission on Prices and the recently established Institute for Market Prices Research in Hanoi. Until 1988, price data were rarely reported by government institutions. However, they were scattered in various publications and government office records. Data on prices were compiled from all available sources at the national and provincial levels. All prices were expressed in dong with prices before 1986 converted to new dong. Expected revenues per hectare for each crop were approximated by gross return per hectare, which was the product of expected price and average yield of the respective crop. Investment in irrigation is the moving average of the most recent 4 yr of total central and provincial investment in irrigation. Data on labor use in crop production are not available. Data on wages for agricultural labor were gathered from several unpublished sources. The average hired-labor wage in rice production was used as an approximation for agricultural labor wage in the analysis.

Empirical estimates and discussion

Quasi-fixed input estimates Total area of the four crops was estimated as an equation of expected food price index, total crop area at time t-1 (the previous year), two time dummies representing policy change, and six intercept dummies out of seven regions. Irrigated rice area was estimated as an equation of expected rice price index, moving average of most recent 4 yr of investment in irrigation, and the same set of dummy variables. Pooled parameter estimates of seven regions are presented in Table 4. Lack of reliable data prevented the inclusion of variables on value-added of other crops and nonagriculture, which might have an effect on response parameters of the quasi-fixed inputs. Total area of the four crops responded positively to the expected price of the four crops. The short-run elasticity of planted area of food crops response to own price is 0.03 and of irrigated rice area to own price is 0.17. The low values of elasticities are consistent with an a priori expectation that small-scale farmers, in terms of land holdings that are producing mostly to satisfy subsistence needs, will have a relatively small adjustment of planted area. However, the long-run response, as indicated by the significant and large value (0.58), is slow but more substantial. The two time dummies for policy change are statistically highly significant. The negative and significant estimate of dummy variable D8188 representing the implementation of the contract system in late 1980 shows the reduction of total area planted to the four food crops after this reform. This is

282 Khiem and Pingali Table 4. Parameter estimates for quasi-fixed input equations. Estimated using generalized least squares with correction for serial correlation and heteroscedasticity.

Total area ('000 ha)

Rice, maize, sweet Irrigated potato, rice and cassava

In (expected food price index) a 0.030 (2.13) b – In (expected rice price index) – 0.171 (3.65) In (total area,,) 0.578 (8.38) 0.171 (1.04) In (investment in irrigation) c – 0.278 (3.67) D8188 -0.032 (-2.86) 0.099 (4.13) D8992 -0.009 (-0.76) 0.288 (6.94) Region 2 dummy 0.038 (2.31) 0.524 (13.40) Region 3 dummy -0.056 (-3.64) 0.000 (0.01) Region 4 dummy -0.200 (-5.68) -0.182 (-2.18) Region 5 dummy -0.600 (-6.05) -1.856 (-7.88) Region 6 dummy -0.387 (-6.12) -0.761 (-5.05) Region 7 dummy 0.360 (6.05) 0.917 (6.41) Constant 2.936 (6.18) 3.198 (2.78) R 2 0.995 0.960

a Weighted average of expected price indexes of rice, maize, potato and cassava. b t -statistic in parentheses. c Moving average of the most recent 4 yr of total investment in irrigation by central and provincial governments deflated by food price index. consistent with the hypothesis that reforms effectively reduced the availability and increased the real price of labor and capital (Huang and David 1992). However, the estimate of the policy dummy D8992 is positive and significant. The complete liberalization of the input-output markets accompanied by the opening of the rice export sector in 1988 induced the increase in rice price and expansion of rice area, which is more apparent in the MRD. The short-run response of irrigated area to changes in expected rice price was highly significant. Rapid expansion of irrigated rice area in the MRD, which accounts for almost all the rice area expansion of the country in the periods 1981-88 and 1988-92, is reflected in the large positive and significant estimates of the two policy dummies D8188 and D8992. Irrigated areas for food crops other than rice was not available. However, because irrigated rice accounts for about 93% of the total irrigated area of all crops, irrigated rice area can be used to represent this quasi-fixed input variable in tho analysis.

Area allocation Results of the parameter estimation for the area-share equation are presented in Table 5. To ensure the homogeneity restriction in estimation, the revenue per hectare of rice, maize, and cassava were normalized by the revenue per hectare of sweet potato. The shares were the ratio of the crop area-share to the weighted geometric mean of the crop area-shares. The weights were the average crop area- shares. Using the average area-shares as the weights is convenient in deriving the area-share elasticities at the mean values. The two quasi-fixed variables were their predicted values obtained from the estimation of the first equation block. Table 5 presents the estimated coefficients for the northern and southern regions. All the estimated response coefficients of the expected crop revenues have the expected sign for the northern

Supply responses 283 Table 5. Parameter estimates a of area-share equations for rice, maize, sweet potato, and cassava. All variables are in logarithms.

Rice Maize Cassava

Northern regions

Normalized expected revenue per ha Rice/sweet potato 0.179 (1.58)c -0.175 (-1.54) 0.268 (1.30) Maize/sweet potato -0.217 (-1.58) 0.182 (1.32) -0.18 (-0.75) Cassava/sweet potato -0.036 (-0.92) 0.062 (1.56) -0.036 (-0.50) Total area -0.047 (-0.07) -0.788 (-1.12) 3.10 (2.42) Irrigated rice area -0.663 (-1.34) 0.714 (1.44) 0.770 (0.86) D8188 0.014 (0.18) -0.091 (-1.17) -0.166 (-1.78) D8992 -0.026 (-0.19) 0.015 (0.11) -0.719 (-2.97) R 2 0.97 0.96 0.67

Southern regions

Normalized expected revenue per ha Rice/sweet potato 0.027 (1.76) 0.444 (3.93) 0.011 (0.09) Maize/sweet potato 0.027 (1.65) 0.389 (3.22) -0.071 (-0.55) Cassava/sweet potato 0.024 (1.80) -0.135 (-1.35) 0.241 (2.29) Total crop area -0.233 (-3.49) -1.42 (-2.88) 0.430 (0.82) Irrigated rice area -0.225 (-5.75) 0.820 (2.84) 0.340 (1.11) D8188 0.032 (4.28) -0.153 (-1.36) -0.528 (-4.42) D8992 0.112 (7.37) -0.153 (-1.36) -0.526 (-4.42) R 2 0.98 0.98 0.99

a Estimated using iterated seemingly unrelated regression. b Ratio of the crop area-share to the weighted geometric mean of the crop area-shares. c t -statistic in parenthesis.

region but the coefficient for rice revenue is not statistically significant. This is expected because both the rice area-share and the absolute rice area of the three northern regions (Table 6) did not change much during 1976-92. There was a slight increase in total food-crop area in the Midland and Mountainous region (from 1,018 thousand ha in 1980-82 to 1,124 thousand ha in 1989-91) and of the RRD (from 1,167 to 1,206 thousand ha) but the rice share area did not change, or even declined slightly in the RRD, from 86.9% in 1980-82 to 86.5% in 1989-91. Given the present cropping practice and investment in irrigation, this reflects the fact that rice area has reached the frontier in the northern regions. The negative and significant value of the estimate of dummy D8992 in the rice-share equation implies that the liberalization policy reduced rice area-share and increased crop diversification. This can be explained further by nonsignificant estimates of total area and irrigated rice area in the share equation. The estimate of rice area-share equation for the southern regions exhibits a contrasting trend. Rice area-share shows a large positive response to the policy dummies as well as to total food crop area and irrigated area. High correlation between policy dummy D8992 and rice price in the period 1989-92 might explain the insignificant estimate of rice expected revenue in the rice share equation for the southern region. Rice area-share of the MRD region increased from 97.4% in 1980-82 to 98.4% in 1989-91. The increase in rice area in the MRD resulted from conversion of single-cropping to double-cropping rice mostly in the former deepwater rice area (Fig. 2). Maize area-share responded positively to crop revenue in the northern regions. The negative coefficients of maize area-share with respect to ratio of irrigated rice area and rice revenue implies that

284 Khiem and Pingali Table 6. Percentage area-share of crops in total food crops area, 1980-82 and 1989-91.

% of area Total area (‘000 ha) Cassava Maize Sweet potato Rice

North Midland and Mountainous Region 1980-82 9.4 15.9 5.9 68.8 1,018.5 1989-91 7.8 17.7 5.6 68.9 1,123.9

Red River Delta 1980-82 2.1 3.0 8.0 86.9 1,167.4 1989-91 1.4 6.6 5.5 86.5 1,205.7

North Central Coast 1980-82 8.3 4.9 14.7 72.0 988.2 1 989-91 4.9 5.4 13.9 75.8 889.9

South Central Coast 1980-82 13.0 5.3 10.3 71.4 653.3 1989-91 9.5 4.5 6.7 79.2 632.0

Central Highland 1980-82 12.0 16.8 7.2 64.0 249.2 1989-91 8.9 19.2 5.2 66.6 248.2

Eastern Mekong River Delta 1980-82 12.9 11.4 3.8 71.9 430.0 1989-91 7.3 12.3 2.0 78.5 391.0

Mekong River Delta 1980-82 0.9 0.5 1.3 97.4 2,334.4 1 989-91 0.5 0.5 0.7 98.4 2,653.2 rice and maize are competitive crops in this region. The increase in maize area-share is reflected in the significant estimate of the policy dummy D8992. In the southern region, although the maize area-share is negatively related to total area, it responded significantly to the irrigated rice area because maize is mostly rotated with irrigated rice in the MRD. Both sweet potato and cassava exhibit similar area-share trends as reflected in the significant and negative estimates of the two policy dummies. Areas of these food crops increased rapidly in 1976-80 when rice procurement was strictly enforced during the collectivization drive in the southern regions. Area-share of these two crops began to decline when the partial liberalization started in early 1981. The proportion of cassava in the MRD is negligble (less than 0.5%). Cassava area-share declined both in the northern and southern regions.

Yield and input demand Table 7 presents the equation estimates of yield response and fertilizer demand for rice in the northern and southern regions. Because the time series of labor use in food crops and fertilizer use in crops other than rice were unavailable, equations of hired labor demand for the four crops and equations of fertilizer demand for maize, sweet potato, and cassava in the system could not be included. In the case of rice, the endogenous variables are yield and fertilizer use per hectare; the exogenous variables are the expected price ratios, which are normalized relative to the expected output or input price of the

Supply responses 285 Table 7. Parameter estimates a for yield response and fertilizer demand for rice.

Yield (kg/ha) Fertilizer (kg/ha)

Northern regions 0.5 b – (Pf /P r ) -379.55 (-2.61) 0.5 – (P r /P f ) 124.39 (4.35) 0.5 – (Pw /Pr ) 185.28 (1.98) 0.5 (Pw /P f ) – 52.28 (2.31) lrrigated/total area 16.68 (1.77) 1.98 (2.11) D8188 352.99 (3.25) 61.89 (5.32) D8992 595.97 (4.26) 128.74 (10.11) R 2 0.84 0.82

Southern regions 0.5 – (Pf /P r) -548.2 (-0.81) 0.5 – (Pr /P f ) 68.02 (2.96) 0.5 79.71 (1.77) – (Pw /P r ) 0.5 – (Pw /P f ) 24.17 (2.95) Irrigated/total area 5.63 (0.75) 0.38 (1.19) D8188 569.60 (6.96) 56.19 (6.53) D8992 1,108.4 (6.52) 96.09 (6.14) R 2 0.87 0.78

Note: P f, fertilizer price; P r, expected paddy price; P w , wage rate a Estimated using iterated seemingly unrelated regression. b t-statistic in parentheses. endogenous variable in the equation. The only quasi-fixed inputs included in the equations are the ratio of irrigated rice area to total rice area and the total area of the specific crop. The rice yield equations have expected signs and significant estimates for the fertilizer/crop price variable. Estimated parameters for the wage/crop price variable all have a sign that is the reverse of what was expected. Mobility of rural labor force and job opportunity induced by the agricultural liberalization seem to be an explanation for this observation. Results from survey panel data in the RRD and the MRD support this hypothesis. Table 8 presents the person-day averages of total labor and hired labor use per hectare in rice production for eight crop seasons from 1989 to 1992. Number of person-days of hired labor per hectare increases steadily with time in the RRD, but there is no clear trend in hired labor use during the same period in the MRD. The normalized wage rate had an upward trend during the study period. For the southern regions, in which the MRD is dominant in terms of rice production, the effect of irrigation and current area expansion on yield were expected to be positive and statistically significant. However, this effect is partially compounded with the effect of the two policy dummies D8188 and D8992. Estimates of these two dummies for policy change have large positive and highly significant values in both northern and southern regions (Table 7). Response of fertilizer demand to the ratio of irrigated rice area is not statistically significant in either region. Large and significant estimates of the two policy dummies show the shift in level of fertilizer use as the effect of policy reforms. However, as discussed above, there was a marked increase in rice area planted to modern varieties in 1981-87 and 1988-92 in the MRD. This growth has induced a higher demand for chemical fertilizer for rice. Figure 3 shows a sharp increase in fertilizer use from the average level of 40 kg/ha in 1976-81 to 120 kg/ha in 1987-88 and 140 kg in 1992. Estimates of the yield-response equations for maize, sweet potato, and cassava are in Table 9. All estimates of yield response to own price are not significant although they all have expected signs

286 Khiem and Pingali Table 8. Labor utilization in rice production (person-day/ha).

Year Season Red River Delta a Mekong River Delta

Total Hired Total Hired

1989 Wet – – 85.2 25.3 Dry – – 84.5 27.1

1990 Wet 239.2 7.8 52.6 20.7 Dry 246.1 8.6 52.3 22.4

1991 Wet 268.5 13.4 66.7 18.6 Dry 250.7 13.8 54.8 18.1

1992 Wet 231.6 15.3 70.8 18.6 Dry 236.4 15.8 71.5 20.1

Note: Average computed from 135 farm households in the Red River Delta and 66 farm households in the Mekong River Delta surveyed in 4 consecutive yr. a Survey was not conducted in the Red River Delta in 1989.

Table 9. Parameter estimatesa for yield response for maize, sweet potato, and cassava.

Maize Sweet potato Cassava (kg/ha) (kg/ha) (kg/ha)

Northern regions 0.5 ( P f / P c ) -71.29 (-0.79) b 74.56 (0.27) -115.44 (-1.18) 0.5 ( P w /P c ) 113.18 (1.83) 281.27 (1.45) 83.97 (1.04) Crop area 3.92 (3.94) 33.61 (5.39) -8.39 (-1.56) D8188 138.32 (2.40) 41.05 (0.15) 706.12 (4.22) D8992 259.45 (3.28) 1,258.3 (3.32) 342.79 (1.44) R 2 0.83 0.71 0.90

Southern regions 0.5 ( P f / P c ) -151.62 (-2.11) -81.86 (-0.45) 71.06 (0.73) 0.5 ( P w/ P c ) 72.03 (1.89) -9.85 (-0.10) 52.73 (0.93) Crop area 9.47 (2.40) -25.05 (-2.19) -13.09 (-1.28) D8188 205.68 (3.29) -12.40 (-0.05) 800.17 (2.90) D8992 312.77 (3.49) -245.48 (-0.72) 928.63 (2.23) R 2 0.83 0.89 0.70

Note. P f , fertilizer price; P c , expected crop price; P w , wage rate. a Estimated using iterated seemingly unrelated regression. b t-statistic in parentheses.

except for sweet potato. It is interesting to note that the estimates of the dummies for policy change turn from negative values in the case of area-share equations to positive values in yield-response equations of these three food crops. Although relative area-share of all food crops other than rice declined with the introduction of the reforms, the liberalization of the decision-making process in production of individual farmers clearly induced higher private investment and yield. Most of the expansion in maize and sweet potato area came mainly from the area that is intercrapped with irrigated rice. Crop area has a negative and statistically significant effect on cassava yield. Cassava is planted in relatively less favorable areas in all regions, hence expansion of cassava

Supply responses 287 Table 10. Yield and input demand elasticities for rice, maize, potato, and cassava.

Rice Fertilizer Maize Cassava Sweet potato yield input yield yield yield Northern regions Crop price 0.021 0.421 0.017 -0.005 0.080 Fertilizer price -0.069 -0.828 -0.022 -0.017 -0.020 Wage 0.048 0.407 0.005 0.021 -0.060 % irrigated 0.312 1.535 – – – Crop area – – 0.274 -0.063 0.529

Southern regions Crop price 0.094 0.172 0.032 -0.021 0.013 Fertilizer price -0.123 -0.364 -0.036 0.009 -0.011 Wage 0.028 0.192 0.004 0.012 -0.002 % irrigated 0.743 1.783 – – – Crop area – – 0.221 -0.059 -0.099

area is observed to have negative impact on yield. The results are clearer in the elasticities (Table 10). All elasticities are evaluated at yield, input, technology, and price levels prevailing in 1989-90. These estimates depend on the prevailing levels of quasi-fixed inputs and do not account for the dynamic effects of prices on quasi-fixed inputs; therefore, they should be interpreted as short-run elasticities. Yields are more sensitive to fertilizer price than crop price both in the northern and southern regions. Rice yield responded positively to the percentage of irrigated area and values of the estimate are much higher in the case of the southern regions. Expansion in the area of rice in the MRD by shifting to higher cropping intensity with modern rice varieties explains this result. The only elasticity of rice yield that does not have the expected sign is the elasticity of yield with respect to labor price. Explanation for this counter-intuitive result is provided above. Maize yield is more sensitive to expansion of maize area than to own price and fertilizer price. Positive elasticity of maize yield with respect to maize area can be explained by the introduction, through the maize-intensification program, of hybrid maize varieties that have higher yield and are more responsive to fertilizer. Expansion of cassava in relatively unfavorable zones resulted in negative elasticity of cassava yield with respect to this quasi-fixed input. Cassava farm price used in the analysis is estimated from market price of dried sliced cassava. Dried cassava has an attractive price for the export market but, because of poor postharvest drying facilities, inaccessibility of the market, and unstable export market, a large proportion of the cassava is consumed fresh at the local market and for feed or household subsistence. Response of sweet potato yield exhibits similar behavior to that of cassava. Estimated yield elasticities of these two crops have relatively small absolute values.

Summary, conclusions, and policy implications

The equations for quasi-fixed inputs show a good fit and estimated parameters have the expected signs. Total area of the four food crops and irrigated rice area responded positively to the expected own prices. Growth of irrigated rice area responded positively to investment in irrigation.

288 Khiem and Pingali The introduction of institutional reforms reduced investment in total food-crop area except in the MRD where irrigated rice area was still expanding rapidly. Estimates of response parameters of crop area-share to the expected crop revenues have the expected signs and significance levels and conform to the expected results. Expected rice revenue had a nonsignificant effect on rice area-share. This was expected because rice area-share declines relatively in the northern regions where rice cropping intensity is already high and frontier land has been exploited. Elasticity of rice area-share with respect to its own expected revenue is almost negligible in northern and southern regions. Elasticities of sweet potato and cassava area-share with respect to own expected revenues are higher those of rice in both regions. The yield equations have the expected signs for the fertilizer/crop price variable except in the case of cassava, and the estimated parameters for rice and maize have high significance level. Estimated elasticities for rice yield with respect to crop own-price are low in both regions, ranging from 0.02 to 0.09. Yields are more sensitive to fertilizer price than crop price. The most remarkable impact of policy reforms is observed on crop yield and input demand. Liberalization of agricultural production induced farmers’ private investment and higher yield. Despite the limitations of data availability and reliability, the parameter estimations are generally good and comparable to other studies in the region. Rice farmers respond positively to own-price change. Except for the MRD, where the rice area still has potential for expansion through a shift in cropping intensity, planted rice area could not be expanded without heavy investment in irrigation and drainage. A slight increase in total planted area and cropping intensity accompanied by a decline in rice area in the three northern regions indicates that crop diversification is taking place. This diversification is induced by market price and by autonomous investment decisions of farmers that have been made possible by the liberalization policy.

References cited

Anh D (1993) Availability of adequate food supply — the case of Vietnam. Paper presented at the National Food Security Seminar, Hanoi, Vietnam. Cuc N S (1991) Vietnam agriculture, rural setting and peasants. 1976-1990 [in Vietnamese]. Statistic Publishing House, Hanoi, Vietnam. Evensoa R E (1993) An expected net profits approach to supply analysis incorporation technology: an application to northern India — Circulation note. Paper presented at the Second Planning Workshop on Projections and Policy Implications of Medium and Long Term Rice Supply and Demand, 13-15 Apr, International Rice Research Institute, Los Baños, Philippines. Huang J, David C C (1992) Chinese rice economy: issues and agenda for research, Paper presented at the Planning Workshop on Projections and Policy Implications of Medium and Long Term Rice Supply and Demand. 25-27 Mar, International Rice Research Institute, Los Baños, Philippines, Khiem N T, Pingali P L (1994) Vietnam: market reforms and food supply response. Paper presented at the Third Workshop on Projections and Policy Implications of Medium and Long Term Rice Supply and Demand, Bangkok, 24-26 Jan, Thailand Development Research Institute and Foundation, Bangkok, Thailand. Kumar P, Rosegrant M W (1993) Dynamic supply response of rice and other food crops in India. Paper presented at the Second Planning Workshop on Projections and Policy Implications of Medium and Long Term Rice Supply and Demand, 13-15 Apr, International Rice Research Institute, Los Baños, Philippines. Lam CV, et a1 (1992) Agricultural collectivization in Vietnam: history, problems, and prospects [in Vietnamese]. Truth Publishing House, Hanoi, Vietnam. Mundlak Y (1988) Endogenous technology and the measurement of productivity. In Agricultural productivity: measurement and explanation. S.M. Capalbo and J.M. Antle, eds. Resource for the Future, Washington, D.C., USA. Parks R W (1967) Efficient estimation of a system of regression equations when disturbances are both serially and contemporaneously correlated. J. Am. Stat. Assoc., 62:500-509, Pingali P L, Xuan V-T (1992) Vietnam: agricultural de-collectivization and rice productivity growth. Econ. Develop. Cultural Change 40:679-718.

Supply responses 289 Rosegrant M W, Kasryno F (1992) Supply response with endogenous technology: food crops in Indonesia. Paper presented at the Planning Workshop on Projections and Policy Implications of Medium and Long Term Rice Supply and Demand, 25–27 Mar, International Rice Research Institute, Los Baños, Philippines. Tiem P V (1991) Ten years of price reforms 1981–1991 [in Vietnamese]. Information Publishing House, Hanoi, Vietnam.

290 Khiem and Pingali Gender roles in rice farming systems in the Mekong River Delta: an exploratory study

Truong Thi Ngoc Chi, 1 Nguyen Thi Khoa, 1 Bui Thi Thanh Tam, 1 and T.R. Paris 2

Abstract. Interviews and focused surveys were conducted in two irrigated villages in Omon District, Cantho Province, to examine the roles of women in farm labor and management, their knowledge of farm-related matters, and their wishes for training. Women contributed about 45% of the labor input on the farms, even in tasks traditionally done by men. Decisions in rice production were generally made by the husbands; however, women generally made those related to buying and selling animals and their by-products and to the household. The labor requirements of intensive crop cultivation require that women acquire more knowledge and skills in farming, particularly in crop management. Thus, the following areas of research into the roles of women farmers should be investigated: pest management practices and gender roles; the implications of increasing labor demand on family welfare; seed manage- ment and postharvest storage of rice and upland crops; and credit for women farmers.

Farming is the main livelihood of the people of Omon District, Cantho Province, in southern Vietnam. Farmers generally practice intensive crop cultivation to maximize the use of their lands. Despite intensive cultivation, income from rice farming has remained low. Thus, the goal of the farming systems research and extension (FSR/E) team at the Cuu Long Delta Rice Research Institute (CLRRI) is to increase the income of rice-farming families by improving the existing cropping systems and by increasing the yields of component crops. These goals can only be achieved, however, by overcoming the physical and socioeconomic constraints that these families face. One socioeconomic constraint to increasing cropping intensity is lack of labor, particularly family labor, for crop cultivation. We hypothesized that increased crop intensity and diversification would increase the demand for physical labor, and require better management skills and new knowledge for the family members, particularly from female members. Thus, in 1993, the FSR/E Research Team at CLRRI, in collaboration with IRRI, conducted an exploratory survey with the following objectives: • TO determine the labor contribution of males and females in the different cropping systems; • To describe seed- and pest-management practices and women’s roles in these activities; and • To identify research and extension activities that could enhance women’s roles in rice farming and in other income-generating activities

Methods

Two irrigated villages, Thoi An and Phuoc Thoi of Omon District, Cantho Province, were selected as sites tor the study. Informal interviews were first conducted with village leaders, the leaders of women’s associations, political leaders, and farmers, but particularly female workers. Individual and group interviews with women only were also conducted. These interviews were followed by focused surveys on the labor input in the three dominant cropping systems.

1Cuu Long Delta Rice Research Institute, Omon, Cantho, Vietnam; 2 International Rice Research Institute. P.O. Box 933, Manila 1099, Philippines. Results and discussion

Study sites As well as being the sites for the present study, Thoi An and Phuoc Thoi are also the sites of on-farm research by CLRRI. Thoi An is 6 km from CLRRI; it has a total land area of 2,448 ha of which 2,414 ha are used for crop cultivation. Of the crop area, 1,964 ha were allocated to rice and 450 ha to orchards. Phuoc Thoi has 2,005 ha of which 1,516 ha are used for rice and 363 ha are devoted to orchards. The area of improved orchard is 257 ha (70% of total orchard area). The average landholding per family is just under 1 ha at Thoi An and just over 1 ha at Phuoc Thoi (Table 1). Most farm-family landholdings are divided into two parts with the larger being allocated to crops and the smaller to orchard. In both villages, water is readily available for crop cultivation from the numerous branches of the main rivers that cross the crop fields. Of the farmers interviewed in Thoi An and Phuoc Thoi, over two-thirds grow double crops (rice-rice or rice-upland crop). About 30% grow three crops (rice-rice-riceor rice-upland crop-rice) and only 1% grow a single crop of rice (Table 2).

Characteristics of women involved in farming Most (90%) of the women we interviewed were married with an average age of about 41 years: above the peak of reproductive age (20-30 yr old). Fewer than half (40%) of the women interviewed had children below 7 yr old: women with children above 7 yr old have more time for farming. On average, the women had borne 5.5 children but only 4.9 children had survived. The average family size was 5.3, although family planning is being promoted to encourage mothers to have fewer children (two per family) so as to enable mothers to have better reproductive health and to improve the nutritional status of chldren (Table 3).

Table 1. Land distribution in households interviewed, Omon, 1993.

Thoi An Phuoc Thoi

Total land area per household (ha) 0.98 1.10 Annual crop area per household (ha) 0.69 0.77 Orchard area per household (ha) 0.24 0.27 Homestead area per household (ha) 0.05 0.06 Farmers renting land for homestead (%) 8 5

Table 2. Percentages of farmers (number of farmers = 200) who adopt different cropping patterns, Omon, 1993.

Cropping pattern Thoi An Phuoc Thoi

Double crop 68.0 67.0 Rice–rice (98.5) (94.0) Rice-soybean (1.5) (6.0) Triple crop 31.0 32.0 Rice–rice–rice (84.0) (44.0) Rice-soybean-rice (16.0) (56.0)

Single crop (traditional rice) 1.0 1.0

Note: Numbers in parentheses are percentages calculated for each crop number per year.

292 Chi et al More than three-quarters (76%) of the wives interviewed had finished primary school; however, very few (9%) had finished secondary school. In contrast, 64% of the husbands had reached primary school, and 22% reached secondary school. Over 10% of the husbands had reached high school or college (Table 4).

Table 3. Socioeconomic profile of the respondents (number of female respondents = 200), Omon, 1993.

Marital status (%) Married 90.0 Single 3.0 Divorced 1.5 Widow 5.5

Average age (yr) Husband 42 Wife 41

Average number of births per mother 5.5 Average number of surviving children per family 4.9 Families with children below 7 yr old (%) 40.5 Average family size 5.3 Average family laborers 3.3

Table 4. Distribution of respondents (%) according to educational attainment, Omon, 1993.

Highest educational level Husband Wife

No schooling 3.0 13.0 Primary school 64.0 76.5 Secondary school 22.5 9.5 High school 9.0 0.5 College 1.5 0.5

Table 5. Distribution of male (M) and female (F) laborers in all activities in different cropping patterns (person-days/ha), Oman, 1993.

Activity Rice-rice Rice-rice-rice Rice-upland crop-rice

M F M F M F

Preparing seed 1.5 1.1 3.0 1.2 2.2 2.3 Preparing land 24.6 20.3 27.4 20.7 30.6 16.9 Sowing 1.8 0.4 2.5 0.6 14.5 15.9 Weeding 21.7 28.6 31.5 40.3 38.3 72.1 Irrigating 2.4 0.3 3.9 0.0 89.0 58.0 Fertilizing 4.4 0.7 5.3 1.5 10.9 3.5 Spraying 5.4 0.1 7.7 0.6 15.2 2.1 Harvesting 16.8 22.0 24.9 30.3 17.1 31.9 Hauling 12.3 3.8 27.9 7.5 12.6 8.6 Drying 13.9 14.3 24.3 20.8 12.0 14.7

Total 104.8 91.6 158.4 123.5 242.4 226.0 Percent 53 47 56 44 52 48

Gender roles in rice farming 293 Labor input in the different cropping systems The total labor input per hectare on a given crop was positively correlated with the intensity of farming (Table 5): rice-upland crop (soybeans and mungbeans)-rice, 468 d/ha; rice-rice-rice,282 d/ha; and rice-rice; 196 d/ha. The contribution of female labor followed the same pattern. Compared with their male counterparts, female workers supply 48% of the total labor input in rice-upland crop-rice, 44% in rice-rice-rice,and 47% in rice-rice.

Table 6. Labor distribution in different cropping patterns (person-days/ha), Omon, 1993.

Activity Family Hired Exchanged

M F M F M F

Rice-rice

Preparing seeds 1.5 1.1 – – – – Preparing land 19.5 20.1 4.8 0.2 0.3 – Sowing 1.8 0.4 – – – – Weeding 21.6 23.9 0.1 4.7 – – Irrigating 2.2 0.3 0.2 – – – Fertilizing 4.4 0.7 – – – – Spraying 5.4 0.1 – – – – Harvesting 6.8 7.3 7.0 12.5 3.0 2.2 Hauling 7.2 3.0 2.0 0.3 3.1 0.5 Drying 12.0 14.0 1.5 0.1 0.4 0.2 Total 82.4 70.9 15.6 17.8 6.8 2.9

Rice-rice-rice

Preparing seeds 3.0 1.2 – – – – Preparing land 23.5 20.7 3.6 – 0.3 – Sowing 2.4 0.6 0.1 – – – Weeding 31.5 35.0 – 5.3 – – Irrigating 2.8 – 1.1 – – – Fertilizing 5.3 1.5 – – – – Spraying 7.7 0.6 – – – – Harvesting 8.2 7.5 13.2 19.5 3.5 3.3 Hauling 10.5 7.0 11.3 0.5 6.1 – Drying 18.8 18.9 4.5 1.4 1.0 0.5

Total 113.7 93.0 33.8 26.7 10.9 3.8

Rice-uplandcrop -rice

Preparing seeds 2.2 2.3 – – – – Preparing land 25.5 16.9 5.1 – – – Sowing 8.9 8.2 5.6 2.7 – 5.0 Weeding 37.0 56.1 1.3 16.0 – – Irrigating 88.8 58.0 0.2 – – – Fertilizing 10.9 3.5 – – – – Spraying 15.2 2.1 – – – – Harvesting 11.4 14.4 3.1 14.2 2.6 3.3 Hauling 3.2 5.0 6.7 1.8 2.7 1.8 Drying 11.1 13.7 0.9 1.0 – –

Total 214.2 180.2 22.9 35.7 5.3 10.1

Note: M, male; and F, female.

294 Chi et al Among the crop activities, land preparation, weeding, and harvesting required the most labor. Female workers in the rice-upland crop-rice pattern contributed 39% of the total labor input in irrigation, a task traditionally done by men only. Female workers also contributed significantly to land preparation in all three cropping patterns even though this is again traditionally done by men because these activities are physically strenuous. However, because of the need to reduce the turn-around time between crops so that farmers can grow more than one crop per year, female workers - particularly female family members — must participate (Table 6). Weeding is another time-consuming job, particularly in the rice–upland crop–rice pattern where female workers provide about twice the labor contributed by men (72.1 versus 38.3 d/ha). One of the reasons for the greater demand for female workers is their lower wages. Weeding is mostly done by female hired laborers because they receive lower wages than men (10,000 versus 15,000 dong: about US$1.00 versus 1.50). In a similar study conducted in Cantho and Soc Trang on the Mekong River Delta (CLRRI 1992). female labor contribution was highest on the onion-onlon-ricecropping pattern (886 d/ha) followed by peanut-onion (562 d/ha), yambean-onion (502 d/ha), and yambean-white beet (501 d/ha). Women contributed more than 50% of the total labor input in these cropping patterns. Surprisingly, some women applied fertilizer and pesticides themselves (Table 5). These are considered to be traditional male jobs in other parts of Asia. Thus, labor by women can substitute for that by men.

Role of women in crop protection We conducted focused interviews with the women who sprayed chemicals. Of them, more than half applied pesticides on rice only, 40% sprayed rice and other crops, and 2.5% sprayed other crops only (Table 7). These women applied chemicals because they substitute for their husbands (78% of responses) or because male labor was not available (22% of responses). The oldest female respondent who applied pesticide was 52 yr old and the youngest was 16 yr old. More than half (52%) of the women interviewed kept the insecticides inside the house, about one-quarter (24%) kept them outside the house; and the others used them immediately after they were purchased (Table 8). Most women were aware of the harmful effect of sprayed chemicals (Table 9) and protected themselves while spraying by wearing long-sleeved shirts, and washing their hands and taking a bath after spraying. However, they rarely used a mask to protect themselves from inhaling the chemicals (Table 8). Over 60% of the women interviewed recognized the insects in the fields and more than half (52%) agreed that leaf-feeding insects caused severe damage to rice: however, 25% disagreed. Most (65.5%) believed that spraying must be done early to control leaf-feeding insects. Few of these women (13%) had heard about integrated pest management (IPM) and knew about natural enemies (Table 9).

Table 7. Participation of women in spraying of chemicals, Omon, 1993.

Percentage

Women spraying chemicals 20.0 For rice (57.5) For rice and other crops (40.0) For other crops (2.5)

Reason for women to spray Husband away 77.5 Lack of male labor 22.5

Note: Values in parentheses are percentages within the category

Gender roles in rice farming 295 Table 8. Knowledge of women on using chemical, Oman, 1993.

Percentage

Place to keep insecticide before use Inside houses 52.0 Outside houses 24.0 Use immediately after purchase 24.0

Safety practices during and after spraying Wear mask 2.7 Cover nose and mouth with cloth 55.5 Wear long-sleeved shirt 97.2 Wash hands and take bath after spraying 100.0

Table 9. Knowledge of women in integrated insect pest management, Omon, 1993.

Percentage

Notice insects in field 65.0

Believe leaf-feeding insects cause severe damage Agree 52.5 Disagree 25.0 No opinion 22.5

Believe spraying early will control leaf-feeding insect Agree 65.5 Disagree 12.0 No opinion 22.5

Believe chemicals harmful to person spraying Agree 73.5 Disagree 25.0 No opinion 1.5

Heard about integrated pest management 13.0 Know some predators in their fields 11.0

Table 10. Practices of women concerning rice varieties, Omon, 1993.

Percentage

Change variety Every season 35.8 Every year 51.0 Less frequently 13.2

Source of seed Exchange with other farmer 70.5 Purchase from market 50.5 Use own stock 30.0 Borrow 3.5

296 Chi et al Sources of seed, seed selection, and management The results of the survey revealed that most of the farmers (51%) changed the variety either every year, 36% every season, and 13% every 2 yr or more. Most of the respondents (71%) exchanged seeds with other farmers, 30% used their own stock, and about half (51%) bought seeds from the market. Very few borrowed from neighbors and friends (Table 10). Wives were predominantly responsible for storing the seeds (Table 11) and they practiced several methods to preserve the quality of the seeds. For instance, 80% rogued or removed off-types; 41% knew how to select the plots or locations where good seeds could be harvested. The majority (85%) were involved in drying and winnowing (separating the unfilled grains from filled grains), 50% removed foreign matter such as stones and wild seeds, and 56% soaked the seeds before sowing to remove the unfilled grains. Very few (11%) treated the seeds with chemicals before sowing. Although these women practiced various methods to maintain the quality of the rice seeds, 37% of them expressed a desire to get training on seed management so as to further increase rice productivity.

Table 11. Seed management practice by farmers, Omon, 1993.

Percentage of farmers

Roguing 79.5 Choosing seed from good crops 40.8 Drying and cleaning the seeds 84.5 Removing inert matter 49.5 Soaking seeds in water to remove light grains before 55.5 sowing Treating seeds with chemicals before sowing 11.3

Responsibility for storage of seeds Women 68.0 Men 18.3 Both 13.7

Women wishing for training on seed storage 37.0

Table 12. Participation in decision-making and control of resources, Omon, 1993.

Activity for decision-making Husband wife Both and control of resources (%) (%) (%)

Spraying chemicals 90.5 5.0 4.5 Changing of crop and cropping pattern 60.0 12.0 28.0 Changing variety 60.0 6.5 33.5 Kind of work for which to hire 54.0 22.0 24.0 Whether to borrow or not 31.0 11.5 57.5 Quantity of crop product to be sold 28.5 35.0 36.5 Selecting and changing children’s job 15.5 6.0 78.5 Having children or not 14.5 3.5 82.0 Allocating budget 12.5 55.0 32.5 Buying animal 12.5 50.5 37.0 Marriage of children 10.0 3.0 87.0 Saving 7.5 80.0 12.5 Selling animal products 7.5 67.0 25.5 Doing housework 3.5 90.0 6.5 Taking care of children 2.0 81.5 16.5

Gender roles in rice farming 297 Decision-making and control of resources Decisions in rice production, such as what specific crop and variety to grow during the season and whether to spray with chemicals, were dominated by the husbands (Table 12). They also dominated in decisions concerning what jobs required hired labor. However, the wives dominated in farm- management decisions related to buying and selling of animals and by-products. They also dominated in decisions related to the household, such as allocation of money for food, health care, and other household matters. Although the husbands had greater access to credit from formal banks, the wives had greater access to private money lenders and were also responsible for repayment of debts (Table 12).

Table 13. Women in information access and training, Omon, 1993.

Percentage

Source of information Neighbor 58.5 Husband 47.0 Parent 27.0 Radio, TV, and newspaper 20.0 Extension staff 3.5

Training courses in which women wish to participate Animal husbandry 34.5 New varieties 10.0 New sowing methods 8.5 Plant-protection methods 7.5 Handicrafts 9.0 Family planning and children’s health care 8.0

Reasons for women not participating in training course Not interested 10.5 Have no time 10.5 Old age 1.5

Table 14. Women’s problems and needs in farming, Omon, 1993.

Problem Percentage of women

Lack of capital 93.5 Lack of technology 91.5 Low price of crop products 38.5 Insufficient seed supply 27.5 Incorrect insect pest management 19.5 Insufficient land or landless 10.0

Need of capital For animal production 60.5 For rice and upland crop production 36.9 For converting rice land into orchards 35.0 For improving an existing orchard 26.8 For small trading 5.0 For mushroom cultivation 4.5

298 Chi et al Women’s access to training and extension More than half of all women interviewed (59%) obtained agricultural information from their neighbors, 47% from their husbands, 27% from the parents, and 20% from the media (newspaper, radio, and TV). Only 3.5% received agricultural information from extension workers. When asked what kind of training programs they would like to receive, 35% wanted greater knowledge and skills in animal husbandry and very few wanted to learn more about new methods in crop production and management (Table 13). This is, perhaps, related to those areas in which women make the household decisions (Table 12).

Problems perceived by women The most important problem for most of the women interviewed (93.5%) was the lack of capital for investing in animals, converting rice lands into orchards, rice and upland production, small trading, or mushroom production. Most also indicated problems in their lack of technical knowledge in raising crops (rice and legumes). Other problems were low prices of crop and fruits, insufficient supply of high-quality seeds, incorrect pest-management practices, and insufficient land for cultivation (Table 14).

Research and extension strategies to enhance the roles of women farmers Four major areas were identified for extension strategies to enhance the role of women farmers. • In-depth and systematic study of pest-management practices and of gender roles in pest management in rice, fruit trees, and upland crops need to be conducted in collaboration with IRRI’s IPM Network. • The implications of increasing labor demand on family welfare must be studied. It is important to examine the implications of intensive crop cultivation on food security, family welfare (particularly of women and children), female heads of households, and the strategies in meeting the labor demands of the different cropping systems. • The knowledge, attitudes, and practices regarding seed management should be studied further and women should be further trained in improved seed management so as to increase crop productivity and reduce postharvest losses. • The methods used by families and their members to generate the required capital for farming should be examined. The information would be useful in providing women access to credit.

Reference cited

CLRRI — Cuu Long Delta Rice Research Institute (1992) Rice-based farming systems in Cantho and Soc Trang, Mekong Delta, Vietnam and a preliminary assessment of women’s participation. Paper presented at the International Workshop on Gender Concerns in Rice Farming, Chrang Mai, Thailand, 20-24 Oct 1992.

Gender roles in rice farming 299

Institution building

Strengthening the Cuu Long Delta Rice Research Institute

Nguyen Van Luat, 1 Pham Sy Tan, 1 and D.W. Puckridge 2

Abstract. The 3-yr project to strengthen the Cuu Long Delta Rice Research Institute (CLRRI) started with the support of the United Nations Development Programme (UNDP, project VIE/91/005) in June 1992. It was the first nationally executed UNDP project in Vietnam. Progress has been completely satisfactory. Training is almost completed with 22 staff trained in the Philippines and two in Thailand. Leaders’ tours to Indonesia, the Philippines, and Thailand have broadened perspectives and initiated contacts for collaborative research. Workshops and meetings have allowed researchers to work in close collaboration with provincial counterparts and to develop an in- country training program. Further development should be linked to the national agriculture research plans.

The Mekong (or Cuu Long) River Delta in Vietnam is the downstream part of the Mekong River basin. It is an area of great productive potential and its development is of crucial importance to Vietnam’s economic prosperity and food balance. At the same time, the Delta is a difficult area with considerable physical and environmental constraints: great annual variation in the Mekong River’s hydrological regime, large tracts of lands with acid sulfate soils, and vulnerable wetlands. (Background information is from the Master Plan of the Mekong Delta, draft 1993, unpublished,) The Mekong Delta has an area of 3.9 million ha, about 12% of the country’s total area. In 1990, it provided 9.7 million t of paddy, about 50% of the national production and accommodated 14.6 million people, which is 22% of the population. It contributes significantly to national exports, particularly rice and fisheries, and over 30% to the gross domestic product (GDP). At 16% urbanization, as against 22% nation-wide, it is a relatively “green” rural region. About 2.4 million ha are currently used for agriculture and aquaculture. The primary sector output is expected to grow by an average rate of 5% per year up to 2000, slowing to 4% in 2015. The country reached self-sufficiency in rice much more quickly than expected and is now a major exporter. Projections of rice demand, expressed in paddy equivalent, for Vietnam as a whole are in the order of 25 million t in 2000 and 32 million t in 2015, including some 3 million t paddy equivalent for export, but market prospects are uncertain. Double-rice and single-rice cropping are the dominant cropping systems in the Mekong River Delta, occupying together 70% of the agricultural land (Table 1). Some 20% is devoted solely to upland crops and perennials; crop diversification in rice-based systems is still limited. The area under triple-rice cropping is increasing, in recent years by some 10,000 ha/yr. Three areas of rice production are of greatest concern: The high harvesting losses due to poor drying, threshing, and storage techniques — estimated to be 10-15%; The inadequate supply of high-quality seed; and The improper application of fertilizers and pesticides.

1Cuu Long Delta Rice Research Institute, Omon, Cantho, Vietnam; 2International Rice Research Institute, Thailand Office, P.O. Box 9-159, Bangkok 10900, Thailand. Table 1. Land use in the Mekong River Delta, 1992.

Land use Crop area Percent of total Percent of (‘000 ha) area agricultural area (3.95 million ha) (2.46 million ha)

Annual crops Double-rice cropping 950 24.0 38.6 Single-rice cropping 762 19.3 31.0 Triple-rice cropping 75 1.9 3.0 Double-rice plus upland crop 35 0.9 1.4 Triple-rice plus upland crop 3 0.1 0.1 Upland crops 144 3.6 5.9

Perennial crops 346 8.7 14.1

Water surface for agricultural use 145 3.7 5.9

Forestry land 377 9.5 –

Others (including waste lands, waterways, and unclassified) 1,118 28.3 –

Source: From Master Plan of the Mekong Delta (draft June 1993).

Rice cultivation has been the focal point of agricultural development so far. Its further intensification, however, has both technical and economic limits, The triple-rice cropping system draws heavily on water from low river levels in the dry season and may not be sustainable. Rotation with upland crops, in combination with integrated pest management (IPM) techniques, would reduce the risk of diseases and the need for pesticides and, at the same time, maintain soil fertility. Crop diversification is of particular relevance. Farmers are already growing many crops but a range of technical, institutional, and economic problems must be resolved to make crop diversification an attractive and sustainable course of development. The net returns to farmers should at least be equal to those of rice cultivation. There is still need to generate additional technologies to exploit the full potential of the Mekong River Delta. Although the severe climatic problems, such as typhoons and low temperatures, which are common in the north of the country, are not present, agriculture in the Delta is practiced under diverse environmental conditions: for example, soils with serious management problems — acid sulfate, salinity, and peat; varied water regimes — drought, waterlogging, and tidal influence; varied cultural practices — zero tillage, normal tillage, dry and wet seeding, seeding into water, and single and double transplanting; various forms of cultivation — rainfed, irrigated, deepwater, and floating; various farming systems — one, two, or three crops per year; and various nonagricultural combinations — rice-fish, rice-shrimp, rice-mangrove-shrimp, and so forth. Under the climatic conditions of the Delta, insect and disease problems are common. There are also institutional limitations: such as inadequate input supplies; credit, processing, and marketing difficulties; and lack of coordination for rice research in the Delta. Government policies have been directed toward greater liberalization of the farm structure by encouraging private enterprise, as against the centralized planning practiced earlier through state farms and cooperatives. Emphasis has been placed on systems of crops, livestock, fish, and wastes. However, several constraints have limited the rate of technology development: the introduction of contract research through which the government gives limited financial support for research with the institutions themselves generating additional funds; weak coordination of activities; a low ratio of professional to

304 Luat et al nonprofessional staff in the research institutions; an unbalanced distribution of extension staff at the regional level; poor staff incentives; and a weak scientific-exchange system with other countries and international institutions. Collaboration and integration need to be strengthened to avoid duplication and at the same time to be able to maximize resource use through multidisciplinary research and a vigorous extension service.

Cuu Long Delta Rice Research Institute

The Cuu Long Delta Rice Research Institute (CLRRl) is the main research institute working on rice and rice-based farming systems in the Delta. The Government of Vietnam established CLRRI in 1977 with a mandate to improve rice production in the Mekong River Delta in particular and in the entire country in general. This mandate included determination of profitable cropping systems and mixed farming systems based on the rice crop. Other institutions making significant contributions to rice and farming systems research in the Delta include the University of Cantho and the Institute of Agricultural Science of South Vietnam (IAS). The government mandate for CLRRI is fourfold: • To carry out basic and applied research in all disciplines of rice culture so as to devise technology for increasing yield per hectare of rice, and for protection and conservation of the rice products; To develop feasible and profitable cropping systems and mixed farming systems based on the rice crop; • To train research and agricultural workers connected with farm production; and To foster international cooperation in rice research and crop production for the well-being of humankind. For the purpose of this project, CLRRI has authority to link with rice research and extension activities in the whole country, but especially in the Delta. CLRRI, IAS, the University of Cantho, and the University of Agriculture and Forestry (UAF) form the main network for agricultural research in the area. Also participating in network activities are the Plant Protection Department, the Institute for Soils and Fertilizers Research, and the Center for Applied Biology. At the extension level are the provincial agricultural extension and service agencies, state farms, cooperatives, and individual farmers. CLRRI started a bilateral agreement with India in 1977. Fifteen staff scientists have been trained (seven with doctoral and eight with master’s of science degrees) and more are undergoing training at present under this bilateral arrangement (nine with doctoral and four with master’s of science degrees). All of them will be back at CLRRI by the end of 1995. The program included the long-term appointment (2-4 years) of Indian scientists at CLRRI from 1982 to 1989, but this ended in 1990. IRRI has collaborated with CLRRI for many years. The greatest impact of the association has been in varietal improvement and farming system research (FSR), including study on improving the role of women in agricultural production. Of the modern rice varieties released in the Mekong River Delta, 90% have been selected from IRRI germplasm. Under the UNDP project reported here (VIE/91/005), IRRI is the technical assistance agency. A senior IRRI staff member works at CLRRI for several days every 2 mo as an agronomist-liaison scientist (ALS) and is assisted by short-term visits of other senior IRRI scientists specializing in various topics. CLRRI also receives a grant from the Food and Agriculture Organization of the United Nations (FAO) for hybrid rice research and for a study on sesame production after floating rice. An FAO consultant helped CLRRI to produce the proposal for VIE/91/005 in 1989.

Strengthening CLRRI 305 CLRRI has a successful seed-multiplication and distribution program and produces about 500-750 t of seed/yr. However, the national seed-multiplication and distribution capacity is still low and the quality of seed used by farmers needs to be improved. The Institute supplies foundation seed to the National Seed Company for multiplication of certified seed. The Institute has promoted technology transfer through large-scale demonstration units combined with field trials and training sessions.

UNDP Project VIE/91/005

The UNDP project has a duration of 3 yr and started in June 1992. The total budget for the project is US$857,125, of which US$305,000 was provided for equipment. It is aimed at assisting CLRRI to strengthen its research capability and its technology-transfer and extension network so that it can play an increasing role in the government’s objective of raising the level of rice production in the Mekong River Delta to 12 million t/yr from the present 9.5 million t by the year 2000. The executing agency for the UNDP project is the Ministry of Science, Technology and Environment (MOSTE), which has been designated by the Government of Vietnam to undertake the management of national scientific research and development programs. The Office for Project Execution, Coordination and Support (OPECS) was established to assume the legal and financial accountability for projects as required by UNDP and the Government. The immediate target beneficiaries are farmers, researchers, technicians, and extension workers of the Delta region. Secondary beneficiaries include agro-based industries such as processors and traders of the government and private sectors. Farmers, processors, and traders in other regions may benefit from a spill-over effect. CLRRI staff will benefit by improving their professional capability and their working conditions.

Project progress

Foreign training Training has occupied a total of over 96 wk, for a total of 49 persons (31 on fellowships, 4 attending workshops, and 14 on study tours). Sixteen staff of CLRRI, two from the University of Cantho, one from the Center for Seed Testing, one from the College of Economic Management, two from the National Institute for Agricultural Planning and Projection (NIAPP), three from IAS, and six from the provinces were trained at IRRI in various disciplines: agricultural engineering, economic analysis, farming systems, fertilizer management, gender data analysis, hybrid rice, laboratory management, plant physiology, research management, rice testing, technology transfer, and weed control. Two CLRRI staff trained with the Department of Agriculture in Thailand, one in grain quality and one in postharvest technology. One other CLRRI staff member was trained on photosynthesis and crop productivity in Thailand. Four people completed a 20-d leaders’ study tour to Indonesia and the Philippines in February-March 1993 and this group made another 10-d leaders’ study tour to Thailand in June 1993. Seven people went to the Philippines for an extension study tour in May 1993 and three joined the leaders’ study tour in November 1993. Individual CLRRI staff members have attended an entomology conference in China, a conference on women’s roles in agriculture in Thailand, the deepwater-rice workshop in Thailand, and

306 Luat et al a genome-analysis training course in India. Two persons of CLRRI and Omon leadership went to Thailand in March 1994 to study extension services. They accompanied 12 provincial leaders who were supported by their own funds.

In-country training A total of 115 master’s of science, bachelor’s of science, and technicians were trained in-country: • Research statistics, a 2-wk course with 54 participants conducted in December 1992 and July 1993; • Laboratory techniques course of 2 wk for 10 CLRRI staff in March 1993; • Training-skills course with 25 participants in April 1993; and • Two computer courses, May and July 1993, with 26 partcifants.

Meetings Eighteen meetings and workshops were organized for a total of 21 d with, in total, 1,135 participants: • Three specialized group meetings with four areas of specialization (in August 1992, March 1993, and August 1993); • Project coordinating group meetings (in August 1992, March 1993, and August 1993); • Two annual rice workshops (December 1992 and December 1993); and • Three workshops on weed control, rice varietal improvement, and orchard improvement.

Equipment Equipment supplied to date includes computers, audiovisual equipment, three vehicles, and an internal telephone system.

Linkages Staff of the University of Cantho, UAF, IAS, NIAPP, Plant Protection Department, Extension Department, various project personnel, provincial officers, and others have taken part in conferences and activities of the Institute. Extensive contacts with provincial agricultural officers in their own provinces have been made, including a 3-d visit to Minh Hai Province by staff of CLRRI and the University of Cantho, the ALS, and two visiting scientists. An extension consultant went to seven provinces and two institutes to exchange experiences. Agreements for cooperation have been signed directly between CLRRI and seven provinces, and between CLRRI, IAS, NIAPP, and 10 provinces. By December 1993, 22 IRRI staff had made 34 visits to CLRRI for a total of 220 person-days. Three international consultants completed their assignments for a total of 61 person-days. To 31 Dec 1993, 18 mo after the start of the project, the ALS had made nine visits to Vietnam for a total of 134 d with 120 d working at CLRRI. Contacts were made with the Department of Agricultural Science and Technology (DAST) and other research institutions in the Hanoi area, and IAS n Ho Chi Minh City. International contacts have been made at CLRRI with the Australian Centre for International Agricultural Research (ACIAR), the British Ambassador, FAO, the Indian Ambassador and Consul General, the consuls general of Thailand and China, the Japanese Embassy in Hanoi, and the Japanese International Cooperation Agency (JICA) in Bangkok, rural development experts from France, United States Agency for International Development (USAID), the World Bank, the University of California, and various individual scientists visiting CLRRI. These contacts have indicated possibilities of additional funds to support the research work. CLRRI has been provided US$336,000 by the World Bank (through the Government of Vietnam) to start implementing a project on rice-improvement research and development for the Mekong River Delta in June 1994.

Strengthening CLRRI 307 Outlook

An extensive program of research is ongoing, but there are limitations. The project has provided good training, but operating funds are still lacking — they need to be supplied for the staff to be as effective as necessary — nor have all sections of the Institute been strengthened. However, although it is too early to release new technologies, CLRRI has been able through improved facilities to extend its program. Research activities are continuing at the five sites selected for this project as representative environments of the farming systems in the Mekong River Delta. In addition, staff of the Institute are actively working in collaboration with other projects, such as the National Project KN01-17, which has research activities at 40 sites in 11 provinces of the Delta. With additional support for plant breeding, pest management, and related areas of research expected in the future, CLRRI has the potential to make significant contributions to agricultural progress in Vietnam.

308 Luat et al Costs and benefits of the Cuu Long Delta Rice Research Institute project in the Mekong River Delta

A.M. Mandac, 1 Dang The Truyen, 2 and Hoang Thi Mai Huong 3

Abstract. Financial, economic, and social appraisal was conducted on a project aimed at assisting the Cuu Long Delta Rice Research Institute (CLRRI) to strengthen its research capability and its technology-transfer and extension network. The project was designed to provide training fellowships for researchers and extension specialists; improve research facilities and equipment; and develop, verify, and transfer appropriate technological packages to farmers for improving rice production in the Mekong River Delta. In the financial appraisal, the project was evaluated using market prices; in the economic analysis, however, the prices were adjusted for distortions in the market. The financial net present value (NPV) is highly attractive to the farmer beneficiaries as well as to the project. The economic NPV showed a net gain to the economy. The social appraisal indicated that the economy is the major gainer in the project.

Investment appraisal indicates, under certain assumptions, the gains (or losses) from a long-term investment. Project appraisal is conducted for five reasons: to stop bad projects; to prevent good projects from being destroyed; to determine if components of the project are consistent; to assess the sources and magnitudes of the risks; and to determine how to reduce those risks and share them efficiently (Jenkins and Harberger 1992). Project appraisal and approval consists of five stages: idea and project definition, prefeasibility study, feasibility, detailed design, and project implementation. • The first stage determines whether there is a significant demand for the goods or services expected from the project. • The prefeasibility study is the first attempt to examine the financial and economic feasibility throughout the project’s life. • The function of the feasibility stage of an appraisal is to improve the measures of key variables if the project has the potential for success. • The detailed design stage involves setting down the basic programs, allocating tasks, determining resources, and setting down in operational form the functions to be carried out and their priorities. • Project implementation involves the coordination and allocation of resources to make the project operational. The conduct of project appraisal has advanced in recent years both on the theoretical side and in the tools of analysis, and risk analysis is now more commonly applied in project appraisal. This was made possible by advances in microcomputer technology and the development of customize computer software that could be integrated with available spreadsheets.

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines; 2 Office of The Prime Minister, la Hoang Hoa Than Hanoi Vietnam; 3 Vietnam Foreign Press Center, 10 Le Phung Hieu, Hanoi, Vietnam In this study, we present the results of an intensive investment appraisal of a rice project in the Mekong River Delta (MRD). We are also concerned with appraisal of investment as a technique for comparing the costs and benefits of public-sector projects. The investigation was conducted while the authors attended the 1993 Program on Investment Appraisal and Management at the Harvard Institute for International Development.

Description of the project

General The project would assist the Cuu Long Delta Rice Research Institute (CLRRI) to strengthen its research capability and its technology-transfer and extension network so that it can play an increasing role in the government’s objective of raising the level of rice production in the MRD. CLRRI is the main research institute in the MRD working on rice and rice-based farming systems. Its location in the Delta, where over 45% of the country’s rice is produced and where the greatest production potential in the country exists, as well as its past experience in the field of rice research, make it ideally suited for this project. The project is part of a program designed to introduce efficient systems of adaptive research and agricultural extension to the MRD. It has become apparent that, if the gains from the new rice technology are to be sustained, adaptive research and extension need additional support. Laboratory equipment and facilities at CLRRT are inadequate and out-moded, training and office facilities for agricultural researchers are extremely poor and limited, transportation for extension staff is scarce, and . there is a critical need to strengthen technical supervision of adaptive research. To alleviate these constraints, the project would include five parts: • Development and upgrading of the grain-quality laboratory and field experimental station, provision of equipment, and laboratory facilities; • Provision of training fellowships for researchers and extension specialists; Provision of vehicles for research and extension; • Provision of technical support to assist in the development of the rice research and extension program; and • Intensification of breeding and selection to combine high yields, good grain quality, pest and disease resistance, and adaptation to the different ecosystems.

Detailed features Research agenda. The research approach follows the -farming systems research stages from an agroeconomic point of view: that is, site selection and description, economic and biological component studies, farming systems design and testing, preproduction programs, and pilot-production programs. This approach is effective in developing improved practices that fit the existing capabilities of target beneficiaries. A major focus of the project will be the release of new rice varieties. Advanced lines will be evaluated and it is expected that 12 promising varieties bred and selected at CLRRI will be released by the end of the project period. A total of 8,000-10,000 lines will be screened for high yields, improved grain quality, pest and disease resistance, and adaptation to the different agroecological regions of the MRD. Training. The project will contribute 30 person-months of short-term training abroad in grain- quality improvement (6 person-months); farming systems (6 person-months); technology transfer (6 person-months); soil management (6 person-months); and laboratory techniques and management (6 person-months). In addition, 12 person-months of study tours will be conducted, which are designed

310 Mandac et al to provide leadership training for senior scientists including programs on technology transfer (4 person- months), genetics and plant breeding (4 person-months), and plant protection (4 person-months). The project will organize an in-service training program for a total of 110 bachelor of science graduates and 60 technicians, including training in research methods and data analysis, computer uses, transfer of technology, communications, and laboratory procedures. Infrastructure. A grain-quality laboratory will be installed with such necessary equipment as a sheller, laboratory mill, micropolisher, seed counter, cyclone mill (for amylose determination), amalgamator, mixer, balance, colorimeter, hot-water bath, microscope, and so forth. A seed-storage unit will be established with a cold room for storing up to 10,000 accessions of rice. These improvements will support the varietal-improvement program.

Extension methods The objective of the project is to provide farmers, on a regular and systematic basis, with up-to-date advice on farming practices that could immediately increase rice yields. The communication system between the Institute and the farming population as well as with other institutions will be improved. Network stations will be established for conducting applied research, field trials, and demonstrations to provide on-the-spot training of farmers. The network of regional sites will be selected according to the main agroecological zones in the MRD. This approach draws from past experience that the farmers of Vietnam are hard-working, skilful, and respond well to new technology once they are convinced that the new technology is appropriate for their social and economic conditions.

Basic methods

An investment project can be evaluated using financial, economic, and distributive (or social) analysis. In financial analysis, projects are evaluated using market prices. By contrast, in an economic analysis, evaluation is conducted using prices adjusted for market distortions so that they reflect their true cost or benefit to society. A social analysis measures the net financial benefits of a project accruing to the different parties directly or indirectly affected by the project.

Financial analysis Financial analysis may be conducted to calculate the returns of a project from the point of view of the banker, owners, or a government budget office and gives the total investment point of view. The banker takes into account the financial flows entering the project (including subsidies) and the benefits (including tax payments). From the analysis, the banker is able to determine the financial feasibility of the project, the need for loans, and the likelihood of repayment. Like the banker, the owners examine the net increment of income of the project relative to what they could have earned without the project. Unlike the banker, however, owners add the loan as a cash receipt, and subtract payments on interest and principal repayment as cash outlays. To the budget office, a project may require outlays in the form of subsidies or other transfer payments and may also generate revenues from direct or indirect taxes and fees.

Economic analysis The economic analysis examines the profitability of a project from the point of view of society as a whole. Profitability in ths context is defined as the capacity of the project to maximize the efficient use of a nation’s scarce resources in producing national income, The economic analysis, which can be prepared from the data used for the financial analysis, differs from the latter in two ways: first, the economic analysis is concerned with flows of real resources, and adjustments for transfer payments (taxes, subsidies, and loans) have to be made; second, resources are valued at their opportunity cost.

Costs and benefits of the CLRRI project 311 Distributive analysis The distributional analysis can be constructed from the economic and financial analyses provided they are done from the viewpoint of all the parties involved in the project.

Riskanalysis Risk analysis, using Monte Carlo simulation techniques, is a method for processing the effects of uncertainty surrounding the key variables on the net present value (NPV) of a project. Until recently, risk analysis was not frequently applied in project appraisal because microcomputers were not powerful enough to handle the Monte Carlo simulation and because of the difficulty in creating a tailor-made computer program for every application. RiskMaster, a spreadsheet-based program for conducting risk analysis, has been developed to facilitate the analysis of project risk (Savvides 1987). Risk analysis employs sensitivity and scenario analysis and Monte Carlo simulation. The former tests, in a static manner, the impact of a change in the value of one or more variables on NPV. Monte Carlo simulation adds the dimension of dynamic analysis to project appraisal by making it possible to construct random scenarios based on the analyst’s key assumptions about risk. As a result, the prospective investor is furnished with data on the “odds” that might be expected with respect to various outcomes that could result from the decision to invest in a particular project (Savvides 1988).

Indicators of project worth Evaluation of a single investment opportunity and ranking of various investment opportunities require a consistent set of criteria. Many different criteria have been used in the past to judge the expected performance of investment projects. We review four of these: NPV, the benefit-cost ratio (BCR), the pay-out or pay-back period (PBP), and the internal rate of return (IRR). Of these four, the NPV is the most satisfactory. The NPV is not only used for ranking projects; but it also measures the surplus generated by the project over and above what would be produced by these funds if not used in these public-sector investments. In calculating the NPV, the first step is to obtain net benefits by subtracting all the costs incurred from the total benefits pertaining to each period. Second, a discount rate is chosen that measures the opportunity cost of funds in alternative uses in the economy. When the NPV is measured in economic terms, a positive NPV implies that the economy will be made better off and a negative NPV that the economy will be worsened. Several decision ‘rules are applicable: first, do not accept any project unless it generates a positive NPV when discounted by the opportunity cost of funds; second, under a limited fixed budget, select that subset of the available projects that maximizes NPV; and, third, under no budget constraints, select the alternative that generates the largest NPV. The BCR has been one of the most widely used criteria. It is calculated by dividing the present value of benefits by the present value of costs, using the opportunity cost of funds as the discount rate. Several rules of thumb may be followed: for a project to be acceptable, the BCR must have a value greater than unity; for mutually exclusive projects, choose the alternative with the highest BCR — however, this criterion may give incorrect ranking of projects if projects differ in size; and the BCR is sensitive to the way in which costs have been defined by the accountants in setting out the cash flows. The PBP measures the number of years that it will take for the undiscounted net benefits to repay the investment. The drawback of this criterion is that it does not take account of subsequent income. The IRR is the discount rate that equalizes the total present values of the negative and positive values in the incremental net-benefit stream. This rate of return may be interpreted as the average rate of interest earned by investing capital in the project over its life (Amerasinghe 1986). The advantage of the IRR is that it can be calculated from project data alone because it is generated within the project by an iterative process of discounting the incremental net-benefit stream (Harberger 1976). However,

312 Mandac et al it has a disadvantage in that it may not always give a unique solution, for example with a project that has a time-profile of net benefits that crosses at zero more than once.

Estimation of benefits

Attributing a precise level of benefits to this type of project is difficult because the expected benefits of improved agricultural practices, which also require additional inputs, cannot be attributed solely to research and extension. In our analysis, the life of the project is assumed to be 10 yr and we test the financial rate of return assuming that only 10% of farmers (or area) participate by Year 6. These assumptions mean that a total of 90,000 farmers will benefit from the project in Year 6. It is also assumed that these farmers will capture only 50% of the potential yield benefit from the new technology. At Year 6, the assumed production difference between the farmer and the project is 5.8 t on 2 ha — the average farm size in the MRD is 2 ha. At this level, project yield is 7.2 t/ha. This yield level can already be achieved — a “model farm” of 50 ha growing F1 seeds and the variety DT10 produced 9.5 t/ha in An Giang Province (Luat 1992).

Project costs

Prices and costs of the project are given in Table 1. The export price of rice (25-35% brokens) was adjusted using the foreign inflation index. By contrast, the operating costs of the farmer beneficiaries were expressed in nominal terms to evaluate the effect of inflation on the project. In deriving the cost stream for the direct costs of the project, costs were aggregated into extension and research costs, separated from costs of building, vehicles, and equipment. A loan-repayment pattern for each farm (Table 2) was developed using the existing nominal annual rate of interest of 30%. The loan is necessary to enable farmers to buy the extra inputs required by the new technology. The government will provide the loan. It is assumed that farmers borrow money at the beginning of the cropping season and pay back at the end of the year.

Interpretation of results

Financial analysis To assess the impact of the project on the farmers, pro-forma financial cash flows for a 2-ha farm were constructed under the existing technology or farmers’ practice and that of the project. The difference between the two, that is, the incremental cash flow shows the effect of the project on the profitability of the individual farmer (Table 3). The results indicate that the NPV under the existing technology is 9.8 million dong (US$873). By contrast, the project NPV is 24.2 million dong (US$2,150). This means an incremental NPV in Year 0 of 14.4 million dong (US$1,277) or US$128/yr for each farmer beneficiary over the 10-yr life of the project. The pro-forma cash flow for the whole project (Table 4) shows that the benefit stream greatly exceeds the cost stream with a very high rate of return (IRR = 80%). The NPV of the project in Year 0 is estimated at 363.9 billion dong (US$32.3 million).

Economic analysis Economic analysis of the project was conducted by adjusting the pro-forma financial cash flow using conversion factors that account for distortions in the Vietnamese economy. These entailed the estimation of the economic opportunity cost of labor, the economic price of rice exports, the economic

Costs and benefits of the CLRRI project 313 Table 1. Prices and costs in domestic currency. a,b

Year

0 1 2 3 4 5 6 7 8 9 10

Domestic inflation index 1.00 1.15 1.32 1.52 1.75 2.01 2.31 2.66 3.06 3.52 4.05

Prices Export price of rice (000 dong/t) 1,173 1,220 1,269 1,320 1,373 1,428 1,485 1,544 1,606 1,670 1,737

Investment costs (000 dong) Vehicles and equipment 621,693 1,295,288 217,762 3,053,180 2,423,588 217,762 – – – – – Training 382,370 473,886 450,068 946,520 1,038,036 788,558 – – – – – Research and extension 722,112 496,452 – 3,091,542 2,752,752 846,225 – – – – – Buildings 267,035 – – 267,035 – – – – – – – Consultancy 936,489 936,489 1,066,244 936,489 936,489 1,066,244 – – – – – Miscellaneous 226,326 93,186 81,903 226,326 93,186 8 1,903 – – – – – Experimental field 178,023 – – 178,023 – – – – – – – development Overhead 172,066 507,735 407,778 172,066 507,735 404,778 – – – – – Evaluation 39,491 67,698 33,849 39,491 67,698 33,849 – – – – – TOTAL 3,545,605 3,870,734 2,254,604 8,910,672 7,819,784 3,439,319 – – – – –

Operating costs (000 dong/ha) Current inputs Existing 1,456 1,514 1,575 1,638 1,703 1,771 1,842 1,916 1,993 2,072 2,155 With project 1,839 1,913 1,989 2,069 2,151 2,237 2,327 2,420 2,517 2,617 2,722 Incremental 383 398 414 431 448 446 485 504 524 545 567 Labor Existing 880 1,012 1,164 1,338 1,539 1,770 2,035 2,341 2,692 3,096 3,560 With project 1,365 1,570 1,805 2,076 2,387 2,746 3,157 3,631 4,176 4,802 5,522 Incremental 485 558 64 1 738 848 976 1,122 1,290 1,484 1,706 1,962

Production (t/2 ha) Farmers’ practice 7.8 7.8 7.9 8.0 8.2 8.4 8.6 8.9 9.3 9.7 10.2 Project – 13.1 13.2 13.4 13.7 14.0 14.4 14.9 15.6 16.3 17.1 Difference – 5.3 5.3 5.4 5.5 5.6 5.8 6.0 6.3 6.5 6.9 a Differences in totals are due to rounding. b US$1 = 11,250 dong. Table 2. Loan profiles of existing farmers’ practice and project for a 2-ha farm (000 dong). a,b

Year

1 2 3 4 5 6 7 8 9 10

Farmers’ practice Loan 3,858 4,104 4,373 4,669 4,994 5,354 5,751 6,193 6,683 7,230 Interest 1,157 1,231 1,312 1,401 1,498 1,606 1,725 1,858 2,005 2,169 Payment of principal 3,858 4,104 4,373 4,669 4,994 5,354 5,751 6,193 6,683 7,230 Total payment 5,016 5,335 5,685 6,069 6,493 6,960 7,477 8,050 8,688 9,399 Project Loan 5,112 5,458 5,840 6,260 6,726 7,243 7,817 8,458 9,172 9,973 Interest 1,534 1,638 1,752 1,878 2,018 2,173 2,345 2,537 2,752 2,992 Payment of principal 5,112 5,458 5,840 6,260 6,726 7,243 7,817 8,458 9,172 9,973 Total payment 6,646 7,096 7,591 8,139 8,744 9,416 10,163 10,995 11,924 12,964 a Differences in totals are due to rounding. b US$1 = 11,250 dong. Table 3. Incremental cash flow of project for a 2-ha farm (000 dong). a,b

Year

1 2 3 4 5 6 7 8 9 10

Receipts Exports 6,418 6,742 7,117 7,551 8,051 8,628 9,292 10,057 10,939 11,959 Loans 1,254 1,354 1,466 1,592 1,732 1,889 2,066 2,265 2,489 2,743 Subsidies – – – – – – – – – – Cash inflow 7,672 8,096 8,584 9,143 9,783 10,517 11,358 12,322 13,428 14,701

Expenditures Current inputs Fertilizer 534 555 577 600 624 649 675 702 730 760 Pesticides 263 273 284 296 308 320 333 346 360 374 Labor Hired 457 526 605 696 800 920 1,058 1,217 1,399 1,609 Owned 658 757 8 70 1,001 1,151 1,324 1,522 1,751 2,013 2,315 interest 376 406 440 478 520 567 620 679 747 823 Payment of loan principal 1,254 1,354 1 ,466 1,592 1,732 1,889 2,066 2,265 2,489 2,743 Tax 321 337 356 378 403 431 465 503 547 598 Cash outflow 3,863 4,209 4,599 5,039 5,537 6,100 6,738 7,463 8,286 9,222

Net cash inflow, nominal 3,809 3,887 3,984 4,103 4,246 4,417 4,619 4,859 5,143 5,480 Net cash flow, deflated 3,312 2,939 2,620 2,346 2,111 1,909 1,736 1,588 1,462 1,354 a Differences in totals are due to rounding. b US$1 = 11,250 dong. Table 4. Incremental financial cash flow of project (million dong). a,b

Year

1 2 3 4 5 6 7 8 9 10

Receipts Exports 5,776 36,406 153,731 326,203 521,727 776,499 836,251 905,104 984,524 1,076,267 Loans 11,286 36,571 79,191 114,602 140,282 170,022 185,930 203,841 224,038 246,851 Subsidies 3,546 3,871 2,255 8,911 7.820 3,439 – – – – Liquidation value (building) – – – – – – – – – 231 Liquidation value (vehicles – – – – – – – – – 2,950 and equipment) Cash inflow 20,608 76,847 235,176 449,716 669,829 949,960 1,022,181 1,108,944 1,208,562 1,326,300

Expenditures Current inputs Fertilizer 4,804 14,988 31,174 43,228 50,577 58,445 60,783 63,214 65,742 68,372 Pesticides 2,366 7,382 15,355 2 1,292 24,911 28,786 29,938 31,135 32,381 33,676 Labor Hired 4,116 14,201 32,662 50,082 64,793 82,791 95,210 109,492 125,915 144,803 Owned 5,923 20,435 47,001 72,069 93,239 119,139 137,010 157,561 181,195 208,375 Interest 3,386 10,971 23,757 34,381 42,085 51,007 55,779 61,152 67,212 74,055 Payment of loan principal 11,286 36,571 79,191 114,602 140,282 170,022 185,930 203,841 224,038 246,851 Tax 2,888 9,101 19,216 27,184 32,608 38,825 41,813 45,255 49,226 53,813 Buildings 267 – – 267 – – – – – – Vehicles and equipment 622 1,295 218 3,053 2,424 218 – – – – Incremental extension cost 632 993 977 2,042 2,403 1,993 – – – – Incremental research cost 2,025 1,583 1,059 3,548 2,993 1,229 – – – – Cash outflow 38,315 11 7,520 250,611 371,747 456,315 552,455 606,462 671,650 745,710 829,944

Net cash inflow (17,707) (40,673) (15,435) 77,969 213,514 397,506 415,719 437,294 462,852 496,355 Net cash flow, deflated (15,397) (30,754) (10,149) 44,579 106,154 171,853 156,284 142,952 131,571 122,691 a Differences in totals are due to rounding. b US$1 = 11,250 dong, Table 5. Incremental economic cash flow of project (million dong). a,b

Conversion Year factorc 1 2 3 4 5 6 7 8 9 10

Receipts Exports 1.20 7,567 47,692 201,389 427,330 683,468 1,017,222 1,095,497 1,185,696 1,289,737 1,409,922 Loans – – – – – – – – – – Subsidies – – – – – – – – – – Liquidation value (building) 1.09 – – – – – – – – – 252 Liquidation value (vehicles 1.08 – – – – – – – – – 3,196 and equipment) Cash inflow 7,567 47,692 201,389 427,330 683,468 1,017,222 1,095,497 1,185,696 1,289,737 1,413,371 Expenditures Current inputs Fertilizer 1.38 5,664 17,671 36,755 50,967 59,631 68,907 71,663 74,530 77,511 80,611 Pesticides 1.08 2,790 8,703 18,103 25,103 29,371 33,939 35,297 36,709 38,177 39,704 Labor Hired 0.72 2,950 10,177 23,408 35,892 46,435 59,334 68,234 78,469 90,239 103,775 Owned 0.72 4,245 14,645 33,684 51,6493 66,821 85,383 98,190 112,919 129,857 149,335 Interest – – – – – – – – – – – Payment of loan principal – – – – – – – – – – – Opportunity cost of land 1.00 2,888 9,101 19,216 27,184 32,608 38,825 41,813 45,255 49,226 53,813 Buildings 1.09 291 0 0 291 0 0 – – – – Vehicles and equipment 1.08 674 1,403 236 3,308 2,626 236 – – – – Incremental extension cost 0.71 450 707 696 1,453 1,710 1,418 6,434 – – – Incremental research cost 0.71 1,441 1,126 754 2,525 2,130 874 – – – – Cash outflow 21,392 63,534 132,852 198,372 241,332 288,916 321,630 347,882 385,010 427,239

Net cash inflow (13,825) (15,842) 68,537 228,958 442,136 728,305 773,867 837,814 904,727 986,131 Net cash flow, deflated (12,022) (11,979) 45,064 130,907 219,820 314,866 290,925 273,883 257,180 243,757 a Differences in totals are due to rounding. b US$1 = 11,250 dong. Table 6. Risk analysis results table.

Farmer Project

Expected value (million dong) a 4.168 293,100.0 Standard deviation 2,393.22 279.17 Coefficient of variation 0.57 0.95 Minimum value -3,092.15 -472.55 Maximum value 10,941.79 1,106.06 Probability of negative return (%) 5.4 13.4

Expected loss (million dong) 0.064 21,100.0 Expected gain (million dong) 4.232 314,200.0 Expected loss ratio (%) 1.5 6.7 Expected value (limited risk) 4,167.61 293.10

a US$1 = 11,250 dong.

1. Distribution of project net present value (NPV). value of inputs, the foreign-exchange premium, and the economic opportunity cost of public funds. The results (Table 5) indicate that the economic NPV is positive at 549.2 billion dong (US$48.7 million) and that the IRR is 190%.

Risk analysis Four variables were included in the risk analysis: domestic inflation rate, cost of farm inputs, incremental yield, and rice export price. The proportion of farmers adopting the project technology was excluded because Vietnamese rice farmers have been observed to be highly responsive to improved technology. Monte Carlo simulation was applied using RiskMaster and the results summarized (Table 6). The expected NPVs for an individual farmer and the whole project are positive. The probabilities of a negative return are acceptable for both the farmer (5.4%) and the project (13.4%). The distribution of project NPVs is given in Fig. 1.

Costs and benefits of the CLRRI project 319 Table 7. Distributive effects of the project (million dong). a,b

Conversion PVFE PVFE PVEE PVExter factor (13%) (22%) (22%)

Receipts Exports 1.19 2,634,898 1,711,452 2,242,020 530,569 Loans 704,365 – – – Subsidies 21,554 17,991 0 (17,991) Liquidation value (building) 1.09 77 39 43 4 Liquidation value (vehicles and 1.08 979 498 539 42 equipment) Cash inflow 3,361,873 2,210,455 2,242,602 32,147

Expenditures Current inputs Fertilizer 1.08 238,275 166,145 195,886 29,742 Pesticides 1.08 117,360 81,832 96,481 14,649 Labor Hired 348,730 232,499 166,624 (65,875) Owned 501,831 334,571 239,776 (94,795) Interest 221,310 114,143 0 (144,143) Payment of loan principal 704,365 480,476 0 (480,476) Tax 161,329 110,878 110,878 0 Buildings 452 415 452 38 Vehicles and equipment 5,654 4,699 5,090 392 Incremental extension cost 6,240 5,065 5,569 504 Incremental research cost 9,209 7,813 5,560 (2,253) Cash outflow 2,304,755 1,568,535 826,318 (742,217)

Net cash inflow 1,057,118 641,921 1,416,284 774,364 Net cash flow, deflated 363,950 220,596 549,250 328,654

a PVFE, Present value financial at economic discount rate; PVEE, Present value economic at economic discount rate; and PVExter, Present value of externalities. b US$1 = 11,250 dong.

Distributional analysis Distributional analysis of the project (Table 7) is intended to determine what group in society will gain from the benefits of the project. The current project is both financially and economically feasible. Therefore, society as a whole will gain from it. The positive present value externality (PVExter) on exports of 530.6 billion dong (US$47.2 million) is a big gain to the economy. The negative externalities arising from subsidies and loans that accrue to the government are small in relation to this amount.

Conclusions

Based on the financial, economic, distributive, and risk analysis of the rice project, we can make the following four points. The financial NPV is highly attractive to both the intended farmer beneficiaries and the project. The results of the risk analysis indicate that the project NPV is sensitive to change in the price of rice, the inflation rate, the proportion of yield increase from the new technology, and the

320 Mandac et al change in cost of farm inputs. Despite the presence of these risk factors, however, the expected value of the project NPV was positive. The probability of negative returns is low from both the farmers’ and the project’s viewpoint. • The project will result in a net gain to the economy as a result of the foreign-exchange premium. A deterioration in the foreign-exchange premium will reduce the net gain. • The economy is the major gainer in the project. The government loses interest and the principal payments from the loan as a result of the distortion on the economic opportunity cost of funds.

References cited

Amerasinghe N (1986) Financial and economic analysis of projects. Asian Development Bank, Manila, Philippines. Harberger AC (1976) Project evaluation. University of Chicago Press, Chicago. IL, USA. Jenkins G P, Harberger A C (1992) Cost-benefit analysis of investment decisions. Program on Investment Appraisal and Management, Harvard Institute for International Development, Harvard University, Cambridge, MA, USA. Manual. Luat N V (1992) Rice production and research in Vietnam. In Proceedings of Annual Workshop on Rice and Rice-Based Farming Systems Research, Cuu Long Delta Rice Research Institute, Cantho, Vietnam. Sawides S (1987) RiskMaster. Harvard Institute for International Development, Harvard University, Cambridge, MA, USA. Sawides S (1988) Risk analysis in investment analysis. Harvard Institute for International Development, Harvard University, Cambridge, MA, USA. Development Discussion Paper 276.

Costs and benefits of the CLRRI project 321

Strengthening social science research capacity in Vietnam

Nguyen Tri Khiem 1 and P.L. Pingali 2

Abstract. The renewal and liberalization of Vietnam’s rice sector has changed the nature and role of agricultural economics. The economy is gradually shifting from centralized planning to a market economy, a change that will dramatically affect all agricultural sectors, especially rice because it is the largest crop. Vietnamese agricultural economists have started seeking new tools for setting research priorities and determining resource allocation; assessing the ex ante and ex post impact of technological change; and evaluating policy options. With the change to a market economy, curriculum and training programs in economics at Vietnamese universities need renewal and a new direction. IRRI is assisting in this transition in three ways: enhancement of collaborative research activities on resource economics between Vietnamese institutions and IRRI; organization of in-country training programs and study tours for Vietnamese scholars and administrators; and improvement of in- country and regional research information exchange through the formation of the Vietnam Society of Agriculture and Forestry Economics.

Vietnam, once a major rice-exporting country, was a net importer of rice for most of the past two decades. The growth in rice output, the primary staple of the people, had fallen short of population growth. The poor performance of the Vietnamese rice sector could be attributed to the historically low farmers’ incentives for increasing production and productivity. Rice yield and production, which were almost stagnant in 1976-80, grew at the rate of 3.23% and 3.41% per year, respectively, in 1981-87, and 2.05% and 5.02% per year, respectively, in 1988-92. Several measures have been taken recently to liberalize agricultural production in Vietnam. In 1982, Vietnam started a new policy of agricultural production — the household “contract system.” The production “contract system,” which is similar to the household “contract responsibility system” introduced in China in 1979, allows individual households to cultivate land independently (rather than as members of working groups) and to be responsible for providing a contracted amount of output to the state. However, the most dramatic policy changes took place in 1988 and early 1989 and resulted in liberalizing all input and output marketing and in allowing households to maximize their outputs and incomes. These changes will enhance the utilization of, and potential benefits from, modern rice technology. The renewal and liberalization of Vietnam’s rice sector has changed the nature and role of agricultural economics and created an urgent demand for social scientists with market-economy training. Economics is gradually shifting from the demands of centralized planning to the interpretation of market signals. This change in direction will dramatically affect all agricultural sectors, especially rice, because it is the largest crop. Vietnamese agricultural economists have started seeking new tools for setting research priorities and determining resource allocation, assessing the ex ante and ex post impact of technological change, and evaluating policy options. IRRI is well placed to assist in this

1 University of Cantho, Cantho, Vietnam; 2 International Rice Research Institute. P.O. Box 933, Manila 1099, Philippines. transition because it has a strong history of microeconomics research, knowledge of Asian economies, and a network of Asian economists with similar experiences. Through a project funded by the International Development Research Centre of Canada (IDRC), IRRI is undertaking activities aimed at improving the understanding of agricultural and resource economics concepts and methods by Vietnamese academic and governmental organizations and at incorporating this knowledge into research priority setting and assessment of the impact of changes in technology and policy. This work is done through three avenues: • Enhancement of collaborative activities in research on agricultural economics between Vietnamese institutions and IRRI; • Organization of in-country training courses in resource economics and social science methods; and • Improvement of in-country and regional research-information exchange through the formation of the Vietnam Society of Agriculture and Forestry Economics (VSAFE). The net result will be to improve in-country coordination of research efforts, to focus efforts in human-resource development, and to increase financial support for research conducted by Vietnamese universities and research centers.

Collaborative research activities

Annual farm surveys have been conducted since 1989 on the same set of households of 120 rice farmers in the Mekong River Delta and 207 rice farmers in the Red river Delta. The survey was not only designed as a collaborative research venture between IRRI and Vietnamese research institutions but also as on-the-job training for Vietnamese research staff. On the research side, these surveys add up to a 5-yr data set, covering 10 consecutive cropping seasons, on farm characteristics, rice-production practices, and farmers’ responses to recent reform policies and changes in institutional arrangements. Farm households in the Mekong River Delta were sampled in three villages representing three production environments. Thanh Thang village, located in the former deepwater rice area, has recently shifted to two crops of modern rice varieties. Thoi Thuan village represents highly intensive rice- production areas. The third village, Phuoc Thoi, which has a very high population density in Hau Giang Province, represents areas where rice is intensively multicropped with upland crops. Sample farm households in the Red River Delta were taken from five cooperatives representing different levels of collective management. On the training side, two training courses on farm-data collection and analysis were incorporated with the farm-survey research. Most of the trainees participating in the courses subsequently joined the annual survey. The surveys generated a very powerful microlevel data set on rice production in Vietnam and is available to Vietnamese researchers as well as to scholars doing graduate work at IRRI and the University of the Philippines at Los Baños (UPLB). The historical and current patterns of mechanization in rice production in Vietnam, including demand-factor analysis and impact assessment, were studied by a researcher of the University of Agriculture and Forestry (UAF) in Ho Chi Minh City. Results of the study were presented in her master’s thesis at UPLB in August 1992 (Tam 1992). A study on rice-market channels and rice-market integration in the Mekong River Delta was done by a Vietnamese IDRC-supported master’s scholar at UPLB. This analysis was based on surveys of rice farmers in Vinh Long Province, and rice wholesalers, rice retailers, and rice millers in the Mekong River Delta and Ho Chi Minh City. Results of the study were presented in his master’s thesis at UPLB in May 1993 (Kim 1993). Research on market reforms and supply of rice and other food

324 Khiem and Pingali crops in Vietnam from 1976 to 1993 was carried out by an IDRC fellow working on his doctorate at IRRI and UPLB (Khiem 1993). A study of the economics of pesticide use in rice production in the Mekong River Delta was undertaken by another graduate student from the UAF (Thong 1993).

Training activities

Two training courses on farm-data collection and analysis were organized. The first was held at Cantho and at Ho Chi Minh City for 15 researchers from the University of Cantho, the UAF, the School of Economics of Ho Chi Minh City, and the National Institute for Agricultural Planning and Projection (NIAPP). The second course was held in Hanoi for 30 participants from universities and research centers in Hanoi and the northern mountainous provinces. Participants at these courses were trained in sampling methods, questionnaire preparation, questionnaire pretest and editing, farmer interviews, data coding and computer data entry, statistical analysis, and data tabulation. Learning-by-doing methods were used in the courses. Most of the trainees in these courses later participated in the collaborative survey in the Mekong River Delta and the Red River Delta of which the University of Cantho and Hanoi Agricultural University are the lead institutions. Three training workshops on the “Logical Framework Approach to Agricultural Research Project Planning” were conducted. The first course at the UAF in Ho Chi Minh City, 11-21 May 1992, was attended by 21 senior agricultural researchers from the UAF, the University of Cantho, the School of Economics of Ho Chi Minh City, Hanoi Agricultural University, Hue Agricultural University, Bac Thai Agricultural University, the Institutes of Agricultural Sciences in Hanoi and Ho Chi Minh City, and VSAFE. The second course was held at the National Economics University in Hanoi, 19-25 Apr 1993, for 25 senior researchers and administrators from that university and from the State Planning Commission, the NIAPP, and the Institute of Agricultural Economics of the Ministry of Agriculture. The third course was organized at the University of Cantho, 22-30 Nov 1993, for 20 researchers from the provinces in the Mekong River Delta. A manual in Vietnamese of the logical framework (Logframe) approach was compiled by participants and printed for distribution. Outputs from these three Logframe workshops were used to revise the manual, A Logical Framework for Planning Agricultural Research Programs (Schubert et al 1991), to reflect the refinements in the Logframe process making it more appropriate to conditions of scarce resources. The revised manual is a powerful self-teaching document in the Logframe approach to planning projects.

Exchange of scientists and study tours

Vietnamese scholars were invited to IRRI to conduct research and write textbooks in Vietnamese to support the national program of curriculum upgrading. Dr. Chu Huu Quy, chief economist of the Central Economic Commission of the Communist Party, was invited to IRRI to write a book on agricultural policy in transition in Vietnam. Mr. Do Van Xe from the University of Cantho stayed at IRRI for 4 mo to compile a textbook on econometrics to be used in universities in Vietnam. A study tour was organized for the deans of agricultural economics from seven universities and for the executive members of VSAFE to discuss with their Philippine partners the renewal of college curricula for economics. To support the first Vietnam agricultural census, to be conducted in 1994, a trip was organized for the director of the Department of Agricultural Statistics to visit the Philippine General Statistics Office and the Bureau of Agricultural Statistics to learn from Philippine experience.

Strengthening social science 325 Vietnam Society of Agriculture and Forestry Economics

One of the weaknesses of the research system in Vietnam is lack of coordination between universities and research institutions and the minimal information exchange with regional and international counterparts, especially in the field of social sciences. With IRRI’s involvement, organization of VSAFE aims to promote better coordination between Vietnamese research and training institutions. The first symposium of the Society was held in Hanoi in December 1991 and was attended by 80 delegates from universities and agricultural research centers in the northern and southern regions, with the theme of “Renovation of Training and Research on Resource Economics in Vietnam Today.” Government approval has been granted to the Society, and a president and a nine-member board of directors have been chosen. A quarterly journal was started in 1992, and the second symposium of the Society was held in Hue in December 1992 with the theme of “Reformation of Training Programs of Agricultural Resource Economics in Vietnamese Universities.” The report of this symposium was submitted to the Ministry of Education and steps have been taken to adopt the new curriculum at the major universities. Lack of qualified teaching staff to implement this new training program was unanimously expressed by the delegates during the symposium. The third symposium was held in Hanoi in December 1993 to further strengthen the status of the Society in influencing the central government in training and research policies in social sciences.

References cited

Khiem N T (1993) Food production systems in transition: the case of Vietnam. Ph D dissertation, University of the Philippines at Los Baños, College, Laguna, Philippines. Kim H M (1993) Rice market channels and market margin in the Mekong Delta. Master’s thesis, University of the Philippines at Los Baños, College, Laguna, Philippines. Schubert B, Nagel U J, Denning G L, Pingali P L (1991) A logical framework for planning agricultural research programs. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. Tam P T G (1992) Identification of mechanization needs in rice production in Vietnam. Master’s Thesis, University of the Philippines at Los Baños, College, Laguna, Philippines. Thong L Q (1993) An economic analysis of pesticide use in rice production in the Mekong Delta. Master’s Thesis, University of the Philippines at Los Baños, College, Laguna, Philippines.

326 Khiem and Pingali Vietnam-IRRI collaboration in training: progress and priorities in human resource development

E.L. Matheny, 1 R.T. Raab, 1 and Vo-Tong Xuan 2

Abstract. Although Vietnamese rice scientists have been trained at IRRI since 1964, 90% of them have attended training activities since 1981. More than 60% of IRRI- trained Vietnamese scientists have been affiliated with northern institutions. However, most of them have attended short-term group and on-the-job training, whereas most from southern institutions have taken master’s of science and doctoral degree training at IRRI in association with Philippine universities. There also have been numerous in- country training activities in Vietnam, some with IRRI assistance but many initiated and implemented by national program scientists. To facilitate future Vietnam-IRRl collaboration in training, a 2-wk training needs assessment was conducted in Vietnam and a Vietnam-IRRI collaborative training plan developed. The plan is based on jointly identified training needs of Vietnamese scientists and on IRRI’s mandate and specialization in rice science. The training plan emphasizes opportunities for Vietnamese scientists in specialized degree or nondegree training and information sharing programs at IRRI headquarters as well as Vietnam-IRRI collaboration for in- country training activities in Vietnamese.

IRRI's training program goal is to increase the capabilities of national rice scientists through degree and nondegree training opportunities and group training courses. Group training is complemented and supported with training materials that document technical content information in multimedia formats that can be readily revised, adapted, and translated. IRRI assists in carrying out these activities to meet specific in-country training needs of national rice scientists.

Collaboration to present Training at IRRl headquarters From 1964 through May 1994, a total of 362 Vietnamese scientists (23% women) completed training in the Philippines with various kinds of support from IRRI. Of these scientists, 90% (325) have been trained at IRRI since 1981 (Table 1). More than 60% of the Vietnamese scientists who have been trained at IRRI were affiliated with institutions in northern Vietnam (Table 2). About twice as many northern scientists as southern scientists have attended either group courses or on-the-job training (OJT) activities at IRRI. However, most degree scholars and research fellows at IRRI have come from southern Vietnam (29 versus 12 from the north). Institutional data for 14 of the Vietnamese participants trained at IRRI are not available. In addition to those who have completed their training, nine master’s of science and three doctoral candidates were conducting thesis research for their degrees at IRRI as of May 1994.

1 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines, 2 University of Cantho, Cantho, Vietnam. Table 1. Vietnamese scientists trained at IRRI, by category and year.

Year MSc PhD Research Nondegree Group Total Sex % fellow and on- training female the-job Male Female training

1964 4 4 3 1 25 1965 1966 1 1 2 1 1 50 1967 1968 4 4 2 2 50 1969 1 4 5 4 1 20 1970 4 4 4 0 0 1971 1 1 1 0 0 1972 1973 1 2 3 2 1 33 1974 1 1 1 2 5 4 1 20 1975 1 1 2 2 0 0 1976 1 1 2 2 0 0 1977 1 1 1 0 0 1978 1 1 2 4 4 0 0 1979 1980 1981 1 8 9 7 2 22 1982 1 6 17 24 19 5 21 1983 1 6 13 20 17 3 15 1984 2 14 16 12 4 25 1985 2 3 22 27 21 6 22 1986 1 3 21 25 18 7 28 1987 1 9 16 26 21 5 19 1988 4 14 18 13 5 28 1989 1 10 23 34 25 9 26 1990 2 1 6 22 31 28 3 10 1991 2 1 5 12 20 17 3 15 1992 4 12 16 32 22 10 31 1993 9 2 9 18 38 26 12 32 May 1994 3 1 1 5 3 2 40

Total 27 9 7 87 232 362 279 83 23

Vietnamese scientists trained at IRRI have been awarded IRRI scholarships or scholarships provided through various IRRI projects with financial assistance coming mainly from the Australian International Development Assistance Bureau (AIDAB), the International Development Research Centre of Canada (IDRC), and the United Nations Development Programme (UNDP).

In-country training In addition to training Vietnamese scientists at IRRI, numerous training activities have been conducted in Vietnam with support and assistance from IRRI and various donor projects (Table 3). Complementing IRRI-supported training, rice-related training has been conducted in Vietnam, since 1988, by provincial and district level agricultural departments and by agricultural education and research institutions in the country. Objectives of this training have been to teach district and village level cadres how to advise farmers on improved production methods for high-yielding rice varieties.

328 Matheny et al Table 2. Numbers of Vietnamese scientists trained at IRRI, by institute and category, 1964 to May 1994.

MSc PhD Research Nondegree Group Total fellows and on-the- training job training

Northern institutions Ministry of Agriculture and Food Industry, Hanoi 1 1 1 16 37 56 Vietnam Agricultural Sciences Institute, Hanoi 1 – – 9 35 45 Institute for Soil and Fertilizers Research, Hanoi – – 1 9 20 30 Food Crops Research Institute, Hai Hung 2 – 1 8 13 24 National Plant Protection Research Institute, 1 1 – 1 14 17 Hanoi Agricultural University, Hanoi – – – 1 9 10 Research Center for Agricultural Genetics, – – – 2 5 7 Hanoi Vietnam Institute of Agriculture Engineering, – – – – 5 5 Hanoi Agriculture Publishing House, Hanoi – – – 4 – 4 Department of Agriculture Development, 1 1 – 1 – 3 Mekong Secretariat, Hanoi Central Seed Agency, Hanoi – – – 2 1 3 Industrial Crops Research Institute, Hanoi – – – – 2 2 National Institute for Agricultural Planning and – – – – 2 2 Projection, Hanoi Agriculture Science and Technique Journal, – – – 1 – 1 Hanoi Center for Agriculture Mech and Elect, Hanoi – – – – 1 1 Institute for Water Resources, Hanoi – – – – 1 1 Institute of Agricultural Mechanization. Hanoi – – – – 1 1 Agricultural Economics Research Institute, – – – – 1 1 Hanoi All northern institutions 6 3 3 54 147 213

Southern institutions Cuu Long Delta Rice Research Institute, Cantho 5 – 1 16 26 48 University of Cantho, Cantho 6 3 1 12 21 43 University of Agriculture and Forestry, Ho Chi 5 1 – 2 14 22 Minh City Institute of Agricultural Technology, Nguyen 1 – – – 6 7 Binh Khiem D rectorate of Research, Ho Chi Minh City – 1 – – 2 3 National Crops Testing and Training Center, My 1 – – – 1 2 Tho Consultant People's Committee, Vinh Long 1 – – – – 1 Fertilizer Company, Ho Chi Minh City 1 – – – – 1 University of Dalat, Dalat – 1 – – – 1 National Agriculture Center, Ho Chi Minh City – – 1 – – 1 Agriculture Service, Tan An City, Long An – – – – 1 1 Directorate of Agricultural Affairs, Ho Chi Minh – – – – 1 1 City Dong Tam Cooperative, Ho Chi Minh City – – – – 1 1 National Extension Service, Ho Chi Minh City – – – – 1 1 Provincial Seed Company, Tien Giang – – – – 1 1 Rice Service, Ho Chi Minh City – – – – 1 1 All southern institutions 20 6 3 30 76 135 lnstitutions not identified 1 1 3 9 14

Total 27 9 7 87 232 362

Collaboration in training 329 Table 3. Training activities conducted in Vietnam with assistance from IRRl scientists, 1989-94.

Title IRRl Dates Site b Number and type of staff a participants b

Data collection and analysis SSD 9-29 Oct 1989 Cantho and Ho 15 lecturers and Chi Minh City researchers

Oct 1990 Hanoi 28 lecturers and researchers

Logical framework (Log-Frame) SSD 11-21 May 1992 Ho Chi Minh City 23 researchers and for agricultural research project academicians planning

19-25 Apr 1993 Hanoi 30 researchers, academicians, and administrators

Agricultural project planning and SSD 20-30 Nov 1993 Cantho 25 researchers and evaluation with Log-Frame administrators approach

Presentation skills development TC 15 Apr-4 May 1993 CLRRI, Cantho 25 researchers and course extension trainers

Farm equipment production AED 30 June 1993 CLRRI, Cantho Manufacturers, farmers, and administrators

Identification of beneficial EPPD 21-22 Oct 1993 CLRRI, Cantho 6 researchers arthropods of rice in nonrice habitats

25-29 Oct 1993 IAS, Ho Chi Minh 3 researchers City

Farming systems research and TC 22 Feb-6 Mar 1993 Cantho 28 farming systems extension researchers

In-situ hydraulic conductivity SWS 23 Nov-4 Dec Ho Chi Minh City 2 researchers and 2 measurement in dry-seeded 1993 support staff and wet-seeded rice area

Using the IRRl-developed insect EPPD 14-26 Sep 1992 Ho Chi Minh City 8 researchers of IAS sampling device and CLRRI, and CLRRI Cantho

Extension course development TC, 10-15Jan 1994 CLRRI, Cantho 12 extension trainers IPMO and 3 consultants

a SSD, Social Sciences Division; TC, Training Center; AED, Agricultural Engineering Division; SWS, Soil and Water Sciences Division; EPPD, Entomology and Plant Pathology Division; and IPMO, International Programs Management Office. b CLRRI, Cuu Long Delta Rice Research Institute; and IAS, Institute of Agricultural Science of South Vietnam.

Provincial and district courses use a variety of popular rice production texts, posters, and slide sets, and some have used translated materials from IRRI’s Training Manual for Rice Production and other IRRI publications. Nondegree rice related training in Vietnam’s provinces could be further enhanced through improved coordination by the Ministry of Agriculture and Food Industries (MAFI), additional financial

330 Matheny et al support from the central government, and development of training specialists. With the exception of a few trainers trained by IRRI, most Vietnamese trainers are ordinary agricultural graduates and few agricultural institutions and universities have specially trained “trainers” for rice based training courses.

Opportunities for future collaboration

To gain a better perspective of human resource development capabilities and future needs of Vietnamese scientists engaged in rice related research and training, a 2-wk training needs assessment was conducted in Vietnam by two IRRI training specialists and a training plan developed. The training needs assessment entailed visits to major Vietnamese research institutes and universities that are involved in rice and rice based farming systems research. Discussions were held with key administrators, researchers and trainers, and university personnel concerning national and institutional rice related research priorities; human, physical, and fiscal institutional resources needed to accomplish these; and strategies to strengthen and develop human resource capabilities to address national program needs. Observations and needs The last decade has witnessed a great leap in food production in the entire country and Vietnam is currently the world’s third largest exporter of rice. The Resolution of the Sixth National Congress of the Vietnamese Communist Party in 1986 was a major factor in this achievement; however, it is the Vietnamese rice scientists and farmers who are principally responsible for this impressive record. During this training needs assessment, it became apparent that these gains were accomplished despite great difficulties and with limited human, physical, financial, and informational resources. Described below are observations related to current and future constraints of many Vietnamese scientists, and areas that need to be addressed to sustain this accelerated agricultural growth in the country. English. A major need for Vietnamese scientists is access to available information sources, for example, from the International Agricultural Research Centers (IARCs) and from international universities and research institutions, of which most is published in English. Also, English proficiency is a prerequisite for international research and training opportunities. Master’s and doctoral degree training. With few exceptions, most scientists at research institutes and universities have only bachelor’s degrees. Postgraduate degree training is vital to enable them to conduct quality research and to offer instruction at the level of available technologies. Officials are acutely aware that opportunities in the nonagricultural private sector during the next decade may preclude interest among highly qualified students to enter agriculture related disciplines, and declining enrolments are already being noted. For university students continuing to choose agricultural careers, the quality of their education will be largely dependent upon the qualifications and knowledge of the faculty, institutional resources available for students’ training, and revised curricula to meet demands of the evolving job market. A critical need in Vietnam is for higher degree training. In the short term, this need appears to be greater for scientists affiliated with northern institutions. However, future attraction from more lucrative employment opportunities in the private sector may erode the current core of highly trained scientists from both the south and the north. Research skills training. In addition to long-term degree training, short-term skills training in various areas and topics can expose selected Vietnamese scientists to new research tools and methods and better prepare them to address national agricultural program needs. This can be accomplished through group training courses and specifically designed OJT and refresher training at IRRI headquarters.

Collaboration in training 331 Research resources. Discussions with key scientists throughout the country during this mission indicated that most agricultural universities and research institutes are hindered by inadequate physical and financial resources in addition to human resource development needs. This is particularly evident in northern Vietnamese institutions that have had considerably less exposure to external sources of training, information, and funding than some institutions in the south. Most research institutes and universities lack the necessary equipment to conduct relevant research and to collaborate with international agencies and the need exists for computer hardware, software, and training in available information technologies. Program and project management. The shift from the former centrally planned programs to a more client driven, market oriented system is placing new and unprecedented demands on institutional administrators and research leaders. A perceived proliferation of development assistance projects in the country will compound their already difficult tasks. Most officials are acutely aware of this situation and recognize the need for increased skills and knowledge in managing research, extension, and development projects and programs. Information dissemination. There is a paucity of available published information dealing with agricultural topics, both in national research and educational institutions and in provincial, district, and village agricultural offices. Information sources need to be developed locally or translated from existing international sources and a national coordinating mechanism (for example, a Vietnamese farming systems research and extension network) is needed to disseminate information to appropriate end-users. Extension training. Many staff members in research institutes and universities are involved in extension activities and are aware of the importance of disseminating information and assessing farmers’ problems and situations. Because of the recent shift in government policies, many previously used extension methods are no longer feasible; thus, training is needed for researchers involved with extension workers, for extension personnel at all levels, and for farmers. Economic planning and management. Recent national policy changes dictate a continued emphasis on economic planning and management at both the macro and micro levels. In this climate, policymakers, economic planners and managers, agricultural scientists, and extension workers need to be knowledgeable about, and guided by, contemporary economic principles. Suggested role for IRRl The identified needs are large and diverse and IRRI has neither the mandate nor the expertise to address all these issues effectively. It is recognized that extensive human resource and institutional development efforts are essential to sustain agricultural productivity in Vietnam. However, such projects are beyond the scope and potential expected funding of the developing Vietnam-IRRI collaboration. As IRRI’s research program evolves to more strategic and ecoregional foci, future Vietnam-IRRI collaboration in training activities should provide Vietnamese rice scientists with help in three areas: Specialized training at IRRI headquarters in degree, short-term group, and OJT that parallels IRRI’s strategic shift in research activities and objectives; Information sharing opportunities that expose selected scientists and leaders to IRRI’s on-going research and comprehensive collection of rice related literature, training, and information programs, with opportunities for Vietnamese scientists to make selected materials available to a wider national audience through translation and in-country dissemination; and Collaborative activities for Vietnam–IRRI in-country training to strengthen research capacities by training critical masses of scientists from national institutions; some of the needed in- country training will require participation by specialists from other international organizations.

332 Matheny et al Vietnam-IRRI collaborative activities on agricultural engineering

Pham Van Lang 1 and G.R. Quick2

Abstract. Collaboration between the Vietnam Institute of Agricultural Engineering (VIAE) and Agricultural Engineering Division at IRRI over the past 10 yr is described. VIAE has received reference materials and technical drawings on several prototypes from IRRI. The prototypes developed by IRRI are, generally, suitable for Vietnamese conditions because they we simple to operate, low-cost, and easy to fabricate in small-scale shops, Scientists and other staff from VIAE have received training at IRRI or through in-county courses. Several recommendations are made.

Over the past 10 yr, collaboration between the Vietnam Institute of Agricultural Engineering (VIAE) and the Agricultural Engineering Division (AED) at IRRI has been promoted. Several items of engineering technologies developed by IRRI have been adopted and applied in Vietnam, aside from the success of the axial-flow thresher, launched in 1975 in the Mekong River Delta. Before 1990, because of limited funding and emphasis on other issues for agricultural development, several joint projects between VIAE and IRRI on research and development of appropriate engineering for rice production were prepared and discussed but could not be initiated. However, several activities with VIAE have been completed since 1990.

Exchange of scientific materials

VIAE has received reference materials and technical drawings on several prototypes from IRRI through trainees taking courses at IRRI as well as through other channels - for example, those for an axial- flow pump, a rice transplanter, an axial-flow thresher, and a power tiller. In addition, publications and other information on agricultural mechanization in developing countries have been received. VIAE has also sent to AED documents describing the development of mobile farm power sources for Vietnamese agriculture for the last decade of this century and literature on the method for determining farm tractor sizes for agriculture.

Exchange of scientists and training

Two scientists in agricultural engineering participated in the workshop on strengthening research, extension, and training capabilities in mechanization engineering for rice in Asia. Each year, one trainee participated in a short engineering training course held at IRRI. Since 1988, two engineers from VIAE have obtained master’s degrees and two engineers have taken part in short courses on agricultural engineering. These trainees have effectively applied the results of their

1 Vietnam Institute of Agricultural Engineering; Phuong Mai, Dong Da, Hanoi, Vietnam; 2 International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines. training to research and development and to the extension of improved technologies for rice production in Vietnam. In 1993, a visit by Dr. G.R. Quick to VIAE allowed the staff there to discuss their experience in applying IRRI prototypes in Vietnam and discuss mechanization of rice cultivation in Vietnam and other developing countries.

Applying IRRl’s appropriate technologies

Based upon the technical drawings obtained through various channels from IRRI, several machines and implements have been selected for manufacture — for example, a 4-HP two-wheeled power tiller, the Hydro Tiller, the axial-flow pump, the cono-weeder, and the axial-flow thresher. The axial-flow pump proved most effective for rice irrigation and drainage in northern Vietnam. With modifications to the prototype by VIAE staff, several thousand units of the axial-flow pump, both vertical and horizontal types, of a range of sizes (3, 7, 14, or 33 kW) have been released for use in the Red River Delta. In addition, about 20 units of the 4-HP power tiller and 15 units of the floating power tiller have been adopted by farmers in this region since 1989. In the Mekong River Delta, with IRRI’s assistance, the IRRI Hydro Tiller has been introduced to meet the needs of the southern farmers for equipment for soil puddling and weeding specifically on the acid sulfate soils. Engineer Herbert Manaligod from AED, in collaboration with the University of Cantho, demonstrated the Hydro Tiller at four locations and provided a training course for 12 Vietnamese engineers in the region. A workshop on equipment for rice cultivation was also held after the course. Recently, the IRRI rice-husk combustor was modified and improved for rice and maize drying with increased capacity and better performance. This work continues.

Recommendations

In general, the machinery designs for rice production developed by IRRI are, with some modification, very relevant under Vietnamese conditions because of they are simple to operate, low-cost, and easy to fabricate in small shops. Collaborative activities during the past 10 years between IRRI and VIAE have given good results. However, the activities are still constrained and cooperation in this field should be developed and promoted. IRRI should continue to send available technical drawings of recently released prototypes, publications, and even the prototypes themselves to VIAE to promote the development, manufacture, and application of improved technologies for rice cultivation and processing in Vietnam. IRRI should continue to offer short- and long-term training courses and opportunities for Vietnamese scientists in agricultural engineering to participate in workshops to get experience from IRRl and other countries.

334 Lang and Quick Workshop output

Workshop output

On the final day of the conference, participants were asked to identify priorities for Vietnam-IRRI collaboration over the next 5-10 yr. Based on an assessment of past progress in rice research, the emerging problems and opportunities, and Vietnam’s agricultural policy priorities, it was decided to focus the discussions on three major ecological conditions: Intensive systems (Red River and Mekong River deltas); Uplands; and Flood-prone and problem-soil areas. In addition, the topic of “Varietal improvement and genetic conservation” was identified as an area of collaboration of high priority to Vietnam and IRRI. Small working groups of Vietnamese and IRRI scientists identified key constraints, research priorities, and potential collaborative projects. Summaries of their outputs follow.

Intensive systems

Problems The central challenge identified by the Intensive Systems working group was how to sustain rice yield increases in intensive rice-based systems — particularly those in the Red River and Mekong River deltas. Problems and issues that relate to sustainability were identified (Table 1). From this analysis, a project concept was outlined.

Title “Sustaining rice yield increases in intensive rice-based systems in Vietnam.”

Goal Intensive rice-based farming systems that generate sustainable farm income with no symptoms of yield decline or declining factor productivity, and with high output–input ratios.

Objective To develop sustainable, gender-neutral, and environment-friendly crop- and pest-management technologies by conducting research on nutrient–pest interactions at pilot sites in the Red River and Mekong River deltas.

Outputs Quantified yield potential in Red River and Mekong River deltas; Integrated pest and nutrient management to increase yield and input efficiency; Increased knowledge of the role of farmers (male and female) and the farming system in pest management; Improved nutrient uptake by rice for reducing pest damage and for increasing yield; Management strategies for durable pest resistance that account for varietal diversity, crop nutrition, cultural techniques, and integrated pest management (IPM); Improved technology transfer mechanisms from researcher to farmer; Quantified nutrient balances for present and future productivity levels; and Standardized data-sets for pests, crop nutrition, and soil-fertility experiments.

Expected impact of outputs Average annual increase of 3% in rice yields; More stable rice yields; Table 1. Problems and issues relating to sustaining rice yield increases in intensive rice-based systems.

Reducing negative Exploiting Increasing value in Direct-seeding Intensification: severe Nutrient-use Lack of externalities linkage to non- rice production technologies nutrient and efficiency sustainable pest farm sector disease/insect management interactions

Environmental Changes in Applied appropriate Lodging in Intensification changes Fertilizer No sustainable problems relative prices equipment and tech- direct soil quality (negative) efficiency resistance to involved with and profits nologies for irrigated seeding rice blast and high versus nonrice farming-systems for Plant protection prob- Potential supply brown plant- intensification crops improving labor Weed control in lems increase with of potassium hopper strength (men and direct intensification: blast, from soil Impact of tech- Changes in women) and for seeding sheath blight, brown Nonintegrated pest nology on envi- gender roles stable production planthopper, possible Imbalance in management ronment and emergence of new nutrition system for rice farmers’ health Nutrition, cooking, and disease diseases and milling quality Straw burning: insect pests Impact on employ- Factor contributing to how to use it ment and Poor postharvest yield gaps in better Low efficiency of income in non- technologies for rice intensive systems pest control farm sector Plant nutrition Poor understanding of problems Lack of resistant intensification on varieties nutrient-pest interaction Poor collection of pest data Reduced risks to farmers’ health from agricultural chemicals; Safer, cleaner environment even with intensification; Improved income-generation options; Average yield increased to 5.0 t/ha in intensive rice systems of Red River and Mekong River deltas; Increased output-input efficiency in rice systems; and Improved capacity for research prioritization, monitoring, and evaluation.

Training needs It was agreed that degree training (master’s and doctoral levels) was needed with specialization in soil science, agronomy, entomology, and plant pathology. Also, 12 topics were identified for short-term, nondegree training: Geographic Information Systems (GIS); Rice nutrient management; Data management and processing; Systems analysis and modeling; Soil and plant-nutrient analysis; Durable host-plant resistance; Crop-loss assessment; Biocontrol of pests; Ecology of insect pests and pathogens; Gender analysis; Impact assessment of technology; and Project evaluation.

Collaborating institutions In the Red River Delta: Institute for Soils and Fertilizers Research (ISFR), Hanoi; National Plant Protection Research Institute (NPPRI), Hanoi; Vietnam Institute of Agricultural Engineering (VIAE), Hanoi; Hanoi Agricultural University; National Agricultural Sciences Institute (INSA), Hanoi; Food Crops Research Institute (FCRI), Hanoi; and IRRI. In the Mekong River Delta: Institute for Agricultural Sciences of South Vietnam (IAS), Ho Chi Minh City; University of Agriculture and Forestry, Ho Chi Minh City; Cuu Long Delta Rice Research Institute (CLRRI), Omon; University of Cantho, Omon; Provincial extension services; NPPRI, Mekong Delta station; and IRRI. In the Central Lowlands: Hue Agricultural University; INSA; NPPRI; provincial agricultural departments in Hue and Da Nang; and IRRI.

Uplands

Problems Five broad areas of problems were identified: socioeconomics, environmental and ecosystem level, soils, water, and biotic constraints.

Socioeconomics: Lack of transportation and access to market; increased population pressure; limited or no access to credit; low valuation of traditional knowledge and institutions; lack of appropriate and adequate extension services; lack of documentation (technical as well as socioeconomic); diversity (social and cultural); and low level of education.

Workshop output 339 Environmental and ecosystem level: Diversity; variability; deforestation; erosion; lack of knowledge on the ecology of the uplands; and lack of food security.

Soils: Soil degradation and erosion; low soil fertility; subsoil acidity; low availability of phosphorus and potassium; lack of organic matter; and lack of nitrogen.

Water: Irrigation not available; and drought,

Biotic constraints: Lack of improved (high-yielding) varieties adapted to the diversity and variability of the uplands; limited number of crop species suitable for upland ecosystems; weeds; blast; nematodes; and rice bugs.

Priorities Five areas for priority action were listed: documentation, erosion, soils, drought, and pests and diseases.

Documentation: Knowledge on biodiversity, sociocultural diversity, and environmental diversity.

Erosion: Land management and sociocultural components.

Soils: Organic matter; phosphorus; and soil acidity.

Drought: Varietal response; and agronomic management.

Pests and diseases: Weeds; blast; nematodes; and rice bugs.

Title “Uplands for life in Vietnam.”

Outputs Outputs from the proposed project were assumed to fall into three areas: ethnobotanical study of upland ecosystems; varietal improvement; and new tools for ecosystem management.

Ethnobotanical study of upland ecosystems: Potential for in situ conservation estimated; crop species of potential use and market value identified; traditional cultivars and wild rice species collected; and indigenous varietal and technical knowledge (how and why of varietal choice and cultural practices) documented.

Varietal improvement: Evaluation of traditional cultivars collected during the ethnobotanical survey; and identification of traditional cultivars tolerant to drought and phosphorus-deficient soils, resistant to blast and nematodes, tolerant to soil acidity, and with good competitiveness for weeds.

New tools for ecosystem management: Crops, hedgerows, and cover-crop species tested and evaluated for their efficiency in protecting the soil surface from erosion and preventing pest and disease buildup; appropriate cropping systems including integration of livestock, fish, and pest and disease management developed; management practices of crop residues tested and evaluated for their effects on the long- term management of organic matter and phosphorus; and new weeding tools developed.

Expected impact of outputs • Improved productivity in the uplands, which represent 75% of the land in Vietnam;

340 Workshop output • Improved life for minority groups; • Prevention of deforestation; • Prevention of soil degradation and soil erosion; • Prevention of siltation in the lowlands; • Biodiversity conserved (traditional varieties and wild rice species); • Traditional knowledge conserved; • Stability of production and food security improved in the uplands; and • Sustainability of the uplands improved.

Training priorities • Ethnobotanical and social research; • Participatory rural appraisal; • Land characterization; and • Upland rice breeding and varietal selection.

Collaborating institutions • For the Central high Plateaux, the University of Tay Nguyen; • For the Northern Mountain Region, the University of Agriculture, Bac Thai; and IRRI.

Flood-prone and problem-soil areas Problems The dominating factors in the flood-prone and problem-soil ecosystems are soil type and distribution of water — both drought and excess. Problem soils are of two major types: acid sulfate soils in the Mekong River Delta and degraded soils in the Red River Delta. We are concerned both with availability of nutrients and toxicities related to acidity and salinity. Water-related problems concern availability in the dry season, the extent and severity of flooding in the latter part of the wet season, salinity, and pollution.

Priorities Soil and water factors are closely related to Vietnam’s on-going rice breeding program, which will continue with inputs from IRRI at Los Baños for modern varieties and from Thailand for deepwater rices. Project identification Apart from plant breeding inputs, the three main areas of research given priority were soil management, efficiency of water use, and improved cropping systems. Within each of these areas, outputs, training needs, resources, and collaborating institutions differ. Soil management Research outputs • Acid sulfate soils: fertilizer management for different types of acid sulfate soil, particularly use of phosphorus; toxicity thresholds for rice and screening for phosphorus efficiency and iron and aluminum toxicity; and improved soil analysis for studies of acid sulfate soils. • Degraded soils: Organic matter management and sustainable agriculture on podzolic, grey, degraded soils; reduced inputs such as ash and other materials for improving soil physical properties; potassium management and nitrogen use efficiency; and research technology for high 15 N recovery in studies of nitrogen balance.

Workshop output 341 Training needs • Soil fertility evaluation; • Soil and plant analysis; and • Modeling skills for nutrient and water balances. Resource needs • 15 N fertilizers and analysis of these materials and budgets for field research. Collaborating institutions • Institutes of Agricultural Science (IAS and INSA); • University of Cantho; • Cuu Long Delta Rice Research Institute (CLRRI); • National Institute for Agricultural Planning and Projection (NIAPP); Institute of Soils and Fertilizers Research; and • IRRI.

Efficiency of water use Research outputs • Analysis of climate (including use of GIS techniques) to determine potential for different alternatives under rainfed and flooded conditions; • Upland crops in rotation with rice in single-rice cropping areas to increase water-use efficiency; Improved methods for conservation and use of rainwater in rainfed rice areas; and • Appropriate leaching of acid sulfate soils. Training needs • Weather data analysis; • GIS techniques; and • Soil and water modeling. Resource needs • Expertise from IRRI; funds; and equipment for field research. Collaborating institutions • Departments of Water Management of the universities of Cantho and of Agriculture and Forestry; • Computer Center of the Ministry of Agriculture and Food Industry; and • IRRI.

Improved cropping systems Research outputs • Rice variety improvement; Crop diversification in combination with fisheries and forestry; • Rice-fish cropping systems in rainfed areas of the Mekong River Delta; and • Rice, soybeans, and winter crops in the Red River Delta. Training needs • Systems analysis and training skills. Collaborating institutions • INSA; • CLRRI; • University of Cantho and • IRRI.

342 Workshop output Impact • Improved nutrient management and sustainable rice-based cropping systems on degraded and acid sulfate soils; • Improved methodologies for extrapolation of results and recommendations for use of acid sulfate soils; • Minimized contamination of the environment due to soil-, water-, and fertilizer-management practices; • Improved economic returns for farmers; and • Better quality of life for rural families.

Genetic conservation and varietal improvement

Problems Genetic conservation • Incomplete collection; • Inadequate characterization; • Insufficient data management; and • Inadequate storage facilities for conservation.

Varietal improvement • Stagnant yields in irrigated lowlands; •Biotic stresses — for example, sheath blight, blast, bacterial blight, brown planthopper, stem borer, thrips, and leaffolder; • Abiotic stresses, for example, acid sulfate soils, salinity, and drought (in rainfed lowlands); • Lack of early maturing high-yielding varieties; • Low seed yields of hybrid rices; • Too few parental lines for developing hybrids for Vietnam; • Too few heterotic hybrids suited to Red River and Mekong River deltas; and • Poor grain quality of inbreds and hybrids.

Priorities Genetic conservation • Improvement of germplasm storage facilities; • Collection of new wild and cultivated germplasm; • Characterization and classification of the available germplasm; and • Management of germplasm database.

Varietal improvement • Increasing yield potential by developing new plant type and hybrid rice; • Breeding for biotic and abiotic stresses; • Improving grain quality of inbreds as well as hybrids; and • Improving seed yields of hybrid rices.

Project identification Three projects were identified: • Germplasm collection, conservation, and characterization in rice; • Raising yield potential and improving grain quality of rice; and • Germplasm improvement for biotic and abiotic stresses in rice.

Workshop output 343 Project description Germplasm collection, conservation, and characterization in rice Duration: 3 years. outputs • Improvement of germplasm storage facilities; • Collection of new wild and cultivated rices; • Characterization of the available germplasm; and • Establishment of data-management system. Expected impact • Establishment of modern germplasm storage facility; • 4,000–5,000 additional rices (wild and cultivated) would be added to the germplasm resources of the country; and • Increased research efficiency through available germplasm database. Training needs • Management of germplasm database; and • Use of molecular techniques to characterize germplasm.

Raising yield potential and improving grain quality of rices Duration: 5 years with prospects for continuation to a second phase. outputs • Breeding of high-yielding varieties possessing early to medium maturity and good grain quality; • Breeding high-yielding hybrid rices, adaptable to Red River and Mekong River deltas and possessing acceptable grain quality; • Breeding of genetically diverse parental lines (cytoplasmic male sterility and temperature-sensitive genetic male sterility — CMS and TGMS) to develop hybrid rices; and • Developing hybrid-rice seed-production technology. Expected impact • Increased rice production and productivity; • Meeting the needs of domestic and international customers with varieties of high quality grain; and • Development of a hybrid-seed industry resulting in generation of rural employment opportunities. Training needs • Hybrid-rice breeding and seed production; and • Techniques of grain quality evaluation.

Germplasm improvement for biotic and abiotic stresses in rice Duration: 5 years. Outputs • Understanding of pest variability; • Identification of sources of durable resistance; • Incorporation of stable (durable) resistance to biotic stresses into improved germplasm; • Breeding of lines with tolerance to abiotic stresses; and • Application of biotechnology tools to develop improved germplasm possessing resistance to stem borer and sheath blight.

344 Workshop output Expected impact • Reduced pest problems; • Reduced inputs for pest management; • Improved stability or rice production; and • Improved environment sustainability

Collaborating institutions INSA; CLRRI; • Food Crops Research Institute; • NPPRI; • University of Cantho; and • IRRI.

Workshop output 345

Appendices

Participants

Agriculture and Genetics Research Institute Institute of Agricultural Sciences of South Co Nhue, Tu Liem, Hanoi, Vietnam Vietnam Nguyen Xuan Linh 121 Nguyen Binh Khiem, 1st District, Ho Chi Pham Tuyet Minh Minh City, Vietnam Tran Duy Quy Cong Doan Sat Mai Van Quyen Pham Van Bien Phan Thi Cong Cuu Long Delta Rice Research Institute Omon, Cantho, Vietnam Bui Chi Buu International Rice Research Institute Duong Van Chin P.O. Box 933, Manila 1099, Philippines Nguyen Mnh Chau K.G. Cassman Nguyen Van Luat E.L. Castillo Pham Sy Tan G.C.R. Croome (editorial consultant) Truong Thi Ngoc Chi R.M. Cu G.L. Denning Mahabub Hossain G.S. Khush Food Crops Research Institute Klaus Lampe Tu Loc District, Hai Hung, Vietnam A.M. Mandac Dinh van Cu E.L . Matheny Nguyen Ngoc Ngan T.W. Mew Nguyen Nhu Viet R.M. Nelson Nguyen Quoc Tuan J.L. Padilla Nguyen Tan Hinh H.O. Pinnschmidt Nguyen Thi Then L.M.L. Price Tong Khiem J.C. Prot Truong Van Kinh D.W. Puckridge U. Singh P.S. Teng Hanoi Agricultural University C. Trostle Tran Quy, Gia Lam, Hanoi, Vietnam To Phuc Tuong Cu Xuan Dan S.S. Virmani Ha Hoc Ngo Minoru Yamauchi Nguyen Thi Tram Tran Dinh Dang Vo Hung International Service for National Agricultural Research POB 93375, The Hague 2509 AJ, Netherlands Byron Mook Institute for Soils and Fertilizers Research Chem, Tu Liem, Hanoi, Vietnam Long An Provincial Agriculture Department Bui Dinh Dinh Bureau of Agricultural Extension, National Nguyen Vy Highway 1, Huong Tho Phu Village, Tan An Thai Phien District, Long An, Vietnam Tran Thuc Son Nguyen Thanh Nghiep Ministry of Agriculture and Food industry Postharvest Research Institute Ngoc Ha, Bach Thao, Hanoi, Vietnam 4 Ngo Quyen Street, Hanoi, Vietnam Bui Huy Tuong Le Doan Dien Do Anh Duong Quang Dieu Le Van Bam University of Agriculture and Forestry Ngo The Dan Thu Duc, Ho Chi Minh City, Vietnam Nguyen Cong Tan Nguyen Dang Long Nguyen Ich Chuong Phan Thi Giac Tam Nguyen Ngoc Kinh Tran Van My Nguyen Thanh Huyen Nguyen Thi Bich Nga Nguyen Tien San University of Cantho Phi Manh Hung Cantho, Vietnam Tran Quy Hung Duong Ngoc Thanh Trinh Quang Tuan Le Quang Minh Vu Tuyen Hoang Le Thanh Duong Nguyen Ngoc De Nguyen Thi Thu Cuc Ministry of Education and Training Nguyen Tri Khiem Dai Co Viet Street, Dong Da District, Hanoi, Pham Van Kim Vietnam Vo Thi Guong Than Duc Hien Vo-Tong Xuan Tran Van Nbung

Ministry of Light Industry Vietnam Institute of Agricultural Engineering Foodstuff Research Institute, Trang Thi Phuong Mai, Dong Da, Hanoi, Vietnam Street, Hoan Kiem District, Hanoi, Vietnam Pham Van Lang Ngo Thi Mai Trinh Ngoc Vinh Vu Dinh Phien

National Agricultural Sciences Institute Van Dien, Tu Liem, Hanoi, Vietnam Others invited Bui Huy Hien Dao The Tuan Dang The Truyen Luu Ngoc Trinh Office of the Prime Minister, la Hoang Nguyen Huu Nghia Hoa Tham, Hanoi, Vietnam Nguyen Van Suan Pham Van Chuong Hoang Thi Mai Huong Ta Minh Son Vietnam Foreign Press Center, 10 Le Phung Hien, Hanoi, Vietnam Tran Long Tran The Dang Vietnam Society of Agriculture and National Plant Protection Research Institute Forestry Economics Chem, Tu Liem, Hanoi, Vietnam Dinh Thi Thanh Ha Minh Trung Ngo Vinh Vien Nguyen Cong Thuat Nguyen Thanh Thuy

350 Appendix Acronyms and abbreviations

ACIAR Australian Centre for DAS days after seeding International Agricultural DAST Department of Agricultural Research Science and Technology AED Agricultural Engineering DAT days after transplanting Division, IRRI DMRT Duncan’s multiple range test AGMI Agricultural Mechanization DS delayed split (fertilizer Institute application) AIDAB Australian International DSR dry-seeded rice Development Assistance Bureau DWR deepwater rice ALS agronomist-liaison scientist ASS acid sulfate soil EC electrical conductivity APPA Agronomy, Plant Physiology, EPPD Entomology and Plant and Agroecology Division, IRRI Pathology Division, IRRI AUDPC area under disease- (damage-) ES early split (fertilizer application) progress curve FAO Food and Agriculture BARC Bangladesh Agricultural Organization of the United Research Council Nations BCR benefit-cost ratio FCRI Food Crops Research Institute BMZ Federal Ministry of Economic FNFP farmer's normal fertilizer Cooperation (Germany) practice BPH brown planthopper FROYT Floating Rice Observational BSFR broadcast-seeded flooded rice Yield Trial FRPYT Floating Rice Preliminary Yield CARP Council for Agricultural Trial Research Policy FSR farming systems research CEC cation exchange capacity FSR/E farming systems research and CERES Crop Evaluation through extension Resource and Environment Synthesis FYM farmyard manure CIAT Centro Internacional de

Agricultura Tropical GA3 gibberellic acid (International Center for GATT General Agreement on Tariffs Tropical Agriculture) and Trade CIMMYT Centro Internacional de GIS geographic information systems Mejoramiento de Maiz y Trigo GDP gross domestic product (International Center for Maize GL generalized Leontief (profit and Wheat Improvement) function) CIP Centro International de la Papa GTZ German Agency for Technical (International Potato Center) Cooperation CLRRI Cuu Long Delta Rice Research GWTD groundwater table depth Institute CMS cytoplasmic male sterility IARC international agricultural research center DAE days after emergence IAS Institute of Agricultural DAP diammonium phosphate Sciences of South Vietnam IBPGR International Board for Plant IRDTN International Rice Drought Genetic Resources Tolerance Nursery IBSNAT International Benchmark Sites IRGC International Rice Germplasm Network for Agrotechnology Center Transfer IRGMN International Rice Gall Mdge ICAR Indian Council of Agricultural Nursery Research IRHON International Rice Hybrid ICRISAT International Crops Research Observational Nursery Institute for the Semi-And IRLON International Rice Lowland Tropics Observational Nursery IDRC International Development IRLYN-E International Rice Lowland Research Centre Yield Nursery — Early IDRON International Deepwater Rice IRLYN-M International Rice Lowland Observational Nursery Yield Nursery — Medium IDRYN International Deepwater Rice IRR internal rate of return Yield Nursery IRRI International Rice Research IFRON International Floating Rice Institute Observational Nursery IRSBN International Rice Stemborer IRON International Irrigated Rice Nursery Observational Nursery IRSSTON International Rice Soil Stress IIRYN-E International Irrigated Rice Tolerance Nursery Yield Nursery — Early IRTN International Rice Tungro IIRYN-M International Irrigated Rice Nursery Yield Nursery — Medium IRTP International Rice Testing IIRYN-VE International Irrigated Rice Program (later INGER) Yield Nursery — Very Early IRWBPHN International Rice Whitebacked IITA International Institute of Planthopper Nursery Tropical Agriculture ISFR Institute for Soils and Fertilizers ILR irrigated lowland rice Research INGER International Network for ISNAR International Service for Genetic Evaluation of Rice National Agricultural Research INSA National Agricultural Sciences ITRON International Tidal Rice Institute Observational Nursery IPM integrated pest management IURON International Upland Rice IPMO International Programs Observational Nursery Management Office, IRRI IURYN International Upland Rice Yield IRAT Institut de Recherches Nursery Agronomiques Tropicales et des IURYN-E International Upland Rice Yield Cultures Vivrieres Nursery — Early IRBBN International Rice Bacterial IURYN-M International Upland Rice Yield Blight Nursery Nursery — Medium IRBN International Rice Blast Nursery IRBN-S International Rice Blast LYD leaf-yellowing disease Nursery — Supplemental IRBPHN International Rice Brown Planthopper Nursery JICA Japan International Cooperation RCTN International Rice Cold Agency Tolerance Nursery JLU Justus-Liebig University

352 Appendix MAFI Ministry of Agriculture and PWD ponding water depth Food Industry MARDI Malaysian Agricultural Research RLR rainfed lowland rice and Development Institute RRA rapid rural appraisal MET Ministry of Education and RH relative humidity Training RRD Red River Delta MOA Ministry of Agriculture MOSTE Ministry of Science, SARBON South Asian Rice Boro Technology and Environment Observational Nursery MOU memorandum of understanding SDC Swiss Development Cooperation MRD Mekong River Delta SSP single superphosphate SURE seemingly unrelated regression NARS national agricultural research equation systems NGO nongovernmental organization TGMS temperature-sensitive genetic NIAPP National Institute for male sterility Agricultural Planning and TN Than Nong Projection TP thermophosphate NPPRI National Plant Protection TPR transplanted rice Research Institute NPV net present value UAF University of Agriculture and Forestry OJT on-the-job training UNDP United Nations Development OPECS Office for Project Execution, Programme Coordination and Support USAID United States Agency for International Development PARC Pakistan Agricultural Research Council VSAFE Vietnam Society of Agriculture PBP pay-out or pay-back period and Forestry Economics PCARRD Philippine Council for VIAE Vietnam Institute of Agriculture and Resources Agricultural Engineering Research and Development VIPESCO Vietnam Pesticide Company PFA preventative fungicide application WARDA West Africa Rice Development PI panicle initiation Association

Acronyms and abbreviations 353