R ICE –F ISH C ULTURE

in

C HINA

EDITED BY

Kenneth T. Mackay

Published by the International Development Research Centre

PO Box 8500, Ottawa, ON, Canada K1G 3H9

June 1995

MacKay, K.T.

Chinese Academy of Agricultural Sciences, Beijing CN

Chinese Academy of Fisheries Sciences, Wuxi CN

rice–fish culture in China. Ottawa, ON, IDRC, 1995. 276 p. : ill.

/Rice/,/plant production/,/fish production/,/mixed farming/,/cultivation systems/,/China/ — /appropriate technology/,/ecology/,/economic aspects/,/on-farm research/,/case studies/,/conference reports/, references.

UDC: 633.18:639.2(510)

ISBN: 0-88936-776-0

A microfiche edition is available.

Material contained in this report is produced as submitted to IDRC Books. Unless otherwise stated, copyright for material in this report is held by the authors. Mention of a proprietary name does not constitute endorsement of the product and is given only for information.

Contents

Preface vii Introduction Wang Hongxi ix Part I: Review and Outlook Rice–Fish Culture in China: The Past, Present, and Future Cai Renkui, Ni Dashu, and Wang Jianguo 3 Rice–Fish Culture in China: Present and Future Chen Defu and Shui Maoxing 15 Scientific and Technological Development of Rice–Fish Culture in China Zhang Rongquan 23 Development of Rice–Fish Farming in Guizhou Province Shi Songfa 31 Reforming Rice–Fish Culture Technology in the Wuling Mountains of Eastern Guizhou Province Chen Guangcheng 37 The Development of Rice–Fish Farming in Chongqing City Xu Shunzhi 43 Development of Rice–Fish Farming in Jiangsu Province Xu Guozhen 49 Rice–Fish Culture and its Macrodevelopment in Ecological Agriculture Yang Jintong 55 Value of the Rice–Fish Production in High-Yielding Areas of Yuyao City, Zhejiang Province Cao Zenghao 63 Developing Rice–Fish Culture in Shallow Waters of Lakes Wan Qianlin, Li Kangmin, Li Peizhen, Gu Huiying, and Zhou Xin 67 Part II: Patterns and Technology Different Methods of Rice–Fish Farming Nie Dashu and Wang Jianguo 77 New Techniques for Raising Fish in Flooded Ricefields Wan Banghuai and Zhang Qianlong 85 Methods of Rice–Fish Culture and their Ecological Efficiency Wu Langhu 91 Ridge-Cultured Rice Integrated with Fish Farming in Trenches, Anhui Province Yan Dejuan, Jiang Ping, Zhu Wenliang, Zhang Chuanlu, and Wang Yingduo 97 Development of Rice–Fish Culture with Fish Pits Feng Kaimao 103 Techniques Adopted in the Rice–Azolla-Fish System with Ridge Culture Yang Guangli, Xiao Qingyuan, and He Tiecheng 107 Semisubmerged Cropping in Rice–Fish Culture in Jiangxi Province Liu Kaishu, Zhang Ningzhen, Zeng Heng, Shi Guoan, and Wu Haixiang 117 Rice–Azolla-Fish Symbiosis Wang Zaide, Wang Pu, and Jie Zengshun 125 Economic and Ecological Benefits of Rice–Fish Culture Li Xieping, Wu Huaixun, and Zhang Yongtai 129 Cultivating Different Breeds of Fish in Ricefields Wang Banghuai and Zhang Qianlong 139 Rice–Fish Culture in Ricefield Ditchponds Luo Guang-Ang 147 Techniques for Rice–Catfish Culture in Zero-Tillage Ricefields Chen Huarong 153 Demonstration of High-Yield Fish Farming in Ricefields Cai Guanghui, Ying Yuguang, Wu Baogan, He Zhangxiong, and Lai Shengyong 163 Rice–Azolla-Fish in Ricefields Chen Defu, Ying Hanquing, and Shui Maoxing 169 Part III: Interactions Material Cycles and Economic Returns in a Rice–Fish Ecosystem Ni Dashu and Wang Jianguo 177 Fish Culture in Ricefields: Rice–Fish Symbiosis Xiao Fan 183 Ecological Effects of Rice–Fish Culture Pan Yinhe 189 Ecological Mechanisms for Increasing Rice and Fish Production Pan Shugen, Huang Zhechun, and Zheng Jicheng 195 Rice–Azolla-Fish Cropping System Liu Chung Chu 201 Effect of Fish on the Growth and Development of Rice Li Duanfu, Wu Neng, and Zhou Tisansheng 209 The Role of Fish in Controlling Mosquitoes in Ricefields Wu Neng, Liao Guohou, Lou Yulin, and Zhong Gemei 213 A Comparative Study of the Ability of Fish to Catch Mosquito Larva Wang Jianguo and Ni Dashu 217 Ability of Fish to Control Rice Diseases, Pests, and Weeds Yu Shui Yan, Wu Wen Shang, Wei Hai Fu, Ke Dao An, Xu Jian Rong, and Wu Quing Zhai 223 Distribution and Residue of Methamidophos in a Rice–Azolla-Fish Ecosystem Xu Yinliang, Xu Yong, and Chen Defu 229 Residue and Application of Fenitrothion in a Rice–Fish Culture System Lou Genlin, Zhang Zhongjun, Wu Gan, Gao Jin, Shen Yuejuan, Xie Zewan, and Deng Hongbing 237 Part IV: Economic Effects Economic Analysis of Rice–Fish Culture Lin Xuegui, Zhang Linxiu, and He Guiting 247 Economic Research on Rice–Fish Farming Jiang Ci Mao and Dai Ge 253 Ecology and Economics of Rice–Fish Culture Quing Daozhu and Gao Jusheng 259

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Preface

A National Rice–Fish Farming Systems Symposium was held in China at the Freshwater Fisheries Research Centre of the Chinese Academy of Fisheries Sciences in Wuxi, Jiangsu Province, 4-8 October 1988. The symposium was cosponsored by the Chinese Academy of Agricultural Sciences (CAAS) and the Chinese Academy of Fisheries Sciences (CAFS). Funding was supplied by IDRC through its project Farming Systems (China) (3-P-87-0237).

Researchers from the major Rice–producing areas of China presented papers at this interdisciplinary symposium. The proceedings of this symposium were originally published in Chinese by the Agriculture Publishing House (Beijing). To share this valuable information with researchers and development workers outside China, the proceedings were translated into English. The initial translation was done either by the researchers themselves or by translators with the Agricultural Publishing House. Initial English editing was carried out by Regina Morales, Manila, Philippines. Final technical editing and preparation of the camera-ready copy was undertaken by Michael Graham, MG Science Editing, Writing, and Publishing, Kemptville, Ontario, Canada. In some cases, two or more papers have been combined to remove redundancy.

Kenneth T MacKay

Winsloe

Prince Edward Island

Canada

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Introduction

This symposium on rice–fish farming in China brought together 55 experts and scholars from the Academia Sinica, the Departments of Agriculture and Hydraulics, the Institutes of Aquacultural Research and Education, and the Administration Bureaus. In addition, there were representatives from the International Development Research Centre, Canada, the Network for Aquaculture Centres in Asia (NACA), Thailand, the Freshwater Aquaculture Center, Central Luzon State University, Philippines, and the International Center for Living Aquatic Resources Management.

China has had a long history of rice–fish farming. As rural areas have been industrialized in recent years, rice–fish farming has gained attention because it is an organic method that combines rice and fish production while maximizing labour and ricefield resources. The Chinese Academy of Agricultural Sciences and the Chinese Aquacultural Research Institute organized this symposium, with financial assistance from the International Development Research Centre, to synthesize the rich experiences and skills of Chinese farmers and to improve rice–fish farming as a way to increase food production in Southeast Asia and in other parts of the world.

Rice has always been the number one grain crop in China in terms of both area and yield. During the 1950s, the tradition of rice–fish farming developed substantially but the benefits were not significant. Fish harvests were poor because the method was based only on traditional experiences and technical difficulties were encountered. However, rice–fish farming developed rapidly and by 1988, 800 000 ha were being harvested with a average yield of 133 kg/ha. In some areas, yields exceeded 3750 kg/ha and many farmers harvested 15000 kg of rice and 1500 kg of fish per hectare. The incomes of these farmers increased considerably. The techniques of rice–fish farming improved markedly as additional skill and experience were acquired.

In 1972, Ni Dashu, of Academia Sinica’s Institute of Hydrobiology, initiated experiments to increase fish production from rice–fish culture. These experiments established the theory for rice–fish integration, which guided the research work of Chinese scientists during the 1980s. Research was focused on the common needs of fish and rice for water, light, and nutrition under local conditions. Many new techniques were developed to suit various locations: ridge and ditch systems; semidry land; ditch manure pits; ditches with floating water; and Rice–duckweed-fish systems. These new methods enriched and further developed the theory of rice–fish integration.

In 1984, the State Economic Commission arranged a project for the extension of these new techniques. The Fisheries Bureau, under the Ministry of Agriculture, Animal Husbandry and Fisheries, ordered a technical coordination group to carry out the work in Sichuan and 17 provinces, municipalities, and autonomous regions. After 3 years, the new techniques were widely adopted and produced economic, social, and ecological benefits that contributed to the large-scale adoption of rice–fish farming in China.

rice–fish farming is no longer limited to the household economy and to production for personal or family consumption. It is now part of farmland improvement, soil improvement, and environmental protection. rice–fish farming has increased the productivity of ricefields and is fast becoming an important part of the commodity economy. It has also played a significant role in reforming the structure of rural industries.

Wang Hongxi

Deputy Director

Chinese Academy of Fishery Sciences

Part I:

Review and Outlook

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Rice–Fish Culture in China: The Past, Present, and Future 1

Cai Renkui,2 Ni Dashu,3 and Wang Jianguo3

The combination of rice and fish has a long history in China. The practice of rice–fish farming may have evolved from pond culture. The canon for fish culture written by Fan Li about 400 BC states:

… dig six mu of land into a pond … put 2000 fry into the pond … sell the rest in the market.

In a good year with ample rainfall and moderate weather, 2000 carp fry could produce numerous eggs. Some wise farmers may have placed excess fry in their ricefields. The fish in the ricefields may have grown better than those in the ponds, and the practice of raising fish in ricefields was born. There are no records of when the practice started, but this seems to be a logical explanation of how rice–fish farming began in China.

The archeological and written records do suggests the rice–fish culture is almost 2000 years old. In 1964-1965, tombs of the mid-Eastern Han Dynasty (25–220 AD) were excavated in the suburbs of Hanzhong County, Shanxi Province. Two clay models were unearthed: a model of a pond and a model of a ricefield. The pond model contained 15 miniature pieces (6 common carp, 1 soft-shell turtle, 3 frogs, and 5 water chestnuts). In 1977, a stone carving of a pond and ricefield model was discovered in the brick tomb of the Eastern Han Dynasty in Emei County, Sichuan Province. Half the stone was carved into a pond with frogs, fish, and ducks. The other half was carved into a ricefield with an inlet and outlet, two farmers toiling on one side, and two heaps of manure on the other. In 1978, four mid-Han Dynasty tombs with 200 relics were excavated in Mian County, Shanxi Province. One of the intact relics was a ricefield model containing 18 pottery miniatures of aquatic plants and animals. In it were sculptured frogs, eels, spiral shells, crucian carp, grass carp, common carp, and turtles. Another of a winter ricefield showed farmland with a reservoir that also contained these fish.

1 This paper is a combination of two papers: The History of Rice–Fish Culture in China by Cai Renkui and The Past, Present, and Future of Rice–Fish Farming in China by Ni Dashu and Wang Jianguo.

2 Freshwater Fisheries Research Centre, Chinese Academy of Fisheries Science, Wuxi, Jiangsu Province.

3 Institute of Hydrobiology, Academia Sinica, Wuhan, Hubei Province.

These relics suggest that at least 1700 years ago, rice–fish culture was practiced in the vicinity of Hanzhong and Mian Counties in Shanxi Province, and in Emei County in Sichuan Province. The fish species stocked in the ricefields were common carp (Cyprinus carpio), crucian carp (Carassius auratus), grass carp (Ctenopharyngodon idellus), and silver carp (Hypophthalmichthys molitrix). The bamboo fish trap and sluice gate that were installed at the inlet and outlet indicate that a primitive model of rice–fish culture existed at that time.

The earliest written record of rice–fish culture is from Recipes for Four Seasons, which was written in the Wei Dynasty (220–265 AD):

A small fish with yellow scales and a red tail, grown in the ricefields of Pi County northeast of Chendu, Sichuan Province can be used for making sauce.

The small fish with yellow scales and a red tail could be common carp. This indicates that common carp may have been grown in ricefields in Pi County. This record coincides with excavated relics. An alternate view4 is that the fish referred to is a type of small carp that “came from rice paddies” but was not necessarily raised in the ricefields. It is possible that, instead of being raised by rice growers, the fish was washed into ricefields during the rainy season through flooded waterways.

rice–fish culture probably continued to develop. The next written record is found during the latter part of the Tang Dynasty. Liu Xun (about 889–904 AD), wrote in Wonders in Southern China:

In Xin, Long, and other prefectures, land on the hillside is wasted but the flat areas near the houses are hoed into fields. When spring rains come, water collects in the fields around the houses. Grass carp fingerlings are then released into the flooded fields. One or two years later, when the fish are grown, the grass roots in the plots are all eaten. This method not only fertilizes the fields, but produces fish as well. Then, rice can be planted without weeds. This is the best way to farm.

The districts of Xin and Long are now in the vicinity of Xinxing and Luoding Counties in Guangdong Province. This means that rotational rice–fish farming was practiced there over 1000 years ago. The chronicle of Shunde County, Guangdong, from the Ming Dynasty (about 1573) states that:

The periphery of a land was trenched as a plot, called the field base. … In the plot, a pond was dug to rear fish. During the dry season, rice seedlings were transplanted to the plot. The area might be several hectares.

4 The first view was expressed in the paper by Cai Renkui; whereas, the alternate view was expressed by in the paper by Ni Dashu and Wang Jianguo.

According to this chronicle, the area for rice–fish culture was expanded in Guangdong 400 years ago.

Formal research appears to have started in the 20th century. In 1935, a rice–fish culture experiment was conducted in Songjian, Jiangsu Province. The species stocked were black carp (Mylopharyngodon piceus), grass carp, silver carp, bighead carp (Aristichthys nobilis), and common carp. During the Rice–growing period, the weight of the silver carp increased 50-fold and the weight of common carp increased 20-fold. After 2 years, 20000 fry hatched and were distributed to farmers for culture in rice paddies. Scientists provided technical assistance.

After the founding of the People’s Republic of China in 1949, rice–fish culture developed quickly. In 1954, the fourth National Aquaculture Meeting proposed the development of rice–fish culture across the country. By 1959, the area of rice–fish culture had been expanded to 666 000 ha.

From early 1960s to the mid 1970s, several factors, including the intensification of rice production and the large-scale application of chemical insecticides, impeded the development of rice–fish culture.5 For example, in Guangdong Province the area of rice–fish culture dropped from 33333 ha in the early 1950s to 320 ha in the mid 1970s, and in Hunan Province the area dropped from 232 000 ha in 1958 to 5333 ha in 1978.

Rice–Fish Farming in China Today

During the late 1970s, there were changes in rice production. Improved modern varieties of rice and less toxic chemicals were used and there were changes in the units of production. The production-contract system was implemented in rural areas starting in 1978 and this allowed individual families to become the main units of production. In addition, there was a rapid development of aquaculture, which required the production of a large amount of fry and fingerlings. This demand was partly met by fingerling production in ricefields. Research and supporting policy and development activities have also encouraged the expansion of rice–fish production.

The research established an optimum ecological system to increase rice production, economize labour, and maximize economic returns. This lead to the evolution of a theory of rice–fish mutualism that has provided the theoretical basis for rice–fish culture. The practice has now spread to all Rice–growing areas in China through the adaptation of rice–fish techniques that are suitable to local agroecological conditions.

5 The years 1965–1975 also coincided with the cultural revolution. During this period, the raising of fish was considered a bourgeois way of making money and was officially discouraged. In addition, there were severe dislocations of research and extension during this period.

A number of regional and national meetings focused attention on rice–fish culture and advanced its development. In 1983, a workshop on Fish Farming for Eradicating Mosquitoes was held in Xinxiang, Henan Province, to exchange information on eradicating mosquitoes by rearing fish in ricefields. The First National Ricefield Fish Culture Seminar was held on 11–15 August 1983 at Wenjian County, Sichuan Province, under the auspices of the Ministry of Agriculture, Animal Husbandry and Fisheries (now the Ministry of Agriculture). The seminar established a large coordination group for Eastern China to popularize rice–fish farming techniques.

The potential and actual production in Eastern China is summarized in Table 1. There are 9 million ha of ricefields in Eastern China. This accounts for one-third of the country’s total rice area, and 45% of it is suitable for raising fish. Before 1982, rice–fish farming was concentrated in the mountainous areas of Jiangxi, Fujian, and Anhui and covered only 26000 ha. The area was expanded to include the plains and, by 1986, 138 000 ha were in production and yielded an average of 183 kg of fish per hectare.

In 1983, a key research project on the economics of aquatic resources in China included a subproject on economic problems related to rice–fish culture. The scientists, who thoroughly studied the economic benefits of rice–fish culture, received the Second Science and Technology Progress Award from the Agriculture Ministry in 1988.

In 1984, the Ministry of Agriculture, Animal Husbandry and Fisheries (MAAHF), organized a project to popularize the technique of raising fish in ricefields in Sichuan, Beijing, Hebei, Shanghai, Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, Henan, Hubei, Hunan, Guangdong, Guangxi, Shaanxi, Guizhou, and Yunnan. To promote the project, a technical group of six researchers was formed to provide guidance.6 The members of the group were: Jiang Cimao of the Aquatic Products Bureau of Sichuan Province, Ni Dashu of the Institute of Hydrobiology of the China Academy of Sciences, Yin Pizhen of the Aquatic Products Institute of Jiangxi Province, Yang Yongshuan of the Aquatic Products Bureau of Hubei Province, Yang Jintong of the Aquatic Products Bureau of Hunan Province and Xu Xushi of the Bureau of Agriculture, Animal Husbandry and Fisheries of Zhongging City. The project sought to popularize the practice on a large scale. Initial achievements won the project a first-class award for technological progress from the MAAHF in 1986.

In 1985, 17 institutes were involved in another key research project called, “Ricefields as Fish Nurseries and Fish Grow-out Systems.” This project, under the auspices of the National Aquatic Products Bureau, aimed to rear hybrids of common carp, tilapia, and crucian carp (Carassius carassius) in ricefields and to nurture grass carp fingerlings in ricefields. Each province was requested to extend rice–fish culture in a 200 ha demonstration area. The target yield was 225–625 kg

6 A number of the researchers in this group were present at this workshop.

Table 1. rice–fish culture in Eastern China in 1985 and 1986.

Province or Municipality Area of for Ricefields (103 ha) Suitable Rice-Fish (103 ha) Area Used for Rice-Fis (103 ha) Fish Production (tonnes) Production (kg/ha) 1985 1986 1985 1986 1985 1986 Jiangxi 2067 1400 52 47 9360 8815 180 188 Fujian 1040 400 2 2 28 2915 4265 131 150 Anhui 1667 667 23 34 650 0 6630 285 195 Zhejiang 1333 667 21 19 3050 2810 149 150 Jiangsu 2400 667 11 10 2585 2760 237 267 Shanghai 200 200 0.8 0.2 1 11 150 450 Shandong 6 6 1 3 0. 7 0.4 3 0. 5 153 - Total/Average 877 3 4014 131 138 24414 25292 183.6 183

of fish per hectare. The total demonstration area of rice–fish culture in the eight provinces south of the Yangtze River was 1600 ha. The project sought to promote the extension of rice–fish culture in the country to cover a total area of 800 000 ha.

There was also an increase in rice–fish culture in Northern China. In 1985, the Aquatic Products Section of the Water Resources Committee of the city of Urumqi in the Xinjiang Uygur Autonomous region in Northwest China, carried out an experiment on rearing fish varieties in ricefields in the northern suburbs of Urumqi. They put 1977 fingerlings in two batches (10 and 2–3 cm in length) into a 0.4-ha experimental field. After 68 and 87 days, they harvested 174 kg of fish per hectare. The largest fish weighed 0.25 kg and the average weight was 0.11 kg. Rice output was 9292.5 kg/ha, 18% more than in 1983. Net profit was CNY 1916/ha.

From 1984 to 1985, the Rice Institute of the Agricultural Reclamation Academy in Heilongjiang Province, Northeast China, conducted experiments on rice–fish farming in high, cold areas. Rice yields increased by 7.2–12.1%, and the survival rate of fingerlings to harvest was 71.3–88.9%. The net value of the output increased by CNY 656–950/ha. Grass carp averaged 0.2 kg in weight; common carp averaged 0.15 kg. Meanwhile, in Huanren County, Liaoning Province, another rice–fish culture experiment stocked grass carp and common carp as major species and tilapia as minor species in a 0.1-ha ricefield. They harvested 85.8 kg of fish and rice yields increased by 7.3–8.4%.

In 1985, Changchun City in Northeast China’s Jilin Province raised common carp fry during the summer in 4.3 ha of ricefields. They harvested 35000 fingerlings that measured 10–15 cm in length and weighed a total of 875.5 kg. The ricefields yielded 279 kg of fish per hectare. The current situation (1986) of rice–fish production in China is summarized in Table 2. There are almost 1 million ha of rice–fish culture in China in 15 provinces and three municipalities (Beijing, Shanghai, and Zhongging). In addition, experimental culture is being carried out in the northern provinces of Jilin, Liaoning, and Heilongjiang and in the Xinjiang Uygur Autonomous Region. rice–fish culture is now practiced from southern Guangdong and Guangxi at 22°N to Beijing at 40°N, and experimental activities as far north as Heilongjiang Province (45°N).

The Development of Rice–Fish Culture Techniques

Concept and Significance of Rice–Fish Farming

The new concept of “mutualism” in raising fish in ricefields is entirely different from the traditional purpose and nature of rice–fish culture. The mutualism concept is to improve rice production by letting herbivorous fish eliminate weeds that compete with rice plants for sunshine, fertilizer, and space. At the same time, fish in ricefields feed on weeds, plankton, and benthos, and form an optimum ecological system that benefits both the fish and the rice. Traditionally, the idea was simply to raise fish with rice as an additional source of food. Now the concept includes the mutualism of both crops and has indeed become an effective way to boost rice yields. There are two basic forms of rice–fish farming: (1) rotating rice and fish, and (2) growing fish and rice together. rice–fish rotation involves growing rice one season and raising fish the next. This method has been extensively adopted in winter ricefields, in fields that need to conserve water, and in low-lying areas in Sichuan Province. The fish raised in these fields are mainly adult or large fish.

The new concept of rice–fish farming combines the otherwise contradictory principles of growing rice and farming fish. By making full use of the mutual benefits of both rice and fish, the new concept provides a modern biological technique to invigorate agriculture in China. The emphasis is on growing rice and the role of the fish is to enhance the growth of the rice plants. But, the ultimate goal is to increase the production of both rice and fish in Rice–growing areas. There are many advantages of growing fish with rice:

The fish increase rice yields by more than 10%;

A 0.07-ha ricefield can yield 300 fingerlings each measuring 10–16.5 cm. When table fish are reared, 150–450 kg/ha can be harvested. In rice–fish rotation, more than 50 kg of fish can be caught from 0.07 ha of surface water;

The fish feed on weeds and worms, and loosening up the soil. This helps reduce labour requirements and is one of the outstanding benefits of raising fish in ricefields;

Table 2. The area (ha) of rice–fish culture in China (1981–1986).

Province or Municipality 1981 1982 1983 1984 1985 1986 Beijing – – 1 21 7 7 Hebei – – – 15 15 100 Shanghai – – 1 23 83 23 Jiangsu – – 26 3133 10886 14000 Anhui – – 2666 10000 22666 34000 Zhejiang – – 13353 17733 26486 18733 Jiangxi 3333 16666 18666 37800 52000 47000 Fujian – – 14666 19113 22353 28433 Henan – – – 20 8766 6666 Hubei 1000 2333 3333 13333 28133 21653 Hunan – 79666 112 613 167 100 188 746 227 000 Guangdong – 4333 4000 5300 8120 13333 Guangxi 20000 35333 31853 34546 45520 54200 Shanxi – – 140 727 1506 5700 Sichuan – 156 666 192 473 241 393 282 186 333 333 Zhongging – – 54000 68666 78000 80000 Guizhou 94666 100 666 106 666 100 000 66920 87333 Yunnan – – 8540 11560 10580 14000 Total 120 980 397 645 564 980 732 467 854 958 987 500

The fish (especially grass carp) conserve and enrich the fertility of the water and soil and therefore stimulate the growth of rice plants and increase grain yields;

The fish eliminate some insect and disease pests of rice, and in addition eat mosquito larvae, which are pests to both animals and people, and thus help to reduce the incidence of meningitis, malaria, and filariasis.

rice–fish farming is closely integrated with freshwater fish farming in China, especially in ponds, reservoirs, lakes, and family ponds. Freshwater aquaculture requires increased quantities of fry. The demand for fry cannot be met by relying on stock fish farms or by expanding stock fishponds.

The use of ricefields to grow fingerlings has allowed the demand to be met. If the area for rice–fish farming in China was expanded by 6.7 million ha, rice production would increase by more than 2 million tonnes and 30–50 billion fingerlings would be produced. This would also help increase the annual harvest of freshwater fish.

Fish Species Stocked in Ricefields

In ancient times, the fish species stocked in ricefields were: common carp, crucian carp, grass carp, silver carp and bighead carp. In the 1950s, the species used were: black carp (Mylopharyngodon piceus), Chinese bream (Megalobrama amblycephala), tilapia (Oreochromis mossambicus and O. niloticus), mud carp (Cirrhina molitorella) in the south, loach (Misgurnus anguillicaudatus and Xenocypris argentea) in Guangxi and Hunan, and snakehead (Ophiocephalus argus) in Guangdong.

In the 1960s and 1970s, rainbow trout (Salmo gairdneri) were introduced in the north, and catfish (Clarius leather) in the south. In the 1980s, the new species used were: carp (Carassius auratus), aquatic crab (Eriocheir sinensis); shrimp (Macrobrachium nipponensis), American snail, pearly clam, and field snail.

Increased Rice Yields After Fish Culture

There is considerable evidence that fish increase the yield of rice. Table 3 summarizes the information from a number of experiments throughout China. All experiments show an increase in rice yield of 2–34% (average of 11.8%).

Chemical Insecticides Applied to Ricefields

There are over 50 pests and 10 diseases that attack rice. The major pests are: yellow stemborer (Tryporyza incertulas and Chilo simplex), green rice leafhopper (Nephatettix apicalis), rice plant skipper (Parana guttatus), and rice blast (Piricularia oryzae), which is the most serious disease. Secondary pests and diseases are: snout beetle (Echinocnemus squameus), rice leafroller (Cnapholocrosis medinalis), yellow-legged lema (Lama flavipes), locust (Oxya chinensis), and brown spot (Cochliobolus miyabeanus).

In the early 1970s, chemical insecticides toxic to fish gained widespread use. Some of these were 666, DDT, and limestone powder. Later, less toxic chemicals (Roxin, Dipterex, Kitazine, and Fenitrothion) were produced. Methods of application were improved to minimize damage to fish and to achieve the maximum effect of the chemicals. For example, the water level in the ricefields was increased before the chemicals were applied. Powdered chemicals were applied

Table 3. Increase in rice production in rice–fish culture.

Experimental Unit Increase (%) Year Guiping, Guangxi 3.6–11 1957 Gaoxi, Lingling, Hunan Institute of Hydrobiology 4.8–13.4 1958 Hubei Agriculture Research Institute and Wuhan Fisheries Research Institute 9315 9051 Guangxi Aquatic Products Experimental Station 8614.5 8697 Fujian Fisheries Research Institute Freshwater Branch 4.6 1965 Southwestern Normal College and Qingshen Hydroelectric Bureau, Sichuan Province 13.6 1976 Zhulou, Yuanyang Counties, Hunan 15 1976 Wenjia, Chendu, Sichuan 4.1–8 1976–1977 Shatou, Fanyu Counties, Guangdong 6–8 1978 Institute of Hydrobiology and Changsha Agriculture Modernization Research Institute, Academia Sinica 19.7 1979 Heyan, Taoyuan, Hunan 34 1981 Qing-guda Lake, Urumqi, Xinjiang 18 1984 Huanren County Broodstock Fish Farm, Liaoning 7.3–8.4 1984 Heilongjiang Academy of Agriculture Reclamation Science, Heilongjiang 7.2–12.1 1984–1985

when the plants were covered in dew, and spray chemicals were applied when there was no dew. In some areas, fish were driven to trenches or sumps before the chemicals were applied. Insecticides were also applied in instalments or in patches. Table 4 shows the current dosages of chemicals that are used.

Development of Rice–Fish Culture

Ricefields can be used as fish nurseries or to produce fish for food. In fingerling production, either 450 000–600 000 eggs/ha or 300 000 fry/ha of common carp are stocked early in the season. By the summer, the fingerlings are ready for harvest. To nurture large-sized fingerlings, the stocking density should be 15000–22500/ha. If grass carp is the dominant species, 12000–15000 grass carp should be stocked per hectare with 3000–4500 silver carp and bighead carp and 4500–6000 common carp and bream.

Table 4. Dosages of chemicals applied in ricefields.

Chemicals Common (g/ha) Maximum (g/ha) Dipterex 1500 2250 DDV 750 1500 Fenitrothion 1125 1500 Calcium methyl arsenate 3000 3750 Kitazine 1500 2250 Methamidophos 750 1500 Roxion 50 100 Chlordimeform 3000 3750 Jiangangmycin 2250 – Farmon condex 15000 18750

In Shanxi Province, rainbow trout was cultured in winter fallows by using slightly running waters. Fish production was very high (30 t/ha). rice–fish culture has been practiced, not only in shallow-water ricefields, but also in deepwater rice fields and in fields of wild rice (Zizania spp). In brackishwater along coastal reclamation areas, a rotational system is used. One crop of rice is grown one year, mullet (Mugil so-iuy) is cultured the next.

During the 1980s, several new developments occurred:

Ridge rice planting – ditch fish farming system. This system is suitable for water-logged ricefields. The system involves a series of ridges and ditch in the ricefield. The rice is grown on top of the ridges and the fish in the ditch. The width of the ridge and the ditch is 40 cm, the height of the ridge is 80 cm, and water depth is 50 cm.7

Rice–azolla–fish system. Rice is planted in the fields, azolla is cultured on the surface of the water, fish are cultured in the water, and squash or legumes are planted on the bunds. This is a multilevel comprehensive system of resource use.

Running water system of trench fish farming. One or two broad trenches (1–1.5 m in width and 60–90 cm in depth) are dug in a ricefield. The trenches account for about 6% of the total area of the ricefield, and fish are cultured in the water running through the trenches.

7 The dimensions of the ridge–ditch system appear to vary considerably. The ridge is often only 25 cm wide and 30 cm in height.

Prospects for Rice–Fish Farming in China

China has 25 million ha of ricefields, and over 90% of this area is south of the Huai He River Basin. Although the practice has achieved excellent results in terms of scale and economic return, its potential to meet the needs of modern development remains untapped. If 10% of the ricefields south of the Huai He River were used (half for commercial fish and half for stocking fish), the commercial fish yields could be 346 000 tonnes (assuming 300 kg/ha) and the number of full-size fingerlings would be 5 billion (assuming 4500/ha). The area north of the Huai He River is not as suitable for rice–fish culture, but if 5% of the rice fields become rice–fish systems, they would produce 8000 tonnes of commercial fish and 243 million fingerlings. The total increase in rice output would be one million tonnes annually on the basis of the 1981 output (if annual increase is calculated at 10%) and commercial fish yields would reach 354 000 tonnes and 5.7 billion fingerlings. The number of fingerlings raised in ricefields would be sufficient to stock 0.75 million ha of water (e.g., ponds and reservoirs). The achievement of these goals would have very large ecological and economic benefits.

If fish farms were used to raise fry, ricefields were to be used to raise full-sized species, and ponds, reservoirs, and lakes were used to raise adult fish, fish farming would undergo considerable change. Fujian Province reported that, if ricefields are used to rear fingerlings, 200 ha of stock fishponds would be freed for intensive farming of commercial fish, and labour and feed, which would otherwise be used for breeding fingerlings, could be used for commercial fish farming. Jiangsu Province reported that, in 1986, Jianhu County used 4700 ha of ricefields to raise fish. Three major stock fish farms supplied enough fry to meet the need for big-sized stock fish for 2000 ha of intensive fish farming in the county. This indicates that the output of freshwater fish could be increased considerably.

rice–fish farming has the potential to fully maximize the use of ricefields. Present trends for popularizing the practice are encouraging, and the area used to grow rice with fish is increasing yearly. In the past, the development of China’s aquatic products has been slow, quality has been poor, and supply was often short. There have also been policy problems that remain unsolved. As the internal structures of agriculture are adjusted, various localities are becoming aware that rice–fish farming is an effective way to increase rice production and improve economic, social, and ecological conditions.

Since the national conference on rice–fish farming in 1983, various provinces, autonomous regions, and municipalities have undertaken measures to popularize the practice in line with local conditions. The Science Commission and Aquatic Products Department of Fujian Province organized several research projects. They achieved success by strengthening their leadership and by coordinating technical forces. East China’s coordinating group met once a year to summarize work experiences and coordinate actions. Representatives from various provinces visited advanced units to draw on their experiences and to increase the awareness of leaders from different areas about the significance of rice–fish farming. They held meetings to discuss the practice and conducted training courses to expand the area of ricefields for fish farming.

rice–fish farming should be combined with intensive fish farming in ponds, reservoirs, lakes, and cages to ensure that more fingerlings can be raised in ricefields. Recently, a national symposium called for the rapid development of ecological agriculture to improve productivity. Ecological agriculture has received increased attention in recent years, and the structure for agricultural production has been improved significantly. Undue emphasis used to be placed on plant culture; however, attention has now shifted to the comprehensive development of farming, forestry, animal husbandry, and fisheries. Instead of focusing only on economic results, both economic and ecological benefits are now considered. In the past, single items of technology were emphasized. Today, due attention is given to the comprehensive application of technical packages.

rice–fish mutualism offers a model of ecological agriculture. However, fish farming has not yet been closely integrated with crop cultivation and the division of labour has not been clear; therefore, development and popularization have been slow. The production of both rice and fish can be maximized if agricultural researchers pay more attention to rice–fish farming and help hasten its development. It is imperative to integrate fish farming with crop cultivation. If the area for rice–fish farming was increased to 6.7 million ha as the area devoted to rice is increased, the supply of freshwater fish could be quadrupled.

rice–fish farming can play an increasingly important role in freshwater fish farming if the nation’s leaders give it due attention, if the technology is sound, and if the practice is carefully adapted to local conditions.

Rice–Fish Culture in China: Present and Future

Chen Defu and Shui Maoxing8

In China, fish are raised in ricefields in the southeast and southwest mountainous areas where there are few bodies of water for growing fish and fishing regions and towns are far away. rice–fish culture is a traditional and popular way for the people to grow their own supply of fresh fish in the mountainous areas of: Qingtian and Yongjia in Zhejiang Province; Jiening, Taining, Saxian, and Yongan Shaowu in Fujian Province; Yulin, Guilin, and Jinzhou in Guangxi Province; the southern part of Guizhou Province; and Pingxian, Jian, and Yichun in Jiangxi Province.

In these areas, the farmers practice rice–fish culture to raise fish for their own consumption, although it requires extensive management and fish harvests are poor. Before 1949, there was no organized extension of the technology; therefore, rice–fish culture did not improve.

Present Situation

Extension of Rice–Fish Culture

Since the founding of the People’s Republic of China in 1949, the government has paid more attention to rice–fish culture. In 1954, the First National Conference on Aquatic Products formally called for the promotion of rice–fish culture. The area devoted to rice–fish culture increased rapidly and reached over 670 000 ha by the end of the 1950s. During the mid 1950s to the early 1960s, rice–fish culture developed rapidly in the mountainous areas of south and north Zhejiang and in the plains and hilly areas of Shaoxin, Jin Hua, and Hangzhou. However, this development suffered a major setback during the 1960s to the mid 1970s when planting systems were reformed and highly toxic pesticides were used. The area devoted to rice–fish culture decreased drastically, but began to increase slowly by the end of the 1970s as improved breeds of rice and less toxic, but effective, pesticides were introduced. In the 1980s, more farmers became interested in rice–fish culture as the government encouraged its adoption and introduced a family contract system in rural areas.

In 1983, the office of the Central Committee of Patriotic Hygiene in Xinxiang City, Henan Province, held a meeting about controlling mosquitoes in ricefields. They decided to promote and disseminate information about rice–fish culture and to advance its development.

8 Soil and Fertilizer Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang Province.

The first national meeting on rice–fish culture was held by the Ministry of Agriculture, Husbandry and Fishery in Wenjiang County, Sichuan Province, in August 1983. Similar meetings followed in provinces, cities, and autonomous regions. rice–fish culture in China began a new period of rapid development. The total area of rice–fish culture increased 65% between 1983 and 1984. In Zhejiang Province, the total area9 was 18127 ha in 1984, a 36% increase from the 12353 ha in 1983.

In 1984, the Bureau of Aquatic Products of the Ministry of Agriculture, Husbandry and Fishery organized and launched a project “Extending the Techniques for Fish-Raising in Ricefields” in 17 provinces, cities, and autonomous regions The total area for rice–fish culture in the country increased to 846 700 ha in 1985 and to 985 300 ha in 1986 and had a positive effects on the economy, society, and ecology. The project received the first grade award for advanced scientific technology from the Ministry of Agriculture, Husbandry and Fishery in 1986.

rice–fish culture has now developed and been adopted in the southeast and southwest mountainous areas and the plains, and the northeast and northwest regions. It is practiced in the ricefields of Sichuan, Hunan, Guizhou, Chongqing, Guangxi, Jiangxi, Anhui, Fujian, Zhejiang, Jiangsu, Yunnan, Guangdong, Henang, Shaanxi, Hebei, Xingjiang, Liaoning, Helongjiang, Beijing, and Shanghai.

Research on Rice–Fish Culture

Since 1949, the main research areas in rice–fish culture have been:

The relationship between rice and fish and ways to increase rice production using rice–fish culture;

The different forms of the ricefield that can be used for rice–fish culture (plain, ditches, pits, wide ditches, and ridges);

Suitable breeds of fish (i.e., grass carp, common carp, crucian carp, murrel, and mud loach). A few silver carp and bighead carp can be raised together with these fishes in ricefields with wide ditches. The raising of grass carp is the most effective way to clear up weeds and pests. Adult grass carp grow quickly in ricefields; therefore, fish yields and economic returns are increased. Techniques to prevent grass carps from injuring the rice plants must be used;

Comprehensive techniques to improve harvests from rice–azolla–fish systems;

Economic evaluations;

9 In some cases the areas differ from the summaries presented in Tables 1 and 2 of the previous paper by Cai et al. The editors have retained the figures presented by the individual authors.

Suitable pesticides, their safe dosage, and methods of use, and the residual effects of methamidophos, carbofuran, and insect-paste in the rice–azolla–fish system;

The control of mosquitoes in ricefields using fish-raising, and the development of the rural economy;

Comprehensive techniques to efficiently manage agriculture, animal husbandry, and fisheries;

The rates of absorption, transfer, and application of N and P, and the use of azolla by fish; and

Feasibility studies.

Types of Rice–Fish Culture

There are two ways to combine rice and fish:

Rice and fish together. Planting rice while raising fish is the main method used. The method makes full use of time, space, energy, and resources of the ricefield and provides economic benefits. Its shortcoming is the rather high requirement for labour and management.

Rice and fish in rotation. Planting rice and raising fish are carried on alternately; therefore, the contradictions between growing rice and raising fish are avoided. After the rice is harvested, fish are raised in deepwater fields, which can improve fish yields. The disadvantages are that the growing period for the fish is shortened, and that the mutually beneficial and efficient relationship of rice–fish culture is lost. In regions with two rice harvests, the rotation of rice and fish will reduce rice yields.

The main methods of the rice and fish rotation are:

early rice – late fish;

early fish – late rice;

after the harvest of one rice crop, fish are raised in deep water;

fish are raised in clean summer fields for 1.5–2 months after the harvest of early rice and before the late rice is transplanted;

fish are raised for 120–130 days in clean winter deepwater fields after the annual harvest of late rice (the fish are caught the following year before the early rice is transplanted); and

in the same ricefield, two harvests of fish are raised and two crops of rice are planted during the same year (i.e., early rice – raising fish in summer, and late rice – raising fish in winter). In Guangdong Province, summer fish are raised for 40–50 days, winter fish for 80–100 days.

Yields and Techniques

Fish yields in ricefields have been low. The average yield of fish per hectare from 1982 to 1987 was 70.5, 82.5, 100.5, 126, 141, and 133.5 kg, respectively. New techniques and high-yield demonstration plots all over the country have led to increased fish yields. However, average yields in large areas of the country are still low. Traditional techniques of rice–fish culture are still used in most parts of China.

The reasons for low yields of fish from ricefields are:

Low water volume and little shelter. Traditionally, ricefields used to raise fish do not have ditches or pits. The low volume of water in these ricefields results in insufficient dissolved oxygen and few plankton, high water temperature in summer, and few places for the fish to hide from predators. The density of the fish, the rate of catching, and yields are limited.

Inbreeding of fish and genetic degeneration. Carp are raised in most ricefields in China. For example, Tian carp are popular in south Zhejiang, West Hunan, and Sichuan, Gao Bei carp and Jin carp are popular in the mountainous area of Guizhou, “Hehua” carp are popular in northern Guangxi. These breeds of carp have mild characteristics and do not jump well; therefore, they cannot escape easily. They are suitable for raising in ricefields. However, because of prolonged inbreeding, the breed characters have degenerated and the fish grow slowly.

Small fish breeds. The old regions of rice–fish culture use the traditional method in which small fish are raised and, in some regions, fingerlings are stocked directly into the field. This has led to slow growth of fish and low survival rates.

Insufficient feed. Artificial feed is not used in the traditional method. However, there is insufficient natural feed in ricefields, especially in mountainous areas. The weeds decrease as the fish grow; therefore, the fish do not get a sufficient supply of weeds during the middle and late growing stages of the rice.

Low density of fish. For breeding, 10500–22500 summer fingerlings are raised per hectare. For food, 1500–7500 summer fingerlings and 750–1200 spring fingerlings are raised per hectare.

Late stocking, early harvest, and short growing periods. Fingerlings are usually stocked a week after the rice seedlings are transplanted and the fish are caught during the rice harvest. The period for the rice and fish to grow together is short — about 90 days in regions with one rice crop and 160–180 days in regions with two rice crops. In southern China, 240 days (Jiangsu) and 330 days (Guadong) are considered suitable.

Once raising and once catching. The fish carrying capacity in ricefields changes during the growing period. Early in the season, the field has many weeds and the fish are small; therefore, the natural feed is sufficient. Later, when the fish are larger, there are fewer weeds. The resources in the field no longer match the density of the fish.

Small-scale production. The farmers consider the fish a by-product; therefore, the area used to raise fish in ricefields is small and scattered.

The Rise of Modern Rice–Fish Culture

Traditional rice–fish culture is no longer suited to the country’s social development, and it hampers the extension of modem methods of rice–fish culture. In the 1980s, several reforms were made:

The layout of the ricefields used to raise fish was improved. The traditional plan was changed to include ditches, wide ditches, pits, and ridges. The volume of water was increased to improve the environment for the fish.

Several breeds of fish are now used instead of a single breed. Fish (e.g., grass carp, common carp, nile tilapia, silver carp, variegated carp, and crucian carp) were selected to suit local conditions.

Fish size was increased. Fingerlings 10-cm or larger are now used instead of fingerlings 6–8 cm in length.

Stocking density of the fish was increased. Depending on the fertility of the soil and feed supply, 4500–6000 adult fish from the previous year and 3000–4000 summer fingerlings are raised per hectare. The numbers can be increased if conditions are improved.

Shifting from late stocking – early harvest to early stocking – late harvest. Because the ditch, pit (pool), and ridge systems have permanent fish pits, fish-raising can begin in the winter. Fish are now raised continuously after the harvest of late rice in deep-water ricefields. If crops are planted in winter for spring harvest, fish are caught 2 weeks before wheat or rapeseed are planted.

Feed or the rice–azolla–fish method are used instead of not feeding the fish.

One-time raising and one-time catching were changed to alternative catching and raising.

The new techniques have improved average yields to 750–3000 kg of fish per hectare while increasing rice production. The highest fish yield reached 5500 kg/ha in two-crop ricefields in Zhejiang. These new approaches have helped to modernize the traditional methods of rice–fish culture in China.

Prospects for Rice–Fish Culture

Potential

Because of the country’s large population and limited agricultural land, agriculture in China is moving toward intensification. rice–fish culture is part of this intensification. It is an effective way to increase the productivity of ricefields by harvesting both rice and fish. It is the quickest method to increase the economic efficiency of the ricefield and to help farmers increase their income.

There are about 25 million ha of ricefields in China. If 30%10 were to be used to raise fish, about 7.5 million ha would be available for rice–fish culture. If 600 kg of rice and 375 kg of fish were harvested per hectare, this would increase the country’s production to 45 billion kg of rice and 28 billion kg of fish. Less than 1 million ha of land, or 3.9% of the total area of ricefields, are now devoted to rice–fish culture. Therefore, there is great potential to develop rice–fish culture.

The rapid development of township industries has improved the skills of farmers. The development of family farms has prepared favourable conditions for the large-scale management of rice–fish culture using advanced scientific techniques. A modern and effective rice–fish industry will alter traditional concepts about rice–fish culture and encourage more farmers to raise rice and fish together.

Factors Limiting Development

Fish can only be raised in ricefields with sufficient water resources and good irrigation and drainage. Poor water resources, drought, serious leakage, and poor water-holding capacity of the soil make rice–fish culture difficult in north China; whereas, south China is rainy and flood-prone.

Higher economic efficiency can be achieved in township industries and trade businesses than in areas that practice traditional methods of rice–fish culture.

The family-contracted fields are scattered and on a small-scale. Advanced and scientific methods of rice–fish culture are difficult for farmers to adopt without further land consolidation.

Support systems for rice–fish culture are inadequate. It is very difficult for farmers to obtain loans, new and improved fish breeds, feed, fertilizer, and pesticides. There are also few technicians available to instruct farmers. Therefore, the breed characters of some carps that are popular with farmers degenerate and as a result the fish grow slowly.

For a long time, traditional techniques have hindered the development of rice–fish culture because they prevent farmers from accepting and grasping modern techniques. Farmers worry that fish pits and ditches will affect grain yield. These ideas hamper the extension of rice–fish culture.

10 Different authors suggest various levels for potential expansion of rice–fish culture in China. The estimates in this paper are probably overly optimistic because only about 25% of the rice area is suitable for rice–fish culture.

Strategies for the Development of Rice–Fish Culture

rice–fish culture must be given as much attention as the production of food grains, and should be seen as a way to develop grain production and to improve the economic conditions of farmers. Several tactics can be used to improve rice–fish culture:

The efficiency of rice–fish culture, and the area devoted to rice–fish culture in traditional regions, should be increased through technical training and increased funding.

Testing sites should be established in plain areas and modern techniques should be extended to farmers to increase yields of rice and fish, and to spark interest in rice–fish culture in these high-production rice areas.

rice–fish culture should be extended to large farm families who mainly grow rice. The technology could help improve their livelihood and become pioneers in the large-scale development and efficient management of rice–fish culture in the country.

Agricultural and aquatic products units should be merged to coordinate research and improve extension of practical techniques for rice–fish culture. The basic theories of rice–fish culture and techniques for good harvests of both rice and fish must be studied.

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Scientific and Technological Development of Rice–Fish Culture in China

Zhang Rongquan11

rice–fish culture is an organic method that integrates rice production and aquaculture. It enhances the growth of both rice and fish, maximizes the use of field and water resources, and effectively increases harvests. Several scientific and technological developments have been made to rice–fish culture techniques in China.

Development of Rice–Fish Culture Techniques

Traditional Aquaculture Techniques in Ricefields

Historical records show that Chinese farmers started raising fish in ricefields more than 1700 years ago. But despite its long history, rice–fish culture did not progress for many years and its development was hindered by feudal relationships. Farmers raised fish in ricefields as a sideline, usually only to augment their own meals. rice–fish culture is described in the Tang Dynasty treatise (about 889–904 AD) Wonders in Southern China by Liu Xun:

… after the spring rains, water collects in the fields lots around the houses. Grass carp fingerlings are then released into the flooded fields. One or two years later, when the fish are grown, the grass roots in the plots are all eaten up. This method not only fertilizes the fields, but produces fish as well. Then, rice can be planted without weeds.

During the Ming and Qing Dynasties, rice–fish culture gradually developed into an important sideline in the countryside. But, because of various restrictions, it did not grow into an organized technique. Operations were often scattered and little information was available; therefore, methods and yields varied considerably in different areas. Yields were low and the scale of production and the techniques did not progress.

Before the founding of the People’s Republic of China, the Ministry of Agriculture and Forestry of the Kuoming-Dang Government promoted the development of rice–fish culture by stocking fingerlings in ricefields of Sichuan. They also published and distributed a brochure entitled An Elementary Introduction to Rice–Fish Culture. In Shong Jiang District, the Jiangsu Province Rice Experiment Station conducted experiments on rice–fish culture and provided technical guidance

11 Chinese Academy of Fisheries Science, Wuxi, Jiangsu Province.

to local farmers. These efforts promoted rice–fish culture locally, but restrictions limited its impact on the rest of the country.

During the early period of the People’s Republic of China, rice–fish culture flourished as agricultural production was restored. Experiences in rice–fish culture were exchanged quickly and more districts began to adopt the technique. By 1959, the total area devoted to rice–fish culture had increased to about 670 000 ha. At this stage, fish were raised on a small-scale with traditional tall rice varieties grown without pesticides on level land. A few farmers dug fish ditches, which took up only 1% of the field area. The species raised were restricted to grass carp and common carp. Usually, the fish were not fed and only weeds were available. Production, efficiency, and benefits were low. Although there were new developments, rice–fish culture remained very traditional.

In later years, the system of rice cultivation was reformed and large quantities of fertilizer and toxic pesticides were used. rice–fish culture decreased. Since 1978 new techniques have been developed.

New Techniques

China is very large and the natural conditions vary substantially between different regions. Since the 1970s, the coexistence of rice and fish had been established based on the traditional system of rice–fish culture. However, reforms in the Rice–growing system and progress in rice–fish culture techniques have intensified the conflicts between rice and fish culture. The traditional techniques did not suit the new situation and this hindered the development of rice–fish culture.

In 1972, Ni Dashu of the Institute of Hydrobiology, Academia Sinica, put forth the theory of feeding fish for rice culture. Later Ni Dashu and Wang Jianguo developed a theory of mutualism that stated that rice and fish could coexist. They conducted experiments on rice–fish culture. Ni Dashu studied the rational use of ricefield resources and deemed that although there were differences in growth and development of rice and fish, they shared common characteristics in terms of their need for water, light, and fertilizer.

Fish were fed in ricefields, and fish-raising was integrated with rice culture. Rice was regarded as the main product, and the biological productivity of ricefields was upgraded. Ricefields were used, not only to raise a single crop, but to grow several crops. Rice and fish could coexist in the same field. Bumper harvests of both rice and fish provided more protein, improved efficiency, and increased economic benefits.

In the 1980s, rice–fish culture made progress. Guided by the mutualism theory of rice and fish, scientific and technological workers developed many new techniques for shallow irrigation fields and adjusted the use of pesticides and fertilizer according to the new production structure and to changes in techniques of rice culture. Many new species of fish were used: grass carp, common carp, crucian carp, Beijing bream, silver carp, bighead carp, and tilapia. New techniques were developed that could produce yields of over 7500 kg of rice and 750 kg of fish per hectare.

rice–fish culture techniques can be divided into three categories: growing rice and raising fish together in the same field, rotating rice and fish, and continuing fish culture in the ricefield after the rice is harvested. In some areas, all three forms are combined. According to engineering facilities, rice–fish culture can be further divided into: feeding fish in furrows and growing rice on ricefield ridges, using ditches, pits, or ditches with flowing water, and additional techniques, such as raising fish and azolla together in the ricefield and raising fish and ducks at the same time in the ricefield.

rice–fish culture, rotation of rice and fish, and continuous rice–fish culture. In rice–fish culture, rice and fish live together in the same field. This technique can be used with early rice, midseason rice, and late rice. Some contradictions between growing rice and raising fish are unavoidable. Therefore, fertilizer and pesticides that can harm the fish are avoided. Generally, excessive engineering facilities are not necessary. Fish feed is not needed because the fish live on natural food in the ricefield. This is extensive culture. Average production is about 150 kg/ha and well-managed fields can produce over 750 kg/ha. The disadvantage of this technique is that the growth period of the fish is comparatively short and the harvested fish are small. Therefore, large fingerlings are usually used. The technique is occasionally used to stock adult fish for 1 year.

In a rotation of rice and fish, the fallow field left after the rice is harvested is used to raise fish. Generally, fish fry or fingerlings are stocked. After the rice harvest, the straw is left in the field. When the land is irrigated, the straw decays, which makes the water suitable for feeding adult fish. In this form of rice–fish culture, fish have more space to move about and it is convenient to spread feed, but the growth period is relatively long. Compared with raising rice with fish, production of fish is higher. Generally, fish yields are 300–450 kg/ha with maximum yields of over 1500 kg/ha. Because it provides remarkable economic benefits, rotation of rice and fish is widely used in fallow winter fields, during the summer with green manure crops, for stocking fingerlings to produce table fish, and in seedling beds to stock fish fry for fingerling culture.

In continuous rice–fish culture, rice and fish are raised together. Because the fish are raised after the ricefield is fallow, their growth period may be over 1 year, which produces better results. Generally, production reaches over 750 kg/ha. This form of culture is widely used in hilly and mountainous regions.

In practice, a combination of these techniques adapted to suit local conditions achieves the best results.

Other techniques. Fish can be raised quite successfully in furrows in ricefields. This method is based on a half-dry cultivation method developed by Hou Guang-jiong. It effectively transforms uncultivated ricefields and can increase rice production in low-yielding fields (e.g., fields in the foothills, cold fields, and water-logged fields). The ridges in the field can be thickened with layers of soil, and the water in the field can be made deeper. This raises the temperature of the soil, improves soil structure, promotes seedling growth, and improves water management. The fish help reduce diseases, pests, and wild grass and as a result, rice production is increased by 10–20%.

Fish can also be raised in ditches that contain water that is deeper than in the surrounding fields. Fish screens and ditches and pits in the centre of the field help improve the environment for the fish. Fish production in ditches is generally two to three times higher than in level fields.

In integrated fish culture in ditches and pits, pits are dug in the ricefields or along the side of the field and are connected with ditches. Fish are raised in the pits and ditches. This technique was developed after the contract-responsibility system was implemented for family operated rice–fish farms. The method offers several advantages. It improves water management, assures a good harvest, maximizes the use of pits in the field, and helps resolve conflicts between rice and fish caused by operations such as shallow irrigation, drainage of fields, and the use of chemical fertilizers and pesticides. The water in the pits helps the rice resist drought and provides a guarantee of steady rice production. The pits also provide more space for the fish, which enhances fish growth and improves yields.

If the pits are used as nursery ponds, the fry develop into fingerlings earlier, which reduces transportation costs for fingerlings. The pits also provide a capture area during harvest. Production is increased and farmers save work and time.

The technique of raising fish in ditches with flowing water is based on flowing-water aquaculture. It is a semi-intensive rice–fish culture technique that is used mainly in ricefields with good irrigation and sufficient water resources. Wide ditches are dug and a small flow of water is led into the ricefield. Because intensive aquaculture techniques and principles have been adopted, production is comparatively high. Farmers are adopting this technique rapidly in areas with the required water resources.

Rice–azolla–fish cultivation involves growing rice, fish, and azolla at the same time in the same field. This cultivation technique makes full use of space and water. The ricefield provides a good environment and rich food for the fish. Azolla, which grows on the water surface, provides feed for the fish and manure for the field. The fish eat pests and weeds and their excretions fertilize the field to improve the growth of rice.

Several other farming methods have also been developed to maximize the use of ricefield resources and involve rice–fish culture (e.g., growing various beans on the ridges of the field and herding ducks in the ricefield).

Comparison of New and Traditional Techniques

Many developments have been made in the new technique for rice–fish culture. The traditional techniques are integrated into the Rice–growing systems found throughout China. This ensures that rice–fish culture is practiced across China. However, the traditional technique does not suit all Rice–growing systems. Because there is only one model, it is difficult to extend and develop this model of rice–fish culture throughout all regions of China.

The new techniques include advanced culture and engineering features adaptable to local conditions. Effective engineering facilities help avoid conflicts between rice and fish and improve the ability of the ricefield to resist drought and flood. Rice production is therefore guaranteed along with substantial increases in both rice and fish harvests. The traditional technique cannot resolve or avoid conflicts between rice and fish. Sometimes fish must be sacrificed to guarantee rice production. This reduces income and discourages initiatives in rice–fish culture.

The new techniques apply lessons learned from alternative aquaculture techniques and new developments with respect to stocking size, variety, management, multispecies culture, feeding, and maintenance of water quality using fertilizers. These developments, together with a certain degree of intensification, play a positive role in improving fish production. The traditional technique does not involve these new aquaculture techniques and harvests of both rice and fish are not as good.

The new techniques fully apply the principles of rice–fish mutualism and soil thermodynamics. Different disciplines and the technical systems of farming and aquaculture are organically integrated. The effects and benefits of economics, sociology, and ecology are unified to promote the development of the rice–fish culture system. The traditional technique does not organically combine agriculture with aquaculture. Because the technical system for rice–fish culture is not perfected steady development of rice–fish culture cannot be assured. Moreover, because the new technique has led to increased harvests of adult fish, it has established the technical foundation for rice–fish culture to move from a self-sufficient economy to a commodity economy.

In 1983, the area for rice–fish culture in China was 441 000 ha. In 1987, it increased to 796 667 ha with 106 000 tonnes of fish production.12 At present, the area for rearing adult fish (excluding fingerling rearing) in ricefields is 708 027 ha with a total production of 124 900 tonnes and an average production of 180 kg/ha. This rapid rate of development is directly related to technical advances in rice–fish culture.

12 These figures differ from those presented in Table 2 of the paper by Cai et al.

Constraints to Rice–Fish Culture

Despite great advances, several technical and production constraints must be resolved:

The new technique has not been properly extended to farmers and there is a considerable yield gap between experimental models and the yields achieved by farmers. Some models yield over 3750 kg/ha, but farmers obtain yields of 150–300 kg/ha.

Fry and fingerling supply is insufficient.

The composition of the species for stocking and stocking density must be more fully studied.

Feed management must be improved to raise unit yields.

Weaknesses in fisheries management discourage initiatives taken by farmers in rice–fish culture.

Development of Rice–Fish Culture Techniques

Experience has proven that rice–fish culture is beneficial. Large amounts of fresh fish can be harvested, while the production of rice increases. In some cases, the production value of fish exceeds that of rice. rice–fish culture therefore offers potential for China, a country with limited land and a large, growing population. The country must develop this potential for food production, while increasing the income of farmers. China’s demand for grain and fish products will likely continue to increase.

There are no marketing problems for the products of rice–fish culture, and income is higher than from growing rice alone. Therefore, farmers are eager to develop rice–fish culture because of the demand for food and the increased economic benefits that can be realized.

rice–fish culture in China combines the principles of water conservation, soil improvement, and biological control into an integrated technique for rice–fish production. The new technique will play a important role in land management and environmental protection. rice–fish culture techniques are expected to develop rapidly in several areas.

Basic Techniques of Rice–Fish Culture

The rice–fish mutualism theory advanced the development of rice–fish culture. When other disciplines were integrated into rice–fish culture, the theory was further developed and improved. It is important to study the mechanisms of rice–fish culture, the natural laws governing aquaculture and agriculture, and the interrelationships among rice and fish, and other factors such as soil, water, and fertilization in the ricefield.

Rice Growing and Aquaculture

The study of the interrelationships between rice and fish will help understand the contradictions between the two production systems and find ways to enhance the harmony between agriculture and aquaculture and to improve yields for both rice and fish.

Integrated Rice–Fish Culture Techniques

rice–fish culture techniques must be integrated with alternative aquaculture (e.g., intensive pond aquaculture, lakes and reservoirs aquaculture, cage aquaculture, and other supporting techniques). This will help increase production per unit area and maximize the widespread practice of rearing fingerlings in ricefields.

Engineering for Rice–Fish Culture

To strengthen the capacity of rice–fish production systems to withstand natural disasters, rice–fish engineering facilities should be integrated with techniques of water conservation. Engineering facilities should also be flexible and adaptable to local conditions.

Management Model for Rice–Fish Culture Techniques

The economic benefits of the different rice–fish culture techniques that are practiced in different areas should be analyzed. Management methods for rice–fish culture must be studied to establish an economic model of rice–fish culture that is adaptable to local conditions, requires less input, but yields increased output.

There are 25 million ha of ricefields in China. Of these, about 10 million ha are suitable for rice–fish culture. If integrated rice–fish farming was further advanced by effective extension work, the area for rice–fish culture in China could be increased by several million hectares within this century. It would then be possible to produce the substantial quantities of fingerlings and adult fish needed to supply further development of freshwater aquaculture in ponds, lakes, and reservoirs. rice–fish culture will play a vital role in freshwater aquaculture, in the commercial economy, and in agriculture. It will produce food for China and the world.

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Development of Rice–Fish Farming in Guizhou Province

Shi Songfa13

rice–fish farming has been practiced for over 1000 years in Guizhou. It is most popular in eastern Guizhou (bordering the provinces of Hunan and Guangxi) in areas where communities of national minorities live. The most commonly cultivated species are “Gaopo” common carp and “river” common carp. Farmers gather fish eggs from ponds, ricefields, and rivers and hatch them to get fry. Because of climatic conditions, most areas have only two crops a year with a single crop of rice. Fish are cultivated at the same time as rice. Flat fields and extensive cultivation are the norm. Normally, fields are not drained and the farmers in southeast Guizhou even cultivate fish in the winter water fields.14

In 1984, the Departments of Aquatic Products, Soil and Fertilizer, and Agricultural Extension were organized to promote high-yielding techniques for rice–fish farming. A number of technical guidelines, such as the Technical Rules for Rice–Fish Farming and Technical Standards for Cultivating Fish in Ridge Box-Ditch Ricefields were published. Many demonstration plots were developed.

By 1987, there were over 3000 ha of high-yield demonstration plots (a 13-fold increase from 1984). The average yield was almost 400 kg/ha (40% more than in 1984). With these encouraging results, rice–fish farming developed rapidly. In 1980, 42700 ha of ricefields yielded 3348 tonnes of fish, by 1983, this had increased to 60000 ha and 4611 tonnes of fish. In 1987, there was a 75% increase in area and a 210% increase in yield (74700 ha and 10400 tonnes of fish). This amounted to 57% of the total fish production of Guizhou in 1987. The unit yield also increased 78% from 1980 to 1987 and reached 139 kg/ha.

Development Trends

With popularization and technical extension, rice–fish farming has improved the ecological environment of the ricefield and is making better use of the carrying capacity of the field and achieving additional benefits from low-level inputs.

13 Aquatic Products Division, Guizhou Aquaculture Bureau, Guiyang, Guizhou Province.

14 Winter water fields are ricefields that are left fallow and collect water during the winter. Rice is transplanted to these fields in the spring. This practice is prevalent in the cooler, mountainous areas of western China, particularly in the provinces of Sichuan and Guizhou.

New Rice–Fish Farming Techniques

Flat-field techniques of rice–fish farming have been replaced by ridge–ditch ricefields (in which the fish are grown in the ditches and the rice is grown on the ridges), box-ditch fish raising, and manure-pit fish raising in flat fields. Instead of farming fish only with rice, farmers now also grow wild rice or lotus.

Fish farming in the ridge–ditch fields does not require inundated irrigation, therefore, the conditions of water, fertilizer, oxygenation, and heat are improved in the soil. This has considerable impact on the rice. It stimulates the early growth of seedlings and early emergence of tillers. The grains of rice increase in number and size, which produces higher yields. This practice also increases field-water storage, improves drought-resistance capability, and provides sufficient deep water for fish. These factors all improve fish growth and lead to higher yields.

The Scientific Association of Southeast Guizhou Prefecture, the Information Institute of Scientific Committee, and the Prefecture Agricultural Institute conducted experiments in 1986 to observe the differences between ridge-field rice and flat-field rice. They found that there were considerable changes to the soil environment that affected the growth of the rice plants. Soil temperature in ridge fields was normally 0.2–0.4°C higher than in the flat fields. Results were particularly obvious in cold, muddy fields that had low soil temperatures. Growth was faster in ridge-rice cultivation. Seedlings recovered quickly after transplanting and tillers emerged 9 days earlier than in flat fields. The activity of soil microorganisms was also enhanced, which improves the breakdown of soil nutrients and helps provide adequate nutrition for root growth. With improved vitality, rice roots grew deep into the soil and the roots were stronger. During the tilling period, rice roots in the ridge fields were 8 cm longer than that in flat fields, and on average there were 20 more roots. During the full-ear period, the roots of plants on the ridges were 13 cm longer and there were 199 more roots. Ridge-rice cultivation can also enhance the resistance of the rice plant to drought and lodging. When fish and rice were grown together, topsoil fertility in ridge fields was significantly higher. There were increases of 0.55% in organic matter, 0.022% in whole nitrogen, 1.2 mg/100 gt in hydrolytic nitrogen, and 27.7 ppm in effective phosphorus.

Experiments carried out in 1986 by the Aquatic Products Station of Chishui County revealed that ridge-rice cultivation could improve rice tillering and increase average grain weight. In these experiments, the average number of grains per ear in the ridge fields was 140–155 compared with only 105–110 in flat fields. The average weight of 1000 grains in the ridge fields was 27.5–28.4 g, compared with 26.5–27.0 g for flat fields. The empty grain rate was 26.5–28% in the ridge fields and 39–41% in the flat fields.

Additional evidence of the benefits come from farmer experiments. A farmer, Jiang Chengxu in Suiyang County, conducted a comparison trial in an area of 0.05 ha (0.025 ha for each of the two methods). In each area, he stocked 2007-cm fingerlings. The flat field yielded 170 kg rice and 12.6 kg fish. The ridge field yielded 200 kg rice and 34 kg fish, or an increase of 18% for rice and 172% for fish. In the Southeast Guizhou Prefecture, ridge-field cultivation required 6–8 more farmer-days of labour, but the value of production increased by 50%.

Raising of fish in box ditches and manure pits in flat fields can also create a good ecological environment for fish because pesticides are not applied and exposure to sun and drought is reduced. This system increases the potential of the ricefield and produces higher fish and rice yields. Manure pits normally only occupy 10% (or less) of the ricefield and poses no threat to rice production. Chishui and Songtao Counties have carried out Rice–wild rice–fish and rice–lotus–fish experiments. Production values were CNY 3809/ha in Chishui and CNY 4170/ha in Songtao.15

New Species

Instead of raising only common carp, farmers now raise several fish species. The temperature of shallow water in ricefields changes with air temperature and is unstable. However, during the warm season, leaves of the rice plants shade the water surface and stabilize the water temperature. This creates a suitable environment for growing grass carp, common carp, silver carp, variegated carp, tilapia, and crucian carp.

The ricefield is an artificial ecosystem that abounds with various grasses, weeds, plankton, and other organisms. If only common carp are grown, these resources are not fully utilized and yields are not very high. In recent years, several species have been raised together and the results have been encouraging. This demonstrates that the ricefield ecosystem is suited for polyculture of fish. Normally, common carp are raised with grass carp or silver carp, grass carp with tilapia, or common carp with crucian carp and catfish. Either fry or adult grass carp can be raised.

With the appropriate number of fish, rice seedlings are not eaten by the grass carp. The fish consume grass and weeds to the benefit of rice growth. For example, 2250–3000 grass carp and common carp (in the ratio of 4:6 of 10-cm fish) can be raised in 1 ha without damage to seedlings. When the fish have grown to 17 cm in length and are able to eat seedlings, the rice plants are tall enough to avoid damage. If the grass carp are over 20 cm in length, 450–750 fingerlings can be put into a 1-ha ricefield. In this case, additional feed (grass) must be provided during the early stage to keep the grass carp from eating the rice seedlings. If silver carp and variegated carp are raised, their number should be limited to 5–10% of the total number of fish raised.

In Huangping County, farmer Yang Zaigui raised fish in a 0.08-ha ricefield. On 12 June 1988, he stocked 49 grass carp fingerlings (8.9 kg), 372 common carp fingerlings (18.4 kg), and two silver carp fingerlings (0.6 kg). After 105 days, he harvested 34 grass carp (31.15 kg), 356 common carp (66.9 kg), and two silver

15 In October 1988, USD1 = CNY 3.7221 and CAD1 = CNY 3.1889.

carp (1.81 kg). Total net production was 73.05 kg. Yield per hectare was 906.8 kg fish and 7875 kg rice.

Species Improvement

Local common carp have been replaced with hybrid common carp. The trend is toward improved species. Local Gaopo carp has long been raised in Southeast Guizhou. It is docile, quiet, and usually does not jump. During floods, it does not panic and swim away. It hides in muddy rice water when disturbed. However, its quality is deteriorating because of poor selection of brood stock. Parent fish are so small that their offspring do not develop properly.

In 1985, the Aquatic Products Bureau of Leishan County sampled 50 Gaopo carp. The heaviest one was 350 g and the smallest 25 g. Five of the fish that weighed 25–95 g were mature. Work by the Aquatic Products Bureau of Luping County revealed that this fish is sexually mature at approximately 100 g. Results from the Aquatic Products Bureau of Guiyang City showed that 35% of the fish with an average weight of 185 g were sexually mature. This suggests that Gaopo carp have seriously deteriorated and are maturing at a small size. Since 1980, many localities like Zunyi, Chishui, Wuchuan, Zheng’an, Jinping, and Tianzhu have worked to improve carp varieties. While paying attention to the selection and improvement of local varieties, they have also introduced improved brood fish.

In 1983, the Aquatic Products Bureau of Zunyi Prefecture introduced parent fish of two common carp varieties, Yuanjiang carp and Wuyuanhese red carp. They achieved good results when they released the hybrid Heyuan carp from these two varieties. In 1988, the Aquatic Products Bureau of Luping County compared improved common carp and local common carp. Growth characteristics were evaluated by taking five samples at monthly intervals after release. Improved common carp gained 1.95 g more each day and relative growth was 1.5% higher. When the improved common carp weighed 520 g each, the local common carp weighed only 200 g (40% less).

In 1987, the entire province began the systematic improvement of common carp. In 44 variety improvement sites, 31.4 million fry and 9.8 million fingerlings of improved common carp were produced. A total of 967 ha of ricefields received this variety and results were good.

Intensive Cultivation

Intensive cultivation of fish is now replacing extensive cultivation. Extensive cultivation only uses natural feed; therefore, yields are low. In 1980, the provincial average yield of fish was 78.3 kg/ha. To achieve high yields, traditional culture systems must be replaced with intensive culture systems that make full use of the carrying capacity of the ricefield ecosystem. Farmer Lu Binlun in Danzai County conducted a comparison trial in 1985. Intensive culture yielded 1242 kg of fish per hectare or 4.6 times more than extensive cultivation (220.5 kg/ha). In 1983, farmer Liu Dingzhong of Longquan Township raised fish in a 0.32-ha ricefield using earthworms and maggots as additional feed. He harvested 580 kg fish or 1812 kg/ha. In 1984, farmer Li Xingji in Suiyang County harvested 325.4 kg from a 0.21-ha field by using wastewater from factories.

Prospects

Guizhou Province is a subtropical area with a humid monsoon climate. It has low latitudes and high elevation. The temperature is relatively high in winter but low in summer. The yearly average temperature is between 14°C and 16°C in most areas. The temperature is above 10°C for 220–240 days a year, and 270 days are frost-free. Annually, there are about 180 rainy days, 1100 mm of rainfall, and 1200 hours of sunlight. There are many cloudy and rainy days and yearly changes in light, heat, and water are synchronized. All these conditions are conducive to growing rice and fish. The longer growth period for fish and the good overwintering conditions allow a sound farmland ecosystem can be established to increase the production of rice and fish.

Ricefields in the province cover a total area of 791 000 ha, over half (about 400 000 ha) of which are low-yielding fields. There are 122 000 ha of winter water fields. These areas are, to various degrees, poor, barren, highly acidic, sticky, sandy, muddy, and cool and therefore do not produce high yields of rice. Fish farming improves the soil and rationally uses the land to produce more rice. Fish farming is profitable and has the potential to improve the economic situation of farmers, particularly in mountainous areas.

In 1984, a survey was conducted of 20 farming households in Danzai County that covered about 1.32 ha of rice–fish farms. The output of fish and rice was valued at CNY 4374/ha, 90% more than rice cultivation alone. Surveys in Danzai and other counties showed that rice–fish farming increased the output value of ricefields by CNY 817.5/ha.

In the future, rice–fish farming will undoubtedly supply a large portion of the fisheries production in Guizhou, especially in mountainous areas where there are large ricefields but few ponds or reservoirs. It is important to develop rice–fish farming and to establish systems for technology extension and for the production and supply of improved varieties. ridge–ditches, box-ditches, manure pits in flat fields, and other forms of rice–fish farming should be adopted to suit local conditions. Improvement of the common carp variety must continue. Mixed culture of species (mainly common carp and grass carp) should be practiced. Intensive cultivation should replace traditional extensive cultivation, which usually has low yields with low input. Improved fish-farming techniques should be adopted in a systematic way to make the best use of ricefield resources and to improve fish yields.

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Reforming Rice–Fish Culture Technology in the Wuling Mountains of Eastern Guizhou Province

Chen Guangcheng16

In the past, traditional methods of rice–fish culture were used in the Wuling Mountains. Because output was very low, several reforms were undertaken to improve rice–fish culture.

Improving the Environment for Fish

Depending on the type of soil, furrows, wide ditches, or pits were dug to culture fish in flat ricefields. In cold, muddy, fertile fields, rice–fish culture can be carried out in furrows and wing ditches. The ridge of the furrow is normally about 26-cm wide and the ditch about 39-cm wide and 26–33 cm deep. In muddy fields, where it is difficult to make ridges, wing ditches were introduced. The wing is 2-m wide and the ditch about 0.8-m wide and 0.5-m deep. This innovation improves soil structure, light, and temperature and increases rice production.

In 1985, these innovations were tested at 54 sites (13.7 ha). The dry rice yield averaged 6712 kg/ha (18.% more than in flat fields). Ditches help solve problems created by shallow water and variations in water temperature in flat fields because they increase the volume of water by about 100%. In summer, changes in water temperature are 2–3°C lower than in flat fields. This improves the environment for the fish. In these tests, average fish yield was 507 kg/ha. In high-yielding fields that can produce 7500 kg of rice per hectare, fish production is often 750 kg/ha. In 1987, a 1.5-ha field averaged 7605 kg of rice and 825 kg of fish (average weight per fish 0.85 kg).

The farmers are given these instructions to implement the new technology:

To culture fish in a field, dig a pit big enough to make up 5–10% of the field. The pit should be 1.5–m deep and it should link to the fish ditch. There is four times more water in this field than in flat fields. This not only benefits fish growth, but increases the quantity of fish and provides the convenience of dry fields, where farmers can apply additional fertilizer and agricultural pesticides.

In terraced fields, a big side ditch is dug in the back ridge. The side ditch should be 1-m wide and 1-m deep and should be linked to the fish ditch. This enhances the growth of rice, which benefits from warmth, and the fish,

16 Bureau of Aquatic Products, Tongren Prefecture, Guizhou Province.

which like the water. These changes provide conditions for high yields in rice–fish culture.

Stocking Large Fingerlings and Late Harvesting

In the past, the fish species were usually breed and cultured by the farmers. Most of the strains have degenerated. A system of elite breeding has now been established based on the district and township fish hatcheries (e.g., there are 104 sites in Yinjiang County).

Instead of small fingerlings, 250–300 large (about 10 cm) fingerlings are stocked in the fields. Fingerlings should be stocked before the seedlings are planted (from February to April). This allows the fish to obtain food when plankton is abundant. Experience has shown that the same-size fingerlings stocked before planting rice seedlings weigh 100 g more than fingerlings stocked after planting.

Keeping water in the fields when the rice is harvested allows the fish to grow for an additional 60 days and to increase their weight (to about 150 g). During this period, the rice that falls into the field and the young rice seedlings that grow from the roots of the rice are good food for fish.

In February 1987, Li Demin, a farmer in Yundu Township, Jiangkou County, put 200 grass carp and 200 common carp, each about 15-cm long, into a 0.2-ha field. In May, he put 1800 small fingerlings into the same field. On 19 October, he harvested 162 kg of adult fish and 31 kg of fingerlings. The adult fish averaged 0.52 kg and some were as large as 1.6 kg. The average yield was 986 kg of fish and 6358 kg of dry rice per hectare.

Polyculture and Intensive Culture

In mountainous areas, the fields are poor and weedy; therefore, a polyculture of grass carp, common carp, and silver carp is used in the ratio of 3:6:1. From May to July each year, 15000 small fingerlings of grass carp and common carp are stocked per hectare of field. By November, the fingerlings reach a length of 12–18 cm and the survival rate is 20–30%. Weeding is not necessary in fields devoted to polyculture.

In intensive culture, a base fertilizer is applied before the fish are stocked into the fields. From April to May, it is not necessary to feed the fish because they are small, water temperature is low, and benthos and weeds are plentiful. From June to September, feed should be applied once a day. After the rice is harvested, the quantity of feed should be reduced.

Scientific Water Management, Proper Irrigation, and Drainage

The basic principal is to consider the needs of both the rice and the fish. When fingerlings are stocked before the rice seedlings are planted, the water level should be maintained to minimize fish deaths. Five to seven days after the rice is planted,

Table 1. Output and value of rice and fish harvests before and after technical reforms.

Rice (1986) Rice (1987) Fish (1987) Fanners Location Area (ha) Output (kg) Value (CNY) Output (kg) Value (CNY) Output (kg) Value (CNY) Liu Tongren 4.4 27056 16234 27571 16543 3286 19717 Shu-chen Yian Yuping 1.5 10545 6327 10605 6363 1175 7050 Zhu-shen WuXiu-shu Songtao 1.3 8360 5016 8740 5244 726 4354 Long Songtao 0.8 5350 3210 5670 3420 481 2886 Tian-ci Li Deming Jiangkou 0.2 1200 720 1238 743 192 1155 Huang Tongren 0.2 1260 756 1462 878 160 959 Xin-tuan Total 8.4 53771 32263 55286 33191 6020 36121

the water level should be reduced to promote tillering. In a furrow or ridge system, the water should flood the roots of the rice seedlings. When the rice seedlings begin to turn green, the water level can be reduced. This will not affect the fish because they are still small.

A month after rice seedlings are planted, the flat fields should be drained for weed control. Later, the rice water level should be raised to about 12 cm to control ineffective tillering of rice and to benefit fish growth. After the rice is harvested, the water should be raised to over 50 cm for continuous fish culture.

Economic Benefits

These technical reforms have produced economic benefits (Tables 1-3).

Value of Output

In 1986, 8.6 ha of ricefields produced 53 771 kg of dry rice, valued at CNY32 262 (Table 1), or an average of CNY3 840/ha. In 1987, with rice–fish culture, these fields produced 6020 kg of fish valued at CNY36121 and 55286 kg of rice valued at CNY33171. The total value of production was CNY69 292, or an average of CNY8249/ha, which was 2.1 times more than in 1986 without fish culture.

Ratio of Investment to Income

In 1987, CNY7 567 was invested in rice–fish culture, an increase of CNY5 252 from 1986. But in 1987, net income was CNY61 725, which was CNY31 778 more

Table 2. Investments (Invest.) and income before and after rice–fish culture (CNY).

1986 1987 Area (ha) Net Income Invest. Income Net Income Invest. Income 4.4 15130 1104 16234 31796 4464 36260 1.5 5869 458 6327 12259 1154 13413 1.3 4610 406 5016 8657 941 9598 0.8 2986 224 3210 5768 520 6288 0.2 650 70 720 1628 270 1898 0.2 703 53 756 1619 218 1837 Total 8.4 29948 2315 32263 61727 7567 69293

Table 3. Achieved value by labour force before and after rice–fish culture (CNY).

1986 1987 Area (ha) Net Income Investment Income Net Income Investment Income 4.4 15130 706 21 31796 1170 27.18 1.5 5869 275 21 12259 440 27.86 1.3 4610 228 20 8657 349 24.8 0.8 2986 137 22 5768 227 25.41 0.2 650 27 24 1628 53 30.71 0.2 703 30 23 1619 51 31.74 Total 8.4 29948 1403 21 61726 2290 26.95

than in 1986 (Table 2). The ratio of investment to income from rice–fish culture was 1:6.

Rate of Return

In 1986, net income was CNY29 947. In total, 1403 workers were employed and each produced an output value of CNY 21.34. In 1987, net income was CNY61 725, which was achieved with 2290 workers; therefore, each produced an output value of CNY 26.95 or CNY 5.61 (26%) more (Table 3).

Value of Fish

Before the reforms in rice–fish culture, fish from the fields weighed about 100 g each. Because the species had degenerated, they could only be sold for food for about CNY 2/kg. After the technical reforms, 11780 fish were caught from 8.4 ha of ricefields. Total weight was 6020 kg, or an average of 0.51 kg/fish. These fish fetched a price of CNY 6/kg; therefore, the commodity value of the fish increased three times after the technical innovations.

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The Development of Rice–Fish Farming in Chongqing City

Xu Shunzhi17

rice–fish farming has been conducted for over 1000 years in the city of Chongqing. For a long time, however, fish yields were poor and unstable because of extensive cultivation, traditional methods, and a variety of limiting factors. Advances in science and technology, the development of the fish industry, changes in the structure of rural industries, and an increase in the commodity market led people to seek new ways to maximize water resources. They pursued new productive technologies that changed the traditional system of rice–fish culture and produced economic, social, and ecological benefits.

The productivity of rice–fish farming in Chongqing has been improved by engineering installations, new technologies for rice–fish farming, and improved circulation of nutrients and energy in the water. The contribution of rice–fish farming to total fish production in the city increased from 2–4% in the 1970s to 29% in 1987. In 1987, rice–fish farming ranked second as a method of fish production and was conducted on 73300 ha of ricefields that produced 10200 tonnes of fish. New cultivation technologies were practiced on 22250 ha of the total area and produced 6680 tonnes of fish. Some demonstration fields produced 3000–4500 kg/ha. Total production from rice–fish farming was valued at more than CNY 50 million.

Rice–Fish Farming in Chongqing

Chongqing, in eastern Sichuan Province, has a subtropical monsoon climate with adequate heat and rainfall during the warm season. The average temperature is 17.5°–18.5°C, and there are 1000–1100 mm of rainfall, 320–340 frost-free days, and 1200–1300 h of sunshine. These conditions are suitable for the cultivation of fish.

For many years, production from rice–fish farming remained poor and unstable. Improvements were not made because of political changes, faulty economic policies, changes in farming systems, primitive cultivation technologies, traditions that were difficult to change, and damage from natural disasters. The area devoted to rice–fish farming eventually decreased to less than 4000 ha with a total production of only 300 tonnes. New cultivation methods that used trenches and sumps were introduced before the 1980s, but results were limited because the

17 Chongqing Bureau of Agriculture, Animal Husbandry and Fishery, Chongqing, Sichuan Province.

trenches were small and the pits were shallow. During the hot, dry season, conflicts between the water requirements for rice and fish could not be solved.

However, recent improvements in the rural-responsibility system, the extension of rice–fish culture technology and the commodity market, and new economic benefits have encouraged farmers to develop rice–fish farming. The units responsible for developing aquatic products advocated, demonstrated, and extended advanced fish-culture technology. These efforts contributed to the rapid development and increased productivity of rice–fish farming in Chongqing (Table 1).

To increase production, a variety of methods were studied and adapted to local conditions of topography, terrain, water quality and temperature, soil, and vegetation. The goal was to enhance the growth of both rice and fish and to achieve bumper harvests of both crops. Gradually, fish culture in ricefields was developed and promoted through demonstrations and extension, and an increased number of farmers adopted the new technology. Farmers started to stock fish rather than depend on natural populations. Ricefields produced multiple, instead of single, crops. The management and administration systems for fisheries were also improved.

Cultivation Models of Rice–Fish Farming

In rice–fish farming, both rice and fish live in the same body of water and help each other by creating a favourable living environment that meets their physiological needs. Optimum conditions include the correct temperature, prop