|Rice - Fish Culture in China (IDRC, 1995, 240 p.)|
|Part II: Patterns and Technology|
The model for rice-fish culture with fish pits was developed as an improvement to traditional rice-fish culture. It has now become the main type of rice-fish culture and, in some regions, the major way for farmers to increase their incomes.
China has a long history of rice-fish culture. The traditional method of rice-fish farming in flat fields faces many conflicts between rice and fish and is easily upset by changes in natural conditions. Farmers often have to sacrifice the fish to save the rice, which has diminished the role of rice-fish farming and hindered its development. Before 1980, rice-fish farming in Dazu County yielded only 22.5-52.5 kg of fish per hectare. In 1981, rice-fish farming in flat fields advanced to some extent, but fish yields were still very low (Table 1).
Before the 1980s, aquaculture scientists in China experimented with fish troughs combined with fish trenches, which had been adopted in ricefields in the southern part of Jiangsu Province. However, during the midsummer droughts in Dazu County, the shallow troughs and small trenches did not provide sufficient water for the rice and fish. As well, the fish were not able to adapt to the high temperatures experienced during the drought.
Researchers in Dazu County studied the factors that influenced fish growth, e.g., the relationship between temperature and depth of the different water layers, the upper and the lower limits of temperature that suit fish growth, the relationship between the appropriate temperature range and the environment of the ricefield, the quantities of dissolved oxygen produced and consumed during the day and at night, and the form of oxygen molecules moving in the water. Based on their research, they developed a new approach to solve the conflicts between fish and rice. They dug 1-m deep fish pits that covered about 6-8% of the ricefield and connected the pits to trenches. Field experiments were conducted in many areas between 1980 and 1983. This new model of rice-fish farming was verified and accepted by farmers and the county government.
Development of the Method
At the beginning of the trials in 1981, the area for rice-fish farming with fish pits was 0.2 ha. In 1982, the area reached 1.1 ha. Multiple-plot trials totalled 14 ha in 1983. By October 1984, the area had expanded to 3080 ha, and by the end of 1985, 3570 ha had been developed. Farmers had discovered that the economic benefits from the new model were 3-8 times greater than from flat field rice-fish culture. Fish yields as high as 3195 kg/ha were obtained. From 21 July to 31 August 1985, Dazu County experienced a midsummer drought and 5800 ha of flat-field rice-fish farming (58.8% of the total area devoted to rice-fish farming) were damaged. However, good harvests of both rice and fish were obtained from rice-fish farming with fish pits. This convinced the farmers of the value of using the new model and the technique became popular. By the end of August 1986, the total area of rice-fish culture with fish pits reached 41 474 ha. It is expected that new developments will move toward combining fish pits with shallow ponds.
Aquaculture production in Dazu County from all types of water areas has increased (Table 2). Rice-fish farming has developed most quickly. Rice-fish farming includes rice-fish farming with fish-pits and flat field rice-fish farming. In the past few years, production changes from both types of farming have been remarkable (Table 3). The fish-pit method shows greater resistance to natural disasters compared with the flat-field style. Although adult fish yields from the fish-pit method increased remarkably in 1984-1985, the unit yield of fish from flat fields decreased, apparently because of the midsummer drought. Since then, the area devoted to the fish-pit method has increased each year. Fish production from fish-pits varies depending on the progress of experiments, demonstrations, and extension efforts. Actual production levels in 1985 are presented in Table 4.
Although the environment in the fish-pit method is superior to the environment in the flat-field style, production of adult fish was directly influenced by management level (Table 5). Large-scale experiments, demonstrations, and extension were carried out in 1984-1985. Yields decreased as the level of researcher involvement decreased. Yields were highest in experimental areas and lowest in the extension areas.
These large-scale areas where used to obtain economic data. The ratios of input and output in 1984 were 1:2.86 for the flat fields, 1:3.59 for the fish-pit method, 1:3.35 for demonstrations, and 1:3.43 for extension. In 1985, the ratios were 1:2.61, 1:3.98, 1:3.16, and 1:3.23, respectively. Average profits from raising fish in flat ricefields was CNY 1833/ha, with 92.5% of the profit from rice and 7.5% from fish in 1984. In 1985, profit was CNY 1600/ha with 90.5% from rice and 5.5% from fish. Because of the midsummer drought in 1985, profits decreased by 2%. In ricefields with fish pits, profits (CNY 3204/ha with 58% from rice and 42% from fish) were highest from the experimental district. The income from ricefields with fish pits was 6.3-9.8 times greater than from the flat fields in 1984 and 17.7 times greater in 1985. Practice has proven the remarkable beneficial results of the new model, and additional developments of this model are expected.
Feng Kaimao is with the Agriculture, Animal Husbandry and Fish Bureau, Dazu County, Dazu, Sichuan Province.