Rice-fish systems in China

Rice-fish farming, an age-old farmer practice in China, can be traced back more than 1,700 years, although recently it has been largely ignored. Integrated rice-fish farming in China is generally characterized by four basic components: (1) extensive use of land; (2) low input; (3) low yield; and, (4) household consumption of rice-fish production.

After the founding of the People's Republic of China, the government organized farmers and encouraged them to develop integrated rice-fish farming systems. As a result, hectarage under rice-fish farming reached 700,000 ha in 1959, but sharply declined in the 1960s and 1970s due to the wide use of pesticides, reformation of the cropping systems and me unfavorable national economic policy during the Cultural evolution" period (1966-1976). During this period, acreage of rice-fish farming dropped from 40,000 ha to 320 ha in Guangdong Province and a similar drop from 230,000 ha to 5300 ha was documented in Hunan Province. However, during the recent "refomnation" and Opening" period, the government is again encouraging the adoption of rice-fish farming.

With farmer initiative and assistance from the government, the adoption of rice-fish farming is rapidly expanding. It has traveled from Guandong Province in the South to Hei-Long-Jiang Province in the north and has reached historical proportions with more than 1 million ha in 1986. Sichuan, Hunan, Guizhou and Fujian are the four top provinces in China.

Rice-fish systems are principally found in the hilly areas of the Yangtze river basin and other parts of Southern China, although some rice-fish can be seen in northern provinces. The traditional rice-fish systems presented here are found in both irrigated and rainfed areas. The improved designs are principally found in irrigated conditions. Most rice-fish farmers in China are cooperatives farmers" with small landholdings of 1,500 sq m or less. Nommal fish pond size is usually 1,000 sq m.

Major component technologies of rice-fish systems in China are presented here.

2 Chinese "mu" (1 mu = 0.67 ha) 1 chinese "mu"

Rice-fish farming system (Hubei China)

1. Appropriate Construction of Paddy Field

· Traditional Paddy-Field Without Trench

The traditional paddy field layout has no trench or pond in the field and the water storage capacity is limited. Fish growth is more directly effected by rice crop management and the result is a low and unstable yielding.

· Trench-Pond Integrated Rice-Fish Designs

“Trench-Pit" Design

This is an improved design with a small, shallow pit (1-2 sq m) in the center of the field. Crossing trenches are dug to connect the pit to all side trenches. Increased water storage capacity offers a better refuge for the fish. This design raises rice yield by 10% and 1-2 times as many fish can be raised as compared with the traditional design.

"Trench-Pond" Design

This design is a further improvement with a larger, deeper pond at one end of the field. Crossing trenches are also dug to connect the pond to all sides. This design significantly increases the water-storage capacity and provides a better environment for the fish. It raises and stabilizes the yield of both rice and fish.

· "Ridged-Field" Rice-Azolla-Fish Model

This design was originally developing for swampy areas with objective of improving soil properties and increasing rice yield. Later, it was step-wise integrated with azolla and fish. Rice is planted on the ridge, azolla as a feed for fish as well as a bio-fertilizer and green manure and fish are stocked in the trenches.

Azolla is a small aquatic (usually 1-5 cm large) which can grow on saturated or moist soils. It is capable of doubling its weight in 3-5 days. Azolla fixes atmospheric Nitrogen and can fix 3-7 kg N/Ha daily. It contains 4% Nitrogen on a dry-weight basis and is an excellent source of nitrogen fertilizer.

Production DATA OF RICE-FISH-AZOLLA SYSTEM (IRRIGATED LOWLANDS).

2. Basal Fertilizer Application

Physical injury to fish caused by inorganic fertilizers used in rice production can be a constraint to rice-fish systems. Necessary measures should be taken to minimize fish injuries. One such measure is to increase the amount of the basal fertilizer application during the land preparation stage to approximately 80% of the total nitrogen and 100% of the total phosphorous requirement

Basal fertilizer application

3. Transplanting

Reduced rice plant population within the ridged field paddy design caused by the construction of trenches and refuge ponds is one farmer constraint to the practice of rice-fish systems. Farmers can lose as much as 10% of their paddy when constructing trenches and refuge ponds for ricefish systems. In order' to minimize reduced plant population (and potentially reducing crop yield), plant spacing can be intensified by reducing the recommended distances between hills while maintaining the row spacing (20-25 cm). Normal hill spacing of 15-20 cm between plants can be cut in half to 7.5-10 cm, thus doubling the plant population in the side-rows of the trench.

Basal Fertilizer Application

4. Fish Stocking Considerations In Rice-Fish Systems

· Grass carp, common carp, Nile tilapia and crucian carp are four predominant species for polyculture rice-fish farming in China. One such system involves four species: grass carp (Cyen opharyngodon idellus), Tilapia sp., common carp (Cyprinus carpio) and crucian carp (carassius aurotus), with the first two species making up the majority. The recommended mix is a 25-45% composition of both the grass carp and tilapia (a total combined composition of 70%) with a 15% mix of both common and crucian carp (remaining 30%) at stocking rate of 2-3 sq m. This mix of species can give an optimal yield of both rice and fish.

Fish stocking

· When stocking fingerlings in the pond or paddy, a large difference in water temperature between the container used to transport the fish and the paddy can lead to fish loss and a poor survival rate. Therefore, it's recommendable to mix water from the paddy with the water in the container to slowly regulate the temperature differences and allow the fish to adjust to the water temperature of the field.

Large difference in water temperature between the container used to transport the fish and the paddy can lead to fish loss and a poor survival rate.

5. Top dressing Fertilizer Application

Top-dressing fertilizer is applied at the panicle differentiation stage (about 28-30 days to heading). A shallow layer of standing water in the paddy is necessary for fertilizer application, but can increase the possibilities of injuring the fish. However, two alternatives exist which can help to minimize these limitations.

Fishes in trench: Fertilizeren

· Slowly drain the water from the paddy allowing the fingerlings to return to the refuge trench/pond. As the water in the ridges almost dries, the top-dressing (broadcast) can be applied, thus controlling injury to the fish as well as achieving fertilizer efficiency. Two to four days after the fertilizer is applied, the field is again flooded. To irrigate and to open the water layer in field before top-dressing.

Fertilizer application can be done by deep placement by hand or by using machinery. The fertilizer should be applied at a depth of 810 cm. Fertilizer efficiency and reduced risk

Fertilizer application to fish health are also attained. (Note: The paddy should also be drained for using the deep-placement method.)

6. Pest Management

· Weeds

Stocking fry in newly transplanted rice field

Stocking fingerlings in established rice paddy

Many weed varieties found in the rice paddy are good feeds for grass carp. Stocking fry at 2-3 pieces/sq m (2-3 cm long) fingerlings at 2-3 pieces/10 sq m or (-10 cm long) one month after transplanting can help to control weeds, thus, reducing the need for other weed-control techniques. As the fingerlings grow, daily supplemental feeding with green grasses is necessary to avoid damage to the young rice plants by the fish. Grass is usually fed to the fish in the pond to avoid damage to the rice plants; while rice bran and other supplemental feeds can be directly fed to the fish in the paddy area.

Fish in the paddy area.

· Insects and Diseases

Fish eat insects, such as stem borer and leaffolder which move through the water among the rice plants and hoppers which catch them as the float on the water from the riceplant. Fish reduces need for pesticide. Fish also eat the pathogens (such as sheath blight disease) floating in water and on the bottom as well as disease infected leaves, therefore, not only reducing the pathogens but also improving plant's health. Thus, the use of fungicides can also be reduced. If pesticides must be applied, certain precautions should be taken. In traditional fields, the field should be flooded with more water.

Insects and diseases

Pesticide Application

Similar to fertilizer application, damage to fish health can be incurred with the application of pesticides to the rice crop. However, using simple techniques such as slow field drainage, allowing the fish to return to the trench/pond, cautious application of the pesticide, an allowance for a brief waiting period and re-irrigation of the field after application can help to ensure minimal losses due to pesticide poisoning.

In fields with trench/pond designs, the water should be drained into the trench or pond, thus driving the fish into the refuge area before the application of pesticides.

In traditional paddy field design, fish can be driven to one half of the field and pesticide application can be done in the other half of the field. The same procedure can be repeated to the other half of the field on the following day.

Prepared by: GUO YIXIAN

FARMER-PROVEN INTEGRATED AGRICULTURE-AQUACULTURE
A TECHNOLOGY INFORMATION KIT (IIRR-ICLARM)