Rice-fish system in Guimba, Hueva Ecija, Philippines

Guimba, Nueva Ecija, in the Philippines has rainfed and irrigated rice-based agriculture. In rainfed areas, rice is grown during the wet season and remains fallow during the rest of the year. In irrigated condition, rice grown during the wet season is followed by another crop of rice during the dry season. Ricefish culture is practiced by some farmers. In areas with extremely light soils, farmers plant vegetables (e.g., squash, cucumber, mungbean, stringbeans, onions, bitter gourd, etc.) and water melon after wet season rice.

The rice-fish system practiced by farmers in Triala Village, Guimba is concurrent rice-fish with pond refuge. This system is for growout of Nile tilapia. The operation is done as follows:

RICE-FISH FIELD DESIGN AND CONSTRUCTION

Rice-fish field

1. Site Selection

· Abundant and dependable water supply. Irrigation water, ground water, spring and other water sources are used when they are not contaminated by pesticides.

· Clay soil is best. Clay holds water, prevents seepage and leaching of fertilizers.

· Choose site with good drainage and is free from flooding.

2. Design and Size of Field

· Independent filling and draining of each rice-fish compartment is considered.

· Ease of fish movement into the rice fields during grazing and draining is also considered. Fishes should be able to get quickly into the canals or refuge when water level is very low.

· Size of rice-fish plot considers the natural partitions of the field. Small plots are easy to manage and fish survival is usually high.

Examples of fish REFUGE LA layout for small and large plots

· Dikes are made strong and big enough to contain 30 cm. of water

3. Fish Refuge

Pond refuge is preferred over trench refuge. It holds more water and is less risky. Refuge size is usually 10% of the ricefield area. Bigger refuge or a pond adjacent to the ricefield may also be connected to it through a canal.

To construct the refuge, the pond is excavated at one end, or two ends if the field is large, inside the ricefield or adjacent/alongside but connected to the field so that the fish can have access to the area planted to rice.

4. Inlet and Outlet Gates and Screens

These are made of bamboo and other low-cost materials. Screens prevent the escape of stocked fish or entry of unwanted fish into the field.

RICE AGRONOMY

1. Rice varieties—High-yielding varieties; maturity period of 120-130 days; resistant to insects and diseases.

2. Seedbed preparation and seeding rate—

Size:	400-500m2
Rate:	100-150 kg /ha
Fertilization:	broadcast urea at 25 kg/ha. 10-15 days after sowing.

3. Land preparation - After plowing once and harrowing thrice, the field is levelled evenly so that every part of it will be uniformly irrigated.

4. Rice transplanting methods -

Age of seedlings:	25-30 days
Planting distance:	20-25 cm between rows
	15-20 cm between hills

Straight-row planting (optional), if mechanical weeding is done.

5. Weed control—Fish stocked in ricefields control certain weeds. Weeds are also controlled through:

· thorough land preparation
· flooding the field at an effective water depth for one to two weeks immediately after transplanting.
· manual weeding

6. Water management—Water depth in the field when rice is newly transplanted is 3 - 5 cm. This is then gradually increased up to 20 cm. to provide better living space for both rice and fish as they grow bigger. One week before the rice harvest, water is slowly drained so that fishes have enough time to move into the refuge.

Water management A

Figure

Water management B

Water management C

7. Fertilizer application—The amount of fertilizer applied follows the recommended rate in the area. In Guimba, the rate applied during wet season is 200 kg/ha of ammonium phosphate and 50 kg/ha of urea for the first or basal application. The basal application is done immediately after the final leveling, (which is followed by transplanting). The rate for the second application or topdressing is 50 kg/ha. This is applied 30 days after transplanting. The amount for top dressing may be split into two equal applications Thus a third application is applied 75 days after transplanting.

During dry season, the same amount for basal application is followed. For topdressing, the rate is 100 kg/ha.

As an example, the amount of fertilizer for a 400 sq m of rice-fish during wet season is: 8 kg ammonium phosphate and 2 kg urea for basal application. For topdressing, 2 kg urea is needed.

8. Insect control—The use of insecticide is not recommended. The farmers, however, apply insecticides known to be less toxic to fish.

COLOCASIA PLANTING

Colocasia sp., an aquatic plant, is an excellent food material. It can be grown as an added commodity in a rice-fish farm. Practically, all parts of the plant can be eaten (tubers, stalks and leaves). It can also be utilized as food for the fish and for animals, especially pigs. The cultural requirement is simple and it requires no expensive inputs.

Colocasia planting

HOW TO RAISE COLOCASIA SP.

1. Obtain young tubers as plant materials.
2. Cut old leaves but retain the young leaves and shoot.
3. Cut the tuber into half

Cut the tuber into half

4. Plant the tuber at 50-70 cm intervals along the side of the dike, about 5-10 cm below the water surface.

5. Start harvesting after 4-5 months.

FISH CULTURE

The species cultured are Nile tilapia (Orechromis niloticus) and common carp (Cyprlnus carpio). Large fingerlings, 15-25 9, are recommended as they reach harvestable size within one rice crop. It only small fingerlings (5-109) are available, fish culture is done in two stages:

Stage I: Raising 5-10 9. fingerlings during one rice cropping (harvest size: mostly 50 9.)
Stage II Extending fish culture period after rice harvest for up to 2 months (harvest size: 50 9.)

Fish Stocking density

· Stocking can be done before or during land preparation in the pond refuge; or 7-10 days after transplanting (DAT), if released direct to the field. If stocked in the pond refuge animal manure should be applied into the refuge 4-5 days before fish stocking. About 15 kg may be applied in a 100 sq m pond refuge.

The stocking rate for Stage I, using either monoculture of Nile tilapia or polyculture of Nile tilapia and common carp is 5,000- 7,500 fish/ha. For polyculture, the stocking ratio of Nile tilapia to common carp is 1:1 or 2:2, depending on which species is more important to farmers.

· Ten days after transplanting, fish stocked in the pond refuge may be released to the field by making openings in the dividing dike. Fish will graze on the natural food available in the ricefield.

Supplemental feeding

· Recommended at the middle culture period or rice (45-50 DAT). During this period, production of natural food in the field water declines due to shading of rice leaves.

· Feeds: rice bran, kitchen refuse, ipil-ipil meal, etc. Animal manure may also be applied in the pond refuge.

· Feeding rate: 3-5% of fish biomass

Harvesting

· Harvest fish by draining the water very slowly one week before rice harvest to avoid trapping the fish in the middle of the field.

· Select large fish for consumption or disposal and confine the small fish (50 g.) for stage 11 culture.

· After removing the harvested rice from the field, it is immediately reflooded to about 30 cm deep and the small fishes in the refuge are released to allow them to grow for another 60 days before the dry season crop.

Timetable for rice-fish culture

Day	Activity
0	Prepare and fertilize seedbed.
1	Soak seeds (IR-36, 42, 52, 54, 64 and 74 as examples).
3	Broadcast germinated seeds in seedbed.
7	Prepare ricefield:
	Start of fish culture (STAGE I): Stock fish (Nile tilapia, 5-10 g in size) at 5,000- 7,500/ha. Insure water supply infields.
24	Pull seedlings. Apply basal fertilizer. Use the kinds and rates of fertilizer recommended for the locality based on soil analysis.
25	Transplant seedlings (wet bed method).
51	Second application of fertilizer (top dressing). May split the amount into two applications hence the third application.
75	Third application of fertilizer (top dressing)
100	Drain water and harvest large/marketable fish.
120-125	Harvest rice.
125	Start of fish culture (STAGE Il): Prolong fish culture period after rice harvest for small-sized fish (30-40 9) stocked at 3,000-5,000/ha.
185	Harvest second batch of fish.

Time for rice-fish culture

BENEFITS AND LIMITATIONS

1. Fish can contribute to increased rice yield by 1 10-15%, through:

· Controlling certain weeds and eating insects such as stemborer, brownplant hopper

· Fish wastes including uneaten feeds add fertility to the soil.

· Helps in increasing availability of nutrient for increased floodwater productivity and uptake by rice.

· Reduces loss of ammonia through volatilization by preventing floodwater pH rise over 8.5. During fertilizer application increased plankton production tends to raise the value of pH beyond 8.5; the value at which ionized ammonia converts into unionized form that is easily lost.

2. The increased size of dikes in the system offers opportunity to plant other crops such as faro (colocasia sp.), stringbeans, cowpea, wingbeans, eggplant and others.

3. The wide scale adoption of rice-fish is still constrained by continued application of pesticide in ricebased farming. The use of pesticide is not recommended in rice-fish farming. There are ways of controlling rice pests that do not need pesticide, such as:

· Quick submergence (for three hours) of rice plants in water. This makes the insects vulnerable to fish predation. Limitation: suitable while rice plants are shorter than the dike.

· Two persons can drag a stretched rope (50-100m) across the ricefields to knock off the insects into the floodwater, after which they can be eaten by the fish. Limitation: suitable before rice plants reach panicle initiation stage.

However, should a farmer insist on using pesticide, here are ways how to do it:

Considerations in applying pesticides:

(1) Choose and apply properly pesticides that have low toxicity to fish.
(2) Minimize the amount of pesticide getting mixed with water.
(3) Apply at suitable time.

Preventing fish poisoning:

- Drive the fish into the refuge by draining the field before spraying. Keep the fish in the sump until the toxicity in the sprayed field is gone.

- Increase water depth (+ 10 cm.) to dilute the concentration of pesticide in the water.

- Flush water through the ricefield. Open the inlet and outlet of the field and allow irrigation water to flow freely, during spraying. Begin spraying from the outlet end of the field. When one-half of the field is already sprayed, stop for a while and allow the pesticides to flow out of the field. Then, continue spraying towards the inlet end of the field until it is finished.

To do items (2) and (3), examples are: apply powder pesticides in the morning when dew drops are still on the leaves; and to apply liquid pesticides in the afternoon when leaves are dry.

There are a number of less toxic pesticides in the market (Examples are Parapest, Sumithlon, Dipterex). Proper application of a toxic insecticide like Furadan 3G or Curaterr 3G can be made safe to fish if applied through soil incorporation during the final harrowing. Furadan 3G is a systemic insecticide, the efficiency of which in controlling insect pests lasts about 50-55 days. Incidence of pests at this period can be controlled by spraying liquid pesticides. At this time, the rice plants have reached their full vegetative stage and the thick leaves will intercept most of the liquid sprays, thus drastically reducing the concentration of pesticide reaching into the water.

Annual budget for a 1-ha rice-fish farm with pond refuge.

Item		Amount (US$)
I. Returns		Rice-Fish		Rice-Fish + Taro
Rice (2 crops)		1,457		1,457
Fish (2 crops)		386		386
Taro (2 crops)		581
Total Returns		1,843		2,424
II. Costs
Labor		402		515
Materials		375		428
Seeds	50		50
Fingerlings	41		41
Taro tubers	-		53
Fertilizers	140		140
Pesticides	37		37
Fuel and oil	86		86
Feeds	16		16
Others (screens, bundling materials, etc.)	5		5
Total costs		777		943
III. Net Returns		1,066		1,481