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
A. 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.
- 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.
Examples of fish refuge layout for small and large plots
B. 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 – Straight-row planting (optional), if mechanical weeding is done.
- Age of seedlings: 25-30 days
- Planting distance: 20-25 cm between rows, 15-20 cm between hills
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.
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 top-dressing is 50 kg/ha. This is applied 30 days after transplanting. The amount for top-dressing may be split into two equal applications. In this case, a third application is applied 75 days after transplanting.
During dry season, the same amount for basal application is followed. For top-dressing, the rate is 100 kg/ha. As an example, the amount of fertilizer for a 400 m2 of rice-fish during wet season is 8 kg of ammonium phosphate and 2 kg of urea for basal application. For top-dressing, 2 kg of urea are needed.
8. Insect control – The use of insecticide is not recommended. Farmers, however, apply insecticides known to be less toxic to fish.
source: www.nzdl.org, photo from howafrica.com