Rice management in rice-fish culture

Rice-fish culture can be carried out under rainted or irrigated conditions, in either direct seeded or transplanted fields. Timing of seeding and transplanting activities are affected by many factors (water availability, rice variety, etc.) but is not usually affected by the fish culture component.

Seedlings are best transplanted 25-30 days after seeding although the best age for traditional varieties may fall outside this. In practice, they often remain in the seedbed longer than this. Sometimes, droughts occur so that the fields are too dry to be transplanted and the farmer must wait for rain. In other cases, the family labor force is limited and the rice in the seedbed must "wait" until the family gets to it.

Most farmers find no problem in applying chemical fertilizers to their rice-fish systems. In some cases where fish have died after exposure have been reported, fish had been fed with pellets and may have ingested fertilizer granules for this reason.

The wide scale of rice-fish is still constrained by continued application of pesticides in rice-based farming. The use of pesticide is not recommended in rice-fish farming. In rice-fish culture, 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 before plants are taller than the dikes.

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

However, should a farmer insist on using pesticides, here are ways on how to do it.

1. Considerations in applying pesticides:

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

2. Considerations in preventing fish poisoning:

· Drive the fish into the sump, draining the field slowly before spraying: keep the fish in the sump until the toxicity in the sprayed field is gone.

· Increase water depth (+ 10 cm 0) to dilute the concentration of pesticides 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) above, examples are: to 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, Dlpterex.) Proper application of a toxic insecticide like Furadan or Curaterr 3G can be made safe to fish if applied through solid incorporation during the final harrowing. Furadan 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 are already at their full vegetative stage and the thick leaves will intercept most of liquid sprays, thus drastically reducing the concentration of pesticides reaching the water.

In It is best to wait until the rice is well-established before releasing seed fish, particularly if the fish are large. Once two or three tillers have appeared, one to three weeks after transplanting is the usual waiting period, depending on the state of the rice and the size of the fish or one month to six weeks after direct seedling.

Small fry (of about one inch length) can be stocked immediately after transplanting, without harm to the rice.

Rice Varieties: We have never seen a variety that does not work with fish, but some are better than others:

Deep water-tolerant varieties are preferable to those which thrive in only very shallow water.

In some areas where rainfalls are highly unpredictable, farmers prefer to wait until very late in the rainy season to stock fish. At this time, surface water accumulation will be at its yearly peak and the chance of flooding from later rains is very slim. In such cases, long-lived, late-maturing rice varieties are best.

Rice varieties which tiller rapidly or under a wide range of water conditions will allow farmers to stock earlier in many cases.

Farmers have succeeded with early and late-maturing photoperiod-sensitive and non-sensitive, glutinous and non-glutinous varieties.

EFFECTS ON RICE YIELD

Our experience indicates that rice yields rise on the average, by about 10 percent, in rice-fish situations. However, there is great variation from farm to farm so guarantees cannot be made.

Yields seem the most enhanced on farms with poor soil where fish are fed intensively. Possible mechanisms include:

· helps in increasing availability of nutrients for increased floodwater productivity and uptake by rice.

· reduces loss of ammonia through volatization after fertilizer application by preventing floodwater pH rise over 8.5

The greatest danger to rice has already been indicated: big fish will damage very young rice; otherwise, some rice varieties do not tolerate deep water. By using very sensible precautions, farmers are not likely to harm their rice yields.

Prepared by: JOHN SOLLOWS & CATALINO DELA CRUZ

FARMER-PROVEN INTEGRATED AGRICULTURE- AQUACULTURE:
A TECHNOLOGY INFORMATION KIT (II RR- ICLARM)