Rice-fish Culture Research Articles

The effect of different fertilizer treatments on water quality parameters in rice-cum-fish culture systems

Summary A rice–fish culture experiment was conducted to determine the effects of different fertilizer treatments on water quality parameters, i.e. dissolved oxygen, temperature, pH and conductivity, as well as the nutrients nitrogen, potassium and phosphorus. Data gathered were subjected to analysis of variance. Dissolved oxygen, nitrogen and potassium concentrations showed significant differences (P 0.05) in the oxygen concentration between rice-only and rice-cum-fish management systems was probably due to the narrow spacing of rice cultivars (20 × 20 cm). Under different fertilizer treatments, dissolved oxygen, nitrogen and potassium concentrations were not significantly different (P>0.05), indicating that different fertilizer treatments had no effect on their concentrations. Mean temperature, pH, conductivity and phosphorus concentrations in all rice-cum-fish management systems and fertilizer treatments did not differ significantly (P>0.05) from each other. This might possibly be due to the hydrogeology and climatic conditions of the area. However, all levels of studied water quality parameters were tolerable to the fish (Oreochromis niloticus) in the rice–fish ecosystem. There was no significant difference (P>0.05) in rice yield between the rice–fish management system and the rice-only management system. However, there was a significant difference (P 0.05) under different rice–fish management systems, but was significant (P<0.05) under different fertilizer treatments. Chicken manure gave the best growth with 17.7±5.97 g; estimated fish yields were 343 and 602 kg ha−1 year−1 in fish monoculture and rice–fish culture respectively. It is recommended that farmers who are more inclined to fish or rice production in integrated rice-cum-fish management systems could use chicken manure and NPK (20 : 10 : 10) respectively.

Fisheries, fish culture, tilapias and politics

In the past few years much attention has been focused on dwindling marine fish stocks and the means available to counter the effects of this growing problem. Over fishing has been targeted as the main cause. Many newspaper and magazine articles on the subject of over fishing have been added to the growing scientific journal publications and books. Conservation measures are being implemented but their impacts will very likely not reverse the trend. One option to provide more fish for human consumption is through fish culture which, since traditional techniques began to be modernized in earnest in the 1950's, has been expanding rapidly. With the exception of production in China, efforts with the major carps have not been very productive, especially in tropical countries, and these and several other fishes currently in culture have relatively limited possibilities of substituting the shortfall of marine fish in the future. The tilapias, on the other hand, have shown much greater potential recently, and are increasingly marketed worldwide. In two or three decades, farming tilapias may prove to be the means of supplying a large quantity of fish to fill the increasing gap between demand and supply. Furthermore, tilapias can contribute additional resources through integration with traditional reservoir fisheries and rice-fish culture. This paper explores these growing changes in tilapia culture and inland fisheries especially in the tropics. We do not claim any deep knowledge nor are we predicting the economical and sociological impacts of the winds of change affecting fisheries worldwide.

Integrated rice-fish culture: Coupled production saves resources

Rice is a key component in global food security, as it is the main ingredient in the daily diets of around 3 billion people, especially in Asia. Like all agricultural production, rice cultivation depends on scarce natural resources. This article briefly outlines the utilization of land and water in rice production, and suggests an approach for optimizing use efficiency, namely through the combination of rice and fish culture. The authors argue that the utilization of land and fresh water is optimized through integrated and complementary production of rice and fish — two basic foods items in daily local diets. The article reviews currently available scientific literature on integrated rice-fish systems. Rice-fish culture systems are briefly characterized, and respective yield potential and interactions between rice and fish are discussed. Results of socio-economic surveys regarding the adoption of integrated rice-fish culture are summarized. The article also reviews literature on the impact of fish culture on rice field ecology as outlined in studies on weed infestation, insect populations, and greenhouse gas emissions. The article concludes that rice-fish culture can be an option to help rice producing countries keep pace with soaring domestic demand for food, especially fish. Integrated rice and fish culture optimizes the benefits of scarce land and water resources through complementary use, and exploits the synergies between fish and plant.

Rice–fish culture: an option for smallholder Sawah rice farmers of the West African lowlands

The introduction of Asian-based Sawah 1 1 Sawah: The term Sawah refers to leveled rice field surrounded by bund with inlet and outlet for irrigation and drainage. farming system through an ecotechnology approach has opened a new frontier for diversification of the rice-based cropping system in West Africa. On-farm rice–fish culture experiments were conducted at Biemso under irrigated Sawah and Nobewam irrigation project sites in Ashanti region, Ghana, during the main cropping season of 2000. The objectives of the study were to evaluate the effect of fish on performance of rice and to assess relative economics of concurrent rice–fish culture and rice monoculture under lowland. The results indicated that the presence of fish did not significantly depress the yield of rice. The size of the fish increased from an initial weight of 25–80 g at Nobewam and to 90 g at Biemso site during the culture period of 100 and 120 days, respectively. The net return from the rice–fish culture ranged from US$ 1106.90 to 1233.80 whilst that of rice monoculture ranged from US$ 1046.40 to 11108.60. Percentage increase in revenue from the rice–fish system over the rice monoculture ranged between 5 and 11%. These results suggest that rice–fish integration could be a viable option for diversification for smallholder rice farmers in lowlands with soil and water conservation structures and reliable source of water for irrigation.

ECONOMIC FEASIBILITY OF COMMUNITY-BASED FISH CULTURE IN SEASONALLY FLOODED RICE FIELDS IN BANGLADESH AND VIETNAM

ABSTRACT During the rainy season in extensive river floodplains and deltaic lowlands, floods lasting several months render the land unavailable for crop production for several months each year. These waters are considerably underutilized in terms of managed aquatic productivity. This raises the opportunity to enclose parts of these annually occurring floodwater areas to produce a crop of specifically stocked aquatic organisms aside from the naturally occurring ‘wild’ species that are traditionally fished and are not affected by the culture activity, overall resulting in more high-quality, nutrient-dense food production and enhanced farm income for all stakeholders, notably the poor. The WorldFish Center and its national partners recently tested two systems in a community based management approach in Bangladesh and Vietnam: (i) concurrent rice-fish culture in shallower flooded areas, and (ii) alternating rice and fish culture in the deep-flooded areas. Results indicate that community-based fish culture in rice fields is technically feasible, economically viable and socially acceptable. It can increase fish production to about 600 kg/ha/year in shallow flooded areas and up to 1.5 t/ha/year in deep-flooded areas, without reduction in rice yield and wild fish catch. For the overall system and in the trials conducted, an additional income of US$135 per ha in southern Vietnam, and up to US$437 per ha in Bangladesh were achieved, which is an increase of 20%to 85% over the previous profitability. The communities neighboring the trial sites have been adopting the technologies widely.

Increased Income from Seasonally Flooded Rice Fields through Community Based Fish Culture in Bangladesh and Vietnam

In extensive river floodplains and deltaic lowlands, floods lasting several months render the land unavailable for crop (often rice) production during the rainy season. Aside from crop production during the flood-free dry season, the land area can be utilized for fish production during the flood season. This can be done by enclosing parts of these floodwater areas to produce a crop of stocked fish aside from the naturally occurring ‘wild’ species. The WorldFish Center and its national partners recently tested (1) concurrent rice-fish culture in the shallower flooded areas and (2) alternating rice and fish culture in the deep-flooded areas of Bangladesh and Vietnam through a community-based management system. This paper presents the key results of this work, focusing on the economics of existing land use patters and the impact of community based fish culture on rice yields and income. Rice production was maintained, or even enhanced. Fish production was increased beyond the wild catch by about 600 kg/ha/year in shallow-flooded areas and up to 1.5 t/ha/year in deep-flooded areas, without reduction in wild fish catch. For the overall system on an annual basis, an additional income ranging from US$ 135 per hectare in southern Vietnam to US$ 437 per hectare in Bangladesh was achieved, which is an increase of 20 to 85 percent over the profitability of the previous systems involving cropping and fish capture. The results indicate that community-based fish culture in rice fields is technically feasible, economically profitable, environmentally non-destructive, and socially acceptable.

A greenhouse experiment on growth and yield effects in integrated rice–fish culture

To study the interaction between rice and fish growth in integrated culture we performed a greenhouse experiment with three treatments: (1) rice combined with a single culture of common carp, Cyprinus carpio L., (2) rice combined with a mixture of common carp and Nile tilapia, Oreochromis niloticus (L.) and (3) rice only. The rice–fish treatments were supplied with a supplementary feed, whereas the rice only was supplied with mineral fertilizer. Monitoring of growth and yield variables was accompanied by continuous determination of water characteristics. Integration of fish resulted in a significant decrease of the afternoon floodwater pH and dissolved oxygen levels, especially in the carp/tilapia treatment ( p<0.05). Likewise that treatment had a lower chlorophyll-a level than the carp culture. Rice growth and yield exhibited controversial effects between the rice–fish treatments. While the carp culture had a rice yield-promoting tendency, the carp/tilapia culture rather affected rice yields negatively as compared to rice only. Differences between the rice–fish treatments were statistically significant ( p<0.05) for the rice stem yield, rice straw yield, and total rice aboveground biomass yield. In contrast to the rice yields, the total fish yield was significantly higher in the carp/tilapia group compared to the carp culture. Within the carp/tilapia treatment, tilapia proved to be highly superior in the interspecific competition for feed with carp, as reflected in a significantly higher metabolic growth rate (10.8 g kg −0.8 day −1 vs. 4.4 g kg −0.8 day −1) and body lipid content (14.7% vs. 4.4%). Analysis of nitrogen and phosphorus of the harvest fractions revealed a different N and P budget of the rice–fish treatments: while the carp treatment had a higher absolute amount of N and P in the rice biomass, the carp/tilapia group had more N and P in the fish body mass. We conclude that there is a trade-off between rice and fish yield in integrated culture with high fish stocking density and input of supplementary feed. The fish species composition stocked seems to be crucial for the productivity of the rice–fish system.

‘Aji gnui assonii’—a practice of organic hill farming among the Apatani tribe of Eastern Himalaya

SUMMARY Apatani, a hill tribe of Arunachal Pradesh, India, has been practising rice fish culture traditionally for many decades. Their practice, locally termed aji ngui assonii, is free from the use of agro-chemicals and additional input of supplementary feed for fish. They basically follow the traditional agronomic practices for rice even in rice-fish combination pertaining to field preparation and maintenance. Field preparation starts in April, occasionally continues up to late May, and rice seedlings are planted in May-June. The strains of common carp are stocked at fry stage (3–5 cm), after just ten days of planting the rice and reared in the field for about 4 months in total. Sometimes they harvest fish partially from the field after an interval of 1.5 months. With multiple harvesting, only 200–300 kg ha-' offish are produced in each harvest whereas with final harvesting the production rate is 500 kg ha-'. The dykes of rice fields are utilized for growing millet in June and are harvested during August-September. The system of such integrated farming is an organic practice, as well as sustainable in the sense that it is based solely on available natural resources in the ecosystem and also preserves the agro-biodiversity, enhancing multidimensional support to the tribal livelihood.

An Economic Study on Alternate Rice-Fish Culture in Selected Areas of Mymensingh District in Bangladesh

An Economic Study on Alternate Rice-Fish Culture in Selected Areas of Mymensingh District in Bangladesh

The effects of shading on phytoplankton photosynthesis in rice–fish fields in Bangladesh

The combined culture of rice and fish in ricefields (rice–fish culture) has been promoted by development agencies in several developing countries as a means of increasing incomes for rice farmers and the amount of protein in the diets of subsistence rice farming communities. The purpose of the present research, carried out in Bangladesh, was to test a ‘low-tech’ method for improving fish yields in rice–fish systems. The method, termed ‘border planting’ (BP), involves alternate planting of closely and widely spaced rows to allow more light to reach the water surface, with the aim of increasing levels of aquatic photosynthesis and thus the supply of autochthonous food for fish, ultimately increasing fish yields. The effects of using BP and different rice cultivars on shading and phytoplankton photosynthesis were investigated in trial rice–fish plots. The rice cultivars used were ‘BR11’ (a high yielding cultivar) and ‘Joshoa’ and ‘Kolojira’ (tall local cultivars). Rice was planted to follow either a regular planting (RP) pattern, 26 cm within/between rows, or in one of two BP patterns (using Joshoa only). In one treatment, no rice was planted. One of the BP patterns (BP1) had relatively narrow maximum spaces between planted rows (36 cm), whereas in the other (BP2), the maximum spaces were wider (75 cm). Rice yields ranged from 1.3 to 1.8 mt ha −1 and did not differ significantly among treatments, suggesting that BP will not lead to a decrease in rice yields. Measurements of photosynthetically active radiation showed that shading was significantly lower (by approximately 120%) within the wide spaces in BP2 compared with the narrow spaces. The BP2 produced open areas within rice–fish fields in which there was reduced shading and increased phytoplankton photosynthesis, and there was no decrease in phytoplankton photosynthesis within the closely planted areas of the treatment. The BP2 is therefore capable of producing an overall increase in aquatic primary production within rice–fish fields, which would be expected to increase levels of secondary production, including fish production. The BP2 may therefore have potential as a low-tech method for enhancing fish production in ricefields in Bangladesh and other developing countries. Further research in this area is recommended.

Effect of fish on the yield and yield components of rice in integrated concurrent rice–fish systems

Many authors report on the effect of rice–fish culture on rice yields. Some reports show increased rice yields, others show no effect or even decreased yields. To verify the impact of rice–fish culture, data gathered over eight experiments (1995–1999) at the Co Do experimental rice–fish station, Vietnam, were analysed through multiple regressions with rice yield and different yield components as the dependent variables. We used eight independent variables: season, water depth, rice variety, rice seeding rate, and the effective stocking density (ESD) of silver barb, Nile tilapia, common carp and snakeskin gourami. Season had the biggest impact on nearly all dependent variables. Rice yields in the wet season were on average 2·42 t/ha lower as compared to the dry season. Higher water levels decreased the number of panicles/m2 and the rice yield. The rice seeding rate affected the yield component variables, but had no impact on the rice yield. Silver barb feeding decreased the number of panicles/m2 but this was compensated by an increased number of grains/panicle. Snakeskin gourami had a positive effect on panicles/m2 and, together with common carp, on sink capacity, probably through improved nutrient cycling in presence of fish and improved nutrient uptake by the rice plant. Snakeskin gourami had a negative effect on the ripening ability, whereas Nile tilapia had a positive effect. Fish did not have any impact on the rice yield. Increased water level and reduced rice arable area, the main two requirements for rice–fish culture, result in lower rice yields from rice–fish systems as compared to monoculture systems.

Growth performance of Barbodes gonionotus (Bleeker) in intensively cultivated rice fields

Barbodes gonionotus (Bleeker) is a popular fish species in rice–fish culture. In Vietnam's Mekong Delta, the species is often grown in polyculture with Oreochromis niloticus (L.) and Cyprinus carpio L. In this study, we used the data of eight experiments into such polycultures at the Co Do rice–fish experimental station to look whether the rice stage or fish biomass had any effect on the specific growth rate (SGR) of B. gonionotus. The B. gonionotus net production figures varied from 1.7 to 547.7 kg/ha, while the SGR varied from 0.27% to 3.58% body weight/day. We found that SGR values did not depend on the developmental stage of the rice crop. However, the SGR values significantly decreased with increasing standing biomass (SB) of B. gonionotus, O. niloticus or wild fish. We concluded that intraspecific and interspecific competition is an important issue in B. gonionotus culture in rice fields. Besides this, SGR values were higher in the wet season and in plots with inorganic fertilizer or pig manure application.

Effect of Carp and Fish Feed on Yield and Soil Nutrient Availability under Integrated Rice-Fish Culture

Effect of Carp and Fish Feed on Yield and Soil Nutrient Availability under Integrated Rice-Fish Culture

The effect of rice seeding rate on rice and fish production, and weed abundance in direct-seeded rice–fish culture

Rice (paddy) and fish yields in concurrent, direct-seeded culture were investigated at the Co Do station located in the Mekong Delta, Vietnam. Three different rice seeding rates (100, 200 and 300 kg ha −1) were used in the absence or presence of fish ( Oreochromis niloticus (all male), Puntius gonionotus, and Cyprinus carpio). Significantly ( P<0.05) higher paddy and fish yields were obtained at the lowest rice seeding rate. No significant effect of the rice seeding rate on aquatic weed biomass was found, whereas water temperature, dissolved oxygen concentration and pH were significantly ( P<0.05) higher at 100 kg rice seed ha −1. The presence of fish resulted in a significant ( P<0.05) reduction of aquatic weed biomass, and significantly ( P<0.05) lower dissolved oxygen and PO 4 concentrations, and higher chlorophyll- a levels in the pond water. Analysis of the results indicated that the effect of rice seeding rate on fish production was most likely to be related to a `growth effect' resulting from increased availability of oxygen and food. Paddy yields at high seeding densities were affected by mutual shading. A further reduction of rice seeding rate may be feasible for rice–fish farmers, given their limited possibilities for weed control through land preparation (field levelling) and water management.

Preliminary studies in rice-fish culture in a rainfed lowland ecology in Ghana

Mixed farms of rice and fish are yet to receive attention in Ghana, despite lowland rice being grown under inundation in most areas nationwide. In a preliminary study, Nile tilapia (Oreochromis niloticus) was successfully cultured in a rainfed lowland rice farm, although no additional care was provided for fishes. The highest yielding rice variety produced 4.8 t/ha (480 kg/1000 m2) which was commensurate with previous yields at the same location. Parent fish yield of 121 g/fish for a period of 139 days was also commensurate with yield from fish ponds. This excluded yield of fish progeny. With proper management, fish yields would greatly complement that of rice. Ghana Jnl.agric. Sci Vol.32(1), 1999: 123

The Effect of Fish on the Abundance of the Rice Caseworm Nymphula depunctalis (Guenee) (Lepidoptera: Pyralidae) in Direct Seeded, Concurrent Rice-Fish Fields

In the 1996-97 dry season, a rice caseworm (Nymphula depunctalis (Guenee)) outbreak occurred at the Co Do rice-fish experimental station, Can Tho province, Mekong Delta, Vietnam. A polyculture of Thai silver barb, common carp and Nile tilapia was able to reduce the number of rice caseworm larvae (P< 0.001) by at least 93%. As a result, the number of rice caseworm adults (P< 0.001) and the percentage of damaged rice leaves (P< 0.001) were also reduced compared with rice fields without introduced fish. As the pest reduction did not differ in fields with high and low seeding densities, it was concluded that the access of fish into the rice field was not severely hampered by high rice seeding densities. The presence of fish or rice caseworms had no effect on the rice yield. The broader acceptance of rice-fish culture could lead to a reduction of the number of pesticide sprays used against highly visible defoliators like the rice caseworm. This would enforce the concept that rice-fish culture and integrated pest management are complementary.

Polyculture of silver barb, Puntius gonionotus (Bleeker), Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinus carpio L., in Vietnamese ricefields: fish production parameters

The fish production parameters of five polyculture combinations, consisting of small and large silver barb, Puntius gonionotus (Bleeker), small and large Nile tilapia, Oreochromis niloticus (L.), and small common carp, Cyprinus carpio L., fingerlings in three replicates, were investigated in a rice-fish culture experiment (duration 149 days) conducted in the Mekong Delta, Vietnam. The survival rate was not significantly (P > 0.05) affected by the polyculture combination, but when grouped according to species, the mean survival of silver barb and tilapia was 64.3% and 63.7%, respectively, significantly higher than the mean common carp survival rate (33.4%). The growth of silver barb and tilapia was proportionally related to the stocking density, probably because of intraspecific competition and a synergistic interaction between silver barb and tilapia. The growth of common carp was not significantly different among the polyculture combinations. The highest net production (474.1 kg ha−1) was obtained in the polyculture combination consisting of 80% small-sized silver barb fingerlings, but the fish was not marketable at that time. In concurrent rice-fish culture, it is recommended to raise large silver barb fingerlings. Small tilapia can be polycul-tured with silver barb, provided a stocking density lower than 1400 ha−1. Common carp is considered less suitable because of a limited tolerance for the water quality conditions in the ricefield and the large size required by the market.

Rice with fish culture in the semi-deep waters of the Mekong Delta, Vietnam: a socio-economical survey

The results of a socio-economical survey of farming systems practising rice culture with introduced fish, rice culture with indigenous fish and rice monoculture in the semi-deep waters of the Mekong Delta, Vietnam, are presented. Rice and fish yields, inputs, and cost-benefits were computed to evaluate the agricultural effects of rice with fish culture. Household size, labour availability and educational level were not significantly different among the three farming systems. Rice-fish farming systems differed mainly from rice monoculture by a higher fertilizer/ water requirement and less pesticide use. The total farm cash and net return did not differ among the farming systems. The main beneficial effects of rice-fish culture are thought to be related to environmental sustainability, system biodiversity, farm diversification and household nutrition.

Environmental hazards of nitrogen loading in wetland rice fields

Rice is the predominant crop in South and Southeast Asian countries, covering an area of 73.7 million ha. It is unique among the major food crops that, it grows well on flooded soil. When applied under flooded condition nitrogen, a major nutrient is prone to different types of losses, which are as high as 60%. With the increase in area under modern rice varieties in different countries, the usage of chemical fertilizer has been increased up to as high as 150 kg N/ha. About 10% of the total nitrogen fertilizer used globally are applied to rice. Chemical fertilizers supply nitrogen in ammonia, nitrate or amide forms. Among the N-fertilizers, about 80% of the demand are met by urea, which is highly water soluble and prone to losses. When any N compound is applied to a submerged paddy field, it is lost through leaching, denitrification, volatilization and runoff. Of the total N loss, leaching contributes about 30–50%, mostly as nitrate, denitrification, about 10–30% as N 2 and volatilization, about 2–30% as ammonia. The escaped nitrogen causes pollution to the atmosphere and water systems. In the lowlands, a dual rice-fish culture is also practised, where loading of high dose of nitrogen can be lethal to the fish. Studies have shown that nitrogen when applied in the form of ammonium sulfate was more lethal than urea. About 50% of the fish, Catla catla (common carp) were killed when ammonia concentration reached 29.4 mg NH 3-N/L. The fish growth was higher under organic based than inorganic based nitrogen fertilizers. The number of phytoplankton species, which are fish food, was also less when chemical fertilizers were used as a nitrogen source. Besides, it is expected that the leached NO 3-N may pollute the groundwater. Thus loading of nitrogenous compounds in rice ecosystems creates an unavoidable continuum of environmental hazards in rice growing countries.

Rice-fish culture: feeding, growth and yield of two size classes of Puntius gonionotus Bleeker and Oreochromis spp. in Bangladesh

Concurrent rice-fish culture experiments were conducted in Bangladesh to compare and evaluate the feeding, growth, condition factor, survival and yields of two sizes of silver barb ( Puntius gonionotus) and tilapia ( Oreochromis spp.) in 1994 and 1995, respectively, and to compare paddy yield and ecological conditions between rice-fish and rice-alone situations. Survival, specific growth rate, condition factor and yields were better with the small-sized (5.6–6.1 cm) P. gonionotus than the larger-sized (8.8–9.6 cm) P. gonionotus and either sizes (4.0–7.5 and 9.5–14.7 cm) of Oreochromis spp. P. gonionotus was found to be a macrophytophagous column feeder with benthic foraging habit on tiny molluscs. There was clear evidence of its foraging on paddy grains. Conversely, Oreochromis spp. was found to be a detritivorous browser or surface grazer. Ontogenetic shifts in diet were pronounced in P. gonionotus while absent in Oreochromis spp. Best mean net fish yield was 271.03 kg ha −1 crop −1 with small P. gonionotus in 78 days culture, significantly higher than with Oreochromis spp. ( P < 0.05). Paddy yields were 1.5–3.7 t ha −1 crop −1 in rice-fish and 1.5–1.8 t ha −1 crop −1 in rice-alone culture with insignificant differences between the years ( P > 0.05). Water quality parameters were, in general, within the acceptable range for aquaculture. Small sizes of P. gonionotus should be preferred over the Oreochromis spp. for the integration of rice-fish nursery systems but further work should be done on the dietary importance of rice grains to P. gonionotus.