Plant Production Science
Online ISSN : 1349-1008
Print ISSN : 1343-943X
Volume 8 , Issue 3
Showing 1-17 articles out of 17 articles from the selected issue
Irrigated Rice-Based Systems
  • David Dawe
    2005 Volume 8 Issue 3 Pages 221-230
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Rice is the largest user of water in Asia, probably accounting for more than half of irrigation water withdrawals. Two key trends in the Asian rice economy that may be affecting water productivity are the rapid spread of pump irrigation and direct seeding. The number of pumps has grown exponentially in Bangladesh and Vietnam, and pump irrigation now dominates gravity irrigation in many countries. Direct seeding accounts for about one-fifth of the rice area in Asia, but this share is increasing. Comparing water productivity values is difficult across space and time; in general, it is more relevant across time. Water productivity has increased over time in several selected systems, primarily due to increased yields of modern varieties and improved management of large-scale water flows. There is less evidence that improved field-level water management has led to increased water productivity, although this may have also contributed. The extent to which agricultural water scarcity will affect poverty in Asia depends crucially on how well societies will be able to create incentives for users to save scarce water, thus facilitating the adoption of new technologies. Because of the rapid spread of pumps, incentives to save water in rice cultivation are growing. Even for gravity-flow surface water, new institutions are developing in China that promise to improve incentives. International trade in agricultural products, or trade in “virtual water,” may also have a role to play and should be encouraged.
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  • —Integrated Approaches for Increasing Water Productivity in Irrigated Rice-Based Systems in Asia—
    To P. Tuong, B.A.M. Bouman, Martin Mortimer
    2005 Volume 8 Issue 3 Pages 231-241
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    The water crisis is threatening the sustainability of the irrigated rice system and food security in Asia. Our challenge is to develop novel technologies and production systems that allow rice production to be maintained or increased in the face of declining water availability. This paper introduces principles that govern technologies and systems for reducing water inputs and increasing water productivity, and assesses the opportunities of such technologies and systems at spatial scale levels from plant to field, to irrigation system, and to agro-ecological zones. We concluded that, while increasing the productivity of irrigated rice with transpired water may require breakthroughs in breeding, many technologies can reduce water inputs at the field level and increase field-level water productivity with respect to irrigation and total water inputs. Most of them, however, come at the cost of decreased yield. More rice with less water can only be achieved when water management is integrated with (i) germplasm selection and other crop and resource management practices to increase yield, and (ii) system-level management such that the water saved at the field level is used more effectively to irrigate previously un-irrigated or low-productivity lands. The amount of water that can be saved at the system level could be far less than assumed from computations of field-level water savings because there is already a high degree of recycling and conjunctive use of water in many rice areas. The impact of reducing water inputs for rice production on weeds, nutrients, sustainability, and environmental services of rice ecosystems warrants further investigation.
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  • E. Humphreys, C. Meisner, R. Gupta, J. Timsina, H.G. Beecher, Tang Yon ...
    2005 Volume 8 Issue 3 Pages 242-258
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Water shortage is a major constraint to sustaining and increasing the productivity of rice-wheat systems. Saving water can be elusive in that reducing seepage, percolation and runoff losses from fields does not necessarily save water if it can be recaptured at some other temporal or spatial scale, for example by groundwater pumping. Many technologies appear to save substantial amounts of water through reducing irrigation water requirement, but whether these are true water savings is uncertain as components of the water balance have not been quantified. Such technologies include laser levelling, direct drilling, raised beds, non-ponded rice culture and irrigation scheduling. It is questionable whether puddling saves water. Reducing non-beneficial evaporation losses is a true water saving, and optimal planting time of rice to avoid the period of highest evaporative demand and changing to non-ponded rice culture can save significant amounts of water. However, moving away from puddled, ponded to more aerobic rice culture sometimes brings new production problems. Furthermore, farmers faced with unreliable water supplies need to store water on their fields as insurance, and puddling assists retention of water during the rice crop. Rehabilitation and improvement of canal and power systems in Asia, funded by charging according to use, are required to facilitate adoption of many water saving technologies. Australian farmers pay fixed plus volumetric charges for water to cover the cost of infrastructure and operation of irrigation systems, which are continuously being improved to provide water on demand and minimise losses. They are able to plan their plantings based on knowledge of the likely amount of irrigation water available each season and crop water use requirement, and thus avoid wasting water and financial loss by overplanting and crop failure. Such approaches have the potential to increase production and water productivity in Asia, however the challenge would be to apply them in an equitable way that benefits many millions of subsistence farmers.
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Future of Asian Cropping Systems
  • Takeshi Horie, Tatsuhiko Shiraiwa, Koki Homma, Keisuke Katsura, Shuhei ...
    2005 Volume 8 Issue 3 Pages 259-274
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    The annual rate of rice yield increase in the world declined from 2.7 % in the 1980s to 1.1 % in the1990s. The continued world population increase requires resumption of the previous rate. The objectives of this paper are to review and assess rice production technologies for increased yield in the past and the current challenge on the basis of crop physiology and agronomy, and to discuss the way to increase irrigated rice yield to fulfil the expanding demand. Field experiments conducted in Kyoto, Japan and Yunnan, China showed that the best recent Chinese hybrid has a yield potential about 10 % higher than the best recent inbred cultivar in Japan. This result, and a review on recent challenges in breeding, suggested only moderate increases in the yield potential of rice genotypes in the coming decades. Contrary to the general understanding, the rapid rice yield increase in central Japan from the mid 1950s to mid 1970s was achieved mostly by improved crop and resource management. This, and the fact that farmers’ contest-winning yields during 1950s and 1960s nearly doubled the current average in Japan, imply that current crop and resource management is exploiting only part of the large yield potential of rice. Some of the ways to increase yields may include components of the system of rice intensification (SRI). The extremely high yields claimed in SRI are probably not real, but its elements, which have been studied and practiced in Japan for the past 50 years, may lead to yield increases. The practice of transplanting one or two young seedlings per hill has advantages in reducing transplanting injury and increasing tiller and root numbers on lower nodes. Such advantages can be realized under direct-seeding systems, where they are applicable. The practice of applying a large amount of compost and intermittent irrigation were also adopted by many of the contest-winning farmers in the 1950s and 1960s. These practices increase roots in deeper soil layers, maintain their activities and presumably promote nitrogen (N) uptake at later stages. Remarkable progress has been made in improved N management; agronomic efficiency of N increased from about 15 kg kg-1 for a single dose at transplanting to 40 kg kg-1 for banded controlled release fertilizer. All of these technological elements will contribute to increased yield when they are rationally integrated into systems that are adaptable to regional environments.
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  • Benjavan Rerkasem
    2005 Volume 8 Issue 3 Pages 275-287
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    The Green Revolution has benefited many people in Asia, but not everyone. This paper examines how many farmers have increased their productivity with more intensive cropping systems of fruit, vegetables, and in some cases, flowers. Total area under these crops more than tripled between 1977 and 2003. Case studies to highlight the transformation include vegetable production to feed Asia’s booming cities, diversification of export crops in Thailand, vegetable production in Malaysia’s Cameron Highlands, flower production in Yunnan Province of China and opium replacement in the Golden Triangle. Access to the market is necessary for transformation, but changes are also driven by farmers’ own innovations combined with contributions from last century’s crop science, from phytohormones to hybrid technology. Other inputs are irrigation, fertilizers and pesticides, with overuse of the last two a serious threat to the environment as well as to human health. Concerns have also been raised regarding soil erosion caused by cropping on steep slopes. In addition to building roads and airports, government support has also come in the form of cheap credit for orchard establishment and more efficient quarantine procedures to facilitate exports. Cross-border trade that brings opportunities to inaccessible border regions will be further enhanced by regional free trade policy, particularly when liberalization of trade in fruit and vegetables is specified such as that just signed by ASEAN and China. Finally, a case is made for the need to improve cropping systems in less favorable environment with limited access to the market and the means through which crop scientists can work with farmers to bring this about.
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  • —Achievements and Potential—
    Mohd. Basri Wahid, Siti Nor Akmar Abdullah, I. E. Henson
    2005 Volume 8 Issue 3 Pages 288-297
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Cultivation of the oil palm (Elaeis guineensis Jacq.) has expanded tremendously in recent years such that it is now second only to soybean as a major source of the world supply of oils and fats. Presently, Southeast Asia is the dominant region of production with Malaysia being the leading producer and exporter of palm oil. This paper reviews the various factors that have led to oil palm occupying its present position, including biological, technical, managerial, environmental, and socio-political aspects. Biological features recognised as critical to the high productivity of the crop are examined. These include its perennial and evergreen nature (giving a continuous year-round canopy cover intercepting a high proportion of incoming radiation), the year-round production of fruit bunches and the high partition of total assimilates into harvested product. Scientific and managerial aspects contributing to the success of the crop include the significant genetic improvements and production of high quality planting materials, the development and application of finely-tuned agronomic practices, the appropriate scale and efficient organisation of oil palm plantations and the continuous R&D and good infra-structural support provided in the main producing countries. The programmes of crop improvement through the utilisation of traditional breeding and selection methods, the development and benefits of vegetative propagation techniques using tissue culture and ongoing efforts to apply molecular and genetic engineering techniques to improve and modify oil composition, are reviewed. Finally, the nutritional qualities of palm oil as a healthy component of diet are briefly described.
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New Pathways for Delivery in Asian Countries
  • Buenafe R. Abdon, Robert T. Raab
    2005 Volume 8 Issue 3 Pages 298-307
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Agriculture is of pre-eminent importance in the Asia Pacific region but is under threat from a number of sources. These include increased demand for food and fibre, complex new domestic and international economic and political forces and changing marketing regulations and requirements. Underlying all these is the rapidly deteriorating natural resource base upon which future productivity and farmer livelihoods depend. Knowledge and information are key requirements to enable farmers to deal with these challenges, particularly as new agricultural technologies are becoming more “Knowledge intensive” Reaching farmers with these prerequisites has been problematic in the past but new information and communication technologies—primarily the Internet—are showing considerable promise. While this approach for directly reaching farmers in developing countries is still in its infancy, information and communication technologies (ICTs) are proving that they can reach “nowledge intermediaries” whose role is to bridge the local and global agricultural knowledge systems. While there are several initiatives at the global, regional, national and the local levels all across the globe, these are proving to be much less than what is required to make a real difference and capitalize on the potential. The donor community can do much to facilitate progress but must consider some fundamental changes in its priorities and how it operates. It must rethink its current faith in the private sector, target institutional support more rationally, develop and follow a clearer strategy and provide more substantial and sustained support for Internet-based initiatives that take advantage of the real potential of this approach.
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  • Rasheed Sulaiman V, Andy Hall
    2005 Volume 8 Issue 3 Pages 308-319
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Extension is clearly facing challenging times in Asia. This paper draws together experiences from across Asia to explore extension policy and the extension policy process. The paper argues that extension policy needs to tackle two major sets of issues. The first concerns the content in view of the broader role extension needs to play in the present context of agriculture systems. The second issue concerns the nature of the policy process itself. Instead of prescribing reforms, the policy process should ideally facilitate continuous incremental change through experimentation, reflection and learning. Four cases are presented to illustrate the challenges involved in developing and implementing extension policy. The experiences indicate that reform processes only informed by prescriptions generated centrally or from outside are bound to fail. The message for extension policy in Asia is that the process of reform must be lead from within. The paper stresses the need for undertaking an institutional analysis of historical and current approaches of implementing different extension approaches and developing capacity within the country on experimenting with different approaches and evaluating them. These learning based approaches should inform policy development. However the existing culture of extension organisations may prevent the emergence of learning based approaches to invigorate extension. Changing these cultures may yet be the biggest challenge of all for reforming extension.
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Improving the Quality of Food in Asia
  • Kazutoshi Okuno
    2005 Volume 8 Issue 3 Pages 320-325
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Rice is the staple food for most Asians. Breeding efforts at the national and international levels have resulted in high-yielding varieties with resistance/tolerance to biotic and abiotic constraints. Consequently Asia has enjoyed rice self-sufficiency in recent years. Now in some countries over-production of rice has occurred, partly because of reduced rice consumption. For instance, in 1962 Japan had a per capita rice consumption of 118.3 kg and then this rapidly declined to about 60kg in 2003. Imbalances between production and consumption in rice and other crops have promoted a paradigm shift of breeding objectives oriented from producers to consumers. Germplasm enhancement (pre-breeding) and breeding strategies now focus on a broad range of crop and food qualities, which are closely associated with industrial and processing properties and human health and nutrition. In particular, physiological functions of chemical compounds involved in crop products are being studied as a part of breeding programs. Diverse plant genetic resources and advances in plant genome research have contributed to successful breeding strategies to improve and manage crop and food quality. Recent progress in germplasm enhancement and breeding strategies for quality improvement of rice, wheat, soybean and sweet potato in Japan is discussed.
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  • Craig Meisner, R. Welch, J.M. Duxbury, J.G. Lauren
    2005 Volume 8 Issue 3 Pages 326-329
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    During the 1970s, the Green Revolution basically used dwarfing genes in wheat and rice that allowed greater water and fertilizer efficiency which dramatically increased the cereal productivity and thus, increased human caloric intake of the developing world. However, having met caloric intake, there is a need to address the issues of malnutrition through a holistic food production system. For example Ca-deficient induced rickets was found in 9% of children in SE Bangladesh, illustrating the failure of that food production system to address this vital nutrient, calcium. A clinical trial has shown a minimum of increase in calcium intake of 250 mg Ca per child per day was enough to prevent rickets. In Bangladesh, a consortium of universities and other medical institutions and the International Center for Wheat and Maize Improvement (CIMMYT) has developed strategies to infuse calcium within the food delivery system. For treatment of ricketic children, a strategy was developed to use live and video drama to create community awareness of the production and/or consumption of high-calicum crops/food and calcium supplement added to the cooking rice (in this case, highly edible CaCO3 readily available throughout the country). Though this represents a very specific case study, this is a useful example of how collaboration based around crop science can address the ‘hidden’ hunger of malnutrition throughout the world.
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  • Theerayut Toojinda, Somvong Tragoonrung, Apichart Vanavichit, Jonaliza ...
    2005 Volume 8 Issue 3 Pages 330-333
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    In the past 20 years, the rice-breeding program in Thailand had little success in developing new cultivars to replace Kao Dawk Mali 105 (KDML105) and Kao Khor 6 (RD6) for the rainfed lowland rice environments. The main reason for the poor adoption of new cultivars by farmers is the susceptibility to diseases and unacceptable grain qualities. The conventional breeding program also takes at least 15 years from initial crossing to the release of new cultivars. A new breeding strategy can be established to shorten the period for cultivar improvement by using marker-assisted selection (MAS), rapid generations advance (RGA), and early generation testing in multi-locations for grain yield and qualities. Four generation of MAS backcross breeding were conducted to transfer genes and QTL for bacterial blight resistance (BLB), submergence tolerance (SUB), brown plant hopper resistance (BPH) and blast resistance (BL) into KDML105. Selected backcross lines, introgressed with target gene/QTL, were tolerant to SUB and resistant to BLB, BPH and BL. The agronomic performance and grain quality of these lines were as good as or better than KDML105.
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  • Rachid Serraj, C. Tom Hash, S. Masood H. Rizvi, Arun Sharma, Rattan S. ...
    2005 Volume 8 Issue 3 Pages 334-337
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Pearl millet [Pennisetum glaucum (L.) R. Br.] is the staple cereal of the hottest, driest areas of the tropics and subtropics. Drought stress is a regular occurrence in these regions, making stress tolerance an essential attribute of new pearl millet cultivars. Recent breeding research has mapped several quantitative trait loci (QTLs) for components of grain and stover yield per se, as well as yield maintenance, under terminal drought stress conditions. We report here the evaluation of these QTLs as possible selection criteria for improving stress tolerance of an elite hybrid cultivar. Initial evaluations, based on hybrids made with topcross pollinators bred from lines selected directly from the mapping population, indicated an advantage to the QTL-based topcross hybrids. This advantage seemed to be related to a particular plant phenotype that was similar to that of the drought tolerant parent of the mapping population. Subsequent evaluations were based on testcross hybrids of drought tolerance QTL introgression lines in the background of the drought-sensitive parent of the mapping population, H 77/833-2. These introgression lines were bred by limited marker-assisted backcrossing of a putative major drought tolerance QTL into H 77/833-2 from the mapping population’s drought tolerant parent. Several of these QTL introgression lines had a significant positive general combining ability for grain yield under terminal stress and significantly out-yielded testcross hybrids made with the original recurrent parent both in unrelieved terminal drought stress and in gradient stress evaluations.
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Diversified Cropping Systems for Asia
  • Sawika Konsaeng, Bernard Dell, Benjavan Rerkasem
    2005 Volume 8 Issue 3 Pages 338-341
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    The mobility in phloem of boron (B) has been reported to vary among plant species. Boron is phloem immobile in many species and completely mobile in others. Recent reports regarding phloem B mobility or immobility only considered temperate plants, and there is no information on tropical species. Information of phloem B mobility is useful for improving the diagnosis of B deficiency and management of B status in crop production. This study aimed to survey tropical species for their B mobility. Leaf samples of 17 species, including cashew (Anacardium occidentale L.), mango (Mangifera indica L.), custard apple (Annona squamosa L.), papaya (Carica papaya L.), cassava (Manihot esculenta Crantz.), Indian walnut (Samanea samen (Jacq.) Marrill.), cork wood tree (Sesbania grandiflora (L.) Pers.), tamarind (Tamarindus indica L.), jackfruit (Artocarpus heterophyllus Lamk.), guava (Psidium guajava L.), star fruit (Averrhoa carambola L.), passion fruit (Passiflora edulis Sims.), coffee (Coffea arabica L.), lime (Citrus aurantifolia Swingle.), longan (Euphoria longana Lam.), lychee (Lychi chinensis Sonn.) and teak (Tectona grandis L.) were collected in the position of the youngest fully expanded leaf (YFEL), the middle leaf age of a branch (ML) and the oldest leaf (OL). Based on a premise that the nutrient concentration gradient between young and old leaves will be steeper in those species in which B is immobile, B concentration in the different leaf positions was examined in comparison with calcium (Ca is phloem immobile) and potassium (K is phloem mobile). Concentrations of K in all leaf types were not significantly different or decreased with leaf age, while Ca concentrations were always higher in the older leaves. Three species; tamarind, guava and teak, showed concentration gradients of B that were similar to K. The results suggested that B may be retranslocated from older to younger leaves of these species, hence indicating that B may be phloem mobile in these species. However, this hypothesis needs confirmation through studies examining retranslocation of B using 10B isotope or identification of B-complexing molecules in the phloem, e.g. sugar alcohols.
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  • Mahrup, Andrew Borrell, Mansur Ma’shum, IGM Kusnarta, Sukarton ...
    2005 Volume 8 Issue 3 Pages 342-344
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Rice (Oryza sativa) grown on rainfed Vertisols in the semi-arid tropics of southern Lombok, Eastern Indonesia, is usually flooded in the short wet season, creating a considerable demand for water. However, rice crops and secondary crops frequently suffer from water stress as the soil dries after the wet season. Four systems of soil management for rice were studied at Wakan and Kawo, with average annual rainfalls of 984 mm and 1665 mm respectively. The objective was to improve water use efficiency (grain yield/m3 water consumed). The four systems were unflooded permanent raised beds with tillage (RMT) or without tillage (RNT), and flooded flat land with tillage (FMT, the conventional system, gogorancah), or without tillage (FNT). Water was kept at 0.1 m depth in the furrows (RMT, RNT) or at 0.05 m depth on flat land (FMT, FNT). Excess water was collected in a dam (embung), and used when necessary to keep the water at the desired depth. Compared with FMT, RNT reduced crop water requirement for rice by 50% at Wakan and by 44% at Kawo. Water use efficiency in RNT was increased by 90% at Wakan, and by 56% at Kawo, compared with that in FMT. There were no differences between treatments in the yield of rice at Kawo (4.5 t/ha), but at Wakan yield was better in FMT or FNT (4.2 t/ha) than RMT or RNT (2.8 t/ha). Hence, on rainfed Vertisols of Southern Lombok, rice grown on permanent raised beds, with or without tillage, could successfully replace rice grown under the conventional flooded system with tillage on flat land (gogorancah), where the rainfall is higher. The extra water saved with permanent raised beds could be used to irrigate secondary crops.
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  • Ling-Hoak Ooi, Heriansyah
    2005 Volume 8 Issue 3 Pages 345-348
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Malaysia has banned open burning of old oil palm biomass at replanting. The most widely adopted zero burn techniques of replanting oil palms in Malaysia currently are the “chipped and windrow” and “under-planting” methods. These methods resulted in very high breeding of Oryctes rhinoceros beetle, which has become the most serious pest in immature and young mature palms in Malaysia currently. Three new no-burn methods of clearing old oil palms for replanting whereby almost the entire palms are pulverized into fine pieces of less than 0.1g dry weight each and spread widely over the entire field and the root mass dug up at felling are reported. More than 50% of the pulverized palm biomass decomposed by 24 weeks after pulverization, which increased to 80% by the 56th week. All the three methods have good potential in reducing the breeding of Oryctes rhinoceros. They also have good potential in reducing the rat and Ganoderma boninense disease problems. In addition, the new clearing methods reduced the fallow period, facilitated replanting and the subsequent field upkeep work, and improved the utilisation of nutrients released by the decomposing palm biomass by the newly replanted palms. The methods of clearing old oil palms for replanting are environmentally less polluting and also improve the sustainability of oil palm plantations.
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  • Madan M. Dey, Mark Prein
    2005 Volume 8 Issue 3 Pages 349-353
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    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.
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  • Mitsuru Tsubo, Shu Fukai, Jayampathi Basnayake, To Phuc Tuong, Bas Bou ...
    2005 Volume 8 Issue 3 Pages 354-357
    Published: 2005
    Released: September 22, 2005
    JOURNALS FREE ACCESS
    Quantifying water losses in paddy fields assists estimation of water availability in rainfed lowland rice ecosystem. Little information is available on water balance in different toposequence positions of sloped rainfed lowland. Therefore, the aim of this work was to quantify percolation and the lateral water flow with special reference to the toposequential variation. Data used for the analysis was collected in Laos and northeast Thailand. Percolation and water tables were measured on a daily basis using a steel cylindrical tube with a lid and perforated PVC tubes, respectively. Percolation rate was determined using linear regression analysis of cumulative percolation. Assuming that the total amount of evaporation and transpiration was equivalent to potential evapotranspiration, the lateral water flow was estimated using the water balance equation. Separate perched water and groundwater tables were observed in paddy fields on coarse-textured soils. The percolation rate varied between 0 and 3 mm/day across locations, and the maximum water loss by lateral movement was more than 20 mm/day. Our results are in agreement with the previously reported findings, and the methodology of estimating water balance components appears reasonably acceptable. With regard to the toposequential variation, the higher the position in the topoesquence, the greater potential for water loss because of higher percolation and lateral flow rates.
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