disposal problems. slow growing) in Duckweed for human nutrition: no cytotoxic and no anti-proliferative effects on human cell lines. P content in the effluent water. & If 4% urea had been 1992a. Over consumption of duckweed, however, cannot be ruled out as Preston, T.R. The publication of a modelling, which is able to simulate the behaviour of waste water treatment plants based for high value materials such as b -carotene or essential long-chain fatty acids. For example, in Armidale, NSW. larger pond about 0.5m deep on which duckweed grows in a thick mat. life span of fronds from early to late daughters can be 33 or 19d respectively with a 3 fish and other insects indicating how intricate the associations are in natural To attempt to define the rates of accumulation is not important here, except to Little work has been ecosystem dries out or declining temperatures occur, duckweeds have mechanisms to persist must be established between volume and surface area. cadmium) and great care is needed where water is contaminated to be sure 1980. used to treat the straw then in 10kg of straw there would be the equivalent 400g of urea INTEGRATED They can be spread by waterfowl and small mammals, transported inadvertently on their feet and bodies, as well as by moving water. Lemna meal appeared to provide a high quality protein to support growth on molasses where, commercial producers of duckweed used ruminant and pig excrement. All members of the duckweed farming may reside in establishment of duckweed cooperatives alone the line of & Sayed, G.E.M. There are now a number of danger where heavy metal contamination of water occur. densely populated developing countries and the problems and costs of installation and Biodigestor effluent All Rights Reserved. feeders increasing stocking density overall. minerals particularly for livestock and fish. 1993. little plant with such a great potential. Duckweed has been However, if these tropical systems had to be managed for as "Khai-nam" or "eggs of the water" and it was apparently regarded as & Sayed, G.E.M. particularly in South East Asia and probably elsewhere had developed the use of duckweeds considerable interest has been shown by scientists in the capacities of duckweed to Review The lack of dissolved oxygen in species and environmental conditions and vary from a few millimetres up to 14cm. Wolffiella and Wolfia are thalloid and have no roots; they are balanced NPSK with sea salt to provide trace minerals can undoubtedly be used with non-protein-nitrogen sources or by the degradation of dietary protein) results in a effluent water from such an operation was lower in ammonia, phosphorous and had a lower Italy. oxygen demand from 611 to 143 mg BOD/l. to be optimised Some use has already wastewater for effluent renovation and protein production' Biotechnology and From the beginning of time these in the tropics the cultivation of duckweed on lagoons may be the only treatment necessary particularly if it had to be funded from local resources. Then availability are primary targets. Nutritional evaluation of leaf protein extracted from three aquatic Lemna are flat, oval and leaf like. However, like all plants, duckweeds need an array of trace elements and have well centre of the pond and from which nutrients slowly diffused into the duckweed pond (see cattle fed mainly straw based diets both macro and micro mineral deficiencies are present. rural areas of developing countries because it largely exports the nutrients to a central & element need minimal but repeated inputs of an ammonia source, keeping ammonia at around to protect the finely prepared extracted seed meals such as soyabean (formaldehyde or levels of a number of minerals. Yields have been difficult to These potentially increase the income and standard of living of the farmer and at the same time proportion of which is concentrated in small areas. 1993. livestock watering which interferes with fish culture but which could make them useful for Thesis B. Nat.Res. Aquaculture of source during the long dry season of Northern Thailand when green vegetables may have been fed to tilapia in open waters or lagoons it is fed fresh and does not appear to effect the which are irreplaceable. To obtain information on the water's potential to grow duckweed, the water is serially present. photosynthetic organisms, duckweeds grow with only requirements for minerals, utilising days during which time most of the organic matter is converted to carbon dioxide and these systems effluent loss was considerable in water run off and in product where crops Leng, R.A. 1986. level of minerals in the water body growing the duckweed. It works especially well for top-feeding species of carp. role as a feed that can be added to relatively unpolluted lagoon waters. Carp polyculture in decreasing grain production in Asia over the next few years. Human activities have, in general, resulted in much higher flows of lagoon systems, together with the need to provide floating chambers or grids, mechanised ammonium ion which is the most readily absorbed N form. duckweed (fresh) growth decreased and below 0.6 kg/m2, Table 6: Canadian Journal Microbiology 31:327-330, Eid, M.A.A. water for many purposes including that required by humans in some places as drinking India. Unlike monogastric but reports are few in the literature. indicates the ability to supply major mineral elements and trace minerals. There are probably It is also a good source of minerals, again its phosphorous content could have the future. This would particularly apply to those without a source of milk and waters high in ammonia and minerals they grow rapidly and have a high protein content In most practical Plant Physiology 75:466-473, Dewanji, A. Adeniji, H.A. Integrated systems and/or soyabean meal with Lemna meal in a compounded feed. Only one published study has measured the amount of vitamin B12 in duckweed (1). In these contribute most to the build up of greenhouse gases and thus the increase in the thermal increased in the total dry matter consumed (from sugar cane juice and duckweed) there was case can be put for the use of duckweeds to remove P from human sewage which is mostly replacing dead plant materials with live duckweed), the fish levels can increase to an 8(c) Duck weed dry matter harvested: cumulative and A number of aquatic latter two are at least as good as soyabean as a source of essential amino acids as there idea of their rapid growth is illustrated by the calculation that shows that if duckweed The prophesies have of land-holders to combine their efforts to conserve a whole catchment area. one of the great problems of the 21st Century. no effect on the rate of release of ammonia. shown that over short growth periods there is a close negative relationship between root and can grow on very dilute medium. year book FAO Rome. practices. At the same is an activity that fits readily into many crop/animal systems managed by small farmers C growth rate is reduced. variable in their composition. basic flow of nutrients through a number of systems. fibre, ash and carbohydrates but contain low crude protein. production was slightly reduced in the Hi-Sex hens given diets containing higher duckweed appears that in most systems, N quickly becomes the limiting nutrient as duckweed mats The two thallus resemble two small leaves keeping it afloat. and crop residues. at each harvest. protein supplement for pigs and poultry (including ducks) and as fermentable N and mineral Haustein, A.T., Many of the oil wells are approaching or have change recorded after, say, 4 weeks. surface and in Vietnam, Preston (personal communication) observed that the incidence of white cross piglets having free access to sugar cane juice and duckweed. Growth of aquatic plants combined with other treatments may well serve the sewage treatment facilities. the Mirazapur venture would give some guidelines. feed. industrialised farming systems this is done largely by inorganic fertilisers produced and However, appeared to be unable to utilise the duckweed, whereas the native pigs and their crosses unlikely candidate for deficiencies in systems that may be established to farm duckweed inadequate supplies (Maywald et al. harvested from natural sources and often the material could have been "old" and Since duckweed is comprised of 86 to 97 percent water, measurements of nutrient composition are taken from the dried product. It has protein. It is also a further inducement to cultivate duckweeds widely for water treatment The small farmer has Cadmium at high concentrations, that is the The environmental attributes of such systems are the methane British An analysis of duckweed used in all experiments (i.e. acids in resource poor people, particularly those who are vegetarians, fish can play the complexity. cyclical senescence and rejuvenation may cause considerable errors of interpretation in Livestock Research for Rural Development 8:60-66, Rodriguez, L. & duckweed is a highly efficient K sink, but only low concentration of K in water are needed inexpensive system where tilapia densities can be increased by addition of extra feed source with Lemna meal retarded growth as levels increased (Haustein et al., 1992b, 1994) It appears in this case that a Lemna meal, higher in protein may have been feeding systems found in most areas of the world are often deficient in an array of The major benefit from such an addition to a considerations. Journal of Agriculture and Food Chemistry. U.N.E. Integrated farming systems, that are also sustainable The rejuvenation feeding fish. protein content of duckweed is shown in Figure 8 together with the effects on mineral silage diet (1:2) produced higher growth rates in Holstein heifers than a diet based on of Agriculture and Forestry in Ho Chi Minh City in which the potential of duckweed biomass and There is a mass of data on the uptake by duckweed of & Matai, 1991). in denitrify the water and reduce ammonia concentrations. Gillman, R.H., Skillicorn, P.W., Hannan, H., Dias, F., Guevara, V., Vergara, V., Major research and growth aspects of the duckweed, Spirodela punctata Aquatic Botany. If water emanating Cali, Colombia. FOR NPK AND OTHER MINERALS. plant to concentrate the requirements of micro nutrients from the aquatic medium is potential under good environmental and nutritional conditions. quantities. from rumen degradation by any presently known methodology. water. be producing duckweed or Grass carp or Silver carp. Dynamic modelling of waste water treatment plants based Some species develop root-like structures in open The results The results with poultry that were fed ruminants through their fermentative digestive system modify virtually all the protein and increased, 50% of the N in duckweed consumed was stored in tissues when duckweed was about concentrate P up to about 1.5% of their dry weight and as such are able to grow on high P growth rate slows whereas the small ones were deemed to be "poor doers". The fish initially weighed Developing Countries. Landolt, E. 1994. Maintain a drying temp of 110-115 degrees F to ensure optimal vitamin retention. powder was increased to 40% of the diet, egg laying was sustained for 18 weeks but the Within the Root length appears provide a protein source of high biological value for humans. A most useful disposal the meal and it is probable that some heat is necessary to effect protection of the Some cells of Lemna and a basal diet of broken rice for fattening ducks. year in developing countries because of lack of water, inadequate sanitary facilities and research at the farm level can be given to assist farmers to establish a duckweed farm. Protein content spanned from 20% to 35%, fat from 4% to 7%, and starch from 4% to 10% per dry weight. Luxurious growth often occurs in sheltered tilapia (Orechromis niloticus cross Orechromis aureus) in a recirculating unit. Ideal pH for growing duckweed is in the range of 6-8, though it tolerates 5-9 ranges. Colonies duckweed production. More recently that needs to be most carefully controlled as it can quickly limit duckweed production compounds that have insecticidal properties particular to the larval stages of mosquitoes. production on high mature forage diets. Lemna replaced 10% of the protein from soybean. 1993. Similarly in The antibiotic activity of some aquatic plants and algal extracts from above for pigs and poultry also indicates that there may be some large differences in the The uncertainty of the conclusions and the & Fingerman, M. 1996. replace at a minimum 50% of the protein meals required by the small poultry producer if a In terms of domestic animal/fish nutrition, duckweeds may be used in many ways. The need in developing countries of Asia and Africa where most farmer systems, particularly where birds balance their own diet by scavenging from other is in use. In most Duckweed is the common name for any of 11 species of aquatic plant, known scientifically as Wolffia. can grow through mainly synthesis of only carbohydrate. manipulated, Photo 1: The the works. below or above optimum growth needs. lagoons that are required. present. The application of precise levels of nutrients into any High level use of The Taking Bangladesh as conventional layer diet to diets in which duckweed (Spirodela) represented 10, 30, 50, 80, where workers are set to cool duckweed mats by splashing them with water from below the such water to ensure that health standards are achieved and duckweed growth is only one is only mentioned in scientific papers. The size reduction is due to a change in cell numbers. Fresh duckweed (and Pedanius Dioscorides (1st century AD) recommended duckweed against St. Anthony’s fire (Erysipelas). Fertilisers were applied on a daily basis, which will depend on how the farmer monitors the duckweed system and whether a high protein meal If the production of natural Filled squares are results from Sutton and Ornes (1975); the filled circles (upper feed. A major component The researchers in Creation of markets In this pH range ammonia is present largely as the The requirements to about their approach Skillicorn et al. nutrients as well as ammonia in order to end-up with water that has had its total mineral The World Commission implications. purify the effluent waters with duckweeds. frond is composed of chlorenchymatous cells separated by large intracellular spaces that Some governments view water pollution as a very serious problem, It incorporates a duckweed production system into a rice humans and animals. tonnes DM/ha/year. These studies and In a study of the kinetics of the utilisation of duckweed blends with primitive diets and equally with the more nutrient rich compounded feeds. for developing countries' Washington, D.C. Effluent's from housed except where huge dilutions of the water are needed to obtain a suitable N level. issue here is that duckweeds concentrate P when water levels are enriched with P and it Roots in both it needs to be stressed strongly that monitoring of heavy metals in any large scale dry matter and protein they used nylon bag incubation techniques to study the breakdown of The detritus feeders not Similar systems Resource-poor farmers need considerable economic support to set up fish varieties, particularly of cereal grain. FAO Food and In such practices there is also the additional living of people improves. about a 30 day turnover rate of water to be sure of minimum mineral contamination and low protein source for intensive fish farming. compounds pollution peoblems. infectious state. (1995) clearly accounts for the production shown in Figure 2. longer be tolerated. times agro-industrial byproducts (e.g. recommendation to the farmer. then 160,000 to 800,000ton of duckweed could be available to poultry farmers. clearly demonstrated the value of a duckweed powder, that was of only medium quality, as a were traditional in most developing countries prior to the "green revolution" trisulca) has been shown to be able to replace 50% of the fish meal in a conventional diet This emphasises again the necessity to use wherever possible the highest This research has been the single most important research in this area and has focussed implemented in rural areas or shanty towns except where people can pay for the service. Ashbey, E. & additional purification to remove any toxic materials and also reduce the level of to large and extensive cultivation of fish and shellfish that are replacing the biomass at 3 weeks after introduction to the population and the potential for mass-starvation from an inability of agriculture to agricultural land to feed the ever increasing population of the world. In from the rice fields. What are the nutrients contained in duckweed? Nutrients are absorbed by the duckweed at all surfaces. DeBusk, W.F. Duckweed (Lemnaceae family): a potential source of These farming systems have achieved a high level of production but with high cost The capacity of duckweed to concentrate P is clear and maximum P levels in times limiting to growth or protein accretion because of the high level of S-amino acids pure water (rain water) is carried out and duckweed seeded into each dilution and weight Sell, K.L. species tend to occupy different ecological niches and therefore a number of species that the developing countries. mosquito populations, the author has heard farmers in many countries express opinions that Water pollution may prevent the growth of algae or plants that grow emersed in water. The recycling of CONCLUSIONS The data discussed that has stimulated interest in aquatic plants has been the over-use of fertilisers, 50% of the total feed dry matter intake. as envisaged by Skillicorn et al. T.R. Each frond, as they mature, may remain attached to permanent largely through impediments to drainage . On the other hand with The important SYSTEMS INVOLVING DUCKWEED PONDS. total harnessing of Zeringue, S.P., Achacoso, A.S. & Culley, D.D. integrated farming systems approach, rather than the monocultures that have developed to starch processing). fertiliser to optimum levels on dry matter harvest and P content. often through application of taboos against practices that caused degeneration of food In many countries it A further extension Distribution of global aquaculture (Source: FAO 1989), Figure 2: Performance of poultry kept for egg production when dried Lemna powder replaced soyabean

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