The increasing interest in the utilization of aquatic plants is shown not only in the many published papers but also in the number of reviews and bibliographies produced since the first edition of this handbook was prepared.
The biology of aquatic vascular plants, by C.D. Sculthorpe (1967) is an important text, containing a wealth of information. It includes a review of the literature on ancient uses of aquatic plants for food and medicines, and a chapter on the economic and aesthetic value of these plants.
D.S. Mitchell (1974) edited Aquatic vegetation and its use and control, which contains a section (pp. 107–15) on utilization of aquatic plants, by C.E. Boyd. It makes no attempt to cover all aspects of the subject but should be consulted; in it many of the more important papers are briefly cited.
N.W. Pirie, well known for his work on the extraction of protein from plants for human and animal consumption, edited the IBP Handbook, “Leaf protein, its agronomy, preparation, quality and use” (1971). This text also contains a chapter by C.E. Boyd on the literature of the leaf protein content of aquatic plants and can be compared with data for terrestrial plants presented in other chapters.
Water hyacinth has been reviewed by A.H. Pieterse (1974). All aspects of the plant, including its utilization, are briefly covered, with a total of 215 references. A useful bibliography is provided. It is divided into sections on distribution; general botany; environmental factors associated with growth and flowering; direct effect of environment; dormancy and germination of seeds; production and regeneration; mechanical, chemical and biological control; chemical composition; utilization (animal fodder, compost and mulch); mineral removal from polluted water, and industrial uses such as paper making, wicker and basket work, soap, gas and alcohol production.
In 1978 Pieterse revised this work in the same style but giving 666 references, which he grouped into eight categories: general information (25 references); general botany, ecology and spread (226 references); chemical and mechanical control (143 references); biological control (139 references); chemical composition and use as fodder (63 references); use as compost and mulch (22 references); production of chemical materials and energy (16 references); use for mineral removal from polluted water (32 references). The remarkable increase in the literature on this plant indicates the concern felt for it as a pest and, more recently, as a potentially useful crop.
An earlier review on water hyacinth by A. Sharma (1971) summarized the work done on its utilization with a total of 50 references and can be read as an introduction to the subject. The author estimates the total area under water hyacinth in India at 200 000 ha which could produce about 5 million tons of compost. He calculates that it could be harvested at a profit for use as fertilizer. Other aspects of use included are: as food for animals, raw material for industry, and a source of gases, proteins and other chemicals. He concludes by suggesting that regular harvesting would lead to extermination of the weed from enclosed areas which could then be used for cultivation of the valuable plant crop Trapa natans (water chestnut).
K.M. Jagadeesh and C.S. Lakshminarayana (1971) have also contributed a brief review on water hyacinth control and utilization (four references), as have V. Ramachandran et al. (1971) with 55 references.
O.P. Gupta and P.S. Lamba (1976) reviewed the use of aquatic plants for fodder, compost, protein carotene, fish food, pulp and paper, culture for yeast and antibiotics, medicinal ingredients, and for pollution abatement (23 references). The authors urge that interdisoiplinary research is needed for the appropriate commercial exploitation of aquatic plants. Such an approach alone could ensure adequate control of important aquatic weeds in the tropics and subtropics. (From Weed Abstracts)
J.L. Fox and H.S. Prentice (1975) have reviewed methods of harvesting aquatic plants with many references. (From Weed Abstracts)
A recent review from the U.S.A. by R.P. Bates and J.F. Hentges (1976) has a bibliography of 71 papers. The authors, after discussing methods of control of aquatic weeds, consider the alternative of cultivating them for use. The possibilities of grazing the plants by manatees or by fish are examined. Aspects of harvesting and subsequent use for compost, or directly as animal or even human food, are also mentioned.
An early reviews, also from the U.S.A. which should be read in conjunction with Bates and Hentges, is by Nelson and Palmer (1938). The detailed experimental results reported are supported byreferences to about 100 papers containing data on the vitamin and protein content of a range of aquatic plants and their consequent potential importance in animal nutrition.
C.E. Boyd (1972) has prepared a comprehensive bibliography on aquatic weed use with 233 references which he has classified into seven groups: chemical composition and nutritive value; nutrient removal; productivity and standing crop; ecology and life history; identification; aquatic plant nutrition and physiology; nutrient relationships in aquatic environments.
In 1976 the Weed Research Organization of the Agricultural Research Council, U.K., published an annotated bibliography (No. 92) containing selected references on the utilization of aquatic plants covering the period 1969–75. Each reference cites the relevant summary from the Commonwealth Agricultural Bureaux Journal, Weed Abstracts, and where these were not available at the time a specially prepared summary is given.
Weed Abstracts is itself a useful source, because it publishes a section on utilization of weeds, including aquatic weeds.
Herbivorous fish can control and utilize aquatic plants. Of these the grass carp (Ctenopharyngodon idella) is the best known and the subject of numerous papers. FAO has published a bibliography of 243 references (Nair, 1968). In 1976 the Weed Research Organization of the Agricultural Research Council, U.K., published a bibliography of 162 references, covering the period 1957–76, on the use of herbivorous fish.
In New Zealand, Hughes (1976) reviewed all aspects of local aquatic weed research. Brief reference is made to seven papers (five unpublished) on the possibilities of harvesting the weeds infesting New Zealand lakes and using them for compost or for stock feed. General conclusions were unfavourable.
The United States National Academy of Sciences published in 1976 a comprehensive book of 175 pages on making use of aquatic weeds. It is directed towards developing countries and contains 4-page summaries in Spanish and French. There are 14 chapters covering all aspects of direct use of the plants, including: foods for various fish, birds and mammals; methods of harvesting and drying, and subsequent use for animal and human food; use for soil additives; for industrial purposes, including energy, and for purification of polluted water. Each chapter details the need for further research, gives relevant literature references, and lists individuals and organizations around the world which are involved in research. The book is well illustrated. The theme is of enthusiastic encouragement to people in developing countries to harvest their vigorous and often dangerous aquatic plants for useful purposes, rather than incur the expense of using herbicides and the mechanical control methods which may be more feasible and acceptable in developed countries.
The review and bibliography presented in this handbook are necessarily incomplete; with the advance of research it will soon require revision. However, it has been brought up to date as far as practicable, and in more detail than other contributions so far published.
Read boat in a channel cut through weeds in Lake Titicaca, Bolivia