Tag Archives: Water

Aquaculture Production in Zambia

Zambia has big potential for fish farming with 37 per cent of its surface area suitable for artisanal and 43 per cent suitable for commercial fish production.

Aquaculture is the rearing of aquatic organisms in an enclosed water body under controlled conditions. Aquatic organisms may be plant life such as phytoplankton, lilies, and other forms of algae or animal life such as fish, crocodiles, oysters etc. Controlled conditions include physio-chemical water parameters (dissolved oxygen, temperature, pH, phosphorous, etc), water level, as well as feed. The basic idea here is to imitate what is prevailing in the natural waters so as to achieve optimum yields.

Aquaculture is in its infant stage of development compared to agriculture. Fish farming in Zambia dates back to the 1950s when the first attempts were made to raise indigenous species of the cichlidae family, mainly tilapias, in dams and earthen fish ponds. A number of donors have subsequently taken an active part in assisting the government to encourage farmers to adopt aquaculture.

Common aquaculture technologies used in Zambia:

  1. Earthen Ponds

This technology involves the use of the sides, bottom, and dykes of a pond to form an ecosystem. Such a system promotes growth of natural food items and so fish benefits extensively from the natural food. Supplementary feed may not be necessary. Production varies depending on management system employed; regardless of pond size. Pond construction and maintenance is relatively cheaper. Examples of species suitable for culture include Oreochromis andersonii or O. niloticus.

earthen-ponds

Earthen Pond

  1. Concrete Ponds

Pond walls and bottom are made of concrete. Since the bottom is cemented, no ecosystem is formed and so no natural food production. In this case, formulated feed is what the cultured organisms rely on. It is expensive to construct and maintain; thereby mainly used for production of high value species e.g. carp fish.

concrete-ponds

Concrete Pond

  1. Raceways

This is a narrow long body of water. It depends on a continuous flow of water and so limited presence of algae, bacteria, or fungi. Only stubborn algae are scarcely found. Catfish, Tilapia, Carp are among species that can be cultured.

raceways

Raceway

  1. Floating Cages

Cages may be made of planks or steel and are placed in running water- in a natural water body (lake, river, sea). Since space is limited, artificial feed supplement is necessary. To curb environmental degradation, positioning of cages, feed type, and frequency is cardinal. Examples of species cultured in this system include i.e. O. niloticus or O. andersonii.

floating-cages

Floating Cages

Cage farming is a relatively new practice in Zambia, which has attracted a lot of concern from the Environmental monitoring bodies such as the Zambia Environmental Management Agency (ZEMA). Their main concern is regarding the negative impacts that the practice has on the natural water body and its resources. For example,

  • In the event of fish escaping from cages, such escapes may cause harm to the inhabitants and the ecosystem (especially if they are exotic species).
  • Uneaten feeds that find themselves on the river bed would cause water pollution;
  • Cages tend to divert or hamper natural water flow;
  • The site of cages may compromise the beautiful scenery of the water body, affecting tourism;
  • Cages would also affect navigation; etc.

There is therefore need to address such concerns before and during the project execution stage. Constraints and benefits must be compared to ensure that even as the farmer is gaining profits, the environmental damage is not compromised. In this vain, it is a requirement by the Zambian law that an environmental impact assessment (EIA) be carried out before project initiation to determine the possible impacts and propose remedial measures thereof.

  1. Tanks

Strong material such as planks, fibre glass, or plastic is used in construction. May be round, square, or rectangular in shape. Shape and size varies depending on purpose. Usually used for high value and delicate species such as breeders, juveniles, or ornamental fishes. Food is totally artificial and water should be allowed to run through or changed regularly.

tanks

Tanks

  1. Conservation Dams

In most cases, the dam is originally intended for other purposes such as irrigation, livestock drinking, or human consumption. Instead of allowing the dam to serve only that intended purpose, fish may be reared in the same dam. In dams meant for livestock, animals fertilize the water (cow dung for instance), thereby promoting primary productivity, and thus natural food for the fish. Production is relatively low. Harvesting is not easy due to depth, stumps, and rocks. This kind of practice is commonly practiced in Southern and Eastern Province of Zambia. Species cultured mainly Tilapia, catfish.

Species Suitable for Aquaculture in Zambia

The commonly used species for aquaculture include the three spotted tilapia (Oreochromis andersonii), the longfin tilapia (Oreochromis macrochir) and the redbreast tilapia (Tilapia rendalli). The Kafue river strain of the three spotted tilapia is the most commonly farmed species, particularly in the commercial sector. Other species include the common carp (Cyprinus carpio), the Nile tilapia (Oreochromis niloticus) and the red swamp crayfish (Procambarus clarkii).

Challenges facing Aquaculture Production in Zambia

Lack of a national policy to guide aquaculture development, unfriendly investment policies, the absence of linkages between farmers, research/technology development and extension, and unfavourable investment climate. Long-term economic sustainability of Zambian aquaculture will depend on the development and implementation of a national policy that ensures the social and environmental sustainability of the industry.

Challenges and Opportunities for the Future

The entry of Zambian aquaculture into global prominence faces considerable challenges. There are, however, reasons for optimism. Despite high risks and investment costs, high and increasing demand and market value of fish are encouraging. If social and environmental sustainability issues can be successfully addressed, increasing market demand and higher prices should open opportunities for a range of producers and investors. Increasing productivity of both large and small-scale aquaculture will require major investments in research, development and extension as well as policy shifts. The strategies for addressing problems of the small-scale and larger commercial operations will probably be different.

 

USES OF MULCHES IN SOIL MOISTURE CONSERVATION

INTRODUCTION
Mulch is a protective covering, usually of organic matter such as leaves, straw, or peat, placed around plants to prevent the evaporation of moisture, and the growth of weeds. The word mulch has probably been derived from the German word “molsch” meaning soft to decay, which apparently referred to the gardener’s use of straw and leaves as a spread over the ground as mulch.
Mulching (1) reduces the deterioration of soil by way of preventing the runoff and Soil loss, (2) minimizes the weed infestation and (3) checks the water evaporation. Thus, it facilitates for more retention of soil moisture and (4) helps in control of temperature fluctuations, (5) improves physical, chemical and biological properties of soil, as it adds (6) nutrients to the soil and ultimately (7) enhances the growth and yield of crops. Further, reported that mulching (8) boosts the yield by 50–60% over no mulching under rain-fed situations.

CLASSIFICATION OF MULCHES
Advancement in plastic chemistry has resulted in development of films with optical properties that are ideal for a specific crop in a given location. Horticulturists need to understand the optimum above and below ground environment of a particular crop before the use of plastic mulch. These are two types.
Photo-degradable plastic mulch: This type of plastic mulch film gets destroyed by sun light in a shorter period.
Bio-degradable plastic mulch: This type of plastic mulch film is easily degraded in the soil over a period of time.

COLOR OF FILM
Soil environment can be managed precisely by a proper selection of plastic mulch composition, colour and thickness. Films are available in variety of colours including black, transparent, white, silver, blue red, etc. But the selection of the colour of plastic mulch film depends on specific targets. Generally, the following types of plastic mulch films are used in horticultural crops.
1. Black plastic film: It helps in conserving moisture, controlling weed and reducing outgoing radiation.
2. Reflective silver film: It generally maintains the root-zone temperature cooler.
3. Transparent film: It increases the soil temperature and preferably used for solarisation.
Apart from the above classification there is another way of classifying Methods in mulching:
1. Surface mulching: Mulches are spread on surface to reduce evaporation and increase soil moisture.
2. Vertical mulching: It involves opening of trenches of 30 cm depth and 15 cm width across the slope at vertical interval of 30 cm.
3. Polythene mulching: Sheets of plastic are spread on the soil surface between the crop rows or around tree trunks.
4. Pebble mulching: Soil is covered with pebbles to prevent transfer of heat from atmosphere.
5. Dust mulching: Interculture operation that creates dust to break continuous capillaries, and deep and wide cracks thus reducing evaporation from the exposed soil areas.
6. Live vegetative barriers on contour key lines not only serve as effective mulch when cut and spread on ground surface, but also supply nitrogen to the extent of 25 to 30 kg per ha, besides improving soil moisture status.

EFFECTS OF MULCHES ON SOIL MOISTURE CONSERVATION
Water is essential for growth and development. It is also a major cost in agricultural systems. The success of many agricultural forms relies on conservative and efficient use of water. Moisture retention is undoubtedly the most common reason for which mulch is applied to soil.
Ingman claimed that the use of things made with plastic or plastic components have become a routine part of our daily lives. In a similar way, over the past 50 years world agricultural systems have rapidly adopted the use of many types of plastic products to grow the food we eat because of the productive advantages they afford. Plastic use in agriculture (plasticulture) continues to increase every year in the ever-diminishing supply of petroleum. There is a common lack of awareness
regarding what plastic mulch is, and also a lack of applied research of its use in agricultural communities. However, the use of plastic mulch may actually be one of the most significant water conservation practices in modern agriculture: quite possibly surpassing the water savings of drip irrigation. Even though most of the world’s use of freshwater is spent for irrigation purposes, little research explores how plastic mulch use as a water conservation practice may influence the current and future status of water resources. He used a multidisciplinary approach to understand why Chinese farmers on the margins of the Gobi desert continue to use plastic mulch, and in particular, how its use may relate to water conservation. Next, the study asks to what extent the plasticization of agriculture may influence the income and standard of living for agricultural communities. He was able to prove the role of plastic mulch in conserving soil moisture.
Mulch is used to protect the soil from direct exposure to the sun, which would evaporate moisture from the soil surface and cause drying of the soil profile. The protective interface established by the mulch stops raindrop splash by absorbing the
impact energy of the rain, hence reducing soil surface crust formation. The mulch permits soil surface to prevent runoff allowing a longer infiltration time. These features result in improved water infiltration rates and higher soil moisture. An auxiliary benefit of mulch reducing soil splash is the decreased need for additional
cleaning prior to processing of the herb foliage. Organic and inorganic mulches have shown to improve the soil moisture retention. This increased water holding ability enables plants to survive during dry periods. The use of plastic mulch can be improved if under-mulch irrigation is used in combination with soil moisture monitoring.
The influence of rainfall events is not as great when plastic mulch is used, necessitating active irrigation management. Under mulch, irrigation of vegetable crops has been shown to improve crop yields more than overhead irrigation systems.
Mulch enables the soil moisture levels to maintain for longer periods. In some cases while providing improved moisture conditions within the soil, the mulch changes microclimate so that it uses more water, thus negating the initial benefits. Plastic mulch conserved 47.08% of water and increased yield by 47.67% in tomato
when compared to nonmulched control. Plastic mulching resulted in 33 to 52% more efficient use of irrigation water in bell pepper compared to bare soil.
The conservation of soil moisture through mulching is one of the important best management practices (BMP). The microclimatic conditions are favourably affected by optimum degree of soil moisture. When soil surface is covered with mulch helps
to prevent weed growth, reduce evaporation and increase infiltration of rainwater during growing season.
Different mulching materials helped bell pepper (C. annuum cv. California Wonder) to perform better at water deficits from 25–75% and plastic mulch had highest water use efficiency. Treatment receiving mulch recorded significantly higher net

Source: Best Management Practices for Drip Irrigated Crops
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