|Sourcebook of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean (UNEP-IETC - OAS, 1998, 247 p.)|
|Part B. Technology profiles|
|4. Water conservation|
This technology consists of using clay pots and porous capsules to improve irrigation practices by increasing storage and improving the distribution of water in the soil. It is not new; it was used by the Romans for many centuries. This ancient irrigation system has been modernized and reapplied in water-scarce areas.
This low-volume irrigation technology is based on storing and distributing water to the soil, using clay pots and porous capsules interconnected by plastic piping. A constant-level reservoir is used to maintain a steady hydrostatic pressure. Clay pots are open at the top and are usually fired in home furnaces after being fabricated from locally obtained clay or clay mixed with sand. The pots, usually conical in shape and of 10 to 121 capacity, are partially buried in the soil with only the top extending above ground. Distribution is by plastic (PVC) piping to ensure a fairly uniform permeability and porosity. Hydrostatic pressure is regulated by maintaining a constant level in the storage reservoir, as shown in Figure 37.
A similar system, tested in Mexico and Brazil, uses smaller, closed containers, or porous capsules, completely buried in the soil. These containers distribute the water either by suction and capillary action within the soil, or by external pressure provided by a constant-level reservoir (as in the previous system). Each capsule normally has two openings to permit connection of the plastic (PVC) piping which interconnects the capsules. The capacity of these capsules ranges between 7 and 151, and the storage tanks supplying the system are elevated 1 or 2 m above the soil surface. The capsules are buried in a line 2 meters apart, at least 10 cm under the top layer of the soil.
The number of pots or capsules used is a function of the area of cultivation, soil conditions, climate, and pot size. Up to 800 pots/ha were installed in Brazil; the system there is shown in Figure 38.
Extent of Use
This technology is being used for small-scale agricultural irrigation in the arid and semi-arid regions of Argentina, Brazil (see case study in Part C, Chapter 5), Ecuador, Bolivia, and Mexico. It has also been used in tropical countries such as Guatemala, Panama, and the Dominican Republic during drought periods.
Operation and Maintenance
The operation is very simple, requiring only the opening of valves to replace the water used from the pots and capsules. However, the installation of the system does require a degree of care since the pots and capsules are made of clay and can be easily broken; also, the gradients must be correct if gravity flows are desired. It is also important to maintain the hydrostatic pressure. If this pressure cannot be maintained, the connections between pots must be checked for possible leaks and/or breakages. Replacement of the pots or capsules is necessary every 3 to 5 years. A soil investigation before the installation is advisable.
Level of Involvement
The participation of the community is essential in the implementation of this technology. Further, the support of the government and research institutions is also desirable. In Brazil, the government of the state of Pernambuco built a factory to manufacture porous capsules and developed small areas of bean cultivation for the application of the technology. In Ecuador and Bolivia, universities and government agricultural institutions are testing it.
Figure 37: Schematic Representation of a Clay Pot Irrigation System.- Plant view
Figure 37: Schematic Representation of a Clay Pot Irrigation System.- Detail of principal and secondary pots
Source: Aderaldo Silva De Souza, et al. Irrigacior Potes de Barro: Descripciel Mdo y Pruebas Preliminares, Petrolina, PE, Brasil, 1982, (EMBRAPA-CPATSA Boletde Investigacio. 10).
Figure 38: Schematic of a Porous Capsule Irrigation System.- General layout
Figure 38: Schematic of a Porous Capsule Irrigation System.- Detailed sketch of porous capsules system
Source: Aderaldo Silva De Souza, et al. Irrigacior Potes de Barro: Descripciel Mdo y Pruebas Preliminares. Petrolina, PE, Brasil, 1982, (EMBRAPA-CPATSA Boletde Investigacio. 10).
Costs vary according to the materials and the type of system used. In Brazil, the reported cost was $1 300/ha cultivated using clay pots, and $1 800/ha cultivated using porous capsules. A clay pot system in the Dominican Republic reported an annual cost of $1 280. Smaller experimental systems in Bolivia and Panama were built for less than $100.
Effectiveness of the Technology
The technology has been shown to improve the stability of the soils. It has allowed agricultural development in areas where climatic conditions and the quality of the soils have prevented the use of conventional irrigation methods. Tests performed in Panama, using fruit trees, show significant improvements in the size of the stem and the number of fruits per plant; a yield of six fruits per plant was achieved with this system versus two with conventional irrigation. In Bolivia, the use of this technology in the cultivation of potatoes resulted in a yield of 42 000 kg/ha versus 18 000 kg/ha using traditional irrigation methods.
This technology is suitable for arid and semi-arid regions, and for small-scale agricultural projects in areas affected by periodic drought. Countries like Bolivia, Brazil, Peru, Argentina, and Chile can definitely benefit from the use of this technology in rural areas.
· This is a low-cost technology.
· Agricultural production is higher with this technology than with other irrigation technologies.
· Agriculture can be undertaken at lower air temperatures.
· Infiltration losses are reduced.
· Weeds can be better controlled, by managing their access to water.
· This system does not cause environmental impacts.
· This technology is very useful in family gardens and in horticulture.
· Water management using this technology allows agricultural development in arid lands and salty soils.
· Vandalism is minimized since most of the equipment is under the soil surface.
· It is easy to operate and maintain.
· It can reduce fertilizer use. by allowing application to defined, cultivated areas.
· Use of this technology can minimize soil erosion.
· The technology is difficult to use in rocky soils.
· Broken pots or capsules can disrupt the irrigation operation and reduce productivity.
· Some plants with extended root systems are difficult to cultivate using this technology.
· In some areas, it may be difficult to purchase or manufacture the clay pots and/or capsules.
· It is only applicable to small-scale agriculture.
This technology is gaining acceptance among agricultural communities in arid areas. It is well developed as a technology for use in household gardening.
Further Development of the Technology
Improvements in the construction of the porous capsules are desirable, perhaps using different materials which have acceptable levels of porosity but are more robust and can avoid breakages. It is also desirable to develop systems using porous capsules or clay pots, that can be used in large-scale or commercial agricultural operations. Educational and informational programming on the benefits of the technology, and training in the manufacture of porous capsules, and pots are required.
Eisa L. Flores, Centro de Investigaciones Hidricas e Hidroticas, Universidad Tecnola de PanamApartado 6-2894, El Dorado, PanamRepa de PanamTel. (507)220-3666. Fax (507)220-3666. E-mail: firstname.lastname@example.org.
NicolC. Ciancaglini, INCYTH-CRA, Casilla de Correo 9,5500 Mendoza, Argentina. Tel. (54-61)28-6998. Fax (54-61)28-8250.
DarAlvarado, Profesor, Facultad de Ciencias Agropecuarias, Universidad de Cuenca, Cuenca, Ecuador. Tel. (593-7)831-688. Fax (593-7)832-183.
Freddy Camocho Villegas, Instituto de Hidrica e Hidrolog(UMSA), Casilla Postal 699, La Paz, Bolivia. Tel. (591-2)79-5724. Fax (591-2)79-2622.
Milagros Martz Esquea, Instituto Nacional de Recursos Hidricos, Programa de Manejo de Agua a Nivel de Fincas, Centro de los Heroes, Apt. 1407, Santo Domingo, Repa Dominicana. Tel. (809)533-5804. Fax (809)532-5884.
Everaldo Rocha Porto, Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA), Centro de Pesquisa Agropecuaria do Tro Semi-ido (CPATSA), BR-428 km 152, Zona Rural, Caixa Postal 23, 56300-000 Petrolina, Pernambuco, Brasil. Tel. (55-81)862-1711. Fax (55-81)862-1744, E-mail: email@example.com.
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Luiza Ternura de Lima Brito, Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA), Centro de Pesquisa Agropecuaria do Tro Semi-Arido (CPATSA), BR-428 km 152, Zona Rural, Caixa Postal 23, 56300-000 Petrolina, PE, Brasil. Tel. (55-81)862-1711. Fax (55-81) 862-1744. E-mail: firstname.lastname@example.org.
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