There are many parts of the Peruvian and Bolivian highlands where it is impossible to grow vegetables between the months of May and September. This is also precisely the period when the low temperatures, and inclement weather make it even more necessary to produce vegetables, which will provide the nutrients and particularly the vitamins required by the body during this crucial period. An international private voluntary agency, World Neighbors, is working with farmers to develop a system of sheltered vegetable gardens or hot-houses installed at altitudes of 10,500 to 13,000 feet above sea level in Bolivia that are capable of producing fresh vegetables during this critical period.
The climatic conditions are so harsh during these months, that it alternatives were required if farmers were to grow vegetables there. However, over the past three years, the local peasant farmers, with great perseverance, have developed appropriate technology to solve the problem of cold and create a model which could be applied in the larger Andean region, to produce enough ŇgreensÓ for family consumption and for sale at the market.
Work began with the desire to raise plants which could be transplanted out to the fields early, to ensure that they would mature during the short Andean summer . It was later discovered that the winter sun was quite strong, and if the sheltered vegetable garden was built below ground level, it provided an environment for the development of the vegetables on a year round basis.
The building materials are very simple. Adobe, lengths of wood, a door, and plastic material or a sheet of transparent plastic for the roof are the materials used by World Neighbors. The dimensions shown in the diagram are for a hot-house to keep a family supplied with vegetables. They can be built on a larger scale for schools, colleges, or agricultural clubs.
A teachers training college in a rural area of Bolivia built a vegetable hot-house three times the size of the prototype shown in the diagram, to produce vegetables for all the pupils, after they had seen for themselves the value of a smaller one.
The most important aspect of the vegetable hot-house is the plastic sheet. If the intention is to start vegetables during one season only, and plant them out early, the most suitable material is the ordinary plastic material that can be bought in rolls at local market stores, because it usually lasts beyond the three months needed for this purpose. However, if the hot-house is to produce vegetables for several years, it is more economical to buy a thicker plastic or glass. The main atmospheric factors which will lead to its deterioration are the sun, the wind, hail and rain. It is important to build the hot-house in a place sheltered from the strong wind, and with enough supporting woodwork, cords or wire mesh to prevent the wind from damaging it easily. Finally, the roof should be sloping, to reduce the adverse effects of the rain and hail.
The plastic roof permits the air inside the construction to warm up during the day-time. At night, however, the temperature in the hot-house may drop to levels which are dangerously cold for the plants. For that reason, it is recommended to cover the roof with a layer of straw at night. One method is to make woven straw frames that can easily be put into place at sundown and removed the next morning.
To keep the hothouse from overheating with poor plant growth and potential buildup of fungi and other diseases, a mechanism to allow ventilation is essential. Windows at either and or actually partially opening the roof are two potential alternatives.
Properly designed and managed these protected hothouses offer a valuable option for farmers to expand both the vegetable growing season and the variety of vegetables grown.
Edward Ruddell, Andean Area Representative
Av. Iavier Prado Este 4921 - Off. 5
Lima 12, PERU