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Raised fields raise yields

For thousands of years the area around Lake Titicaca, which straddles the border between Bolivia and Peru, has been home to civilizations which have prospered and then disappeared. In the 1960's, archaeologists began studying vast areas of land criss-crossed with the remains of raised fields. However, it wasn't until the 1980's that applied archaeologist, Dr. Clark Erickson, decided to reconstruct the fields and test their efficiency. The project was so successful that, twenty years later, many of the region's farmers have built and are now farming their own raised fields.

Raised fields are generally found in areas to prone to seasonal flooding or where the water table is permanently high. The most famous are the 'chinampas', or 'floating gardens' built by the Aztecs in Mexico, some of which are still being farmed today.Around Lake Titicaca, the remains of raised fields cover almost 120,000 hectares, and were first used about three thousand years ago by a pre-Inca civilization. However, they were then abandoned, either when the Spanish conquistadors arrived, or possibly shortly before. Nowadays, much of the land is used for grazing animals and is too degraded to grow crops.

In the early 1980's, Dr. Erickson of the University of Pennsylvania's Museum of Archaeology and Anthropology, began his research in the region. "Wherever possible we rebuilt or 'rehabilitated' the ancient fields, keeping the old patterns of fields and canals intact," he explains. "The ancient farmers probably knew what they were doing, so why change things?" Raised fields are built by digging into the top soil and raising a large, low platform about 1 metre high, and they are from 1 to 20 metres wide and from 10 to hundreds metres long. The fields are divided from one another by a series of canals, the soil from which is used to build the raised plots. By piling up the earth to create the fields, the depth of the topsoil is increased, giving plants' roots valuable breathing space above the water table. During the rainy season, the canals fill with water, providing essential irrigation for the crops. Decomposing aquatic plants and nutrients captured in the canals also provide a 'green manure' which is periodically removed and spread onto the raised fields as a fertilizer.

Early success

The first season of trials produced such high yields of potatoes that local farmers thought a super-fertilizer had been used whereas, in fact, no fertilizer at all had been applied to the plots. Also, although he used only local potato varieties, there were accusations that Dr. Erickson had used a modern, high-yielding cultivar. By providing no incentives other than supplying seed potatoes, Dr. Erickson managed to convince some farmers to try the system for themselves. The farmers built the raised fields and, in return for their labour, were allowed to keep the harvest from the plots. For his part, Dr. Erickson collected scientific data on yields, other agronomic factors, and even how the work was organized by the community.

Current practice among the farmers of the Lake Titicaca basin is to farm a field for three to four years and then abandon it for anything from three to ten years to allow it to recover its fertility. Dr. Erickson's research showed that the raised fields could be farmed more continuously, helped by the supply of nutrients from the canals. The raised fields also warm up during the day and water vapour released from the canals at night acts as a buffer against frosts that otherwise can severely damage crops growing in this region of the Andean high plateau.

Although Dr. Erickson's project was completed in 1986, raised field agriculture is still spreading throughout the region. Many small farmers in the pampas surrounding Huata, Peru, for example, took part in community projects, or saw their results, and decided to build their own raised fields. NGOs are also active in educating the local farmers. The Interinstitutional Programme for Waru Waru (PIWA) in Peru, for example, works directly with farmers to rehabilitate traditional agriculture. As well as conducting social and agronomic research and mapping potential zones for building more raised fields, they also publish books and guides for extension agents and farmers.

By 1990, farmers from several hundred Quechua and Aymara communities in Bolivia (who respectively make up 30 and 25% of the Bolivian people) had rehabilitated between 500 and 1500 hectares of raised fields. "If there is a future for raised fields, it is probably at the level of the individual farm family," concludes Dr. Erickson. "Family raised fields are well-built and maintained for longer periods. The success of the 'multiplier effect', the adoption and promotion by individual families, is difficult to track, but remains an important means of diffusion and adoption of raised field technology."

Article submitted by Peter McGrath

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