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What is Raised Field Agriculture?

A Lesson in Applied Archaeology, Part 1

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Prehispanic Raised Fields

Pre-hispanic raised fields in the lake plain (pampa) of Huatta, Peru

Clark Erickson

A Lesson in Applied Archaeology

Table of Contents
What are raised fields?

Raised fields are large artificial platforms of soil created to protect crops from flooding. They are generally found in areas of permanent high water table or seasonal flooding. The addition of earth for drainage also increases the depth of the rich topsoil available to plants. In the process of building raised fields, canals are excavated adjacent to and between fields. These depressions fill with water during the growing season and provide irrigation when necessary. Decomposing aquatic plants and nutrients captured in the canals provide a fertile "muck" or "green manure" for periodically renewing the soils of the platforms. We found that in the high Andes where "killer" frost is a serious problem at night, the water in the canals of raised fields helps to store the sun’s heat and blanket the fields in warm air at night—protecting crops against the cold. Raised fields have been found to be highly productive, and if managed properly, can be planted and harvested for many years.

The most famous raised fields are the "chinampas" or so-called "floating gardens" (they don’t actually float!) built by the Aztecs of Mexico. These fields are still being farmed today, on a greatly reduced scale, to raise vegetables and flowers for the urban markets of Mexico City.

How are raised fields built?

Raised fields are essentially big piles of dirt. They are created by digging into the top soil and raising a large, low platform. The farmers that we worked with have a lot of experience building with sod. They use the chakitaqlla (chah key talk’ ya) to cut square blocks of sod and use them just like adobes (mud bricks) to build walls, temporary houses, and corrals. They decided that the fields would look better and last longer if the retaining walls were made of sod blocks. They placed irregular chunks of sod and loose soil between the walls to build up the field. The sod had an additional benefit in that sod in the walls actually took root and formed a "living wall" which kept the fields from eroding.

Whenever possible, we rebuilt or "rehabilitated" the ancient fields, keeping the old patterns of fields and canals intact. There were several clear advantages of doing this 1) rebuilding meant less work than creating completely new fields, 2) the organic-rich soils in the old canals (used to raise the platforms) was very fertile, and 3) the ancient farmers probably knew what they were doing (so why change things?).

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