The most impressive achievement of the Tiwanaku civilization was undoubtedly the intensification of agriculture along the shores of Lago Titicaca using a system of raised fields known in Aymara as sukakullo. This system enabled the inhabitants of Tiwanaku to overcome the problems of drought, floods, frost and soil exhaustion. The Altiplano, the plain surrounding the ruins – which today provides a marginal living for just over seven thousand campesinos – was 1500 years ago producing harvests big enough to feed over one hundred thousand people.
The platforms stand over 1m high, with planting surfaces up to 200m long and 15m wide, and each is carefully structured, with a base of stones followed by a layer of clay to prevent salination by the slightly brackish waters of Lago Titicaca. Above this is a layer of gravel, followed by one of sandy soil and finally a coating of rich, organic topsoil. The raised fields run in parallel lines, with water-filled ditches running between them, providing irrigation during the dry season and preventing flooding when the level of the lake rose. By storing the heat of the sun during the day and releasing it at night, the water in the ditches also protected crops from frost, extending the growing season considerably. Whereas present-day farmers produce about three tons of potatoes per hectare, research suggests that the sukakullo produced astonishing yields of up to twenty tonnes a hectare. Experimental projects are now under way to help local campesinos reintroduce these techniques.