What agricultural technique did the Inca use on mountain slopes?

The Inca used agricultural terraces to farm mountain slopes.

Called andenes in the Andes, these step-like platforms transformed steep hillsides into level planting areas. Stone retaining walls held soil in place, reducing erosion and preventing valuable earth from washing downhill during heavy rain. Terraces also helped farmers manage water, retain moisture, and moderate temperature changes at high elevations.

The technique supported cultivation across the Inca Empire’s dramatically varied environments. Potatoes and other tubers grew at high elevations, while maize was generally cultivated lower down where conditions were warmer. Some terrace systems included canals, drainage layers, and carefully engineered water channels. At sites such as Pisac and Tipón, the construction is extensive and remains visible centuries later.

Terracing was not invented by the Incas; Andean peoples had built terraces long before the imperial period. The Incas expanded, standardized, and maintained the technology on a large scale. Irrigation was also important, but it supplied water to fields; the specific technique for turning mountain slopes into farmland was terracing, not irrigation.