Abstract
Distant but cognate, pre-contact southern Polynesians created extensive rocky cultivation sediments and soils. This early agronomy is evaluated as evidence of innovation or diffusion associated with South American sweet potato (kumara) introductions. For South Island Maori, soil temperatures and drainage were improved in kumara cultivation under and within transported gravel and sand deposits. On Rapa Nui/Easter Island, rocky sediment was spread over cultivation fields to conserve soil and moisture against desiccating winds. While there is overlap in lithic sediment, anthrosol thickness and size classes from both distant islands, the evidence of discrete physical properties and environments is more consistent with innovation. On Rapa Nui, low-elevation lithic cultivation has continued to the present. Extensive northern South Island lithic fields were abandoned before the nineteenth century ad, perhaps because of social disruption or climate change.