Soil nutrients and intensive dryland agricultural production in Kaupō, Maui, Hawaiian Islands

Rain-fed, intensive field systems based on sweet potato and to a lesser extent dryland taro were essential to the political economies of emergent archaic states in late pre-contact Hawai'i. The productivity of these dryland field systems was dependent upon soil nutrient pools that are constrained primarily by geological substrate age and rainfall. We investigated soil nutrient properties across the Kaupō fan, locus of the largest intensive field system on eastern Maui Island. Thirty-six soil samples were obtained along three rough transects, and analyzed for exchangeable bases (calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), base saturation, pH, and rock content). Although some variation in soil properties is evident across the Kaupō fan, in aggregate the samples exhibit high levels of base saturation and exchangeable Ca, indicating good potential for sustained, intensive cultivation. When compared with the Leeward Kohala Field System on Hawai'i Island, the Kaupō field system was likely to have been even more productive based on the relative soil nutrient pools. The high productive capacity of the Kaupō field system is likely to have played a key role in the decision of the early 18th century Maui King Kekaulike to move the island's royal center to Kaupō.