Soil Nutrients and Agricultural Infrastructure in the South Kohala Field System, South Kohala, Hawaiʻi

ABSTRACT

The leeward uplands of Kohala, Hawaiʻi Island, contain a dense network of ancient agricultural fields that were intensively cultivated by Native Hawaiians for centuries. Previous archaeological research in the region has focused on the Leeward Kohala Field System, where most agricultural infrastructure is found at or above the hypothesized minimum rainfall threshold (750 mm/year) required for intensively cultivating sweet potato. The South Kohala Field System, conversely, contains a dense network of fields that fall below this threshold (< 750 mm/year), an anomaly which could be explained by multiple anthropogenic or natural factors. To assess the role of soil nutrients in the field system's agricultural patterning, we sampled soils from five geologically distinct substrates that contained varying densities of agricultural infrastructure. Soil pH, bioavailable nutrients, and total elemental concentrations were estimated and compared to the agricultural field density of each sample area. We observed that the high agricultural alignment density was not closely associated with high soil nutrient availability. However, the most nutrient‐poor sample area in our study had the lowest agricultural alignment density. These results suggest that planters in the SKFS prioritized factors other than soil fertility when making decisions about where to invest most intensively in constructing agricultural infrastructure.