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Prehistoric agricultural depletion of soil nutrients in Hawai‘i

We investigated the fate of soil nutrients after centuries of indigenous dryland agriculture in Hawai‘i using a coupled geochemical and archaeological approach. Beginning 500 years ago, farmers began growing dryland taro and sweet potato on the leeward slopes of East Maui. Their digging sticks pierced a subsurface layer of cinders, enhancing crop access to the soil water stored below the intact cinders. Cultivation also catalyzed nutrient losses, directly by facilitating leaching of mobile nutrients after disturbing a stratigraphic barrier to vertical water movement, and indirectly by increasing mineral weathering and subsequent uptake and harvest. ...