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The Mined Lands Agricultural Research Project: Summary of Experiments and Extension Recommendations


The Polk County Mined Lands Agricultural Research/Demonstration Project (MLAR/DP) has proven that reclaimed phosphatic clays can support intensive agricultural production systems. Phosphatic clay is both highly fertile and productive. Additional physical and chemical characteristics, such as relatively high water holding capacity and inherently high plant nutrient supply, are superior to surrounding unmined sandy soils. Phosphatic clay does contain elevated levels of radionuclides. This project has shown that these naturally occurring radionuclide levels are not passed to plants and animals in the human food chain, and pose minimal risk to human or animal health. Drainage must be provided because of the slow infiltration rate and propensity of water to pond on flat phosphatic clay surfaces. Results from drainage research showed that the formation of macrobeds provided the needed surface relief and subsequent drainage at minimal cost for construction. Numerous trials conducted through the MLAR/DP demonstrated which cultivars and commodities, both agronomic and horticultural crops, could be successfully grown. Fertilization trials with these commodities demonstrated that nitrogen was required for adequate commercial production, that specific crops required additional manganese, and that the irrigation requirements were considerably less than that needed for the same crops being grown on adjacent sandy soils. This document summarizes the findings of the MLAR/DP, and provides management strategies specific to intensive agricultural operations on the phosphatic clay.