Movement of applied phosphorus following the mining and revegetation of mineral sands on Australia's east coast

Abstract

The magnitude of phosphorus movement through a range of mined and unmined sands on Australia's east coast was measured under saturated and unsaturated flow in laboratory columns and in a field experiment of 16 months' duration. Relationships were examined between the amounts of leaching observed and the chemical and physical characteristics of the sands and the rates (0-306 kg P/ha) and forms (KH2PO4,, triple superphosphate and rock phosphate) in which phosphorus was added. Moderate movement of phosphorus was observed in all of the sand types examined, with the greatest movement occurring in A, and stockpiled A, horizon material from a podzol profile and the least being in B horizon material from the same profile. The extent of movement was related to the phosphorus adsorption capacity of the sands, the solubility of the phosphorus source, and the amount and rate of water movement. The adsorption capacity of the sands was positively correlated with the amount of aluminium and iron oxyhydroxides on the quartz grains; the coefficients of correlation (r) between the maximum phosphorus adsorbed and the aluminium and iron extracted by H2SO4- HClO4, were 0.98 and 0.84 respectively. The relevance of the findings to ground water quality and native species regeneration are briefly discussed.