Calcined Christmas Island C-grade rock phosphate as a fertilizer

Abstract

A series of four pot experiments and one field experiment was conducted on two soils in northern Tasmania to compare calcined Christmas Island C-grade rock phosphate (CIP) with superphosphate as a source of phosphorus for pasture plants. On an acid, loamy sand CIP alone was better than superphosphate alone for the establishment of pasture plants. The initial response to CIP was best where a high rate of fine material was mixed into the surface soil. The residual response from the coarser CIP was greater than from the fine material. Yield responses from CIP plus ground limestone were lower than from CIP alone, particularly from the coarser grade of CIP. On the other soil, a krasnozem, CIP was inferior to superphosphate as a source of phosphorus.