Comparison of behavior of natural and synthetic phosphate fertilizers in moderately water-repellent sandy loam soil under winter rainfall

This study compares the mobility of phosphate-phosphorus (PO 4 -P) and total P derived from two commercial phosphate blends, namely a naturally reactive rock phosphate containing 12.5% P, and an synthetic phosphate containing 9% P, in small, undisturbed soil cores extracted from a paddock in a dairy farm approximately 35 km southeast of Warrnambool in the Western Region of Victoria, Australia. Since both fertilizers contained major ions, the transport of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) were also studied. The farm's soil, a water repellent, acid, dark brownish grey, sand loam is typical of many found in this rich beef and dairy region, and is used for pasture. Our results suggest that there was little difference in chemical dynamics, and by inference chemical bioavailability and ecological safety, between the two commercial phosphate materials.