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 (PO4-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 daily f arm approximately 35 km southeast of Warrnambool in the Western Region of V ictoria, Australia. Since both fertilizers contained major ions, the transp ort of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) were al so studied. The farm's soil, a water repellent, acid, dark brownish grey, s and loam is typical of many found in this rich beef and dairy region, and i s used for pasture. Our results suggest that there was little difference in chemical dynamics, and by inference chemical bioavailability and ecologica l safety, between the two commercial phosphate materials.