Enhanced efficiency phosphate fertilizers and phosphorus availability in Acrudox

Abstract

The objective of this study was to evaluate the influence on P availability of the application of polymer-coated phosphate and organophosphate fertilizers to the soil under different soil water matric potentials and contact times. The experiment was laid out in a randomized block design and replicated four times, with treatments distributed in a split-plot arrangement. The main plot comprised four phosphate fertilizers (conventional mono-ammonium phosphate, MAP; polymer-coated mono-ammonium phosphate, POL; pelletized mono-ammonium phosphate with filter cake, FC; and granulated mono-ammonium phosphate with swine compost, SC) and two soil water contents corresponding to two matric potentials (-10 and-50 kPa). The subplot comprised six contact times (2, 4, 6, 8, 10 and 14 days after fertilizer addition). P content was determined after extraction with Mehlich-1 or water. The highest available P contents in soil were obtained using MAP (1474.3 mg dm-3) followed by POL (1355.7 mg dm-3), FC (1235.5 mg dm-3) and SC (804.2 mg dm-3). The available P contents during the 14 days of the experiment relative to the control (MAP) values ranged from 88.5 to 95.4% for POL, 83.2 to 84.4% for FC and 54.9 to 54.2% for SC. These results evidenced the effects of the organic coating applied to the phosphate fertilizer on fertilizer solubility and the short-term release of P. A decrease in the soil water matric potential decreased P availability in the short term for fertilizers with coating technologies, especially for SC compared to MAP. This result indicates that organic coating technologies may hold promise for maintaining P availability over time.