Enhanced-efficiency phosphate fertilisers, diffusive flux of phosphorus and matric potential in Acrudox

Abstract

Enhanced-efficiency phosphate fertilisers may play an important role in phosphorus (P) availability in tropical soils by increasing their concentration in solution and enhancing the diffusive flux of P (DFP). This work evaluated the DFP in soil influenced by polymer-coated phosphate fertilisers and organophosphates (enhanced-efficiency phosphate fertilisers) applied to soil, at two matric potentials. The experiment was conducted using a 4 × 2 × 4 + 2 factorial design in which four phosphate fertilisers (conventional monoammonium phosphate (MAP), polymer-coated monoammonium phosphate (POL), pelletised monoammonium phosphate with filter cake (FC) and granulated monoammonium phosphate with swine compost (SC)), two soil water contents corresponding to two matric potentials (–10 and –50 kPa), four anion exchange resin insertion distances (0.5, 1.0, 1.5 and 2.0 cm from the phosphate fertiliser granules) and two control treatments (matric potential of –10 and –50 kPa without fertiliser) were studied across four replicates. Enhanced-efficiency phosphate fertilisers increased the release of P into the soil solution. The values of DFP (nmol m–2 15 days–1) for MAP were in the range of 0.18–48.69, for POL were 0.19–32.20, for FC were 0.17–19.74 and for SC were 0.17–18.50. For –10 and –50 kPa matric potentials, the values ranged within 0.18–43.07 and 0.17–48.69 nmol m–2 15 days–1 respectively. In relation to the distances 0.5, 1.0, 1.5 and 2.0 cm, DFP (nmol m–2 15 days–1) ranged within 17.56–48.69, 0.42–11.39, 0.22–0.57 and 0.17–0.22 respectively. The decrease in the soil water matric potential decreased DFP in the short term for fertilisers with coating technologies compared to MAP. This result indicates that coating technologies hold promise for maintaining DFP over time.