Phosphorus Availability in Soils Previously Fertilized with Slow-Release Phosphate Fertilizers

Most tropical soils exhibit low phosphorus (P) availability and a high adsorption capacity, resulting in low recovery of fertilizer-applied P. In addition to soil mineralogy, contact time, fertilizer source, and the type of coating (technology) employed also influence P availability in the soil. In this context, the development of fertilizers incorporating new technologies has been proposed to increase the efficiency of phosphate fertilization. This study aimed to evaluate the effect of different technologies associated with MAP on soil phosphorus availability, assessed by water-extractable P (P-H2O) and Mehlich-1-extractable P (P-M1), and on maize development, assessed by shoot dry matter production (SDMP) and leaf area (LA), after soil pre-incubation with the fertilizers for periods of up to 150 days. The treatments consisted of conventional monoammonium phosphate (MAP), polymer-coated MAP (MAPPOL), MAP combined with sugarcane filter cake (MAPFC), and MAP combined with coffee-husk biochar (MAPBIO). Treatments were arranged in a split-plot design with four replications, where the main plot consisted of four phosphate fertilizers MAP, MAPPOL, MAPFC, and MAPBIO, and the subplot consisted of incubation periods (15, 30, 60, 90, 120, and 150 days). Two successive cultivation cycles, each lasting 30 days, were conducted. Collectively, the three slow-release fertilizers evaluated—polymer-coated MAP (MAPPOL), MAP combined with filter cake (MAPFC), and biochar-coated MAP (MAPBIO)—resulted in higher mean P-H2O than conventional MAP (31.48 versus 26.10 mg dm−3, respectively). These fertilizers also resulted in higher P-M1 mean values than conventional MAP (273.04 and 194.44 mg dm−3, respectively). The coated fertilizers (MAPPOL and MAPBIO) generally promoted higher P-H2O and P-M1 values than the fertilizer containing the organic additive (MAPFC) throughout the 150-day incubation period. MAPBIO exhibited higher P-H2O and P-M1 values than MAPPOL during the evaluated period. In the first cultivation cycle, MAP produced better results than the slow-release fertilizers for SDMP-1 and LA-1, with average values of 14.59 g and 4061.28 cm2 for MAP and 14.12 g and 3513.63 cm2 for the slow-release fertilizers, respectively. In the second 30-day cultivation cycle, however, slow-release fertilizers outperformed MAP, with average values of 13.17 g and 3590.29 cm2 for the slow-release fertilizers and 11.83 g and 3282.22 cm2 for MAP, respectively. For both variables, MAPPOL and MAPBIO performed better than MAPFC.