Fontes e doses de fertilizantes fosfatados com tecnologia redutora de fixação : efeitos no crescimento inicial do milho e no fósforo disponível no solo

Abstract

Phosphate fertilization is essential for the initial establishment of maize, especially in tropical soils with low natural phosphorus availability and high nutrient retention capacity. This study aimed to evaluate the effect of different phosphorus sources and rates on the initial growth of maize and on the phosphorus available in the soil after cultivation, in an experiment conducted under greenhouse conditions at the Federal University of Sergipe, in the municipality of São Cristóvão, state of Sergipe, Brazil, from June to October 2025, using soil collected in Frei Paulo, Sergipe, Brazil. Three phosphate sources (MAP, Top-Phos and Solotek/P35), four P₂O₅ rates (40, 80, 100 and 120 kg ha⁻¹), and a control treatment without phosphorus were evaluated. Growth variables were obtained by image analysis, with quantification of shoot area and root area, and by chlorophyll a fluorescence (OJIP test), through the parameters Fv/Fm, PI and OJIP transient Area. At the end of the experimental period, soil available phosphorus was determined using the Mehlich-1 extractor. In general, treatments with phosphorus application showed higher values than the control, and an increase in shoot area was observed with increasing rates for all three evaluated sources. For root area, the response to increasing rates was more consistent for Top-Phos and Solotek/P35, whereas MAP showed greater variation among rates. Soil available phosphorus after cultivation varied according to source and rate, with a significant linear fit for Solotek/P35 and a significant quadratic fit for Top-Phos, while no significant fit was observed for MAP within the evaluated range. Regarding fluorescence, Fv/Fm and PI remained relatively stable among sources and rates; for the Area variable, a reduction was observed with increasing rates in MAP, without concomitant changes in the global indicators. In the correlation analysis, Solotek/P35 showed a significant positive association between residual soil phosphorus and morphological variables, whereas no consistent association was observed for MAP and Top-Phos. It is concluded that, under the evaluated conditions, increasing phosphorus rates favored the initial growth of maize, while the behavior of residual soil phosphorus depended on the source used.