Abstract

The purpose of this research was to evaluate the effects of P and Si fertilizer rates in dynamic of P fractions in clay soil under greenhouse. The research was carried out in a Dystroferric Red Latosol of a very loamy texture from Lavras city, Minas Gerais State, Brazil. The experimental design was entirely randomized, arranged in 4 × 3 factorial design, with four repetitions. The treatments included four inorganic fertilizer P rates (0, 110, 330 and 560 mg dm^-3) and three Si rates (0, 110, 330 and 560 mg dm^-3). The preview application of Si fertilizer did not contribute to decrease P desorption. Possibly, the silicate has lower affinity with the bound sites of adsorption than phosphates. The effects of inorganic fertilizer P were higher in increasing the moderately labile and labile P inorganic fractions. Among the organic P fractions, the NaHCO₃-Po fraction was the only one that contributes to plant nutrition. The Hedley sequential phosphorus fractionation promoted information about different pools where P was accumulated in the soil after common bean cultivation. The highest amount of P was obtained in stable P fraction, followed by moderately labile and labile P fraction. The moderately labile P fraction decreased after common bean cultivation possibly due to the time of P contact in the soil and redistribution to stable P fraction. The labile form was the lowest P pool in soil; nevertheless the increase in fertilizer P rates increases the amount of P content in labile fraction.

Key words: P fertilizer, Si fertilizer, nutrients interaction, Phaseolus vulgaris.