Zeta Potential and Point of Zero Charge of Clay Fraction As Affected by Vinasse and Phosphorus.

Although the effects of vinasse in soils are well elucidated, little is known about its effects on variable charges of soils mainly associated with other farming practices such as phosphate fertilization. The objective of this work was to evaluate the effect of vinasse, P sorption and the interaction vinasse-phosphorus on zeta potential and point of zero charge (PZC) of clay-fraction samples from two soils with different iron contents (Dystroferric Red Latosol and Gleysol according to Brazilian System of Soil Classification). The clay fraction from Gleysol was referenced as natural gibbsite due to its high crystallinity degree and Al₂O₃ content (> 950 g kg^-1 in the clay fraction). The vinasse influenced the zeta potential of clay fraction of both soils. In the Red Latosol, the PZC was reduced from 7.5 to 5.0, and the particles became more negatively charged. For gibbsite, the PZC was not changed, but the positive charges were significantly reduced. The P sorption increased negative charges to the soil particles and reduced the PZC. These effects were more pronounced when the clay fraction was previously treated with vinasse. Financial support: Fapemig.