Potassium adsorption in soil cultivated with sugarcane

Area of Science:

• Soil Science
• Agronomy
• Environmental Chemistry

Background:

• Vinasse, a sugarcane processing byproduct, is nutrient-rich, particularly in potassium (K).
• It's commonly applied to soils via fertigation as a fertilizer without fully understanding potassium's fate.
• Understanding potassium interactions in soil is crucial for sustainable agricultural practices.

Purpose of the Study:

• To investigate the adsorption behavior of potassium ions (K+) from vinasse in a representative sugarcane soil.
• To determine the most suitable adsorption isotherm model for describing K+ interactions.
• To identify soil components responsible for potassium adsorption.

Main Methods:

• Soil characterization (physical, chemical, mineralogical).
• Equilibrium batch adsorption experiments.
• Fitting experimental data to Langmuir and Freundlich isotherm models.

Main Results:

• The Freundlich isotherm model provided a better fit for potassium adsorption data, especially in its non-linear form.
• Potassium adsorption was primarily mediated by soil organic matter and kaolinite clay minerals.
• Higher potassium adsorption capacity was observed in the topsoil layer (0-20 cm), decreasing with depth.

Conclusions:

• Vinasse application influences soil potassium dynamics, with adsorption being a key process.
• Soil organic matter and kaolinite play significant roles in retaining potassium from vinasse.
• Fertigation management strategies should consider the decreasing adsorption capacity with soil depth.