The present experiment was conducted at the Experimental Soils and Water Laboratory (LECASA) at EARTH University campus. The objective of the experiment was to evaluate the interaction and behavior of a vertisol cultivated with sugarcane ( Saccharum officinarum CP-72 2086) under commercial applications of vinasse, with emphasis on the substitution of K⁺ in three treatments of four replicates. The treatments were as follows: T1 with KCl (433 kg ha^-1); T2 with a cane-vinasse (125 m³/ha) and T3 with a cane vinasse (250 m³/ha). The vinasse applications rates were representative of the practices in the sugarcane industry in Costa Rica. The effect of the applications was assessed through soil, leaches, foliar analysis, biometry and crop yield during the 25-week study. In the soil analysis, K⁺ increased significantly (p≤0.05) in T2 and T3 and was maintained in the optimal range with T2 and in excess in T3, during the experimental time. The K⁺,BOD₅ and COD increased significantly (p≤0.05) in T2 and T3 leaches, 15 days after vinasse application, and exceeded the permissible limits established by the Costa Rican law. There were no statistically significant differences (p≤0.05) in pH, extractable acidity, P and Ca⁺². Concentrations of K, N, and Zn in the plant showed no significant statistical differences (p≤0.05) and remained under the respective optimum range for each element.