According to obtained data (Figure 7), a significant cor- relation between soil pH and increasing doses of cassava wastewater was detected only at 21 days after the application of cassava wastewater (DAM); therefore, the pH data fits a positive quadratic model and depends on the application of increasing doses of wastewater. At 21 days after the application of cassava wastewater (DAM), the soil pH, estimated by the regression equation, in the absence of cassava (0 m3 ha−1 ) was 7.20; addition of increasing doses of cassava wastewater increased the pH to a maximum value of 7.81, which corresponds to the application of the maximum dose (136 m3 ha−1 )of wastewater.