The levels of exchangeable potassium in the soil above
0.2 cmolc dm−3 are considered high or adequate [18], indicating that cassava waste water used in this experiment served asa source of potassium and supporting the hypothesis that the potassium content in such effluents was sufficient to increase the levels of this cation in the soil and meet the demand of the cultivated sunflower during the experiment. This outcome was expected since cassava waste water is rich in nutrients (Table 2) especially in potassium