ABSTRACT The sim this experiment is to study the effect of the dosage and the time application time of Potassium fertilizer on the yield of sweet potato (Ipomoea batatas (L) Lem). The experiment was visualized from July 11, 1990 up to November 5 1990 done at Kedungsari village, Kort Magelang sub distrik central Java, the soil type is Latonal and elevationally 10- cated 380 meters above se…