ABSTRACT The research with "The Effect of KCl Fertilizer Dose On The Yield Of Some Potato Varieties (Solanum tuberosum L.) On Medium Plain" had been conducted at Ngargosoko Village, Sub Distrect Srumbung, Kabupaten Magelang, Cen- tral Java at date 26 September until 20 December 1990. The soil type was from Regosol, pH 6,5, elevation of 615 metres above sea level. The research us…