Kokeikuzyu and carnallite obtained from bitterns were studied to ascertain their fertilizing values on certain crops. For rice in pot cultures and as well as on fields, Kokeikuzyu and carnallite gave nearly equal amounts of yields to potassium chloride when suppling the same weight of potassium while for barley larger increments of yields than potassium chloride in pots. It was shown that carnallite did more serious damage to rice than Kokeikuzyu when appling large quantity, but the former was less injurious than the latter when working on the basis of equal amount of potassium supplied. A product calcined with calcium carbonate gave less amount of yield than original Kokeikuzyu, though its hygroscopicity would decrease in some degree.