Colloidal fertilizer is manufactured by ammoniation on the free acid to make it chemically neutral and protected from fixation of phosphorous with colloid in the form of granulars as it will prevent the readily solving out of the element. The purpose of this experiment is to compare the effectiveness of colloidal fertilizer with that of other fertilizers, and was carried out in Taipei and Shanchung. The results show that the difference between the effectiveness of colloidal fertilizer and that of others is not significant so far as the yields of tubers and leaves are concerned. However, farmer may spare the labour of mixing fertilizers.