Abstract
From 2007 to2009, we examined the growth and yield of potato without application of phosphorus and potassium fertilizer in the brown Andosol field in the Abashiri area, Hokkaido. Although the content of both available phosphoric acid and exchangeable potassium were lower in the plot without these fertilizer than in the fertilized plot, the number of tubers, the tuber yield and starch content were not significantly influenced by the absence of applied phosphorus and potassium fertilizers. We also examined the occurrence of common scab of potato, but found no significant difference in the occurrence of disease between the plants with and without application of phosphate and potassium fertilizers. Thus, the growth and yield of potato was not reduced on the field without applied phosphorus and potassium fertilizer in brown Andosol field, which contain a large amount of available phosphoric acid and the exchangeable potassium. This study also suggested that no phosphorus and potassium fertilizer need be applied for at least two years, since the amount of available phosphoric acid and the exchangeable potassium is kept above the criterion level in this type of soil.
