Abstract
1. Irish potatoes were grown on the cultivated volcanic ash soil and 2 placements A10 and A7B3 to which combinated all of 3 level of nitrogen and phosphorus to 1 level of potassium. A and B denote the depth of fertilizer applied in band, namely, 10 and 20 cm from the surface respectively. Side number shows the ratio of fertilizers applied. 2. Tuber yields of A10 were the highest on second level combination of nitrogen and phosphorus respectively, and the tuber yields of A7B3 were the highest on the third level combination of nitrogen phosphorus respectively. A7B3 exceeded A10 on the third level of nitrogen. 3. Differences of each character depend on greatly the effect of nitrogen, the effect of phosphorus were little comparatively, and the differences of placement significantly were the result of mutual action of placement and nitrogen. 4. On the highest nitrogen level, A10 was liable to become the excessive top growth and those values were liable to become large1y than the theoritical values of each components to gain maximum yields but A7B3 became not so. 5. If we maintain the optimum L. A. I. 3.6 from the bud stage to top muximum stage and also the same N. A. R. and distributed rate to tuber as A7B3, the yields which be gain by its will be about 6, 000 kg per 10 a perhaps, on the basis of this condition.
