Hiroshi Kurihara

Studies on the Growth Control by Application of Fertilizers : 1. The expected growing process of potato plants depend on the differences of placement and quantity of fertilizers

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.

Studies on the Growing Process of Potato Plant : V. The effects of various combinations of spacing of hills, amounts of fertilizer and number of stem per tuber on the growth and yields

1) In order to obtain some fundamental informations for potato cultivation, the responses under various combinations of plant spacing, amounts of fertilizer and number of stem per tuber were investigated by using two varieties. 2) The dry-weight of top per hill increased proportionnally with the increase of the spacing-area of one plant. However, the larger the spacing-area is, the longer the time is taken to reach a given yield per unit area, thus the plants continuing the vegetative growth for a long time. Consequently, the tuber yields per unit area increased in proportion to the decrease of the spacing-area. 3) Factors influencing the tuber yields per unit area varied with the branching habits of potato varieties used. For Danshaku-imo (Irish Cobbler), a mild branching variety, the increase of either fertilizers or number of stem per tuber brought high yields as spacing of hills increased. While, for Norin No. 1, a highly branching variety, the increase of both fertilizers and number of stem per tuber was necessary to get high yields. 4) Four growth types were classified based on the difference between two parts of the stem which were divided at the 1st flower cluster, and it was found that there is a close relation between the growth type and the tuber yields, and there exists favourable growth type expecting high yields. 5) It was concluded that the regulation of the growth of potatoes by the combinations of spacing of hills, amounts of fertilizer and number of stem per tuber should be changed with the ecological characteristics of the varieties used.

Studies on the Growing Process of Potato Plant : III. Effects of changing planting time on the top growth and tuber yields.

In order to obtain some fundamental information for potato cultivation, this experiment was performed to study responses of the plant to temperature during its growing season. Judging from the mode of the top growth in earlier and later stages each, divided at the flowering time of the 1st cluster, the development of which closely relates to the tuber yield, we distinguished 4 types, namely, A) normal-normal, B) normal-abnormal, C) abnormal-normal, and D) abnormal-abnormal. The types A, B and C are all common in Japan, and main factors deciding the type are the localitiy and the growing season, which are closely related with air temperature.