Studies on the Growing Process of Potato Plant : VIII. Studies on the relation between plant spacing and planting time of potato

Abstract

1) In order to find the best planting space in the field with different fertility and under different temperature condition, spacing, fertilizer and planting time experiments were carried out. 2) The stem length as a whole became longer with the delay of planting time. The growth type became more unfavorable with the delay of panting time, as the stem below the first flower cluster grew shorter and the stem above the first flower cluster longer. 3) The optimum temperature for dry matter production of potatoes was considered to be 19∼20°C (daily mean temperature), and the rate of translocation of dry matter into underground part was lowered when the daily mean temperature was higher than 20°C. Even in the high mean temperature, however, depreciation of the tuber weight/total weight ratio was somewhat reduced by means of the dense planting. 4) The nitrogen and phosphorous content of leaves became higher with the delay of planting time. But the potassium content showed slightly different tendency. In the case of the late planting, unusual balance between nitrogen and potassium was brought about in the late growing stage. 5) Tuber yields of the late planting plots decreased on account of decreased number of stolons and tubers and weight of one tuber. 6) It may be concluded that in the case of late planting, the number of tubers must be secured by means of dense planting, and not by the increase of amounts of fertilizer.