Abstract
1. The rates of vegetative growth of the non-tuberous roots of sweet potatoes were tested according to various soil treatments in the later growth stage of sweet potatoes. Such test proved that no appreciably great effect was found in the prodution of dry matter (total dry weight), while a striking effect was found in the distribution of dry matter. 2. Namely, according to the increase of non- tuberous roots it showed increase in the weight of tops, while decrease in the weight of tuberous roots, thus the ratio of tuberous root weight to the total dry weight became lower (correlation coefficient : r=-0.891**). And a high positive correlation was also found between the ratio of tuberous root weight to non-tuberous root weight and the ratio of tuberous root weight to total dry weight (r=+0.952**). This fact made clear that for the purpose of keeping the ratio between tuberous root weight and total dry weight at the rate of 40 per cent or higher, the ratio between tuberous root weight and non-tuberous root weight should to be kept at the rate of 1O times or higher. 3. It was also found that high in ground temperattlre, much in soil moisture and low in the concentration of oxygen are soil conditions for acceleration of the growth of non-tuberous roots as well as of the excessive vegetable growth of sweet potatoes.
