ソバ

The present work has been undertaken to determine the critical point of soil moisture, at which the water content, the amount of transpiring water and the transpiring power of plants begin to lessen because of the superfluous water content or water-supplying power of the soil. Four kinds of plants potted in f our kinds of soil with different water-holding capacity of 61.5, 69.6, 73.6 and 102.0% respectively were employed for this study. To determine the water content and the amount of transpiring water of plants, their percentage was calculated on the basis of their weight both of fresh and dry material, and also their value per unit volume of dry tissue-powder, after Prof. KOKETSU'S "Pulvermethode". Because this latter method proved preferable to the percentage methods, the values found by the "Pulvermethode" were principally used for discussion. For the determination of the transpiring power was used Prof. LIVINGSTON's spherical atmometer. The water content of the soil was also calculated per unit volume of dry soil powder, which was estimated by Prof. KOKETSU's automatic machine for estimating the volume of powder materials. As the water-supplying power determined by the soil point method and the water content of each soil were almost in proportion to each other, the latter was principally used as the index of soil moisture condition of a soil.