On the land of dry field or forest in Japan there prevail commonly brown forest soil and its relative. Besides brown forest soil wet forest soil (nasse Waldboden) is also considered to exist on some part of the above land where drainage is impeded. Recently a certain kind of wet forest soil was found by the author on Uenodai Field of Oou-experimental Farm, Imperial Agricultural Experiment Station. On the field, where wet forest soil was observed to be transformed to brown forest soil in a short distance, it was convenient to ascertain the difference of productivity between the dry field of wet forest soil and that of brown forest soil. From the result of sweet potato cultivation dry field of wet forest soil was concluded to incline to be inferior to that of brown forest soil in the productivity.

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In the previous paper the author has reported the fact that the potato tubers which were grown in potash deficient condition contained much less amount of starch than those in full nutrient state, and that the difference in the starch content of tubers under the two potash conditions above indicated was attributable to the quantity of potassium supplied in soil. Further, it was stated that the starch grains in the tubers was directly proportional to the amount of potassium. Since according to the author's opinion, the direct relationship between the accumulation of carbohydrate and the enzyme activity or respiration should exist, he thinks that it will be very interesting to ascertain whether different amounts of potassium will play by itself an active part on them or not. The present experiment was undertaken to prove the effect of potash on the respiration rates, activities of enzymes, and ascorbic acic contents in potato tubers. Two varieties used for the experiments were Danshakuimo and Snow Flake, and the procedure employed to get tubers has been outlined in the previous paper. The results are summarized as follows. (1) The potassium starved plants seemed to have a consistently higher respiration rates, and its respiratory quotient is greater than that of fully manured. (2) The reducing sugar content in the tubers of the potash deficient plants were markedly higher. (3) The potassium deprived plants had the greatest diastase activity in the tuber. (4) The invertase activity in the plants was higher in the potash starved or no manured conditions. (5) The peroxidase activity of the plants supplied with potassium was werker than that of the potash deprived plants. (6) Generally the activity of oxidase was greater in the potash deficient plants than in the control. (7) The activity of catalase was greater in the plants received with potassium than in the potash starved plants. (8) Plants grown under different potash conditions had almost the same activities of the petase. (9) Greater activity of ereptase in tubers occured in the case of potash deficiency. (10) The quantity of the ascorbic acid within tubers was directly proportional to the amount of potassium added in soil.

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It is generally recognized in Japan that paddy rice plant is a little or not at all responsive to phosphate manuring even in case where barley requires much its application and it is supposed that the above fact may be connected with different behavior of soil phosphate under two conditions. From the above reason, the present author studied the solubility of soil phosphate at various hydrogen ion concentrations under two conditions. And the result will be summarized as follows; 1) The solubility of soil phosphate was very small at pH between 5 and 7 under both conditions. 2) Under the paddy field condition, the solubility at pH smaller than 5 and that. larger than 7,was both remarkably higher than that under dry field condition. 3) From the above different state of the solubility under two soil conditions, it may be concluded that the main part of soil phosphate under dry field condition is ferric phosphate and under paddy field condition, it is changed into ferrous phosphate.

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