Abstract
Seasonal changes of pH values in the tea garden soils in Uji district, where the poor tea garden soils are distributed, were investigated during from june 1935 to nobember 1937. The results are summarized as follows : 1) The pH value of tea garden soil was generally varied with the season. During summer and early autumn, the pH value was usually lower, mostly about 4,and the fluctuations were not remarkable. On the other hand, during late autumn and spring it was higher with a considerable variation and mostly was about 5 to 7 and over, and this increase and variation of the pH value may be chiefly due to the manuring of much nitrogenous organic fertilizer in the season. 2) The fluctuations are connected with rainfall, by which pH is generally increased. The absorption of nutrient by tea plant and microbial activity also seem to have some influence on the fluctuation. 3) The maximum changes were from 1.12 to 3.72 in pH unit during from june 1935 to may 1536,from 1.90 to 3.81 during from june 1936 to may 1937 in the manured field, and from 1.42 to 1.49 during from december 1936 to november 1937 in the unmanured. 4) The pH value of the poor soil was slightly lower than that of the good soil during summer and early autumn, while during late autumn and spring, it was higher, and therefore the fluctuation through year was greater in the poor soil. 5) Above lower and higher pH values frequently found in the tea garden soil, may be unfavorable for the tea plant growth and it might be one of the causes which make tea garden soils so low productivity.
