摘要：Water pollution is a deep concern due to mid-summer drainage in the rice cultivation. In this study, the authors investigated the effect of underdrainage during the mid-summer drainage on the dissolved substance dynamics in paddy soil test columns. Control experiment was conducted with two types of soil test columns: one column with underdrainage, and the other without. Rice plants were individually planted in these columns. Dynamics of dissolved substances (NO 3 -N, NH 4 -N, PO 4 -P, K, Ca, Mg, Na, Fe, Mn) were observed in these columns. Experimental results revealed the following facts: (1) underdrainage impacted growth of rice plants in mid-summer drainage; (2) underdrainage caused downward infiltration; (3) the downward infiltration leached dissolved substances from the paddy soil; (4) the amount of drained dissolved substances through underdrainage was more than through surface.
