抄録
(1) In 1949, at rice nursery, in order to know the effects of 2.4-D on rice plants growing as well as weeds, the following tests were made. A) Two or three weeks before the sowing of rice seeds, 2.4-D which were disolved each 0.25g, 0.5g, and 1.0g in water of 1.5 liter per 1.8m2 (1 tsubo) were sprayed. To save from the toxity of 2.4-D, at the time of sowing, the rice seeds were treated with anti-2.4-D (the mixture of active carbon and active clay). The method is as follow. a) The rice seeds were covered with powder of anti-2.4-D. b) On the nursery bed, 2% suspension solution of anti-2.4-D were sprayed and 30g were used per are. c) No treatment. Morever, each section ((a), (b) and (C)) divided into two parts, the one covering the seeds with sand and the other with ash of boked chaffs. B) On Jun. 11th and 23th, 2.4-D of 20-200g were sprayed per 10 ares. (2) At half-drained nursery (flooded only furrows), the treatment of soil with 2.4-D of 0.5-1.0g per tsubo was benificial to control of the weeds, on the other hand, many abnormal and dead seedlings were appeared. Only in the plots which was applied 2.4-D of 0.25g with anti-2.4-D the normal seedling was found. (3) At flooded nursery all seedlings were normal when seeds covered with ash after pretreatment of 2.4-D. But on the occasion of 1.0g covered with sand abnormal seedlings appeared, while no abnormality was found by the use of anti-2.4-D and the weeds reduced to 1/2∼1/(10) compared with the untreated section. (4) The reduction of the toxic action of 2.4-D (neutralize action) was more efficiently when seed covered with anti-2.4-D powder than it sprayed on the soil. (5) The rice seedling which were slightly injured at nursery bed recovered their activity afterwards, and after transplanting they had grown up as well as the untreated seedlings. At flooded nursery, rice yield of the plots which were treated by 2.4-D, in some cases, were somewhat great compared with untreated section. (6) At the plots in which were applied 2.4-D of 20-50g on Jun.11th and 25th, the control effect of weeds was not remarkable but the injury of seedling was not great, and yield of rice were increased when sprayed 20 grams. On the other hand, at the plots in which were used 2.4-D of 100-200g, the weeds were fairly killed, but the growth of seedlings were prevented and have little yield.
