| Summary: | 碩士 === 國立臺灣大學 === 農藝學研究所 === 65 === The purpose of this experiment was to determine in which growing stage of rice spraying which concentratlon of 2,4-D would make the least injury and better production of rice. The effects of 2,4-D on the plant height, yield components, top dry weight and yield of the rice were also investigated. The results were summarized as follows:
1.In the early growing stage of rice i.e. tillering stage, sprays of 500 ppm and 1000 ppm of 2,4-D reduced the plant height, but it could recover after subsequent growth.
2.2,4-D at 500 and 1000 ppm decreased the no, of tillers of the rice cultivar, Tainan 5 but it was not observed in Taichung Native 1.
3.Analysis of yield components indicated that time of 2,4-D spray was more sensitive to both cultivars than the concentrations being used in the present experiment.
4.Number of panicles per hill was increased in the first crop of the rice cultivar, Tainan 5 but was decreased in the second crop when 2,4-D was sprayed at later stage of growth.
5.In the first crop of the rice cultivar, Taichung Native 1 after maximum tillering stage 2,4-D would decrease its number of panicles. However, in the second crop, number of panicles was decreased with the later date of 2,4-D application.
6.The weight of 1000 grains of both cultivars was not affected by 2,4-D spray at any conoentration or time of application.
7.In the first crop of Tainan 5 rice yield was increased when 2,4-D was sprayed before booting stage but after maximum tillering stage. In the second crop, this effect was not investigated. In Taichung Native 1 rice yield was increased only when the 2,4-D was sprayed before maximum tillering stage.
8.Spray of 2,4-D at concentration higher than 500 ppm in the early growing stage induced the formation of tubular leaves. This was more apparent in Tainan 5 than Taichung Native 1.
9.The angle of the tillers increased after spray of 500 and 1000 ppm 2,4-D.
10.Spray of 2,4-D in the early growing stage or the 2,4-D concentration higher than 500 ppm delayed the heading stage and maturity of rice.
|
|---|
