Studies on Chemicals Effective for Breaking Seed-dormancy and for Killing Dormant Seed of Barnyardgrass (Echinochloa Crus-galli Beauv. var. oryzicola Ohwi) : 3. Activity of several chemicals used in contact with soil

[摘要] Effectiveness of four chemicals, NIP (2, 4-dichlorophenyl-4-nitrophenyl ether), 1-isothio-cyanato-2-bromopropene (U-3), 1-thiocyanato-2-bromopropene (U-4) and DNBP (4, 6-dinitro-o-sec-buthylphenol), which showed high activity in the soaking treatment, was examined under the presence of soil using petri-dishes or 1/5000 a pots. Three methods were used for the treatment: spraying of the chemical solution to the seeds placed on the surface of water-drained soil, applying of the chemical solution to the seeds placed on the surface of water-submerged soil, and incorporating of the chemical solution to the upper layer of water-drained soil with the seeds. The results obtained were as follows: 1. Effectiveness of each chemical varied according to the method of treatment. NTP, U-3 and U-4 were more effective in the following cases: in case the effect of breaking dormancy by the method of treatment itself was higher, or in case the concentration of chemical solution in contact with the seeds was higher. This fact was especially remakable in NIP. DNBP was most effective when it is sprayed directly to the seeds. 2. The effectiveness in these treatments in contact with soil, in general, was markedly less than in the soaking treatment. Therefore, it was assumed that the treatment given under the presence of soil might have several factors decreasing the activity such as the adsorption and decomposition by soil or the vaporization of chemicals. 3. Generally speaking, such dosages as above 400 g/a in NIP, 200 g/a in U-3 or U-4 and 400 g/a in DNBP were required for full activity. 4. In order to establish the technique for breaking the dormancy or for destroying the germinability of dormant barnyardgrass seeds in soil by chemicals, it is important to find out not only chemicals with higher activity but also methods or factors which will improve the permeability of such chemicals into the seeds.

[学科分类] 农业科学（综合）