Phytotoxic activity of pethoxamid in soil under different moisture conditions
2005
Dhareesank, A.(Tsukuba Univ., Ibaraki (Japan)) | Kobayashi, K. | Usui, K.
The phytotoxic activity of soil-applied pethoxamid [2-chloro-N-(2-ethoxyethyl)-N-(2-methyl-1-phenyl-1-propanyl) acetamide], (TKC-94), on the plant growth of rice (Oryza sativa cv. Kiyohatamochi) seedlings as an assay plant in soil was investigated under different soil moisture conditions. The phytotoxic activity of pethoxamid mixed with soil on the shoot and root growth of rice seedlings was uppermost under the highest soil moisture condition and it decreased with declining soil moisture content, while the inhibition was greater on the root growth than the shoot growth. The amount of pethoxamid adsorbed on soil solid and the concentration of pethoxamid in soil water from soil applied with this herbicide were not influenced by the soil moisture content. In addition, the phytotoxic activity on the growth of rice seedlings in sea sand culture applied with the soil water from the herbicide-applied soil was not influenced by the soil moisture content. In the sea sand culture, the phytotoxic activity of pethoxamid was significantly reduced in negative water potential as the concentration of polyethylene glycol-6000 added to the water increased. It is suggested that the phytotoxic activity of pethoxamid in the soil primarily depends on the concentration in soil water, but the phytotoxic activity was affected by soil moisture through the effect on absorption of this herbicide by rice seedlings.
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