The effect of environmental factors on the herbicidal activity of pyrazosulfuron-ethyl under paddy [Oryza sativa] [fields] conditions

The effect of environmental factors on the herbicidal activity of pyrazosulfuron-ethyl was examined by pot tests in a greenhouse. Uptake site of pyrazosulfuron-ethyl in Cyperus serotinus Rottb. was determined by two application methods, i. e., surface water application for shoot uptake and soil incorporation for root up-take. Pyrazosulfuron-ethyl significantly reduced the growth with soil incorporation, while no reduction was observed with surface water application. Leaching and shallow planting depth, which increase the root uptake of pyrazosulfur-on-ethyl in C. serotinus, enhanced the activity. Lower temperature conditions (20/15°C) resulted in higher activity than did higher temperature (25/20, 30/25°C). Soil relations were examined using 15 paddy soils in Japan. Pyrazosulfuron-ethyl adsorption to soil was significantly related to soil pH. However, no relationship was observed between soil adsorption and effectiveness against Echinochloa oryzicola Vasing.. Higher activity of pyrazosulfuron-ethyl tended to be found in soils containing less organic matter.