Simulating weed management in glyphosate-tolerant crops: greenhouse and field studies

Field dose-response curves showed that, in an oilseed rape crop, the prostrate growth of Stellaria media (L) Vill was protected against the glyphosate spray by the crop canopy, The erect growth of Chenopodium album L allowed it to penetrate the oilseed rape canopy and thus it became exposed to the spray. Consequently, S media was consistently less sensitive to glyphosate than C album. Tn the greenhouse without crop cover the situation was reversed, as S media was consistently more sensitive to glyphosate than C album. An empirical simulation model of a crop rotation including glyphosate-tolerant oilseed rape predicted, that the accumulation of seeds in the soil for either species was similar at a held rate (445 g AE ha(-1)), based on field or greenhouse data. With a quarter of the recommended rate, however, the model predicted a large buildup of S media in the seedbank, especially when the simulation was based on field dose-response curves. (C) 2000 Society of Chemical Industry.