Thresholds in spring wheat on sandy soils?

GROPPER (Metsulfuron-methyl) was applied with 25 g/ha (standard) and 12,5 g to spring wheat from 1996 to 1998. The dominant weed Chenopodium album had developed kotyledons and the first true leaves at the time of application. Even though the reduced herbicide doses had a 14% lower effect, crop yields were the same as in the standard, but had a better economy due to lower co sts. The regression analyses of weed dry matters (WDM) and yields showed weak re lationships in 1996 and 1997 due to unfavourable site conditions. The thres holds were calculated in g WDM/m(2). By reduced herbicide rates these were very low. The hight of the C. album plant can be calculated from the WDM by means of a regression equation. The here presented results and results in further literature allow the reco mmendation for reduced herbicide applications in spring cereals in the earl y stage of main species by low infestations. The reliability of thresholds and ecological effects of reduced herbicide doses are discussed.