Biologically active residues of the herbicides metsulfuron-methyl, chlorsulfuron and triasulfuron were estimated with field pea bioassays in soil samples to 80 cm depth from 4 field trials in south-eastern Australia situated on neutral to highly alkaline soil. Residues were both mobile and persistent at low levels. Leaching occurred beyond the lowest sampling depth during the winter–spring growing season. Metsulfuron-methyl was the most mobile of the 3 herbicides. Plant-back experiments involving susceptible crop and pasture species on 2 of the sites showed that the rates of decline of these residues in the sampling zone were slower than might be inferred from label plant-back recommendations in 1 of 2 seasons.

SaminaTyMCPA is antagonistic to a range of herbicides but there is limited research on its compatibility with other broad-leaved weed herbicides. In this study we assessed the joint action of MCPA ester and metsulfuron-methy! on Brassica napus L, using the additive dose model (ADM). The fresh weight responses for selected ratios of the mixture were plotted on the ADM and compared to the predicted mixture response at three assessment levels -50, 75 and 90% control. The mixture demonstrated increasing synergism as the response level increased from 50 to 90%, This restiit for MCPA ester is in marked contrast to that of the MCPA amine formulation, which was shown in previous studies to be antagonistic towards sulfonyiurea herbicides. Formulation is the major deciding factor in determining the compatability of phenoxy herbicides with other herbicides.

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