The invention provides a berbicidal composition comprising a mixture of: (a) polymeric microparticles containing a first herbicide, wherein the first herbicide is a synthetic auxin herbicide (e.g. dicamba, MCPA or 2,4-D) or an acetolactate synthase (ALS) inhibitor herbicide(e.g. triasulfuron, tribenuron-methyl, iodosulfuron-methyl, mesosulfuron-methyl, sulfosulfuron, flupyrsulfuron-methyl, or pyroxsulam) wherein the first herbicide, when in a salt-free form and when not contained within polymeric microparticles, antagonises the herbicidal activity of pinoxaden and (b) pinoxaden wherein the polymeric microparticles are controlled-release matrices, within which is the first herbicide, and which function in such a way as to control and/or slow down the release of the first herbicide from the polymeric microparticles into a liquid (e.g. aqueous) medium when the polymeric microparticles are placed (e.g. dispersed) in and in contact with the liquid medium. The containing of the first herbicide within the controlled-release polymeric microparticles is thought to mitigate the antagonism of the grass-weed-herbicidal activity of pinoxaden which might otherwise be caused by the first herbicide depending on the circumstances. The invention also provides a method of reducing the antagonistic effect on the control of monocotyledonous weeds in non-oat cereals which is shown by a herbicidal mixture of either a synthetic auxin herbicide with pinoxadenor an ALS inhibitor herbicide with pinoxaden, which comprises applying a herbicidal compositionaccording to the invention. The invention also provides a herbicidal compositon comprising (a) polymeric microparticles (e.g. controlled-release matrices), containing a first herbicide as defined above, and either (x) a nonionic surfactant or (y) a surface-modified clay, as defined herein.Linvention concerne une composition herbicide comprenant un mélange de : (a) des microparticules polymères contenant un premier herbicide, le premier herbici
