Synergistic herbicidal compositions comprising 1,3-oxazin-4-one compounds

A herbicidal composition containing as active ingredients the following two components A and B.

• Component A:
• at least one derivative selected from the 1,3-oxazin-4-one derivatives represented by the following general formula (I) ##STR21## wherein, R is a methyl or an ethyl group, Y is a halogen atom, a lower haloalkyl or a lower haloalkoxy group, and n is 0, 1, 2 or 3, and
• Component B:
• at least one compound selected from
• 5-tert-butyl-3-(2,4-dichloro-5-isopropoxy-phenyl)-1,3,4-oxadiazol-2-(3H)one
• 1,3-dimethyl-4-(2,4-dichloro-3-methylbenzoyl)-5-(4-methyl-phenacyloxy)pyraz ole,
• 2-(2,4-dichloro-m-tolyloxy)propionanilide,
• (RS)-2-bromo-3,3-dimethyl-N-(1-methyl-1-phenylethyl)-3,3-dimethylbutylamide
• 2,3-dihydro-3,3-dimethylbenzofuran-5-yl ethanesulfonate,
• 1-(.alpha.,.alpha.-dimethylbenzyl)-3-p-tolylurea,
• 1-(2-chlorobenzyl)-3-(.alpha.,.alpha.-dimethylbenzyl)urea,
• 4'-nitrophenyl-2,4,6-trichlorophenyl ether, methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate,
• 2,4-bis(ethylamino)-6-methylthio-S-triazine and
• 2-(1,2-dimethylpropylamino)-4-ethylamino-6-methylthio-1,3,5-triazine,
• N'-(2-chloroimidazol›1,2,-a!pyridin-3-yl-sulfonyl)-N'-(4,6-dimethoxy-2-pyri midyl)urea,
• methyl 2-›››››(4,6-dimethoxy-2-pyrimidinyl)-amino!carbonyl!amino!sulfonyl!methyl! benzoate,
• ethyl 5-(4,6-dimethoxypyrimidin-2-yl-carbamoyl-sulfamoyl)-1-methylpyrazole-4-car boxylate, and
• 5-›(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl-aminosulfonyl!-1-methyl-4-(2- methyl-1,2,3,4-tetrazol-5-yl)-pyrazole.