A triketone compound of the following formula: ##STR1## wherein Y.sup.1 is C.sub.1 to C.sub.4 alkyl, a halogen or a C.sub.1 to C.sub.4 haloalkyl; each of Y.sup.2 and Y.sup.3 is independently C.sub.1 to C.sub.4 alkyl; Y.sup.4 is hydrogen, C.sub.1 to C.sub.4 alkyl or a halogen; n is 0, 1 or 2; p is 0 or 1; each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is independently hydrogen, C.sub.1 to C.sub.4 alkyl or phenyl; or when p is 1, either R.sup.1 or R.sup.2 and either R.sup.3 or R.sup.4 optionally bond to each other to form an intramolecular double bond; and X is oxygen or sulfur. The triketone compound is useful as a herbicide to control a broad range of upland weeds at a low dosage without causing phytotoxicity on corn.