Herbicidally active phenyldiketone compounds

A phenyldiketone compound of the formula I ##STR17## in which the substituents have the following meanings:

• L and M are hydrogen, C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.2 -C.sub.6 -alkynyl, C.sub.1 -C.sub.4 -alkoxy, it being possible for these groups to be unsubstituted or substituted by one to five halogen atoms or C.sub.1 -C.sub.4 -alkoxy, or halogen, cyano, nitro, a group --(Y).sub.n --S(O).sub.m R.sup.7 or a group --(Y).sub.n --CO--R.sup.8,
• Z is a 5- or 6-membered heterocyclic saturated or unsaturated radical which has one to three hetero atoms selected from the group consisting of oxygen, sulfur or nitrogen and which is unsubstituted or substituted by halogen, cyano, nitro, a group --CO--R.sup.8, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.3 -C.sub.8 -cycloalkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -alkylthio, C.sub.1 -C.sub.4 -haloalkylthio, di-C.sub.1 -C.sub.4 -alkylamino or phenyl which is unsubstituted or substituted by halogen, cyano, nitro, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -haloalkyl or an oxo group which may also exist as a hydroxyl group in the tautomeric form, or which forms a bicyclic system with a fused phenyl ring which is unsubstituted or substituted by halogen, cyano, nitro, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -haloalkyl, a fused carbocycle or a fused, second heterocycle which is unsubstituted or substituted by halogen, cyano, nitro, C.sub.1 -C.sub.4 -alkyl, di-C.sub.1 -C.sub.4 -alkylamino, C.sub.1 -C.sub.6 -alkoxy, C.sub.1 -C.sub.4 -haloalkoxy or C.sub.1 -C.sub.4 -haloalkyl,
• Y is O or NR.sup.9,
• n is zero or one,
• m is zero, one or two,
• R.sup.7 is C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl or NR.sup.9 R.sup.10,
• R.sup.8 is C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -alkoxy or NR.sup.9 R.sup.10,
• R.sup.9 is hydrogen or C.sub.1 -C.sub.4 -alkyl,
• R.sup.10 is C.sub.1 -C.sub.4 -alkyl,
• R.sup.1 is cyclopropyl, 1-methylcyclopropyl, 1-methylthiocyclopropyl or tert-butyl;
• or an agriculturally customary salt of the compound I.