The novel compounds of formula I:
wherein
Het represents an optionally substituted, optionally benzofused nitrogen containing 5- or 6-membered heteroaromatic group;
R1 represents an alkyl, alkoxyalkyl or cycloalkyl group;
R2 each independently represent an alkyl or alkenyl group, and
m is 0 or an integer from 1 to 6,
and herbicidal compositions containing such compounds as active ingredients can be utilized in various agricultural methods.