Triazole herbicides

Herbicidal triazole sulphonamides of the formula: and salts thereof, where: R1 represents hydrogen or a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, acyl, alkoxycarbonyl, aminocarbonyl, sulphonyl or heterocyclic group;R2 represents hydrogen, halo, cyano, hydroxy, mercapto, a substituted or unsubstituted alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulphinyl, alkylsulphonyl, acyl, alkoxycarbonyl, aminocarbonyl, aryl or amino group, or a heterocyclic group;R3 represents a substituted or unsubstituted heterocyclic, benzheterocyclic, aryl or aralkyl group; andR4 represents hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, acyl, aroyl, alkylsulphonyl, alkoxycarbonyl, aminocarbonyl, aralkyl, or a group of the formula: - where RI and R2 are as defined hereinbefore, processes for their preparation and compositions containing them.