The invention relates to novel substituted phenyl uracils of the formula (I) ##STR1##

in which

R¹ represents hydrogen, amino or in each case optionally substituted alkyl, alkenyl or alkynyl,

R² represents cyano, carboxy, carbamoyl, thiocarbamoyl or optionally substituted alkyl or alkoxycarbonyl,

R³ represents hydrogen, halogen or optionally substituted alkyl,

R⁴ represents hydrogen, nitro, cyano, alkoxy or halogen,

R⁵ represents cyano, thiocarbamoyl, halogen or optionally substituted alkyl or alkoxy and

R⁶ represents an optionally substituted nitrogen-containing heterocyclic group which is attached to R⁶ via N,

to processes for their preparation, to their use as crop treatment agents, and to intermediates and processes for their preparation.