Si application alleviates influence of some abiotic stresses on crop plants. Meanwhile, scarce information is avaiable about the significance of Si for helping the plants to overcome the injuries of N deficiency and herbicides pressure. Thus, two–year 2–field experiments were carried out in wheat. Experiment I involved three Si concentrations (Si_0ppm, Si_250ppm and Si_500ppm) and two N levels(N_100% and N_50%). Experiment II examined four combinations of fenoxaprop–p–ethyl and Si: fenoxaprop–p–ethyl+Si_250ppm and fenoxaprop–p–ethyl+Si_500ppm (each either in sequence or in tank mixture), fenoxaprop–p–ethyl alone, hand weeding and weedy check. Under N deficiency (N_50%), Si_500ppm increased plant height as compared to the control. No significant differences in SPAD values were detected amongst Si concentrations under each of the two tested N levels. Si can partially alleviate negative N deficiency effect on wheat yield, causing its increase to level obtained under normal N supply. Si has no effect on weed biomass when applied with fenoxaprop–p–ethyl either in sequence or in tank mixing. The most promising treatment for maximizing wheat grain yield was the application of 100 kg N ha^–1 (N_50%) x fenoxaprop–p–ethyl+Si_250ppm in sequence", which also, in the same time, means reducing both cost of crop production and environment pollution.