RESUMO
A competitive crop utilizes resources before they are available to the weeds. The essential steps of developing a competitive crop begin with good stand establishment. A vigorously growing crop is also important towards establishing a competitive stand. Components of establishing a good and vigorous crop stand include crop rotation, seedbed preparation, crop type and variety selection, seed quality and treatment, seeding rate (stand density), seeding date, fertilizer rate and placement, pest and disease control, etc. Failure to properly manage these components leads to poor germination, week seedlings with poor grows and vigor therefore promotes weed competition with the crop. Biomass production and density of weeds and winter wheat plants was studied in a seeding time and nitrogen application small-plot field trial. This trial was a perfect example of how the proper management practices help us to decrease weediness and increase competition of winter wheat. The trial included 3 planting date treatments (early, optimum and late) and 2 nitrogen rate treatments (56 kg N ha-1 and 110 kg N ha-1) in spring top-dressing application. The influence of treatments on the weed infestation and crop plant vs. weed competition was studied at beginning of steam extension (BBCH 32-33, two visible nodes on the steam) and after harvest on the stubble-field. The competitiveness of weeds and crop plants were evaluated by biomass production and also by nutrient content of plant samples. Biomass forming of weeds in wheat canopy was negligible compared to that of weeds, but it was strong on the stubble. Delayed planting Leaded to poorer wheat growth and better weed biomass production. The higher rate of nitrogen resuited in a less weediness on early and optimum time seeded plots, but the tendency was opposite in the late seeded treatment.