Considering the effect of crop-weed competition the rate of weed growing, the competitiveness of the occurring weed species and the duration of competition are determining factors. Experiments were carried out on fields in order to collect data on the effect of early weed competition on maize, including the competition for nutrients and the possible rate of nutrient removal by weeds. From 7 sampling areas of the 9.2 ha field weeds and maize samples were collected 1 month after the sowing of maize. We determined the total numbers and the species numbers of weeds by plots. The removed plant species and maize were weighed then dried until the weight balance was reached. The samples were tested for N, P, K and Ca. Comparison was done with the weight and nutrient element content of maize plants taken from the treated, weed-free area. At the same time comparative analyses were made with the mass and nutrient contents of maize plants. There were 12 occurring weed species in this experiment. Based on the rate of weed cover the following species were dominant: Datum stramonium L., Cannabis sativa L., Amaranthus chlorostachis Willd., Chenopodium album L., Chenopodium hybridum L. Our experiments revealed that in the areas being likely to produce high weed populations and showing a considerable high nutrient removal by weeds, the competition between weed plants and maize occurs at an earlier stage of the vegetation period of maize than on fields with moderate weed populations. Weeds have utilised significant amount of nutrients which has been many fold of maize in case of unit area.