This paper deals with the effect of fertilization systems on weed infestation degree and grain yield of some small grains on the vertisol soil type. The trial was set in random complete block design with three replications. The trial included control variant and three variants fertilized by mineral fertilizers, lime and manure (1. NP 1K, 2. NP 2K, and 3. NP 1K+CaCO 3+manure). Small grain crops involved in the trial were wheat, barley, triticale and rye. Results of the study showed significant effect of fertilization on decreasing weed infestation degree of the all investigated small grain crops. The highest degree of infestation by weeds (average 2.2) was observed at the variant without fertilization, while the lowest one (1.2) was found at the variant fertilized by the combination of mineral fertilizers, lime and manure. The highest degree of infestation by weeds was observed in wheat, and the lowest one in rye. Grain yield at fertilized variants was significantly higher comparing with the control variant. The highest average grain yield of the all small grains (3961 kg ha -1) was reached at the variant with combined application of mineral fertilizers, lime and manure, while the lowest one was observed at the unfertilized variant (1378 kg ha -1). Combined application of mineral fertilizers, lime and manure gave high-significantly greater grain yield in regard to mineral fertilizers alone with lower phosphorus dose. The difference between the variant with combined NPK, lime and manure and the variant NP 2K was not statistically significant. The highest average grain yield in the all variants of 3884 kg ha -1 was given by wheat, and it was high-significantly greater than in the other crops, while the lowest one (2290 kg ha -1) was observed in rye. The difference between grain yields of barley and triticale was not significant. The highest grain yield of 4770 kg ha -1 was given by wheat at the variant with combination of NPK, lime and manure. The lowest grain yield was observed in rye and it was significantly lower than in other crops at every variant, which was expected. Triticale had greater grain yield than barley at the all variants, but the difference at the variant with combination of NPK, lime and manure was not significant.
