Wheat yield (Triticum aestivum L. – cv. Enola) obtained under different main soil tillage systems in 4-field crop rotation (common bean-wheat-sunflower-grain maize), is strongly influenced by the regional soil (Haplic Chernozems) and the climatic conditions. This study was carried out at the trial field of Dobrudzha Agricultural Institute-General Toshevo from 2014 to 2016. The influence of seven main soil tillage systems (MSTS) on the yield and the physical properties of wheat grain was investigated. Four of these MSTS were applied independently and annually in crop rotation: 1. CP - conventional plowing (24-26 cm); 2. D – disking (10-12 cm) 3. C – cutting; 4. NT - nil tillage (direct sowing). The other three MSTS systems included: 5. Plowing (for spring crops) – Direct sowing (of wheat); 6. Cutting (for spring crops) - Disking (for wheat) and 7. Plowing (for spring crops) - Disking (for wheat). The mineral fertilization in the crop rotation was as follows: Common bean – N60P60K60; Wheat – N120P120K60; Sunflower - N60P120K120 and Maize – N120P60K60.The objectives were: (i) to investigate the seasonal variability in wheat yield as influenced by the tillage systems; (ii) to investigate the variability in the physical properties of wheat grain and (iii) to evaluate the correlations between the grain yield and the physical properties of wheat grain. A significant differentiation in the productivity of wheat was found depending on the tested MSTS systems. Lowest mean yields were obtained at the annual use of systems 3 and 4 - 4541 kg ha-1. Among the annually applied systems, constant disking was the most favorable for expression of the crop’s production potential. The mean addition to yield according to constant plowing in the crop rotation was 4541 kg ha-1. The systems involving annual alternation of tillage types with and without turning of the plow layer exceeded with 232.0 kg ha-1 (4.77%) the same systems, which were applied independently. The alternation of plowing for root crops with direct sowing of wheat was most efficient from an agronomic point of view. In comparison to annual plowing, the increase of productivity was with 280.5 kg ha-1 (5.62%). The values of the physical properties of grain were also highly differentiated according to MSTS. The constant application of disking in the crop rotation contributed to the production of grain with the best physical indices – absolute weight 43.15 g and test weight 76.86 kg. The use of the systems Cutting – Cutting and Direct sowing – Direct sowing had negative effect on both the yield and the physical properties of gain. Averaged for the period, the correlation between the grain yield and the physical indices of grain was high and positive. The mean value of the correlation coefficient between the yield and the test weight (0.930**) was higher than the correlation coefficient of the yield with 1000 kernel weight (0.780**). The correlation between the absolute and the test weight of grain was very high in all three years of the investigation
