The productivity of grain and grain protein of the Progress durum wheat variety was studied under fertilizing systems (1. N0P0; 2. N0P80; 3. N0P120; 4. N0P160; 5. N120P80; 6. N120P120; 7. N120P160) within a long-term fertilizing experiment. It was established that the system of phosphorus fertilization alone, in rates of 80, 120 and 160 kg/ha, reduced the grain and grain protein yields to the level of a non-fertilized control variant when the available soil phosphorus (DL-method) exceeded 15 mg P2O5/100 g soil. Independent phosphorus fertilizing above 120 kg P2O5/ha significantly decreased the harvest index. The systems with nitrogen fertilization at a rate of 120 kg N/ha, at rates of phosphorus fertilization 80-160 kg P2O5/ha yielded 728 kg grain protein per hectare in average, which exceeded 3.37 times those with independent phosphorus fertilization.