Increasing the yield of pea grain in agricultural production is an important task for modern agriculture in the Orenburg region. To expand it, long-term studies on the influence of weeds and ammophos on the yield of pea grain were carried out. The article presents the research results for 2002-2019 by weediness of crops, the content of macronutrients and the productivity of pea grain in six-field and two-field crop rotations. Among the main factors affecting the yield of pea grain such as the total number of weeds and the content of accumulated nutrients in the 0-30 cm, soil layer were considered. The total number of weeds on two nutritional backgrounds in the pea germination phase was from 102.0 to 137.0. During the ripening period, respectively, it was from 44.0 to 56.0 pcs / m2. The maximum yield of pea grain is observed in crops after soft wheat with ammophos - 1.03 t / ha, without the use of fertilizer - 0.98 t / ha. The lowest yield of peas was obtained after durum wheat in a two-field crop rotation: according to the fertilized nutrition background - 0.76, unfertilized - 0.70 t / ha. As a result of statistical data processing in the third variant of the experiment (sowing peas after soft wheat in the aftereffect of a busy fallow), it was found that the increase in the productivity of pea grain slightly depended on the weediness of crops and the share of its influence ranged from 13.98 to 18.37%. However, the decrease in the yield of peas in the fifth variant of the experiment (sowing peas in alternation with durum wheat) was largely determined by weeds and the level of their influence was from 40.21 to 54.41%. The content of accumulated nitrate nitrogen and mobile phosphorus from ammophos before all sowing of peas in crop rotations ranged from 1.4 to 2.9 mg / 100 g of soil. The increase in pea grain from mineral fertilizers for 18 years, respectively, for all predecessors was 0.07; 0.05; 0.08 and 0.06 t / ha, except for the second variant of the experiment, where peas were sown after soft wheat in the aftereffect of black steam. The results of mathematical processing of the data on the increase in grain of peas show the effect of ammophos on the increase in grain by options in the range from 55.41 to 81.88%.