Ten competition periods as treatments (T_1-10) could be valuable for predicting increase productivity (W) T₁ to T₅ were allowed to infest the crop and (WF) T₆ to T₁₀ was kept weed free, weed competition periods for W and WFi.e. 3, 6, 9, 12 Weeks after emergence (WAE) and up to harvest. So, two field experiments were conducted season 2018 and 2019. Critical Periods for Weed Control (CPWC) was determined based on relative percentage yield ton/h^-1 (SY %) of weed free as a check by fitting curves regression models (linear and non-linear, which recommended losing yield value 10%. with seed yield reduction t/h^-1 declined from 2.3, 2.28 WF to 0.39- 0.36 W as a checked treatment for 1^st, 2^nd seasons, respectively about 83.33%, 85% due to relative seed yield. Gompertz as a non linear regression equation recorded 0.99* The effects of treatment classified into 3 groups where A involved 5 superior treatments (T₁, T₇, T₈, T₉ and T₁₀). However, T₄ and T₅ described inferior treatments which  located in group C. Low of weed density and increasing of weed index (WI %) 80% observed for 1^st season of T₄ but T₅ was translocated with increasing both weeds number and severed for weed index. It could be summarized that it should be keeping crop weed-free during stages 2^nd week and continue until 8^th week after crop emergence, which is providing maximum seed yield of soybean.