Overreliance on herbicides for weed control has led to the evolution of herbicide-resistant Palmer amaranth populations. Farm managers should consider the long-term consequences of their short-term management decisions, especially when considering the soil weed seedbank. The objectives of this research were to 1) determine how soybean population and POST herbicide application timing affects in-season Palmer amaranth control and soybean yield, and 2) how those variables influence Palmer amaranth densities and cotton yields the following season. Soybean were planted (19-cm row spacing) at a low, medium, and high population (268,000, 546,000, and 778,000 plants ha-1, respectively). Fomesafen and clethodim (280 and 210 g ai ha-1, respectively) were applied at the VE, V1, or V2 to V3 soybean growth stage. Non-treated plots were also included to assess the effect of soybean population alone. The following season, cotton was planted into these plots in order to understand the effects of soybean planting population on Palmer amaranth densities in the subsequent crop. When an herbicide application occurred at the V1 or V2 to V3 soybean stage, weed control in the high soybean population increased 17 to 23% compared to the low population. Economic return was not influenced by soybean population and was increased 72 to 94% with herbicide application compared to no treatment. In the subsequent cotton, Palmer amaranth densities were 24 to 39% lower 3 wk after planting when following soybean sprayed with herbicides compared to soybean without herbicides. Additionally, Palmer amaranth densities in cotton were 19% lower when soybean was treated at the VE stage compared to later stages. Thus, increasing soybean population can improve Palmer amaranth control without adversely effecting economic returns and can reduce future weed densities. Reducing the weed seedbank and selection pressure from herbicides are critical in mitigating resistance evolution.