This study investigated the adsorption behavior of Nicosulfuron (NIF) in black soil and red soil, as well as the impact of dissolved organic matter (DOM) derived from manure and straw on NIF adsorption. Results showed that black soil, with its higher organic matter content, had significantly stronger adsorption capacity for NIF than red soil. The addition of exogenous DOM significantly inhibited NIF adsorption in both soils, with manure-derived DOM having a more pronounced inhibitory effect than straw-derived DOM. The adsorption kinetics followed the Elovich model, where DOM reduced the initial adsorption rate through competitive adsorption, site shielding, and complex formation. Isotherm models indicated that NIF adsorption in black soil was mainly driven by chemical adsorption, while in red soil, it was dominated by hydrophobic interactions. FT-IR analysis revealed that DOM enhanced the binding of NIF to soil-DOM complexes through hydrogen bonding and coordination. This study elucidates the regulatory role of DOM on environmental behavior of NIF and provides a theoretical basis for assessing the impact of exogenous DOM input on herbicide behavior in agricultural soils.