In the framework of the ERDC-CRREL program for the more rapid establishment of native plants in western and eastern US military lands to avoid possible out competition by introduced ones during the initial year after seedling, it is important to ascertain if the presence of humic acids (HAs) may make native grasses more competitive when grown in combination with introduced grasses. The objective of this work was to evaluate the effect of three HAs isolated from two Wyoming soils and a Utah soil in suspension at two concentrations (10 and 100 mg/l) on seed germination and seedling early growth of two varieties of introduced Siberian wheatgrass, the cv.Vavilov and the germplasm line SERDP-select developed by ERDC-CRREL. After 6-days germination in Petri dishes in the dark in a thermostated chamber at 20°C, the seedlings were grown on Nitch nutrient solution, in the absence (control) or presence of of each HA, for 21 days in controlled temperature, humidity and illumination conditions in a Fitotron chamber. All experiments were conducted in five replicates. Statistical analysis of data by ANOVA showed that the HA origin and concentration affet at different extent germination and early growth of both Siberian wheatgrass varieties. In particular, the germination and shoot and root lengths and fresh and dry weights of the germplasm line SERDP-select was affected positively, often very significantly, by the presence of any HA at any concentration, whereas the response of the cv. Vavilov in the same growth conditions was generally negative or null.