The perennial, graminaceous, plant quackgrass (Elymus repens (L.) Gould) is a serious weed problem. When corn is grown continuously, the high amounts of nitrogen fertilizer applied can alter the pH of the soil, and this decrease in soil pH with time may change the weed spectrum present in corn fields. Studies were conducted to determine the effect of four different pH soils (3.7, 4.3, 5.5, 6.2) on the growth of quackgrass rhizome fragments in terms of biomass accumulation and tissue nutrient content. As the soil pH decreased from 6.2 to 3.7, quackgrass plants accumulated less shoot, rhizome and root biomass, as well as less shoot height and numbers of main axis shoots, leaves and rhizome buds. This inhibitory effect of soil pH on quackgrass growth was most apparent in the later six weeks of development, until seedhead anthesis was apparent. In the first four weeks after planting the rhizomes, the reductions in quackgrass growth were best indicated by numbers of leaves and main axis shoots, as well as by shoot height. This reduction in growth associated with lower pH soils probably was due to two mechanisms. The first mechanism could be interference with uptake and incorporation of magnesium and phosphorus into both above and below ground plant parts, as well as with copper and calcium in shoots, and zinc in rhizome and root tissue. A second mechanism could be due to toxicity caused by excessive amounts of manganese in all plant parts, as well as excessive boron in shoot plant parts.