Invasion of western United States rangelands by Bromus tectorum (cheatgrass) is an environmental and economic concern. To increase understanding of soil factors that affect growth and site invasibility by B. tectorum, the invasion of a Krascheninnikovia lanata (winterfat) community in the Honey Lake Valley of northeastern CA has been monitored for a 5 year period. Overall, sites invaded by B. tectorum have greater soil-solution ortho-P, Ca⁺², Mg⁺² and Na⁺, greater extractable NH₄⁺, greater phosphatase and amidase enzyme activities, and lower pH than non-invaded sites. Complementary greenhouse studies indicate that non-invaded soil is inhibitory to the growth of B. tectorum; aboveground mass was over 27 times greater when grown in soil previously invaded for several years relative to growth in freshly-collected non-invaded soil. The inhibitory factor(s) was muted upon soil storage and repeated growth cycles (harvest and new planting). Subsequent experiments did not clarify the nature of the inhibitory facture, but it may be related to microbial acetate metabolism. The data suggest that B. tectorum engineers the soil to provide a more favorable growth medium. Greater understanding of the inhibitory factor(s) may lead to viable strategies to control invasive annual grasses.