Recent attention has focused on management of soil acidity in no-till (NT) soils due to the limited movement of surface-applied lime in these systems. Interactions of exchangeable Al and organic matter have been recognized for many years, but limited data exist investigating how these interactions should affect management decisions for NT soils. This study was conducted to identify effects of rotation and tillage on soil pH and soil organic carbon (OC) content and to determine the influence of soil pH and OC on KCl and CuCl 2 extractable-Al (Al KCl and Al CuCl2, respectively). Soil samples were collected to a depth of 15 cm, in 2.5-cm increments, from a long-term rotation and tillage study near Manhattan, KS. Soil pH and OC concentrations were influenced by rotation and tillage, especially in the surface 2.5 cm. Organic C concentrations were on average 2.3 g kg -1 greater with NT than with conventional tillage in the surface 15 cm of soil. Aluminum extracted with KCl and Al CuCl2 increased exponentially with decreasing soil pH. Copper chloride extractable-Al values were on average 8% greater than Al KCl values. When using a regression model to predict the difference between Al CuCl2 and Al KCl, inclusion of OC explained only 4% more variability compared with inclusion of only soil pH in the model. A change in OC concentrations of 2.3 g kg -1, as observed in this study, after reducing tillage would likely not alleviate Al toxicity if pH became very acidic (pH
