Recent attention has focused on management of acid soils in no-till (NT) due to the limited movement of surface-applied lime in these systems observed in Kansas. Interactions of exchangeable Al and organic matter (OM) have been recognized for many years, but limited data exists considering how these interactions should affect management decisions for NT soils. Our objectives were to determine how OM influences extractable Al in NT cropping systems and how this interaction could influence management decisions. 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. Main plot treatments included continuous wheat [Triticum aestivum (L.) sp. aestivum], soybean [Glycine max (L) Merr.], grain sorghum (Sorghum bicolor (L.) Moench], and rotations of soybean-sorghum or wheat-soybean. Sub-plot treatments were NT and conventional till (CT). Results from analysis of soil samples indicated that KCl extractable Al (KCl-Al) increased exponentially with decreasing soil pH. Soil pH of the continuous wheat treatment was significantly lower compared with the other cropping systems. Within the continuous wheat treatment the pH of the NT was 0.2 units lower compared with the CT. Inclusion of total carbon (TC) in a regression analysis model (KCl-Al as dependent variable) explained 5% greater variability compared with inclusion of only soil pH in the model. When NT plots were separated, the R2 increased to 0.86 considering pH and TC as model variables compared with 0.72 for pH alone. The observed reduction in KCl-Al with increased surface OM in NT systems suggests that delayed lime applications are a viable option for producers utilizing these systems.
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