Ironstone and Red Mud Soil Amendment: Phosphorus Solubility and Bermudagrass Growth.

Increasing phosphorus (P) sorption in buffer zones may reduce runoff P.  Sorption / desorption of P by a native rock in many coastal plain soils (ironstone), an industrial by-product (red mud) and a high P Ruston soil (fine-loamy, siliceous, semiactive, thermic Typic Paleudults) was measured in a batch study.  Effects of amending the soil (0, 5, 10 and 20%) on P drainage and bermudagrass (BG; Cynodon dactylon) were examined in a greenhouse study.  Both amendments had Langmuir sorption maxima approximately 5x that of the soil.  Sorption affinity was substantially greater with ironstone than red mud.  Results to date indicate greater reduction in P loss from the high P soil when amended with ironstone, with no effect on BG.