Influence of Aeration Implements, Ammendment and Soil Taxa On Phosphorus Losses in Grasslands.

Attenuation of rainfall within the solum can help extend forage productivity during droughty periods or it can retard flooding during periods of heavy rainfall.  Application of broiler litter to grasslands can result in excess phosphorus (P) in runoff and potentially cause eutrophication of surface waters.  Reductions in runoff P loss can be achieved by reducing runoff volume and/or reducing P concentrations. A practice that may accomplish these results is soil aeration. We will present results from two small plot aeration studies and one field scale paired watershed study. Over all objective of all three studies was to determine the impact of aeration on runoff volume and P losses in runoff from mixed fescue-bermudagrass [tall fescue (Festuca arundinacea Schreb.)/bermudagrass (Cynodon dactylon L.) ] grasslands fertilized with P ammendments (diary slurry, mineral and broiler litter).  Small scale rainfall simulations were done on two soil taxa using three types of aeration implements. The field scale study was conducted in six 0.7–ha, bermed field-scale watersheds, near Eatonton, Georgia. Bermed fields were paired based on their propensity to generate surface runoff.   We regressed loss of runoff volume, DRP and TKP from the aerated plots against loss of runoff volume, DRP, and TKP from the non-aerated plots before and after application of the aeration treatment.  Regression line slopes were compared to understand differences before and after applying aeration.   Results varied depending on soils and drainage class.  Small plot studies showed that broiler litter loss less TKP (p< 0.05) and that core aeration reduced TKP (46 %) and DRP (62%) losses from plots fertilized with broiler litter.  The field-scale study showed that in fields with well-drained soils, aeration reduced DRP losses by 35% but not in poorly drained soils. Overall, reductions appeared to have been caused by a combination of reductions in runoff volume and DRP concentration.