Reducing Phosphorus Runoff and Leaching from Poultry Litter with Alum: Twenty‐Year Small Plot and Paired‐Watershed Studies. Issue 4 (1st July 2016) - Huang, Lidong
Abstract : Treating poultry litter with alum has been shown to lower ammonia (NH3 ) emissions and phosphorus (P) runoff losses. Two long‐term studies were conducted to assess the effects of alum‐treated poultry litter on P availability, leaching, and runoff under pasture conditions. From 1995 to 2015, litter was applied annually in a paired watershed study comparing alum‐treated and untreated litter and in a small plot study comparing 13 treatments (an unfertilized control, four rates of alum‐treated litter, four rates of untreated litter, and four rates of NH4 NO3 ). In the paired watershed study, total P loads in runoff were 231% higher from pasture receiving untreated litter (1.96 kg P ha −1 ) than from that receiving alum‐treated litter (0.85 kg P ha −1 ). In both studies, alum‐treated litter resulted in significantly higher Mehlich III P (M3‐P) and lower water‐extractable P at the soil surface, reflecting greater retention of applied P and lesser availability of that P to runoff or leaching. In soils fertilized with alum‐treated litter, M3‐P was much higher when analyzed by inductively coupled argon plasma emission spectrometry than by colorimetry, possibly due to the formation of aluminum phytate. Indeed, alum‐treated poultry litter leached less P over the 20‐yr study: M3‐P at 10 to 50 cm was 266% greater in plots fertilized with untreated litter (331 kg M3‐P ha −1 ) than with alum‐treated litter (124 kg M3‐P ha −1 ). This research provides compelling evidence that treating poultry litter with alum provides short‐term and long‐term benefits to P conservation and water quality. Core Ideas: Two 20‐yr studies were conducted on the effects of treating poultry litter with alum. Phosphorus runoff from paired watersheds was 231% higher with normal litter than alum‐treated litter. Surface soil samples had significantly higher M3‐P levels when fertilized with alum‐treated litter. Mehlich 3 results indicate alum additions to poultry litter reduce organic P leaching. Phosphorus leaching from plots fertilized with normal litter was 266% greater than with alum‐treated litter.