Effect of Using Aluminum Sulfate (Alum) as a Surface Amendment in Beef Cattle Feedlots on Ammonia and Sulfide Emissions

The objective of this study was to measure NH3 from feedlot surface material (FSM) containing aluminum sulfate (alum). A 33-day lab-scale study was conducted using pans containing FSM and either 0, 2.5, 5, or 10% alum. The pH of the FSM was significantly lower (p < 0.01) when treated with 2.5, 5, and 10% alum as opposed to the 0% alum treatment. No NH3 volatilization occurred below a pH of 6.5. A second study determined that small, weekly doses of 5% alum did not lower NH3 emissions further than a single dose of 5% alum. Two studies on the feedlot surface demonstrated a significant decrease (p < 0.01) in pH in the areas of the pens where alum was added compared to those that did not receive alum. Ammonia concentrations were lower (p < 0.05) for the areas that received alum compared to those that did not receive alum for 7 days when 5% alum was applied and 14 days when 10% alum was applied. In all the studies, sulfide emissions increased when alum was added to the FSM. We concluded 10% alum may reduce NH3 emissions from beef feedlots temporarily, but higher sulfide emissions offset this benefit.