SURFACE AMENDMENTS TO MINIMIZE AMMONIA EMISSIONS FROM BEEF CATTLE FEEDLOTS

Amendments for reducing ammonia emissions from open–lot beef cattle feedlots were evaluated in the laboratory. A mixture of 1550 g of soil, 133 g of feces, and 267 g of urine was placed into plastic containers that were 20 cm U 20 cm U 12 cm deep. Using a vacuum system, clean air (3.2 L/min) was passed over the soil–manure surface and ammonia was trapped by bubbling the air through dilute sulfuric acid. Treatments were a blank (soil with no manure), control (soil–manure mixture with no amendment), 4500 kg/ha Al2(SO4)3 (alum), 9000 kg/ha alum, 375 kg/ha commercial product (CP) for reducing ammonia emissions, 750 kg/ha CP, 4500 kg/ha calcium chloride (CaCl2), 9000 kg/ha CaCl2, 9000 kg/ha brown humate, 9000 kg/ha black humate, 1 kg/ha of the urease inhibitor N–(n–butyl) thiophosphoric triamide (NBPT), and 2 kg/ha NBPT. There were four replications of each treatment. Ammonia emissions were measured for 21 days following application of the amendments. Cumulative ammonia emissions after 21 days, expressed as a percentage of the control, were 0.4% for the blank, 8.5% for 4500 kg/ha alum, 1.7% for 9000 kg/ha alum, 73.6% for 375 kg/ha CP, 68.2% for 750 kg/ha CP, 28.8% for 4500 kg/ha CaCl2, 22.5% for 9000 kg/ha CaCl2, 32.4% for 9000 kg/ha brown humate, 39.8% for 9000 kg/ha black humate, 35.9% for 1 kg/ha NBPT, and 34.4% for 2 kg/ha NBPT. Calculated costs of the amendments ranged from $0.12 to $5.53 per application per head. Only one treatment had a benefit/cost ratio greater than 1.0. Results suggest that amendments can reduce ammonia emissions from open feedlots, but the costs may be prohibitive. Site–specific environmental impacts should be evaluated before using these amendments in a commercial setting.