Surface amendments to minimize ammonia emissions from beef cattle feedlots

Amendments for reducing ammonia emissions from open-lot beef cattle feedlot s were evaluated in the laboratory. A mixture of 1550 g of soil, 133 g of f eces, and 267 g of urine was placed into plastic containers that were 20 cm X 20 cm X 12 cm deep. Using a vacuum system, clean air (3.2 L/min) was pas sed over the soil-manure surface and ammonia was trapped by bubbling the ai r through dilute sulfric acid. Treatments were a blank (soil with no manure ), control (soil-manure mixture with no amendment), 4500 kg/ha Al-2(SO4)(3) (alum), 9000 kg/ha alum, 375 kg/ha commercial product (CP)for reducing amm onia 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 N BPT There were four replications of each treatment. Ammonia emissions were measured for 21 days following application of the amendments. Cumulative am monia emissions after 21 days, expressed as a percentage of the control, we re 0.4% for the blank, 8.5% for 4500 kg/ha alum, 1.7% for 9000 kg/ha alum 7 3.6% for 375 kg/ha. CP, 68.2 % for 750 kg/ha. CP, 28.8% for 4500 kg/ha CaCl 2, 22.5% for 9000 kg/ha CaCl2, 32.4% for 9000 kg/ha brown humate, 39.8% for 9000 kg/ha black hum-ate, 35.9% for 1 kg/ha. NBPT, and 34.4% for 2 kg/ha N BPT Calculated costs of the amendments ranged from $0.12 to $5.53 per appli cation 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 imp acts should be evaluated before using these amendments in a commercial sett ing.