Surface amendments to minimize ammonia emissions from beef cattle feedlots
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abstract
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 20 cm 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.
