Ammonia Volatilization after Surface Application of Laying-Hen and Broiler-Chicken Manures

Ammonia (NH₃) losses after field application of animal manure are affected by manure characteristics. The objectives of this study were to quantify NH₃ losses from poultry manures obtained from varied handling and storage systems commonly found in eastern Canada and to relate NH₃ emissions to manure characteristics. We measured NH₃ volatilization using wind tunnels for 22 d after soil-surface application of seven solid poultry manures originating from farms varying in production type (laying hens and broiler chickens) and in storage duration and conditions. Cumulative emissions (2.7–7.0 g NH₃–N m⁻²) accounted for 13.6 to 35.0% of the total N applied and 51 to 84% (mean, 70%) of the sum of ammoniacal N, urea N, and uric acid N applied (TAUA). On average, 20% of these losses occurred during the first 4.5 h after application for manures that were not dried in the barn shortly after excretion. Production type and storage durations could not explain differences in NH₃ volatilization between manures. Volatilization losses were linearly related to manure dry matter and to manure-derived NH₄⁺–N, but sources of N changed with time after application. During the first 7 d, variations in total ammoniacal N applied (TANA) among manures explained most of the variations in cumulative NH₃ losses (r² = 0.85 after 26 h and 0.92 after 7 d). After a simulated rainfall (5 mm) on Day 7 that stimulated the decomposition of uric acid in manures, TAUA rather than TANA was related to cumulative emissions (r² = 0.77 after 14 and 22 d). Our results indicate that reliable estimates of NH₃ volatilization after land spreading of poultry manures should be based not only on TANA but also on NH₄⁺–N derived from the decomposition of uric acid, that volatilization losses reported in the literature (including the present study) averaged 50% of TAUA, and that estimates for a given situation also need to account for local environmental conditions.