Ammonia volatilization from animal excreta in contrasting grazing systems

Authors: TRUMPP, KEVIN - University Of Florida; DUBEUX, JOSE - University Of Florida; PORTUGUEZ, JAVIER - University Of Florida; BERNARDINI, MARLILIA - University Of Florida; BRETAS, IGOR - University Of Florida; DANTAS, LUANA - University Of Florida; ODUOR, KENNETH - University Of Florida; RUIZ-MORENO, MARTIN - University Of Florida; GARCIA, LIZA - University Of Florida; Jaramillo, David; SOLLENBERGER, LYNN - University Of Florida; DILORENZO, NICOLAS - University Of Florida; VENDRAMINI, JOAO - University Of Florida

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/29/2023
Publication Date: 10/29/2023
Citation: Trumpp, K., Dubeux, J., Portuguez, J., Bernardini, M., Bretas, I., Dantas, L., Oduor, K., Ruiz-Moreno, M., Garcia, L., Jaramillo, D.M., Sollenberger, L., Dilorenzo, N., Vendramini, J. 2023. Ammonia volatilization from animal excreta in contrasting grazing systems. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-ASSA Meeting, St. Louis, MO, Oct. 29- Nov. 2, 2023.

Interpretive Summary: Legume inclusion in grazing systems provide alternative nitrogen sources since legumes can fix atmospheric nitrogen and transfer to companion grasses. The objective of this study was to compare ammonia volatilization from a nitrogen-fertilized grass or grass-legume grazing system, during the winter and summer seasons. The ammonia volatilization rates from feces and dung from grazing cattle were overall greater from grass-legume systems, when considering the ammonia volatilization as a proportion of nitrogen applied. However, this study did not account for the emissions from fertilizers, which likely underestimate the emissions from the nitrogen-fertilized grass system.

Technical Abstract: Grasslands are used worldwide as the main source of feed for ruminant production. Legume inclusion in grazing systems can be a viable nitrogen source because legumes can fix atmospheric N through biological N-fixation (BNF). This study compared ammonia (NH3) volatilization from an N-fertilized grass (Grass+N) vs. a grass-legume mixture (Grass+RP) during the warm and cool seasons in Florida. The N fertilized system included Argentine bahiagrass (Paspalum notatum Flügge) receiving 112 kg N/ha during the warm-season, overseeded with cool-season grasses [oats (Avena sativa L.), annual ryegrass (Lolium multiflorum)] receiving 112 kg N/ha during the cool-season (total of 224 kg N/ha/yr). The grass-legume system consisted of Argentine bahiagrass-Rhizoma peanut (Arachis glabrata Benth) during the summer with no N fertilizer, overseeded with a mixture of cool-season grasses and a blend of clovers [crimson (Trifolium incarnatum L.), red (Trifolium pratense L.), and ball (Trifolium nigrescens Viv.)] receiving 34 kg N/ha/yr. Daily ammonia emissions rates from urine during the warm and cool season peaked on day 2 after application, declining steadily until day 8. On the other hand, emissions from dung varied compared to season and treatment, where the emissions peak was reached earlier during the warm season compared to the cool-season, indicating faster volatilization rates. Total N volatilized as NH3, expressed as a percentage of N applied from urine, was 11.5% for Grass+RP and 8.1% for Grass+N during the warm season and 4.3% for Grass+RP and 3.3% for Grass+N during the cool season. Overall, the NH3 volatilization from Grass+RP was greater compared to Grass+N. However, emissions from fertilizers were not considered, which may be underestimating the total emissions of the Grass+N system.