Manure Application Timing and Incorporation Effects on Ammonia and Greenhouse Gas Emissions in Corn

Manure application influences ammonia (NH 3 ) and greenhouse gas emissions; however, few studies have quantified the effects of manure application methods and timing on NH 3 , nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and methane (CH 4 ) fluxes simultaneously. We evaluated surface-applied liquid manure application with disk incorporation versus injection on NH 3 , N 2 O, CO 2 , and CH 4 fluxes in central Wisconsin corn silage ( Zea mays L.) plots during pre-plant (PP) and sidedress (SD) application windows from 2009 to 2011. Manure treatments were PP injection (PP-Inject) and injection at sidedress time (SD-Inject) to growing corn, along with two incorporation times for PP surface application (within 24 h—PP-1-hr; within 3 days—PP-3-day). Mean NH 3 emissions were 95% lower for injected treatments compared to surface application in both years, with larger losses for PP-3-day and SD-Surf. While N 2 O fluxes were generally low, larger increases after manure application were associated with injection and triggered by soil moisture/temperature changes. Mean CO 2 and CH 4 were unaffected by manure treatments and influenced more by weather. Overall, injection conserved more available soil N while contributing to modest N 2 O emission, suggesting manure injection may offer greater agri-environmental benefits on the whole over surface application.