Manure application influences ammonia (NH₃) and greenhouse gas emissions; however, few studies have quantified the effects of manure application methods and timing on NH₃, nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) fluxes simultaneously. We evaluated surface-applied liquid manure application with disk incorporation versus injection on NH₃, N₂O, CO₂, and CH₄ 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 NH₃ 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 N₂O fluxes were generally low, larger increases after manure application were associated with injection and triggered by soil moisture/temperature changes. Mean CO₂ and CH₄ were unaffected by manure treatments and influenced more by weather. Overall, injection conserved more available soil N while contributing to modest N₂O emission, suggesting manure injection may offer greater agri-environmental benefits on the whole over surface application.

Best management practices (BMPs) can mitigate erosion and nutrient runoff. We evaluated runoff losses for silage corn management systems using paired watershed fields in central Wisconsin. A two-year calibration period of fall-applied liquid dairy manure incorporated with chisel plow tillage (FMT) was followed by a three and a half-year treatment period. During the treatment period FMT was continued on one field, and three different systems on the others: (a) fall-applied manure and chisel tillage plus a vegetative buffer strip (BFMT); (b) a fall rye cover crop with spring manure application and chisel tillage (RSMT), both BMPs; a common system (c) fall manure application with spring chisel tillage (FMST). Year-round runoff monitoring included flow, suspended sediment (SS), total phosphorus (TP), dissolved reactive phosphorus (DRP), ammonium (NH₄⁺-N), nitrate, and total nitrogen (TN). Results showed BFMT reduced runoff SS, TP, and TN concentration and load compared to FMT. The RSMT system reduced concentrations of SS, TP, and TN, but not load because of increased runoff. The FMST practice increased TP, DRP, and NH₄⁺-N loads by 39, 376, and 197%, respectively. While BMPs showed mitigation potential for SS, TN, and TP, none controlled DRP, suggesting additional practices may be needed in manured corn silage fields with high runoff potential.

Surface applied liquid dairy manure application (i.e., broadcasting) after alfalfa (Medicago sativa L.) harvest is a common practice. Low disturbance manure incorporation (LDMI) may offer multiple benefits including lower ammonia (NH₃), greenhouse gas (GHG) and hydrologic nutrient losses compared to broadcast. However, few studies have simultaneously quantified LDMI impacts on alfalfa yield, NH₃ and greenhouse gas (GHG) fluxes. We measured NH₃, nitrous oxide (N₂O), and methane (CH₄) fluxes for liquid dairy manure treatments applied to alfalfa plots for broadcast and LDMI over three seasons (2014 to 2016) in central Wisconsin, USA. There were minor differences in alfalfa yield and nitrogen (N) uptake across treatments and years. Shallow disk injection and aerator/band reduced NH₃ loss by 95 and 52% of broadcast, respectively, however both substantially increased N₂O fluxes (6 and 4.5 kg ha⁻¹ year⁻¹ versus 3.6 kg ha⁻¹ year⁻¹ for broadcast, respectively). The magnitude and timing of N₂O fluxes were related to manure application and precipitation events. Average CH₄ fluxes were similar among methods and increased with soil moisture after manure application. Results highlight the importance of quantitatively evaluating agri-environmental tradeoffs of LDMI versus broadcast manure application for dairy farms.