Eric O. Young’s research while affiliated with Dairy Science Institute, Inc. and other places

Dairy manure is an important nitrogen (N) source for crops, but its role in greenhouse gas (GHG) emissions and farm sustainability is not fully understood. We evaluated the effects of application of two dairy manure sources (bedded pack heifer, BP, and separated dairy solids, SDS) on corn silage yield and GHG emissions (carbon dioxide, CO2; methane, CH4; nitrous oxide, N2O) compared to a urea-fertilizer-only control (80 kg N ha⁻¹ yr⁻¹). The BP and SDS were applied at 18.4 and 19.4 Mg dry matter ha⁻¹ in fall 2020 in the final year of ryegrass production. No-till corn was planted from 2021 to 2023, and GHG emissions were measured each season (from May to November). The results showed significantly greater CO2-C emissions for BP in 2021 and no differences in 2022 or 2023. A small N2O-N emission increase for BP occurred in the spring after application; however, seasonal fluxes were low or negative. Mean CH4-C emissions ranged from 2 to 7 kg ha⁻¹ yr⁻¹ with no treatment differences. Lack of soil aeration appeared to be an important factor affecting seasonal N2O-N and CH4-C emissions. The results suggest that GHG models should account for field-level nutrient management factors in addition to soil aeration status.

Grazing and hay forage crops reduce erosion compared to annual crops, but few studies have compared soil and nutrient loss among grazing systems compared to a control. We evaluated runoff water quality and nutrient loss among three grazing systems and a hay crop production field with manure application (control) using a paired watershed design. Four edge-of-field sites at a research farm in central Wisconsin were managed as hay during calibration (2013–2018) followed by a grazing treatment phase (2018–2020). Grazing treatments of different stocking methods included continuous stocking (CS), primary paddock stocking (PPS), and adaptive multi-paddock stocking (AMPS). Runoff, sediment, nitrogen (N), and phosphorus (P) loads were monitored year-round. Grazing increased average runoff volume by as much as 1.7-fold depending on stocking method and tended to decrease event mean N and P concentrations. CS had larger mean sediment (2.0-fold), total N (1.9-fold), and total P loads (1.2-fold) compared to the control and had the lowest average pasture forage mass. AMPS had lower N and P loss as a percentage of that applied from manure application/livestock excretion (1.3 and 1.6%, respectively) compared to the control (2.5 and 2.1%), PPS (2.5 and 2.6%), and CS (3.2 and 3.0%). Stocking method had a marked impact on nutrient loss in runoff from these systems, suggesting water quality models should account for pasture management, but nutrient losses from all perennial forage systems were small relative to previous data from annual cropping systems.

Ammonia-nitrogen (NH3-N) loss from agriculture decreases crop yield potential and environmental quality. Incorporating animal manures by chisel plowing (CP) can reduce NH3 loss but may increase crop residue loss compared to lower disturbance incorporation methods and vertical tillage (VT). Few studies have evaluated VT efficacy for incorporating manure and reducing NH3 concentrations compared to traditional tillage tools, such as CP. Six trials during 2013 to 2016 were conducted to evaluate the impacts of manure incorporation method (CP, VT, or broadcast) and weather conditions at the time of application on NH3-N concentrations at a dairy research farm in central Wisconsin, USA. Passive samplers measured NH3-N concentrations at 30-cm above the ground during the first 0 to 24 and 24 to 48 h post-manure application/incorporation. Average NH3-N concentrations for CP and VT were 44 to 86% of broadcast and similar for most trials, while crop residue coverage for VT was greater than CP (39 and 22% of control plots, respectively). Concentrations of NH3-N were correlated with the amount of plot area covered by manure for the first (r = 0.56, p < 0.0001) and second measurement periods (r = 0.85, p < 0.0001). Results show that VT had comparable NH3-N concentration reductions to CP while conserving more crop residue.

Ammonia-nitrogen (NH3 -N) loss from agriculture decreases crop yield potential and environ-mental quality. Incorporating animal manures by chisel plowing (CP) can reduce NH3 loss but may increase erosion and compaction potential compared to lower disturbance methods. Vertical tillage (VT) is designed to reduce disturbance and conserve more crop residue than CP, however its effect on NH3 loss from manure application is largely unknown. Six trials in corn production systems were conducted to evaluate the impacts of manure incorporation method (CP, VT, or broadcast) and weather conditions on NH3-N concentrations during 2013 to 2016 at a research farm in central Wisconsin, USA. Passive samplers were used to measure NH3-N concentrations at 30-cm above the ground during the first 0 to 24 and 24 to 48 hr post-application/incorporation. Average NH3 -N concentrations for CP and VT were 44 to 86% of surface broadcast and similar for most trials, while crop residue coverage was greater for VT than CP (39 and 22% of control plots, respectively). Concentrations of NH3 -N were correlated with the amount of plot area covered by manure for the first (r = 0.56, P<0.0001) and second measurement periods (r = 0.85, P<0.0001). Results show that VT had comparable NH3-N concentration reductions to CP while conserving more crop residue.

Dairy manure is an important nutrient source for crops but can also contribute to ammonia (NH3) and greenhouse gas (GHG) emissions. While incorporating manure into the soil reduces nutrient loss potential in surface runoff, impacts on GHGs are unclear. Here, our objective was to quantify NH3, nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) fluxes for two seasons after liquid dairy manure was spring-applied to a live winter cereal cover crop-corn system with different incorporation methods. Broadcast application and no manure controls were compared to manure incorporated by vertical tillage (VT) or chisel plowing (CP). Corn yields did not differ in 2018 but were greater for CP in 2019. Mean NH3 emissions for VT were 70 and 23% of broadcast and 7 and 11% of broadcast for CP in 2018 and 2019, respectively. While VT N2O-N fluxes were also about 70% lower than broadcast both years, CO2 fluxes were larger for VT. On average, CP and VT had 16 and 4% lower global warming potential (GWP) index values than broadcast, respectively. Despite differing effects on N2O, our results showed that CP more effectively conserved NH3 while reducing GWP from liquid manure compared to VT, stressing the importance of site-specific soil-manure-tillage interactions when quantifying dairy system GHG fluxes.

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.

Snowmelt nutrient loss is an important but poorly understood process in cold climates. We measured nutrient losses at three sites after dairy manure was applied on top of an established snowpack. Treatments included no manure controls and three manure solids levels (12–19.4% solids = High; 7.5–8.0% = Medium; 2.9–5.5% = Low) applied at 26,670 L ha−1 to all treatments. Snowmelt runoff was monitored and analyzed for dissolved reactive P (DRP), total P (TP), total N (TN), ammonium-N, organic-N, and total solids (TS) concentrations. Results showed that manure application dramatically increased N and P loading compared to controls. Across site-years, manure application increased average runoff TP, DRP, and TN concentrations by 1.3- to 13.3-fold, 1.5- to 21-fold, and 1.4- to 14.2-fold, respectively, relative to controls. While cumulative N, P, and TS losses generally increased with manure solids, Medium/Low showed equal or greater nutrient transfer to runoff for some events. TN and TP lost in runoff were linearly related to manure solids concentration; however, N and P loss as a percent of applied showed the opposite trend. The results indicate that applying manure on top of snow resulted in high nutrient losses when runoff occurred regardless of manure solids content.

The anthropogenic loading of phosphorus (P) to water bodies continues to increase worldwide, in many cases leading to increased eutrophication and harmful algal blooms [...]

Dairy manure is an important crop nutrient source in Wisconsin and other parts of the upper Midwest but can contribute to nitrogen (N) and phosphorus (P) losses in overland flow/surface runoff. Winter cereal grain cover crops can help reduce erosion and nutrient transport in corn systems. However, few studies have compared tillage impacts on nutrient loss in live cover crop systems. The objective of this study was to evaluate vertical (VT) and chisel tillage (CT) effects on overland flow nutrient and sediment loss potential after spring-applied liquid manure. A surface application treatment (i.e., broadcast) and a no manure control were also included for comparison. After corn (Zea mays L.) planting into a live triticale (Triticale hexaploide L.) cover crop, four artificial rainfall-overland flow events were generated (42 mm h−1 for 30 min) on replicated field-scale plots in central Wisconsin. Mean total P, total N, and suspended solids loads were consistently lower for VT at 2 days post-manure application (with 97 to 99% lower losses than broadcast, respectively). Dissolved reactive P and ammonium-N concentrations for both CT and VT were significantly lower three weeks after manure application compared to broadcast. Results suggest that VT reduced soil/residue disturbance while incorporating manure sufficiently to reduce sediment, N, and P transport potential under simulated high overland flow conditions.

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.