Gas emissions from dairy barnyards
Dairy cattle spend considerable time in outside barnyards. Nine barnyards were constructed to examine impacts of surface materials (bark, sand, soil) and timing of cattle corralling (before and after 3-14-day corralling periods) on fluxes of carbon dioxide (CO2), methane (CH4), ammonia (NH3), nitrous oxide (N2O) and CO2 equivalents (CO2eq). Surface, year, and surface*year interactions accounted for 64%, 6% and 16% of CO2 flux variability. Average CO2 flux from bark (2552 mg/m 2 .h) was 3.1-3.9 times greater than from sand or soil, especially after bark replenishment. Timing, year, timing*year and surface*year accounted for 40%, 17%, 14%, and 17% of CH4 variability. Average CH4 flux after corralling (10.6 mg/m 2 .h) was 3.8 times greater than before corralling, and 5.2 times greater the year following bark replenishment. Timing accounted for 67% of NH3 variability. After corralling, NH3 fluxes (1622 mg/m 2 .h) were 95 times greater than before corralling. Timing, surface, surface*timing and timing*year accounted for 33%, 10%, 24% and 13% of N2O variability. Average N2O flux after corralling (2252 mg/m 2 .h) was 3.7 times greater than before corralling. Surface and surface*year accounted for 71% and 16% of CO2eq variability. Average CO2eq flux from bark (3188 mg/m 2 .h) was 2.5-3.0 times greater than sand or soil. Greatest CO2eq flux occurred the year after bark replenishment. Tradeoffs between gas emissions, nutrient runoff and leaching, and cow comfort and health need to be assessed more fully before recommending beneficial practices for barnyard surface type and management.
Read the whole study here: