Greenhouse gas mitigation potential of annual and perennial dairy feed crop systems

Dairy production constitutes a significant amount of the total global anthropogenic greenhouse gas (GHG) emission. One of the proposed strategies to mitigate GHG emission from dairy production is by enhancing soil carbon sequestration through promoting the growing of perennial over annual dairy feed crop. We determined the net ecosystem carbon budget (NECB) of a hay and corn field grown side-by-side over three years to compare the GHG mitigation potential of perennial over annual feed crops in Elora, Ontario, Canada. The NECB was determined using measurements of net ecosystem exchange (NEE), total plant carbon content, and carbon content in applied dairy manure. The greenhouse gas balance (GHGB) were determined using the NECB plus the total nitrous oxide (N2O) fluxes measured by a complementary study at the same site. The effect of plowing of the hay field on the NECB and GHGB was also investigated. Our observations indicate that on average over the three study years, NECB of hay (7 ± 51 g C m−2 yr−1) was significantly lower than corn (154 ± 79 g C m−2 yr−1) indicating that corn was a larger carbon source than hay. The three-year average GHGB of 796 and 127 g CO2-eq m−2 yr−1 for corn and hay, respectively, indicated that corn was a larger emitter of GHG than hay. The NECB was the more dominant factor than N2O emissions in influencing the outcome of the annual GHGB. We conclude that hay has a larger potential than corn in sequestering carbon and mitigating GHG emission even when emissions from hay plow-down are included

Turbulent air flow in forest stands: a wind tunnel study

This study used a wind tunnel to examine turbulent flow in thinned forests and downwind of shelterbelts. High frequency measurements of the wind components were made using a Dantec triaxial hot-wire probe. Four thinning treatments were studied, consisting of uniformly spaced model trees with plant area index (PAT) = 4.5, 1.7, 0.7 and 0.4. Turbulence statistics up to the fourth order, as well as results from quadrant analysis and spectral densities, were compared to a similar field study, showing good agreement between model and field results. Length and time scales associated with the canopy turbulence were described with linear stability theory. Forest thinning was shown to increase turbulent energy and momentum transport within the canopy. Four shelterbelt widths were studied in both laminar and turbulent flows. Profiles were measured at both upstream and downstream positions, and without shelterbelts present. Turbulence statistics up to the fourth order, spectral densities and results from quadrant analysis were examined. The turbulent flow cases showed little variation with width due to mixing of the flow by turbulence, while the laminar flow cases showed strong differences between widths extending much further downwind.Land and Food Systems, Faculty ofGraduat

Development of a simple and affordable method of measuring ammonia volatilization from land applied manures

Quantifying ammonia (NH3) flux following fertilizer and manure nitrogen (N) application is crucial to develop sound management practices. Traditional methods used for obtaining these measures are either expensive, inefficient, or inaccurate. The objective of this study is to develop a method using a passive dosimeter and a semi-open static chamber to provide an economical and simple solution to measure NH3 loss following nitrogen application. Dosimeter tubes were commercially developed to measure ammonia exposure, providing a time-weighted-average. In this study,chicken manure was applied to short grass and the ppm h reading obtained using the dositube ammonia method (DAM) was calibrated against a reference measure of NH3 loss (kg N ha-1) using a wind tunnel and acid trap method. A calibration was developed (Estimated Total Loss (kg N ha-1) = (0.217Dw) - (0.034D) + 0.71) which requires the dositube (D) to be read every 24 h and placed at a height of 0.15 m in the Dositube chamber, with wind speed (w, m s-1) measured at a height of 0.3 m and averaged over the coinciding time period. This calibration may also be applied where dositubes are read every 48 h; however, 24 h periods are recommended to achieve the greatest accuracy.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The carbon budget and greenhouse gas balance of annual and perennial crops for dairy feed

Dairy production emits significant amount of greenhouse gases (GHG) to the atmosphere. Nevertheless, cultivation of hay and corn for dairy feed have the potential to partially mitigate GHG emission from dairy production by sequestering carbon in soil as soil organic matter. The present study investigated the net ecosystem carbon budget (NECB) and greenhouse gas balance (GHGB) of a hay and corn field grown side-by-side over three years in Elora, Ontario, Canada, as an indicator of net sequestered carbon. The NECB of the two crops were determined using measurements of net ecosystem exchange (NEE) and carbon in plant and applied manure. The greenhouse gas balance (GHGB) were determined using the NECB plus the total nitrous oxide (N2O) fluxes. On average over the three study years, NECB of hay (7 ± 51 g C m−2 yr−1) was significantly lower than corn (154 ± 79 g C m−2 yr−1) indicating that corn was a larger carbon source than hay. The three-year average GHGB of 796 and 127 g CO2-eq m−2 yr−1 for corn and hay, respectively, indicated that corn was a larger emitter of GHG than hay. The NECB was the more dominant factor than N2O emissions in influencing the outcome of the annual GHGB. In conclusion, hay has a larger potential than corn in sequestering carbon and mitigating GHG emission