|VAREL, VINCENT - FORMER ARS EMPLOYEE|
|Wells, James - Jim|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2016
Publication Date: 7/7/2016
Publication URL: http://handle.nal.usda.gov/10113/62789
Citation: Miller, D.N., Spiehs, M.J., Varel, V.H., Woodbury, B.L., Wells, J., Berry, E.D. 2016. Distillers by-product cattle diets enhance reduced sulfur gas fluxes from feedlot soils and manures. Journal of Environmental Quality. 45:1161-1168.
Interpretive Summary: Enhanced production and emission of total reduced sulfur (TRS) from confined animal feeding operations (CAFOs) is a concern associated with increased feeding of high-sulfur distiller’s byproducts in large feedlots. Three feeding trials were conducted to evaluate the relative impact of feeding wet distiller’s grain plus solubles (WDGS) on relative fluxes of TRS. In the first trial, the relative TRS flux were 3 to 22-fold greater when 60% WDGS was fed to cattle compared to 0% WDGS. In the second feeding trial on a production-scale feedlot, the relative TRS fluxes were 3.5 times greater on two of four dates from mixed manure and soil when animals were 40% WDGS compared to 0% WDGS. On the other two dates the result was consistent, but the difference was not as great (1.8 to 1.9-fold higher for 40% WDGS) and not statistically significant. After animals were removed TRS flux decreased by 83% over a 19-day period but were 50% greater from the pen surface when animals were fed distiller’s byproducts. TRS fluxes were principally from the wetter edges of the pen compared to the drier central mound area of the pen. In the third feeding trial, TRS fluxes were measured across the feedlot pen surface over two cycles of cattle production. Largest TRS fluxes again were principally from the wetter edges of the pen and when cattle were fed higher (35%) WDGS levels in their diet. For the six sampling events, the relative TRS flux from WDGS pens ranged from 0.3 to 4-fold higher compared to a standard dry-rolled corn (0% WDGS) diet. Examining a variety of environmental parameters, manure pack temperature correlated the strongest with TRS flux. Several other weak, but significant correlations were also observed between TRS flux and manure-associated constituents. Consistent results among these three feeding trials indicate that reduced sulfur fluxes increase when cattle were fed higher levels of WDGS.
Technical Abstract: Total reduced sulfur (TRS) emissions from animal feeding operations are a concern with increased feeding of high-sulfur distillers by-products. Three feeding trials were conducted to evaluate feeding wet distillers grain plus solubles (WDGS) on TRS fluxes. Fresh manure was collected three times during Feeding Trial 1 from cattle fed 0, 20, 40, and 60% WDGS. Fluxes of TRS from 40 and 60% WDGS manures were 3- to 13-fold greater than the 0 and 20% WDGS manures during the first two periods. In the final period, TRS flux from 60% WDGS was 5- to 22-fold greater than other WDGS manures. During Feeding Trial 2, 0 and 40% WDGS diets on four dates were compared in feedlot-scale pens. On two dates, fluxes from mixed manure and soil near the feed bunk were 3.5-fold greater from 40% WDGS pens. After removing animals, soil TRS flux decreased 82% over 19 d but remained 50% greater in 40% WDGS pens, principally from the wetter pen edges (1.9-fold greater than the drier central mound). During two cycles of cattle production in Feeding Trial 3, TRS soil fluxes were 0.3- to 4-fold greater over six dates for pens feeding WDGS compared with dry-rolled corn diet and principally from wetter pen edges. Soil TRS flux correlated with %WDGS, total N, total P, manure pack temperature, and surface temperature. Consistent results among these three trials indicate that TRS fluxes increase by two- to fivefold when cattle were fed greater levels of WDGS, but specific manure management practices may help control TRS fluxes.