MANURE AND RUNOFF WATER QUALITY FROM FEEDLOTS AS AFFECTED BY DIET AND PEN SURFACE
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Environmental management of confined animal feeding operations is closely regulated. Hence, understanding management practices that affect nutrient outputs and the potential risk of transport in the environment is of importance. The objective of this research was to evaluate the impact of feeding corn-based wet distillers grains plus solubles (WDGS) and the type of pen surface material on manure nutrient composition and runoff water quality. Rainfall simulations were conducted at an experimental feedyard that contained soil and fly ash surfaced pens. Two diets, steam-flaked corn (SFC) and 30% WDGS, were fed to cattle on each surface type. Diets containing WDGS resulted in greater manure nitrogen (N) and phosphorus (P) concentrations than SFC diets. Runoff volumes were significantly higher from soil pens where WDGS diets were fed. Runoff volumes were consistent for fly ash pens; however, there was a 3-fold difference between soil surfaced pens, indicating great variability between soil surfaced pens. Feeding WDGS increased soluble reactive P (SRP) concentrations in runoff water by 38% and total P concentrations by 27% compared to SFC. This increase in P runoff concentrations as a result of feeding WDGS was expected, as manure WEP concentrations were greater in pens where WDGS was part of the diet. Pen surfaces with fly ash resulted in increased total P and ammonium-N (NH 4-N) concentrations in runoff water. Mass losses of SRP, total P, NH4-N, and total Kjeldahl N (TKN) were highest from soil surfaced pens in which cattle were fed WDGS. While manure nutrient concentration can be an excellent indicator of the potential of nutrient runoff, hydrological properties can be the single most important factor in actually transporting nutrients offsite. 2012 American Society of Agricultural and Biological Engineers.
