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Impacts of a Manure Composting Program on Stream Water Quality

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18129)
Authors:   Asfaw Bekele and Anne McFarland
Keywords:   TMDL, orthophosphate phosphorus, manure, compost, water quality

In February 2001 the Texas Commission on Environmental Quality (TCEQ) adopted a total maximum daily load (TMDL) for orthophosphate phosphorus (PO4-P) along the North Bosque River (NBR). Within the TMDL dairy waste application fields were identified as the major nonpoint source contributing nutrients to the NBR. In September 2000 the Texas State Soil and Water Conservation Board (TSSWCB) initiated the Dairy Manure Export Support (DMES) project as a way to export dairy manure from the watershed. A goal of the DMES project was to reduce nutrient loading from conventional land application practices through the relocation of manure from the watershed. As a result of the project, over 458,000 tons of dairy manure was hauled to composting facilities between November 2000 and August 2003. To evaluate the impact of DMES on stream water quality, event mean concentrations of PO4-P, total phosphorus (Total P), total suspended solids (TSS), ammonia-nitrogen (NH3-N), nitrite-nitrogen plus nitrate-nitrogen (NO2-N+NO3-N), and total Kjeldahl nitrogen (TKN) from individual storm events were compared before and after the start of the composting project from microwatersheds stream sites. Seven monitoring sites with long-term data representing a range of land uses and participation in the composting program were evaluated. The data were analyzed as a "Before/After" monitoring design using the analysis of covariance (ANCOVA) procedure. Although the manure composting program has only been in place about three years, water quality appears to be improving. PO4-P concentrations decreased up to 39% at sites with the highest levels of manure removed per cow and drainage area. Statistically significant improvements in water quality were not seen at stream sites with lower levels of manure hauled off normalized on a per area and cow basis, however this was attributed to the relatively short monitoring period (three years) after the start of the manure composting project.

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