@article{miner_humenik_rice_rashash_williams_robarge_harris_sheffield_2003, title={Evaluation of a permeable, 5 cm thick, polyethylene foam lagoon cover}, volume={46}, DOI={10.13031/2013.15442}, abstractNote={Anaerobic lagoons and liquid manure storage basins are widely used for the treatment and storage of livestock and poultry manure. Although relatively inexpensive to construct, these devices have been widely criticized based upon their odor and ammonia release. A floating, permeable, composite cover manufactured from recycled polyethylene chips topped with a geotextile layer containing zeolite particles was evaluated under both laboratory and field conditions. Under laboratory conditions, the cover was found essentially to eliminate odor release and to reduce ammonia emissions by approximately 80%. When installed on a 0.4 ha swine manure lagoon in eastern North Carolina, the cover survived severe storms and allowed even intense rainfall to pass through without causing cover inundation. Under these field conditions, the cover was found to reduce ammonia emissions approximately 80%. Odor emissions measured twice during one month of the study were consistently low in concentration and near neutral relative to quality, as determined by an analysis by a trained odor panel. Microbiological examination of the cover after four months of use showed an active population of aerobic bacteria and protozoa; analysis showed that nitrifying, sulfide oxidizing, and methanotrophic bacteria were likely trophic components of the microbial populations observed. The surface of the cover became covered with an algal population within two weeks of installation. This and other vegetative growth had no discernable impact on the performance of the cover.}, number={5}, journal={Transactions of the ASAE}, author={Miner, J. R. and Humenik, F. J. and Rice, J. M. and Rashash, D. M. C. and Williams, C. and Robarge, W. and Harris, D. B. and Sheffield, R.}, year={2003}, pages={1421–1426} }
 @article{white_sheffield_washburn_king_green_2001, title={Spatial and time distribution of dairy cattle excreta in an intensive pasture system}, volume={30}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2001.2180}, abstractNote={ABSTRACTThis study determined distribution of feces and urine from 36 lactating dairy cattle (Bos taurus) managed in a rotationally grazed 0.74‐ha endophyte‐free tall fescue (Festuca arundinacea Schreb.)–white clover (Trifolium repens L.) pasture. Cows were observed for 24 h five times from July 1997 to April 1998, and for 13.5 h in September 1997. During each 24‐h observation period, the first grazing period (12 h) used 54% of the paddock and the second grazing period (8 h) used the entire paddock. Times and locations of all defecations and urinations from a subgroup of eight cows, observed while in the pasture, feed area, milking parlor, or in transit were recorded during the observation periods listed above and another time in May 1997. On pasture, all defecations and urinations were surveyed and mapped for all 36 cows. Feces and urine from six observation periods covered an estimated 10% of the paddock area in one year. Within 30 m of the water tank, concentrations of feces and urine from three warm‐season observations were significantly greater than concentrations during three cool‐season observations. Percentages of defecations and urinations on the pasture, feeding, and milking areas were highly correlated (r > 0.90) with time spent in those areas. Pasture‐based systems could reduce manure handling and storage requirements proportional to the time cattle are on pastures. Manure on the pasture was evenly distributed, except around the water tank during warm‐weather grazings. Results indicate that pasture‐based dairy systems may require smaller, less‐expensive manure management systems compared with confinement dairy farms.}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={White, SL and Sheffield, RE and Washburn, SP and King, LD and Green, JT}, year={2001}, pages={2180–2187} }
 @article{sheffield_barker_1997, title={North Carolina animal waste management operator certification program}, number={972084}, journal={Paper (American Society of Agricultural Engineers)}, author={Sheffield, R. E. and Barker, J. C.}, year={1997}, pages={4} }
 @article{sheffield_barker_1997, title={North Carolina's animal waste regulations to protect water quality}, number={972083}, journal={Paper (American Society of Agricultural Engineers)}, author={Sheffield, R. E. and Barker, J. C.}, year={1997}, pages={11} }
 @article{sheffield_mostaghimi_vaughan_collins_allen_1997, title={Off-stream water sources for grazing cattle as a stream bank stabilization and water quality BMP}, volume={40}, number={3}, journal={Transactions of the ASAE}, author={Sheffield, R. E. and Mostaghimi, S. and Vaughan, D. H. and Collins, E. R. and Allen, V. G.}, year={1997}, pages={595–604} }