Location: Agroecosystem Management Research2012 Annual Report
1a. Objectives (from AD-416):
A field study will be conducted to evaluate the effectiveness of a vegetative treatment system (VTS) in removing nutrients, pathogens and fecal indicator microorganisms, and hormones in the runoff from a beef cattle feedlot in central Nebraska over a two-year period. Collaborations with University of Nebraska, Lincoln (UNL) engineers and scientists will be utilized to accomplish this research objective. Two sub-objectives have been developed to answer key questions about the effectiveness of the VTS system. These sub-objectives are: 1. Evaluate the removal efficiency of the VTS during standard operation. 2. Determine the vertical movement and persistence of nutrients and pathogens and fecal indicator organisms within the VTA.
1b. Approach (from AD-416):
Sub-objective #1, Normal VTS operation: …during 2010 and 2011… [add to the end]--Pooled samples of ‘clean’ rainwater runoff (two per event), feedlot runoff (four per event) and excess infiltration runoff (two per event) will be analyzed in the University of Nebraska Water Science Laboratory for hormones (nearly three dozen, including estradiols, testosterones, progesterones, estriols, and trenbolone) and antibiotics (tetracyclines/sulfonamides and macrolide/betalactams). These samples will also be screened for resistance the third generation antibiotic ceftiofur that is widely used in cattle (Excede, Naxcel) for problems such as foot rot or eye infections. Sub-objective #2, Movement and persistence of nutrients and pathogens and fecal indicator organisms: Once each year, wastewater will be applied to four of the VTA treatment cells followed by collection of surface soil samples from five sites within each of the four cells and then sample those sites periodically over two weeks in order to understand how constituents in the wastewater are utilized, transformed, or removed. Soil depth profiles down to 30 cm (5 cm increments) will also be determined at those five sites in each of the four cells to help gauge the downward movement of microbes and nutrients. The 30-cm soil profile will be collected once each year to determine the movement of constituent over the two-year study.
3. Progress Report:
Water and/or soil samples were collected with help from UNL collaborators from the vegetative treatment system (VTS) demonstration site near Rockford, NE on ten occasions since the beginning of this project. Three types of water samples were collected including rainfall runoff from the vegetative treatment areas (VTA), rainfall runoff from the feedlot applied to the VTA, and excess feedlot runoff that was not adsorbed by the VTA. Soil sampling was also conducted on three dates—two dates for soil profiles and on one date a time series study were conducted. Soil profiles were collected in 2010 and 2011 to a 30 cm depth in four treatment cells at five locations along the wastewater flow path. Constituents (microorganisms, nutrients, and pharmaceutical compounds) were measured in each core which was subdivided by depth into six intervals. A berm area between treatment cells that did not receive feedlot runoff served as a control site for the other soil samples. The remaining soil sampling event associated with a time series study was conducted in June 2011. Three cells received feedlot runoff and surface soil samples (0 to 5 cm depth) were hand collected from five sites along the water flow path. Soil samples were collected on day 0, 1, 3, 7 and 14. Samples were also collected that included negative control berm samples, manure samples, and grasses from the treatment cells after application. One additional study conducted in September 2010 utilized irrigation well water applied to the treatment areas to see if pathogenic and fecal indicator microorganisms could be mobilized during a simulated rainfall event. Well water was applied to three cells and excess water was collected at the downslope end of the treatment area. Total coliforms, E. coli, Enterococcus, and E. coli O157 were measured using culture-based and molecular methods over two years in feedlot runoff and in treatment area soil samples. Tetracycline- and cephalosporin-resistant bacteria were also enumerated in runoff events and from soil samples using selective media. The average nutrient compositions of the three water sample types (rainfall runoff from the VTA, wastewater from the feedlot, and excess wastewater runoff from the VTA) were measured using a contract laboratory located near the field site. Total nitrogen, organic nitrogen, and ammonium concentrations fell by roughly half during the transport across the VTA. Whereas nitrate increased four-fold. Phosphorous also was decreased by almost 30%. Although not fully analyzed, the pattern of nutrients in the soil of the treatment cells shows trends for greater nutrient concentration at the surface compared to the deeper samples (50 cm). Phosphorus clearly shows this trend, and it is related to feedlot runoff inputs since the berm samples were generally uniform and lower in concentration. Sodium appears to show a general increase in treatment cells throughout the profile (compared to berm samples). Further analysis is needed to examine temporal trends from older samples.