2007 Annual Report
A study was completed that found feedlot runoff to VTA’s introduces pathogens to the system; however, isolation frequencies of E. coli O157 and Campylobacter spp. from VTA soils decrease over time between discharge events. Isolation of generic E. coli from fresh-cut hay from regions of the VTA that received runoff indicates a slight risk for contamination but no pathogen were ever recovered from hay following baling.
A study was conducted to evaluate kill date timing of a cover crop on corn silage production. Preliminary findings suggest early destruction of the cover crop increased silage yield. EMI surveys taken throughout the growing season indicate the release of N from the early cover crop destruction corresponded with the rapid uptake of N by the corn crop. It is suspected that destruction of the cover crop early in the spring reduces this competition and releases stored nutrients when the following corn crop is rapidly taking up nutrients. It is not expected that early destruction will hinder nutrient retention by the cover crop.
A corn silage field plot received 10 years of animal manure at various rates resulting in excess phosphorus build-up in the soil. Following the 10 year study, alfalfa was planted to the field plot and one season of harvest has been completed. Preliminary analysis indicates some increase in phosphorus uptake by the alfalfa receiving animal manure, particularly the treatments to meet the corn silage nitrogen requirement.
Runoff control systems incorporated in the USMARC NPDES permit application include seven Alternative Control Technology (ACT) systems with vegetative treatment areas (VTA). Construction on all seven systems was completed in 2006. Performance monitoring began in October of 2006 using electromagnetic induction. Subsequent surveys have been conducted to examine management effects of the VTA’s. The use of this methodology has identified regions of nutrient buildup as well as areas that are deficit in liquid distribution.
ACT systems may provide equivalent or better performance compared to traditional capture and hold runoff control systems. Evaluation of ACT systems requires a determination of nutrient distribution across the VTA of the ACT. However, soil sampling is labor intensive, and costly and selection of sampling sites to adequately determine spatial variability may be difficult. The most significant outcome of this year was the adaptation of methods developed for the management of saline soils to inventory a VTA designed to control feedlot runoff. Soil conductivity maps were generated at a VTA site using electromagnetic induction equipment. A software package, ESAP, developed by the Soil Salinity Lab at Riverside, CA was used to determine soil sampling locations and to estimate constituent distribution across the VTA. Model validation tests indicated that the ESAP generated sampling design can be reliably used to adequately predict sample sites that were independently chosen by a random sampling design. Based on this work, the ESAP program can be used to determine model estimates of nutrient levels across a VTA to monitor system performance. This accomplishment aligns with NP206, Manure and Byproduct Utilization, and specifically addresses Problem Area 2 (Innovative Technology for Collection, Storage, and Treatment) with emphasis in Objective 1 (Improve and evaluate alternative feedlot runoff control systems using vegetative treatment areas).